AI Proves Its Mettle in Reconstruction of Antarctic Temperatures

In a 2025 post, I described the largely unsuccessful attempt of an AI to spearhead research in climate science. Now, however, another AI appears to have succeeded in the more technical task of accurately reconstructing surface air temperatures across Antarctica – something that standard temperature datasets have been unable to achieve. The work is reported in a recent paper by a team of Chinese researchers.

The figure below illustrates the geographical distribution of available observational data in Antarctica from 1979 to 2023. The data comes from a number of manned and automatic weather stations, together with meteorological observations over the ocean collected from ships and buoys. As can be seen, the majority of observations are in coastal or near-coastal regions, precluding full spatial coverage of the continent.

To overcome this shortfall, the limited station observations have traditionally been interpolated using various reanalyses. But it’s difficult for reanalysis datasets to capture complex spatial patterns, say the researchers, and such datasets often contain significant uncertainties. Moreover, deriving surface air temperatures from reanalysis datasets depends in part on model simulations rather than actual instrumental measurements.

In the light of these limitations to an accurate reconstruction of Antarctic temperatures, the Chinese research team has applied deep learning methods. This approach has already been utilized successfully to reconstruct Arctic temperatures.

Antarctic temperatures were reconstructed using daily surface air temperature data from the various sources depicted in the figure above. Daily average temperatures were calculated from observations made at 3-hour intervals for some sources, 1-hour intervals for others. Training data for the deep learning model was provided by surface air temperatures from the three reanalysis datasets that showed the best agreement with observed temperatures.

The training data, which covered the period from 1979 to 2005, totaled 29,211 daily temperature samples. Using reanalysis data from different time periods, such as 1995 to 2021, as the training set had little impact on the temperature reconstruction. Validation of the training data and testing of the reconstructed temperature set employed reanalysis data from 2006 to 2012 and 2013 to 2018, respectively.

Testing of the reconstructed Antarctic temperatures was conducted for three specific days in 2015: January 1, July 1 and November 1. For these days, the reconstructed temperatures were found to be highly correlated with their reanalysis counterparts, with spatial correlation coefficients >0.99. The researchers say this correlation shows that the trained deep learning model is capable of accurately reproducing Antarctic surface air temperatures, even with the limited observational data available.

Just how different the reconstructed surface temperatures are from global observational temperature datasets for Antarctica is depicted in the next figure. The figure shows linear trends in annual Antarctic surface air temperatures from 1979 to 2023, measured in degrees Celsius per decade. The datasets are: (a) this reconstruction; (b) Berkeley Earth; (c) ERA reanalysis; (d) NOAAGlobalTemp5.1; (e) GISTEMPv4; and (f) HadCRUT5.

You can see that none of the standard datasets exhibit the pronounced cooling trend in East Antarctica in (a), something that was inferred earlier from the ERA reanalysis dataset by a different group of Chinese researchers. Nevertheless, all datasets show warming in the Antarctic Peninsula (on the left of the continent in the maps above).

Differing from the annual trends is the pattern for the summer months (November to April) only, presented in the figure below for the period from 1989 to 2022. Although the cooling trend still dominates in East Antarctica, warming is no longer prominent in the Peninsula but is found in West Antarctica and the southern portion of East Antarctica.

East Antarctica actually experienced a summer heat wave in 2022, when the temperature soared to -10.1 degrees Celsius (13.8 degrees Fahrenheit) at the Concordia weather station, located at the 4 o’clock position from the South Pole, on March 18. This balmy reading was the highest recorded hourly temperature at that station since its establishment in 1996, and 20 degrees Celsius (36 degrees Fahrenheit) above the previous March record high there. Remarkably, the temperature remained above that record for three consecutive days, including nighttime.

But Antarctica is nothing if not unpredictable. Despite the 2022 heat wave, the mercury dropped to -51.2 degrees Celsius (-60.2 degrees Fahrenheit) on January 31, 2023. This marked the lowest January temperature recorded anywhere in Antarctica since the first meteorological observations there in 1956. Two days earlier on January 29, the nearby Vostok station, about 400 km (250) miles closer to the South Pole, registered a low temperature of -48.7 degrees Celsius (-55.7 degrees Fahrenheit), that location’s lowest January temperature since 1957.

Such swings from record highs to record lows remain a puzzle, but the present reconstruction at least helps to characterize long-term trends.

Next: The Atlantic “Cold Blob” – Cause for Alarm or Just a Curiosity?

Challenges to the CO2 Global Warming Hypothesis: (13) Global Warming Entirely from Declining Planetary Albedo

One of my early posts in this series on challenges to the CO₂ global warming hypothesis featured a paper claiming that the greenhouse effect doesn’t exist. Now the same authors appear to have sidestepped that claim in proposing instead that current global warming can be explained entirely by the observed decrease in planetary albedo over the last few decades.

In a new paper, U.S. research scientists Ned Nikolov and Karl Zeller compare empirical observations of albedo made by CERES (Clouds and the Earth’s Radiant Energy System) satellites to the output of a semiempirical mathematical model used in their earlier work. In their model, the radiative effects integral to the greenhouse effect are replaced by a thermodynamic relationship between air temperature, solar heating and atmospheric pressure, analogous to compression heating of the atmosphere.

Nikolov and Zeller conclude that the observed decrease of planetary albedo, together with variations of solar output or TSI (total solar irradiance), account for 100% of the global warming trend as well as 83% of the interannual variability in global surface air temperature. They find that temperature changes are driven primarily by albedo changes, with only a marginal contribution from TSI.

Albedo is a measure of the earth’s ability to reflect incoming solar radiation. Melting of light-colored snow and sea ice due to warming exposes darker surfaces such as soil, rock and seawater, which have lower albedo. The less reflective surfaces absorb more of the sun’s radiation and thus push temperatures higher.

The same effect occurs with low-level clouds, which are the majority of the planet’s cloud cover. Low-level clouds such as cumulus and stratus clouds are thick enough to reflect 30-60% of the sun’s radiation that strikes them back into space, so they act like a parasol and normally cool the earth’s surface. But less cloud cover lowers albedo and therefore results in warming.

The figure below shows CERES measurements of global albedo from 2000 to 2024, expressed as a percentage anomaly of the 2001 to 2022 mean. The albedo decrease since 2000 is approximately 0.79%, which implies an increase in absorbed shortwave solar radiation of 2.7 watts per square meter over that period. The two researchers point out that this absorption is very close to the total anthropogenic forcing of 2.72 watts per square meter from 1750 to 2019 estimated by the IPCC (Intergovernmental Panel on Climate Change) in its AR6 (Sixth Assessment Report). 

The decline in albedo corresponds to a similar reduction in low cloud cover studied by a trio of German environmental scientists, which I discussed in a 2025 post. Their data for total (red curve) and low cloud (lower black curve) cover, calculated by the study authors from two separate sets of satellite data, is presented in the next figure. The lowered cloud cover is most prominent in northern mid-latitudes and the tropics.

The next figure shows CERES measurements of absorbed shortwave radiation from 2000 to 2024 along with global surface air temperature, measured as the average of six temperature datasets (HadCRUT5, GISTEMP4, NOAA Global, BEST, RSS and NOAA STAR). The temperature anomaly tracks changes in the absorbed solar flux with an average lag of approximately 4 months. Nikolov and Zeller say this close empirical relationship suggests that temperature is directly controlled by the absorbed solar flux.

The researchers quantify the individual effects of albedo and TSI on surface temperatures by using their semiempirical mathematical model. The following figure compares modeled temperatures based on each of these two factors with observations. It’s clear that variations in TSI play only a minimal role while variations in albedo dominate the temperature trend.

This conclusion is also supported by the next figure, which depicts the modeled contribution to albedo and TSI separately going back to 1981. According to Nikolov and Zeller’s model, the low contribution from TSI variation indicates that the earth’s climate is 5.6 times more sensitive to changes in solar absorption than to TSI variations.

The estimate is in good agreement with a conclusion reached by Israeli physicist Nir Shaviv, who has investigated the effect of TSI cycles on several climatic variables. Shaviv found that total solar forcing of the earth’s climate, which includes indirect effects, is 5 to 7 times larger than that associated with direct solar warming.  Such a large amplification factor would imply that the climate is much more sensitive to the sun than to CO₂. Of the various possible indirect amplification mechanisms, Shaviv favors the influence of cosmic rays on low cloud cover.

Nonetheless, the observation of declining albedo or low cloud cover begs the chicken-and-egg question: is decreased albedo the cause or effect of current warming? While Nikolov and Zeller argue for the former, they also call for large-scale interdisciplinary research into the physical mechanisms controlling the earth’s albedo and cloud physics, in order to resolve the question.

Next: AI Proves Its Mettle in Reconstruction of Antarctic Temperatures

Southern Ocean Cooling: Climate Scientists Unable to Agree on Explanation

Contrary to the predictions of climate models, surface sea temperatures in the Southern Ocean around Antarctica have cooled for several decades. Over the last 15 months, three completely different explanations have been proposed for this global warming anomaly.

The first paper, published in November 2024 by a team of mostly Spanish researchers, postulated that the cooling comes from previously unstudied marine sulfur emissions. It’s been known for some time that sulfate aerosol particles linger in the atmosphere, reflecting incoming sunlight and also acting as condensation nuclei for the formation of reflective clouds. Both effects cause global cooling.

But what wasn’t known before is that there are two sources of marine sulfur emissions, both of which emanate from microscopic plankton that live on the ocean surface and emit aerosol-forming gaseous sulfur. The previously known sulfur source is dimethyl sulfide ((CH₃)₂S), mainly responsible for the distinctively pungent smell of seafood. Emission of the more reactive methyl sulfur hydride (CH₃SH), hitherto neglected, has been quantified for the first time by the Spanish research team.

The researchers found that emissions of CH₃SH increase the formation of sulfate aerosols in the atmosphere by 30% to 70% over the Southern Ocean; this decreases incident solar radiation in summer by between 0.3 and 1.5 watts per square meter, enhancing the expected aerosol cooling effect. The maximum effect, which occurs at 65^oS, is illustrated in the figure below, where the red line denotes the increase in total sulfate aerosol emission as a function of latitude.

The second paper, published in March 2025, takes a rather different tack in proposing that the unexpected Southern Ocean cooling results from an influx of freshwater that’s not incorporated in state-of-the-art climate models, and restricts the exchange of surface waters with deeper warmer waters.

The authors, an international team of earth scientists, found that over the period from 1990 to 2021, underestimated freshwater fluxes can explain up to 60% of the difference between observed and modeled sea surface temperatures in the Southern Ocean. The freshwater consists of both Antarctic meltwater, which is completely missing from most climate models, and underestimated rainfall over the ocean. 

To quantify the effect of freshwater on Southern Ocean sea surface temperatures, the researchers used an ensemble of 17 coupled climate and ocean models that simulate ocean density and circulation changes. Separate simulations investigated step changes in forcing caused by surface freshwater fluxes from Antarctic ice sheet melting, and from atmospheric rain combined with sea ice melting, respectively.

Some of their results are displayed in the next figure which shows estimates of the freshwater flux, measured in gigatonnes (Gt, where 1 gigatonne = 1.102 U.S. gigatons) per year, from 1990 to 2021. The steadily increasing rainfall (plus sea ice) contribution is represented by the blue line and shading; the green line represents the Antarctic meltwater contribution – seen to be diminishing with time.  

The figure to the left depicts the influence of these “missing” contributions to the rate of warming or cooling of Southern Ocean sea surface temperatures, measured in degrees Celsius per decade. The overestimated warming predicted by climate models is indicated by the gray box on the left; the calculated contributions from rainfall and meltwater by the blue and green boxes, respectively; and the combined contribution by the black box on the right. 

You can see that the combined contribution brings the climate model warming rate down to almost zero. So this research provides a much better representation of the actual cooling rate than before and helps to resolve the decades-long mismatch between predicted and observed Southern Ocean temperatures.

The third paper, published just two months ago in December 2025, attributes the inability of climate models to correctly predict Southern Ocean cooling on the models’ underestimation of Southern Ocean storm strength and thus the heat transfer from atmosphere to ocean. Storminess draws colder deepwater upward, keeping the surface cooler which enables the surface to take up more atmospheric heat.

The Swedish, South African and UK researchers employed a robotic “glider” to measure ocean temperature and salinity, together with atmospheric properties above the waves. The robotic observations were then combined with satellite and multi-year climate model data.

Their results are summarized in the figure below, showing the difference in atmosphere-ocean heat flux between the interior of summer storms and the whole ice-free Southern Ocean. LHF (latent heat flux), SHF (sensible heat flux) and LWR (longwave radiation) all contribute to ocean heat loss; SWR (shortwave radiation) results in ocean heat gain. The black line with dots indicates the net heat flux, which is seen to produce slight cooling overall – though less cooling than from weaker storms.

Each of these different explanations accounts partially for underestimated Southern Ocean cooling in climate models, so perhaps a combination of all three will resolve the discrepancy.

Next: Challenges to the CO2 Global Warming Hypothesis: (13) Global Warming Entirely from Declining Planetary Albedo

Ongoing Attacks on Livestock Methane Emissions Based on Faulty Science

Farmers around the world have become a scapegoat for global warming, based on the assumption that emissions of methane (CH₄) from ruminant animals trap far more heat than carbon dioxide (CO₂) over shorter timeframes.

However, despite the ongoing attacks on agriculture, this assumption is wrong and stems from a fundamental misunderstanding of the underlying science. Methane is indeed a potent greenhouse gas but, because its atmospheric concentration is increasing at a negligible rate compared with that of CO₂, its contribution to global warming is small in comparison.

Let me explain. As I discussed in a 2023 post, the actual warming produced by a greenhouse gas depends on its so-called “global warming potential” – a quantity determined by how efficiently the gas absorbs heat, its lifetime in the atmosphere, and its atmospheric concentration.

The conventional global warming potential (GWP) is a dimensionless metric, created by the UN’s IPCC (Intergovernmental Panel on Climate Change), in which the GWP per molecule of a particular greenhouse gas is normalized to that of CO₂; the GWP takes into account the atmospheric lifetime of the gas. The following table shows both GWP-20 and GWP-100, the warming potentials calculated over a 20-year and 100-year time horizon, respectively, for both CO₂ and CH₄.

The GWP value for CH₄ over 20 years suggests, erroneously, that CH₄is a whopping 83 times more potent than CO₂ as a greenhouse gas. It’s this number that has been used by climate alarmists to demonize farmers and their livestock.

Farmers caught something of a break when a group of physicists at the University of Oxford realized that the IPCC’s GWP can overestimate the warming effect of short-lived greenhouse gases such as CH₄, compared to longer-lived gases like CO₂. The Oxford researchers proposed replacing the GWP with a metric called GWP*, in which the CO₂-equivalence of short-lived greenhouse gas emissions is determined predominantly by changes in emission rate.

Nevertheless, even though using GWP* leads to smaller estimates of CH₄’s contribution to warming, the estimates are still too high because both the GWP and GWP* fail to account for the relative rate of concentration increase for CH₄ compared with CO₂.

The yearly abundance of CH₄ in the atmosphere since 1980, as measured by NOAA (the U.S. National Oceanic and Atmospheric Administration), is depicted in the next figure. Currently, the global average CH₄ concentration is approaching 1.95 ppm (1950 ppb), more than two orders of magnitude lower than the CO₂ level of approximately 420 ppm. The rate of increase in the CH₄ level over the last 10 years averages about 0.011 ppm (11 ppb) per year, which is approximately 225 times smaller than the average rate of increase in the CO₂ level of around 2.5 ppm per year.

Including this data in the GWP calculation means that the contribution of CH₄ to global warming is only 83/225 that of CO₂ over 20 years or 30/225 over 100 years. These values of what I’ve designated “True GWP” are shown as percentages in the table below, which is an extension of the previous table above.

So CH₄ is only 37% (0.37) as potent a greenhouse gas as CO₂ over 20 years – a far cry from the 83 times as potent number promoted by climate activists and the mainstream media.

Farmers, sensing that official pronouncements on the warming effect of CH₄ are exaggerated, even without this revelation about True GWP, have begun to push back. At the II World Congress on Sustainable Livestock in Extremadura, Spain in November 2025, an international group of livestock farmers and producers came together to highlight “the true environmental sustainability of livestock farming based on the latest climate science,” emphasizing that it has supported human civilization for millennia.

At the Congress, New Zealand farmer and former parliamentarian Owen Jennings briefly discussed the misuse of GWP and GWP*, adding that: Much of the science relating to ruminant methane emissions is plain wrong. IPCC claims have been found to be outdated and erroneous. Curtailing methane is distracting, expensive and unnecessary.

Another speaker pointed out that small farms of less than 20 hectares (50 acres) provide more than 50 % of the world’s livestock, with more than 70% in emerging and developing economies, as illustrated in the figure below. Anti-livestock journalism, based in part on a misunderstanding of ruminant CH₄’s minimal contribution to current warming, is far more of a threat to these farms than climate change itself.

Next: Southern Ocean Cooling: Climate Scientists Unable to Agree on Explanation

No U.S. Landfalling Hurricanes in 2025 Refutes Alarmist Rhetoric on Weather Extremes

It’s like a football game where one team didn’t show up.

Or champagne without the fizz.

Or Christmas without the tree.

That was the U.S. 2025 hurricane season, in which not a single Atlantic hurricane made landfall in the U.S. And this despite the steady drumbeat of articles in the mainstream media and pronouncements by climate alarmists, proclaiming that weather extremes such as hurricanes are on the rise.

The 2025 no-show is illustrated in the figure immediately below; the second figure shows the much more active 2024 season.  

The closest to landfall of the 2025 hurricanes were tropical storms Barry (2) and Chantal (3), neither of which actually qualifies as a fully fledged hurricane. Tropical storms have sustained wind speeds up to 117 km per hour (73 mph), while the weakest Category 1 hurricanes have top wind speeds from 119 to 153 km per hour (74 to 95 mph).

Although the last time no hurricanes made landfall in the continental U.S. was in 2015, the preceding 15 years from 2000 to 2014 saw the same phenomenon no less than 6 times. Before that, the decades of the 1960s, 1970s, 1980s and 1990s each saw just 2 landfalling hurricanes. Clearly there is no pattern or connection to climate change, as the globe was cooling in the 1960s and early 1970s, but has warmed since then.

The total number of all North Atlantic hurricanes or major hurricanes in 2025 and 2024 was 9 and 16, respectively. The lower number in 2025 is reflected in what is known as the Accumulated Cy­clone Energy (ACE) index for the North Atlantic Basin. The ACE index is an integrated metric combining the number of storms each year, how long they survive and how intense they be­come.

The next figure shows the ACE North Atlantic index since 1851. The highest index in the record was 259 in 1933. The 2025 no-landfall season had an ACE index of 133 (measured to December 4), which is just slightly higher than the long-term average; the index for 2024 was 162.

A comprehensive report on 2024 hurricanes by UK climate writer Paul Homewood, discussing long-term trends in North Atlantic hurricanes, found at that time no evidence for any increase in hurricane frequency, intensity or both associated with global warming. Homewood’s compilation of frequency data for North Atlantic hurricanes and major hurricanes from 1851 to 2024 is presented in the figure below.

While it may appear from the figure that hurricanes have indeed become more common since the 19th century, Homewood points out that the apparent increase “has been due to changes in observation practices over the years, rather than an actual increase” – as concluded in a 2021 study by a team of hurricane experts.  Prior to the satellite era, which dates only from the 1960s, many storms were not spotted at all.

Back then, most data on hurricane frequency in the U.S. was based on eyewitness accounts, thus excluding most hurricanes that never made landfall – as well as many landfalling ones in sparsely populated areas. And even the recording of non-landfall­ing hurricanes relied on observations made by ships at sea, which almost certainly resulted in an undercount. So it is hardly surprising that the public falsely sees today’s more complete coverage enabled by satellite technology as an uptick in hurricane occurrence.

The perception that extreme weather events are increasing in frequency and severity is primar­ily a consequence of modern technology – the Internet and smart phones – which have revo­lutionized communication and made us much more aware of such disasters than we were 50 or 100 years ago. Before 21st-century electron­ics arrived, many hurricanes and other weather extremes went unre­corded. The misperception has only been amplified by the mainstream media, eager to promote the latest climate scare.

Another aspect of hurricane measurement is maximum wind speeds. There is growing evidence, says Homewood, that wind speeds of the most powerful current hurricanes may be overestimated compared to those in the pre-satellite era, because of changing methods of measurement.

In the past, hurricane wind speeds were estimated from the central pressure of the system, which could be more readily measured. But more recently, wind speeds have been calculated from satellite and aircraft data. This has created an anomaly, because estimates of wind speeds for hurricanes now tend to be higher than past ones with similar central pressure. What this means is that wind speeds before the advent of satellite technology were underestimated in comparison with hurricanes today.

As with frequency, the data clearly reveals no evidence that hurricanes are becoming more intense, or that extremely intense ones are becoming more common, as global warming continues.

Climate Alarmism and Net Zero Strategy on the Wane

While it has been clear to rational thinkers for some time that widespread climate alarmism is losing its impact, it took a recent pronouncement by Microsoft co-founder and philanthropist Bill Gates to inject a dose of much-needed reality into the climate debate. In a memo titled “Three tough truths about climate,” Gates declared that:

Climate change is a serious problem, but it will not be the end of civilization.

and,    

Health and prosperity are the best defense against climate change.

Although as a skeptic, I disagree with Gates that global warming is largely the result of human activity, his memo is symbolic of the current move away from the highly exaggerated notion of a “climate crisis,” espoused by our leaders and the mainstream media. At the same time, the political drive toward the adoption of Net Zero policies is faltering in many countries.

Climate activists are being reined in too, at least Just Stop Oil protesters who have been jailed for disrupting UK motorways and airports, and defacing priceless pieces of art all over Europe. Their most recent efforts seem tame by comparison, such as the spraying of Stonehenge with an environmentally harmless orange powder that washes off.   

The pied-piper-like campaign sparked by former Swedish schoolgirl Greta Thunberg has all but died, as Thunberg has diverted her activism to other issues like the war in the Gaza Strip. Her 2019 speech to the UN Climate Action Summit, in which she admonished the world for having “stolen my dreams and my childhood,” and claimed we are on the verge of a mass extinction with her accusatory “How dare you!”, is but a distant memory.

Even the UN Secretary-General is toning down his previously incendiary rhetoric on climate change. Just a few years after hysterically describing the IPCC (Intergovernmental Panel on Climate Change)’s Sixth Assessment Report as “code red for humanity” and proclaiming that “the era of global boiling has arrived,” all he could muster in his speech to the latest UN climate conference was a call for the gathering to “ignite a decade of acceleration and delivery.”

Along with the falloff in climate activism, the lemming-like drive by many governments toward Net Zero – the achievement of zero net CO₂ emissions by 2050 – is losing steam. One of the reasons is the realization that surprisingly little global warming would actually be averted by adoption of Net-Zero policies. But nonscientific objections, especially the costs of implementing Net Zero, are gaining increasing attention as well.

Discussion of likely costs is most advanced in the UK, which was the first major economy to establish a legally binding Net-Zero target in 2019. Estimates of total cost vary wildly, but most are in the range of £1-10 trillion ($1.3-13 trillion), as shown in the figure below based on various scenarios. A total of £3 trillion ($3.9 trillion) would be equivalent to an unacceptable £100,000 ($130,000) per household, according to a recent report.

The enormous cost of Net Zero is reflected in the cost of electricity – a driving force in the economy and of particular concern to electricity users, both industrial and domestic. The next figure illustrates the average cost of electricity over the last 30 years in both the UK and U.S. While the U.S. cost has remained level during that period, the UK cost has soared, prompting fears of the nation committing economic suicide by bankrupting industrial users.

The marked difference can be attributed entirely to the UK’s quest for Net Zero, founded on intermittent and unreliable renewable energy which provided 51% of the country’s electricity in 2024. In the U.S., cooler heads have prevailed and only 21% of electricity generation was from renewable sources in 2023. However, the wheel may be turning as the UK and other European countries previously dedicated to Net Zero are having second thoughts.

A major concern all over the UK and EU is potential deindustrialization, the viability of industry being heavily dependent on electricity costs. The UK currently has the highest industrial electricity prices in the developed world. Numerous manufacturers of automobiles, steel and other products have already pulled up their British roots and moved to countries where electricity (and labor) is cheaper or simply gone out of business altogether. Germany, where the cost of electricity has also risen steeply, is also struggling to keep its economy afloat.   

Meanwhile, China and India – the largest and 3rd largest emitters of CO₂, respectively – are all but ignoring Net Zero. India has a Net-Zero goal of 2070, while China has not set any goal at all.

China currently leads the world in building new coal-fired power plants, construction of which reached a 10-year high in 2024; at the same time, renewables contributed 32% of the country’s electricity that year. India burns less coal than China but still relies heavily on coal for electricity generation.

Next: No U.S. Landfalling Hurricanes in 2025 Refutes Alarmist Rhetoric on Weather Extremes

Past Global Warming More Rapid than Today’s: The Younger Dryas

Skeptics of the climate change narrative often point to periods of warming in the distant past when global temperatures were far above today’s, but CO₂ levels were lower, as ruling out human emissions of CO₂ as the cause of modern global warming. But this assertion is rejected by advocates of the CO₂ narrative, who argue that current warming is happening far more rapidly than in any past episodes.

However, there are numerous examples of rapid climate change in the historical record, some as recently as the last ice age. One of the best documented is a period of climate upheaval known as the Younger Dryas, which occurred approximately 12,900 to 11,700 years ago and temporarily reversed the earth’s recovery from frigid glacial conditions.

The effect on temperature and ice accumulation in Greenland is illustrated in the figure below, but a similar phenomenon took place all over the Northern Hemisphere. The Younger Dryas is named after a wildflower, Dryas Octopetala, that thrives in very cold European climates.

As the earth slowly warmed from the ice age, the temperature (red line) suddenly took a steep upward turn – to almost present-day levels – around 15,000 years ago. This event is known as the Oldest Dryas and is clearly visible on the left of the figure. This was soon followed by the Younger Dryas, when the temperature plunged back to near-glacial conditions and which must have been devastating for early humans.

But then the Younger Dryas ended abruptly, with temperatures soaring upward again to where they would have been had the Dryas events not happened. By many accounts (see, for example, here and here), the mean annual global temperature rose by as much as 10 degrees Celsius (18 degrees Fahrenheit) in only 10 years.

That’s an increase of 1 degree Celsius (1.8 degrees Fahrenheit) in just one year – far in excess of modern global warming, in which the same 1-degree Celsius increase has taken more than 50 years.

However, the Younger Dryas is not an isolated instance of abrupt climate change in our planet’s past. As I discussed in a 2024 blog post, temperatures in Greenland rose suddenly and fell again at least 25 times during the last ice age, which spanned the period from about 115,000 to 10,000 years ago. Corresponding temperature swings occurred in Antarctica too, although they were less pronounced than those in Greenland.

The striking but fleeting bursts of heat are known as Dansgaard–Oeschger (D-O) events, named after palaeoclimatologists Willi Dansgaard and Hans Oeschger who examined ice cores obtained by deep drilling the Greenland ice sheet. They found a series of rapid climate fluctuations, when the earth warmed to near-interglacial conditions over just a few decades, and then gradually cooled back down to frigid ice-age temperatures.

The phenomenon can be seen in the next figure, depicting ice-core data from both Greenland and Antarctica; two sets of measurements, recorded at different locations, are shown for each. The isotopic ratios of ¹⁸O to ¹⁶O, or δ¹⁸O, and ²H to ¹H, or δ²H, in the cores are used as proxies for the past surface temperature in Greenland and Antarctica, respectively. The Younger Dryas is merely the last of 25 or 26 D–O events over the past 120,000 years, albeit an extra strong one.

Several hypotheses have been put forward to explain the Younger Dryas. The leading hypothesis postulates that enormous amounts of freshwater were discharged into the North Atlantic Ocean about 12,900 years ago, in the form of rapidly melting icebergs disgorged from the massive Laurentide ice sheet which covered most of Canada and the northern U.S.

This vast influx of freshwater would have disrupted the deep-ocean thermohaline circulation (shown in the figure below) by lowering ocean salinity, which in turn suppressed deepwater formation and weakened the AMOC (Atlantic Meridional Overturning Circulation). Eventually, as the meltwater flux abated, the AMOC would have strengthened again, enabling the climate to recover.

A problem with this hypothesis is the timing: a second meltwater pulse, while slightly smaller than the first one 1,200 years earlier, occurred at the end of the Younger Dryas. Yet the second pulse didn't result in a similar weakening of the AMOC.

An alternative explanation is the impact hypothesis. This involves the impact of a large extraterrestrial object that burst in the atmosphere, creating fragments which struck various areas around the world 12,900 years ago. The fragments are thought to have sparked widespread wildfires and even caused a number of extinctions.

Proponents of the hypothesis point to geological layers known as “black mats,” as well as the formation of nanodiamonds, as evidence of past fiery events. But others dismiss such claims, saying that it’s equally likely that volcanic eruptions were the cause.

Next: Climate Alarmism and Net Zero Strategy on the Wane

Vaccine Hesitancy on the Rise

Further evidence of the current attack on science is the opposition to vaccination against infectious diseases such as measles, hepatitis and polio. More and more parents are ignoring science by choosing not to vaccinate their children, even with vaccines that have a long history of extensive testing for adverse health effects. The WHO (World Health Organization), for the first time, listed so-called vaccine hesitancy as one of the top 10 global threats in 2019.

According to a new poll from health policy information nonprofit KFF, 16% of U.S. parents have skipped or delayed vaccinating their children against diseases other than COVID-19 or the flu during the 2024-25 school year. The same poll reveals that white parents, Republicans, the religious and those who homeschool their kids are more likely to avoid the shots.

Data for the MMR (measles-mumps-rubella) vaccine exemplifies vaccine hesitancy. The KFF poll found that only 92.5% of U.S. kindergarteners received the MMR vaccine in 2024-25, a significant drop from 2019-20 when the percentage was 95%.

The reason this drop is significant involves herd immunity. Herd immunity is the mass protection from an infectious disease that results when enough members of the community become immune to the disease through vaccination, just as sheer numbers protect a herd of animals from predators. Once a sufficiently large number of people have been vaccinated, viruses and bacteria can no longer spread in that community.

The threshold for herd immunity, which is the minimum percentage of the population that needs to be vaccinated for the herd effect to take hold, depends on the contagiousness of the disease, the effectiveness of the vaccine and other factors.  For highly contagious measles, herd immunity requires up to 95% of the populace to be immunized, while for polio the percentage ranges up to a slightly lower 86%.

KFF reports that 39 U.S. states had MMR vaccination rates for kindergarteners below the target rate of 95% for the 2024-25 school year, an increase from just 28 states during the 2019-20 (pre-pandemic) school year. And of the 39 states, 16 reported even lower rates of below 90% for 2024-25, compared to only 3 states in 2019-20; the particular states are shown in the figure below. (Montana and West Virginia didn’t report data for the 2024-25 school year).

MMR coverage rates among kindergarteners for the latest school year varied widely from state to state: from a low of 78.5% in Idaho to a high of 98.2% in Connecticut. In 2024-25 alone, over half the states experienced declines in vaccination rates for all state-required vaccines, including MMR, DTP (diphtheria-tetanus-pertussis), polio, and chicken pox.

One of the factors contributing to this decline in vaccination rates is exemptions from mandatory vaccination, both religious and philosophical, the latter exemption being based on strongly held personal, moral or other nonreligious beliefs. Although fewer U.S. states allow philosophical exemptions than grant religious exemptions, all 50 states provide exemptions on medical grounds.

The share of U.S. children claiming an exemption from one or more vaccinations rose from 2.5% in the 2019-20 school year to 3.6% in 2024-25. However, the increase comes from an increase in nonmedical exemptions; medical exemptions actually decreased slightly over this interval.

The uptick in exemptions is clearly visible in the next figure, which displays the number of states with exemption rates in select percentage groups by school year, for one or more vaccines. While fewer and fewer states are reporting exemption rates below 3%, the number with exemption rates above 5% is on the rise; this means that those states cannot reach the target vaccination rate of 95% for the MMR vaccine, even if all nonexempt children receive their vaccinations.

But religious and genuine philosophical exemptions constitute only a small fraction of overall objections to vaccination.  By far the greatest number of objections come from those who are fearful of side effects or do not trust vaccine safety. Vaccine hesistancy is also fueled by widespread misinformation, including misunderstandings about herd immunity.

It’s true that serious adverse reactions to a vaccine shot do occur occasionally – typically about once in every million vaccinations. But this is a minuscule risk compared with the risk of contracting the disease itself in an unvaccinated community during an epidemic.

Unvaccinated children exposed to someone infected with measles, for instance, have a 90% chance of contracting the disease, and one of 1,000 children who get the measles will develop encephalitis, an often debilitating aftereffect that can lead to seizures and mental retardation.  That’s a risk of about one in 1,100 of experiencing a serious aftereffect for a child who comes down with measles, compared with the much lower risk of one in one million following vaccination. Some children still die from measles, often after getting pneumonia.

Science tells us that it’s much more risky for a child to forgo vaccination and suffer the consequences of catching a potentially deadly disease, than to be vaccinated against it.

Next: Past Global Warming Was More Rapid than Today’s: The Younger Dryas

Scientific Fraud Growing Exponentially

Nowhere is the attack on science more evident than in the burgeoning incidence of scientific fraud, in the form of both falsification and fabrication of observational data. I first wrote about this in a blog post in 2019, since when the problem has only escalated. It’s now estimated that 1% to 2% of all scientific research papers are fraudulent – a fraud rate approaching that of industries such as healthcare and financial services.

A recent study from Northwestern University has examined scientific fraud in depth. Rather than the traditional focus on scientific misconduct by lone individuals, which is comparatively rare, the new study exposes numerous instances of large-scale fraud enabled by a far-flung network of editors and authors who cooperate to publish low-quality or fabricated research papers. This coordinated fraud combines clandestine “paper mills,” intermediary brokers, and so-called predatory journals that charge a fee without offering any services other than publication itself.

Paper mills are shady businesses that sell bogus manuscripts and authorships to researchers who need journal publications to advance their careers. The Northwestern researchers say that a 2022–23 survey of medical residents at hospitals in southwest China found that 47% of respondents had bought and sold papers, allowed other people to write their papers, or written papers for others.

A 2023 report in Nature magazine identified more than 400,000 research articles published over the previous two decades that show strong textual similarities to known studies produced by paper mills; the rising trend is illustrated in the figure below.

The new Northwestern study assembled an extensive database derived from major aggregators of the scientific literature, retracted publications, editorial records, and reports of image duplication in research papers.

A portion of the study focused on the massive online open access journal PLOS ONE, which has a higher-than-average retraction rate. The journal also lists the handling editor of every published paper. Of PLOS ONE editors who have accepted articles for publication, 22 accepted papers that were later retracted much more frequently than one would expect by chance. This number of flagged editors increased to 33 when mostly negative comments recorded by the watchdog PubPeer Foundation were considered.

Altogether, 45 PLOS ONE editors were flagged due to the anomalous rate at which they accepted eventually retracted or PubPeer commented publications, or because their submissions were handled by other flagged editors. Although these individuals edited only 1.3% of all papers published in PLOS ONE up to 2024, they edited a sizable 30% of the journal’s retracted papers. And 25 of these 45 editors themselves authored papers that were subsequently retracted.

These anomalous patterns are not restricted to PLOS ONE, say the Northwestern researchers. Across ten journals from the publisher Hindawi, which also disclose the editors of published manuscripts, they found 53 editors who accept eventually retracted articles anomalously often, and 96 who accept fast-tracked articles unusually frequently.

Apart from these examples of potentially fraudulent behavior, the study authors investigated whether certain scientific disciplines were more prone to fraud than others. It was found that the phenomenon is much more pronounced in six subfields in the area of RNA biology. As shown in the next figure, papers involving “lncRNAs” and “miRNAs, cancer” feature retraction rates that peak at around 4%, higher than even the rates of papers withdrawn due to errors.

Sadly, the authors conclude that scientific fraud is growing much faster than science as a whole. The number of retracted articles has been increasing exponentially over the last 30 years as seen in the figure below, in which the vertical scale is logarithmic and the dashed lines are projections.

The researchers note that the number of retracted articles and PubPeer commented articles have been doubling every 3.3 years and 3.6 years, respectively, while the total number of publications has doubled only every 15 years. The literature in some fields “may have already been irreparably damaged by fraud,” they say.

The Northwestern researchers go on to state:

Collectively, these findings show that the integrity of the extant scientific record and of future science is being undermined through the shortcomings in the very systems through which scientists infer the trustworthiness of each other’s work.

In the face of this onslaught, fortunately, the scientific community has not been silent. An informal network of research-integrity sleuths or paper-mill detectives now scrutinize thousands of published papers each year and frequently find evidence of manipulation and fabrication. Their detailed examinations, usually published online in PubPeer, often form the basis of subsequent retractions and misconduct investigations.

But sleuths and watchdog websites such as Retraction Watch can’t keep up with the rising tide of fraud. Lead author of the Northwestern study, Reese Richardson, is pessimistic about the future influence of AI (artificial intelligence):

If we're not prepared to deal with the fraud that's already occurring, then we're certainly not prepared to deal with what generative AI can do to scientific literature.

Next: Vaccine Hesitancy on the Rise

Sea Ice Not Currently Shrinking at Either Pole

To the surprise of many climate scientists, not only have the massive Antarctic and Greenland ice sheets stopped melting for now – as I recently documented (here and here) – but Arctic and Antarctic sea ice are not currently shrinking either.

As I discussed in an earlier post, the loss of Arctic sea ice has paused during the past two decades. Despite rising global temperatures, and contrary to alarmist projections of an ice-free summer by 2020, no statistically significant decline in Arctic summer minimum sea ice extent occurred between 2005 and 2024. Sea ice expands to its maximum extent during the winter and shrinks during summer months.

This unexpected trend has continued, with the minimum summer Arctic ice extent for 2025, reached on September 10, showing a slight uptick from 2024. The 2025 Arctic minimum extent is illustrated in the satellite-derived image on the left below.

The other two images above show the annual Arctic ice trend month by month, from January on the left to December on the right. The center image depicts the annual trend by year since 2014, while the image on the right compares 2025 with various intervals during the satellite era which began in 1979, and with the low-summer-ice year of 2012. The insets supply details about the ice extent on August 31, 10 days before this year’s minimum.

At the other end of the globe, Antarctic sea ice achieves its maximum in September during the southern winter and shrinks to its summer minimum extent in February. The left panel of the figure below shows a satellite image of the 2025 Antarctic maximum that occurred on September 18, just 8 days after the Arctic minimum. On the right is a 5-month plot of the ice extent for 2025 compared to 2024 and to the median extent from 1981 to 2010.

The historical behavior of Antarctic sea ice has been quite different from its North Pole counterpart. During the satellite era, rather than shrinking, the sea ice around Antarctica expanded steadily up until 2016, growing at an average rate between 1% and 2% per decade, with considerable fluctuations from year to year. But it took a tumble in 2017, as depicted in the figure below; this figure shows the February minimum, expressed as an anomaly relative to the 1981 to 2010 mean.

The overall trend from 1979 to 2025 is an insignificant 0.1% per decade relative to the mean. Yet a prolonged increase above the mean occurred from 2008 to 2017, followed by an eight-year decline since then. As can be seen in the graph, the summer ice minimum recovered briefly in 2020 and 2021, only to fall once more and pick up again in 2024 and 2025.

It appears that Antarctic summer sea ice extent has stabilized at a new, lower level over the past eight years. Yet the downward trend has sparked debate and several possible reasons for it have been advanced, not all of which are linked to global warming. One analysis attributes the big losses of sea ice in 2017 and 2023 to extra strong El Niños.

But a recent research paper paints a different picture. The mostly Australian authors point out that the abrupt decline in the Antarctic winter sea ice maximum since 2014 appears to have occurred 4.4 times faster than the decline in the Arctic sea ice maximum since 1979; the Antarctic winter sea ice loss over just the last decade is comparable to the winter sea ice loss in the Arctic over the whole 46 years of the satellite record. Both these effects are visible in part a of the figure below, in which the thin lines indicate possible linear trends.

Part b of the figure reveals that the decline in the Antarctic summer sea ice minimum since 2014 may have been 1.9 times faster than the summer sea ice decline in the Arctic since 1979. The researchers argue that the apparently more rapid decline in Antarctic summer sea ice, together with the fact that there is less summer sea ice surrounding Antarctica compared with the Arctic, means that if current trends were to continue, Antarctica could become essentially free of sea ice in summer sooner than the Arctic.

Such a regime change would have far-reaching consequences, they say, such as a feedback effect resulting in amplified Antarctic warming, and a slowing or collapse of the Antarctic Overturning Circulation – which in turn could induce more rapid melting of the Antarctic ice sheet.

However, the linear trends drawn in the figure above are misleading. The Antarctic summer sea ice minimum (thick blue line in b) should be compared with the previous figure, showing a pause in declining minimum ice extent since 2017. Likewise, the Arctic winter ice maximum (thick gold line in a) should be compared with the next figure, which shows the prolonged pause in Arctic sea ice loss between 2005 and 2024.

Next: Scientific Fraud Growing Exponentially

New Evidence Confirms That Sea Level Rise Is Not Accelerating

A blog post I wrote six years ago featured the lack of reliable scientific evidence at that time for any acceleration in the rate of average global sea level rise. Although several research reports since then claim to have found evidence that the rate of rise is accelerating, a new study puts the kibosh on that notion – and finds that the current rate of rise is less than half what is commonly accepted by climate scientists.

The study, by an engineer and researcher duo in The Netherlands, compiled sea level rise data from local observations worldwide, but mostly in the Northern Hemisphere, between approximately 1960 and 2020. The observations come from tide gauge records, which provide a more complete dataset than satellite altimetry that dates from only 1993.

It’s tide gauge measurements that matter to the local community and its engineers and planners. Tide gauges measure the height of the sea relative to the land to which the gauge is attached, the so-called RSL (Relative Sea Level) metric. Satellite observations of absolute sea level measure the height of the sea, which is the distance of its surface to the center of the earth. Land subsidence artificially amplifies any local RSL rise and makes satellite-measured sea levels higher than tide gauge RSLs.

The Dutch study used two datasets. The first, known as the PSMSL (Permanent Service for Mean Sea Level) provides historic records of monthly and yearly sea levels. The second dataset, called the GLOSS (Global Sea Level Observing System) provides hourly data; yearly mean sea levels are derived from the hourly data via so-called tidal analysis, which takes multi-year tidal forces into account. All data were downloaded in 2023, and only full years were utilized.

The PSMSL network consists of 1,533 locations for which data are recorded. Of these, only 204 locations met the study’s selection criteria of data being available over a period of at least 60 years, and for at least 80% of that period. The results are presented in the figure below. The rate of sea level rise is indicated by the color of the circles and triangles; triangles designate statistically significant acceleration of sea level rise, while circles designate non-significant acceleration. Statistical significance was determined by what is known as the F-test.

The acceleration is statistically significant in just 9 locations, or 4% of the total 204. Several of these locations form a cluster in Japan, while the remainder are solitary sites in Spain, Thailand, India, Australia and the Pacific. The meager amount of usable data in the Southern hemisphere is clearly visible.

Of the locations without significant acceleration, high rates of rise (up to 10 mm per year) are found in one location in the Pacific, in the US along the Gulf Coast, on the west coast of India, and in Japan, Thailand and Australia. Negative rates of rise, caused by rebound after melting of the last ice age’s heavy ice sheet, are found in the Baltic and along the west coast of Canada.

Similar but more limited results were obtained from the GLOSS network. Only 39 locations met the study’s selection criteria, and statistically significant acceleration is detected in a mere 3 of these. The highest rates of rise are found in the Pacific and Latin America, in this case coinciding with the locations showing acceleration.

Both datasets, nevertheless, yield a mean rate of sea level rise in 2020 considerably lower than NASA’s estimated 2020 rate of about 3.3 mm per year. For the more extensive PSMSL network, the 2020 median rate of sea level rise is found to be 1.5 mm per year as seen in the next figure, while the median rate for the GLOSS network is 1.9 mm per year.

The same overestimation of sea level rise rates can be found in reports of the UN’s IPCC (Intergovernmental Panel on Climate Change). In the figure below that compares the rise rates calculated in the Dutch study, from PSMSL data, with those in the IPCC Sixth Assessment Report, it can be seen that the IPCC’s median rate (blue line) is too high by about 2 mm per year compared with most of the actual observations.   

For both datasets, approximately 95% of the locations studied show no statistically significant acceleration of sea level rise. The study authors conclude that the accelerated sea level rise observed at the remaining 5% of locations can be explained by local, nonclimatic phenomena such as land subsidence or, in a few cases, plate tectonics. They say that the observed behavior is inconsistent with sea level acceleration driven by climate change.

Land subsidence arises predominantly from groundwater extraction, but also from mineral mining, rapid urban development that leads to compaction due to construction, and loading by river sediments.

Next: Sea Ice Not Currently Shrinking at Either Pole

Interloper Speeding Through Solar System Is Interstellar Comet, Not Alien Spacecraft

In early July, an observation made by a NASA-funded survey telescope in Chile sent the astrophysics community into a frenzy. The telescope, whose purpose is to search for objects that might collide with Earth, had discovered an intruder in our solar system – a stranger in our cosmic backyard, zipping along at speeds exceeding 210,000 km per hour (130,000 mph).

The initial consensus among astronomers was that the mystery object, named 3I/ATLAS after the Chilean telescope, was a comet from interstellar space, the third such object ever detected (3I standing for “3rd interstellar”). The evidence showed that its size was just a few km across and that it would not come closer than 270 million km (170 million miles) to Earth. But puzzling questions remained.

If the interloper was indeed a comet, why wasn’t it accompanied by the usual “tail,” the stream of gas and dust millions of km long stretching out behind a comet’s path? Why was it moving so fast, much faster than typical solar system comets? And why, contrary to most comets, was it traveling close to the so-called ecliptic, the orbital plane of Earth and most planets around the sun?

Enter famed Harvard astrophysicist Avi Loeb, recognized for his work on the evolution of the first stars. Rejecting the consensus, Loeb postulated that 3I/ATLAS could be an “extraterrestrial artifact” — maybe even an “alien mothership” on a reconnaissance mission through our solar system.

Loeb quickly submitted a preprint espousing his hypothesis, setting out his arguments for 3I/ATLAS being technological and possibly even hostile. One argument, put forward separately in a blog post of his, was that subsequent study of the extraterrestrial visitor by the Hubble space-based telescope suggested that it could now be producing its own light, as seen in the figure below.

The glow of light ahead of its motion had been interpreted by other astronomers as evaporation of dust from the sun-facing side of the object. But Loeb had a different interpretation: that 3I/ATLAS could be “a spacecraft powered by nuclear energy,” the dust emitted from its front surface being dirt that accumulated during its interstellar travel.

In his preprint, Loeb expounds his other arguments. Spectroscopic analysis has so far showed no sign of a cometary tail, essentially ruling out the comet hypothesis, he maintains. Furthermore, the interloper’s extremely high speed at its present large distance from the sun, which could give it a future gravitational “push,’’ means it cannot have come from the solar system. Most comets originate in the Kuiper Belt in the outer reaches of the solar system, but not beyond; 3I/ATLAS passed through the Kuiper Belt eight years ago, says Loeb.

As for its near alignment with the ecliptic plane, Loeb calculates that the probability of such a trajectory for an incoming object is a low 0.2%. In addition, the trajectory takes the unknown intruder unusually close to Venus, Mars and Jupiter, as indicated in the next figure, without coming too close to Earth. Assuming that 3I/ATLAS could have entered the solar system at any time, the probability of this trajectory is a vanishingly small 0.005%.

Loeb finds such estimates, together with other observations, suspicious. He speculates that the trajectory of 3I/ATLAS has all the hallmarks of an alien spacecraft dispatched to investigate the solar system while remaining beyond the range of our most powerful ballistic missiles.

Needless to say, other astrophysicists have found Loeb’s ideas outlandish – and for good reason.

On August 6, the awesome capabilities of the James Webb Space Telescope were brought to bear on the apparent trespasser, when the telescope’s near-infrared spectrograph was employed for a detailed study of the light emitted by the object. One of the many spectrograph images is displayed in the figure below, the arrow (S,v) denoting the direction of motion.   

The James Webb images show the light emitted by 3I/ATLAS much more clearly than the earlier pictures obtained by the Hubble telescope. The light pattern is in fact confirming evidence of the “coma” characteristic of a typical comet. A coma is the luminous halo of gas and dust that forms around the cometary nucleus as the comet approaches the sun; the coma appears as a diffuse “head” to the comet, the material eventually being swept into the comet’s tail.

What’s unusual about the coma of 3I/ATLAS is that it’s rich in CO₂ and has less water than most ordinary solar system comets. In another preprint, a research group headed by two NASA astrophysicists proposes that the comet contains ices exposed to higher levels of radiation than normal comets, accumulated as it traveled for probably billions of years through interstellar space, or that it formed close to the CO₂ ice line in another star system.

Even Loeb in his earlier preprint conceded that 3I/ATLAS was most likely a comet. He defended his paper as “largely a pedagogical exercise.”

Next: New Evidence Confirms That Sea Level Rise Is Not Accelerating

No Evidence That Jet Stream Waviness, Atlantic Ocean Overturning Becoming More Unstable

Despite the predictions of computer climate models that both atmospheric and ocean currents will weaken in a warming world, two recent papers (here and here) have found just the opposite.

Waviness in the polar jet stream, which is currently on the rise and plays a role in outbreaks of extreme winter cold in the Northern Hemisphere, is not as strong as it was in the 1940s, 1960s and 1980s, state three U.S. earth scientists in one paper. And a separate study concludes that the AMOC (Atlantic Meridional Overturning Circulation) has not declined for the past 55 years.

The jet stream is a narrow, high-altitude air current that flows rapidly from west to east in each hemisphere and governs much of our weather. It separates cold air toward the North or South Pole and warmer air on the equatorial side.

Inherently wavy due to the earth’s rotation and the temperature difference between low and high latitudes, the jet stream in winter becomes even wavier than normal. This leads to phenomena such as the well-known polar vortex which, in northern climes, causes long troughs of frigid air to descend from the Arctic.

Exceptionally large jet stream waves since the 1990s have prompted many climatologists to ascribe the behavior to global warming. But the three earth scientists say that this apparent volatility is not so unusual, and that the jet stream has undergone sporadic periods of enhanced waviness since before climate change was considered to be significant.

What the researchers did was to compile a record of the jet stream’s wintertime variability going back to 1901, by using AI to analyze long‐term climate data. Most previous studies concentrated only on the post-satellite era since 1979.

To their surprise, the analysis revealed that jet stream waviness from the 1940s to the 1980s surpassed modern waviness levels. So it’s highly unlikely that climate change has any influence on waviness.

The researchers also found that an extra strong wavy period lasting from the early 1960s to the 1980s, shown in the figure below, was the main driver of the “warming hole,” a prolonged period of abnormally cold winter temperatures in the U.S. that caused average winter temperatures to drop more than 1.3 degrees Celsius (2.3 degrees Fahrenheit). Their study estimates that pronounced jet stream waviness was responsible for two thirds of warming hole cooling between 1958 and 1988.

The AMOC, illustrated below, forms part of the ocean conveyor belt that redistributes seawater and heat around the globe. Exactly how global warming is changing the AMOC, if at all, is currently unknown. Alarmist proclamations in both the scientific literature and the mainstream media have suggested there are signs of the AMOC slowing, or even reaching a tipping point and shutting down altogether.   

Proxies that have been employed to reconstruct the past strength of the AMOC include sea surface temperatures, ocean density and salinity, ¹⁸O isotopes in sediment cores, and corals. Reconstructions based on several of these proxies have estimated declines in AMOC strength of up to 15% (see, for example, here and here).

But the new study finds no evidence of any slowdown in the AMOC since the mid-20th century, which is when the majority of today’s global warming began. The study’s multinational authors explain the discrepancy with earlier studies by pointing to the reliance of most such studies on sea surface temperature measurements. However, say the authors, sea surface temperature is not a reliable proxy for reconstructing the AMOC.

Instead, the new study focused on anomalies in air-sea heat fluxes in the North Atlantic Ocean, at latitudes between 26.5^oN and 50^oN. The air-sea heat flux is the amount of heat released from the ocean to the atmosphere; more heat is released when the AMOC is stronger.

The study authors used 24 different CMIP6 climate models to reconstruct the AMOC, by identifying a relationship between any change in the AMOC at a given latitude and the corresponding change in the air-sea heat flux north of that latitude in the North Atlantic basin. The adjacent figure presents some of their results, showing estimated changes in the AMOC from 1963 to 2017 at four different latitudes. The ERA5 and JRA-55 are different climate datasets.

No sign of any decline in the AMOC is seen during the 55-year period of the study, over the whole latitude range.

Additionally, the researchers found that when they looked for a relationship between AMOC changes and sea surface temperature in the same region, the trend was “not significantly different from zero” if they used the 24 CMIP6 climate models utilized in their own work. Many earlier studies that incorrectly predicted a weakened AMOC used now outdated CMIP5 models.

Next: Interloper Speeding Through Solar System Is Interstellar Comet, Not Alien Spacecraft

Challenges to the CO2 Global Warming Hypothesis (12): CO2 from Antimicrobials Far Exceeds CO2 from Fossil Fuels

My series on challenges to the CO₂ global warming hypothesis has featured a number of possible alternative sources to CO₂ as the source of warming, as well as scenarios that question the greenhouse effect. This post reports a new challenge that embraces the greenhouse effect and the CO₂ hypothesis, but disputes the belief that increased CO₂ comes primarily from burning fossil fuels.

The revolutionary proposal attributes the bulk of human CO₂ emissions into the atmosphere to a biological source, namely antimicrobials or, more precisely, antimicrobial resistance. This heretical idea comes from UK husband-and-wife team Frank and Jeanette Sams-Dodd, scientists with backgrounds in biology and veterinary medicine, respectively.

So what exactly are antimicrobials and how do they inject so much CO₂ into the air? Antimicrobials are simply chemical compounds that kill microbes. These include antibiotics, antiseptics, antifungals, antivirals, antiparasitics, disinfectants, surfactants, pesticides and herbicides.

Antimicrobial resistance occurs when microbes are able to withstand antimicrobials at the concentration they are exposed to in their environment. Use of antimicrobials eliminates nonresistant species, bolstering antimicrobial resistance and disrupting the microbiome. A microbiome is a community of bacteria and other microbes in the air, soil and water; everything on Earth has its own microbiome.

Disruption of microbiomes by antimicrobials, the Sams-Dodds explain, sets off a chain of events that leads to a severe imbalance in ecological systems that rely on a microbiome to release, absorb and retain certain gases, moisture and nutrients. This is illustrated in the figure below.

As indicated, antimicrobials find their way to sewage plants or landfills, from where they enter the wider environment unhindered, carried by water leaching through the soil. Antimicrobials are also carried by water that evaporates into the air, where they are transported through the atmosphere by winds and clouds before falling back to the earth as precipitation.

This widespread dispersal of antimicrobials is a major source of atmospheric CO₂.

As far back as 1954, it was shown that adding antibiotics to soil releases substantial amounts of CO₂ into the atmosphere. Several subsequent studies have confirmed that antimicrobials not only cause enhanced release of greenhouse gases, including CO₂, methane (CH₄) and nitrous oxide (N₂O), from soil and aquatic environments, but they also reduce carbon capture and storage. It is microbial communities that mainly regulate the earth’s carbon, nitrogen and other biogeochemical cycles.

To quantify the effect of antibiotics alone on CO₂ emissions, the Sams-Dodds have performed a detailed calculation of how a standard course of tetracycline affects the ability of soil to store carbon. They first estimate that the amount of tetracycline from a single course that escapes metabolic breakdown at a sewage treatment plant and is released into the environment is 2.0 grams.

They then draw on a 2023 study which found that 1.155 milligrams of tetracycline in soil reduces its storage capacity by 1.55 kilograms of carbon, or 5.68 kilograms of CO₂, per square meter of soil surface. Dividing 2,000 milligrams of tetracycline by 1.155 milligrams per square meter of soil surface equals 1,732 square meters. Multiplying by 5.68 kilograms of CO₂ per square meter gives a total of 9,835 kilograms (9.84 tonnes) of CO₂ released per course of tetracycline.

This calculation is based on data from cattle graziers, some of whom feed antibiotics to their cattle and some of whom don’t. A more realistic number for the reduction in carbon storage capacity worldwide from tetracycline use is a lower 3.82 kilograms of CO₂ per square meter of soil surface. When this number is multiplied by the area of fertile soil surface, which constitutes about 10% of the earth’s land surface, the reduction in long-term CO₂ storage capacity from tetracycline alone is 194.8 gigatonnes (214.7 gigatons).

What this means is that 194.8 gigatonnes (214.7 gigatons) of the CO₂ currently in the atmosphere, or about 6% of the total 3,341 gigatonnes (3,683 gigatons), would have been sequestered in soil were it not for the spread of human-made antimicrobials. More importantly, the CO₂ no longer stored in the soil is 5.2 times the estimated CO₂ emissions from fossil fuel combustion and industrial processes, of 37.6 gigatonnes (41.4 gigatons) in 2024.

So, if one subscribes to the CO₂ global warming hypothesis, CO₂ from fossil fuels makes only a minor contribution to warming; the major contribution by far comes from antimicrobial CO₂. Curbing fossil fuel emissions is therefore a fool’s errand.

Such a finding also turns on its head the conventional wisdom in the healthcare community that the increase in antimicrobial resistance over the last 70 years is a result of the CO₂-induced warming of approximately 1.25 degrees Celsius (2.25 degrees Fahrenheit) during that period. Rather, the Sams-Dodds conclude, the increase in antimicrobial resistance is responsible for the lion’s share of that warming.

The two scientists note that the rapid increase in the atmospheric CO₂ level since the late 1950s coincides with an upturn in use of both antimicrobials and fossil fuels.

Next: No Evidence That Jet Stream Waviness, Atlantic Ocean Overturning Becoming More Unstable

A Novel Geoengineering Strategy to Combat Sea Level Rise (2)

In the first part of this post, I described a revolutionary concept to offset global sea level rise by constructing a series of large deepwater lakes in arid environments such as Australia and the Sahara. In this second part, I’ll discuss further scaling up of the concept and some of the many engineering challenges involved.

The final figure in the previous post depicted the first of what Russ Walsh, the guiding force behind this strategy, calls “basic lakes,” 56 by 56 km (35 by 35 miles) in surface area and with depths up to 760 meters (2,500 feet). The next phase of the project would be more of the same – two more basic lakes, as shown in the figure below.

copyright © russ walsh

To hold even more seawater, Walsh envisions building even larger lakes further inland from the basic lakes: a “mega-lake” with a surface area of 100 by 225 km (60 by 140 miles), and a “super-lake” with a surface area of 160 by 240 km (100 by 150 miles). The depths of these massive lakes would range up to a staggering 1.6 to 8 km (1 to 5 miles). For comparison, a super-lake would be about two thirds the surface area of Lake Huron, the 2nd largest U.S. Great Lake, but considerably deeper. The average depth of the world’s oceans is about 3.7 km (2.3 miles).

Clearly, all this construction could not be done at once. The initial goal is to complete the first pilot lake by 2040, the first basic lake by 2050 and the massive mega-lake and super-lake by 2060-80.    

Among the many engineering questions that arise, the most important probably involve the sheer magnitude of the project. As Walsh himself admits, the total amount of earth to be moved will be unprecedented and could fill the Grand Canyon many times over. Past excavation of the Suez and Panama canals pales in comparison. Specialized large-scale digging equipment, from bulldozers to dump trucks and bigger than anything used in mining operations today, may need to be designed and built.

Digging such deep lakes will come with its own problems too, such as possible leaking of groundwater from aquifers or springs, or even flash floods, into the dig site before seawater is allowed to enter. Innovations in pumping and other measures could be necessary. A potential hazard is landslides, although these are more likely to be a problem in surrounding manmade hills than the carefully chosen slopes of the lakes themselves.

Another significant issue is exactly where to locate such a venture. As I’ve mentioned, the ideal location is a long stretch of flat, arid and mostly uninhabited coastal land – something not so easily found in practice. For example, much of the Sahara Desert, while sparsely populated, is unsuitable because it’s at too high an elevation.

A better prospect is Australia. With a vast landmass and a relatively small population, especially in the drier regions that characterize most of the continent, Australia has a geographical climate conducive to year-round construction. It also has a political climate that encourages the shipping of water to inland areas for both people and farming.

The next figure demonstrates just how thinly populated a large percentage of the country is (red and orange areas). And although it’s not evident from the figure, much of the coastline embracing the emptiness is at low elevations highly suited to the out-of-the-box thinking that Walsh espouses. He is currently in the process of identifying other, probably smaller tracts of land worldwide suitable for this gigantic undertaking.

Returning to the issue of repopulation, Walsh expects even the early phases of the project involving construction of pilot lakes to draw people to the region. Initially these would be construction workers, but later arrivals would include millions of others enticed by the prospect of living in a resort-like metropolitan area, replete with rail systems and other infrastructure, and hundreds of miles of walking, biking, and hiking trails. The larger, inland basic, mega- and super-lakes would likely be developed by the pilot lake areas’ new inhabitants.

Seawater lakes in the new settlements could conceivably support ocean habitats, and could serve as carbon sinks via mangroves along the lakeshore, coral reefs near the shoreline and floating kelp farms. New residents living on surrounding hills created by lake excavation could view sea creatures frolicking or watch sailboat races from their balconies and terraces.

While many such possibilities may seem fantasy, Walsh is realistic enough to have estimated the potential costs of the first stages of his venture, which are likely to range up to tens of billions of U.S. dollars. Nevertheless, he sees the project as ultimately yielding a positive ROI (return on investment) for investors, provided funding comes from private corporations rather than government sources.

Further details of both the project itself and its financing are contained in a soon-to-be-published book titled “The SeaNet Vision.”

Next: Challenges to the CO2 Global Warming Hypothesis (12): CO2 from Antimicrobials Far Exceeds CO2 from Fossil Fuels

A Novel Geoengineering Strategy to Combat Sea Level Rise (1)

In the ongoing debate over what to do, if anything, about rising global temperatures, adaptation has so far played second fiddle to mitigation. Grandiose geoengineering proposals to reflect the sun’s rays by injecting aerosols into the stratosphere or placing giant reflectors in orbit have been largely dismissed because of the unknown risks and possible unintended consequences of such moves.

But now a new geoengineering strategy with relatively benign and even beneficial consequences has been proposed by Russ Walsh, a California cybersecurity engineer: moving water from the world’s oceans to arid regions like Australia and the Sahara, in order to combat sea level rise.

Rising sea levels is a controversial topic. While there’s no doubt that the average global sea level has been increasing ever since the world started to warm after the Little Ice Age ended around 1850, no reliable scientific evidence exists that the rate of rise is currently accelerating over time, as is sometimes claimed. Nevertheless, the average sea level is currently going up at about 4.3 mm per year, according to NASA. If that continues for the next 50 years, the rise will be 21.5 cm (8.5 inches) – enough to cause serious problems and flooding in low-lying coastal areas.

Although extracting seawater from the oceans will be a massive and difficult project, it would avoid the problems of encroaching seas and the need to build seawalls all across the globe, or to eventually relocate nearly a third of the world’s population and infrastructure to higher ground.

The project would comprise four or five major components: pumping seawater from the ocean; possible desalination; transporting the water to its destination via waterways or canals; excavation of inland lakes to hold the water; and finishing work such as creation of surrounding hills or coastal protection with excavated earth.

Walsh is a visionary undaunted by the technical challenges of such an undertaking. With decades of experience working with major corporations, he is well connected with the types of companies his fledgling venture would need to work with to realize his vision. And he has bounced his concept off several of these companies, as well as water management experts and Stanford University engineering professors, all of whom have found it promising.

The concept is illustrated in the figure below, which shows schematically what the first phases of the project would entail. Built on an extended stretch of relatively flat, arid and mostly uninhabited land along the coastline, small test ponds and mini-lakes, ranging in surface area from 150 by 150 meters (500 by 500 feet) to 1.6 by 1.6 km (1 by 1 miles), would be connected to the nearby ocean via a dredged canal.

COPYRIGHT © RUSS WALSH

The next step would be excavation of a larger pilot lake, with a surface area of perhaps 8 by 8 km (5 by 5 miles), connected to the smaller lakes by the same canal. All lakes would of course have sloping sides, the exact slope determined by the local soil type and the need to avoid landslides. As indicated in the figure, pilot lakes could be as deep as 460 meters (1,500 feet) at their centers.

The following figure shows the next phase of proposed development, involving excavation of much larger “basic lakes,” now 56 by 56 km (35 by 35 miles) in surface area and with depths up to 760 meters (2,500 feet); a second canal would probably be required to help fill such large lakes. The enormous volumes of excavated earth could be used to create artificial hills in the region surrounding the lakes or to protect the coastline from erosion.

COPYRIGHT © RUSS WALSH

The lakes shown would all contain seawater, although a desalination plant could if necessary be placed near where the canals enter the ocean. The freshwater reservoir depicted in the first schematic figure above is an option, constructed on a nearby river which perhaps wends its way to the ocean through an existing town or seaport. If the river is large enough, the freshwater could be used to fill one of the planned basic lakes. Freshwater would be needed for any future residents of the lake area or for future farms in the same region.

Walsh in fact envisages the area surrounding the lakes as a kind of newly created oasis, a thriving transformed region drawing millions of residents and tourists. Many of the new arrivals might even live on the lakes themselves, in houseboats or possibly cruise ships. Even the initial pilot lake region would actually be about the size of the Las Vegas valley in Nevada, which is currently home to approximately 3 million people.

In the second part of this post, I’ll discuss further scaling up of this revolutionary concept, together with some of the engineering challenges and hopes of bringing the concept to fruition.

Next: A Novel Geoengineering Strategy to Combat Sea Level Rise (2)

Ice Sheet Update (2): Greenland Ice Sheet Loss Slows Down

Two big surprises have characterized recent warming-induced melting of the Antarctic and Greenland ice sheets. As I described in another post, the huge Antarctic ice sheet actually stopped melting – at least for now – and rebounded between 2021 and 2023, despite rising temperatures. And a new report highlights how the Greenland ice sheet in 2024 experienced its lowest annual ice loss since 2013.

Greenland’s ice sheet holds only about 10% as much ice as Antarctica’s. We hear more about it because the Greenland ice sheet is melting at a faster rate and contributes more to sea level rise. But the melt rate is no faster today than it was 90 years ago and appears to have slowed over the last few years.

The figure below shows the declining ice sheet mass from 2002 to 2024, based on NASA satellite data. In (a), the mass is shown relative to its value at the end of the spring/summer melt season in 2023, while (b) depicts the seasonal change in mass.

The average annual loss of ice between 2002 and 2023 was 266 gigatonnes (293 gigatons). As can be seen from the thick black line in (b), the 2023-24 loss was 55 gigatonnes (61 gigatons), the third lowest annual ice loss in the 23-year record; the thick green line is from a different satellite dataset. The report authors attribute the low ice loss in 2024 to above-average snowfall. Also apparent in (b) is that the Greenland ice sheet first increases in mass during winter months, due to snowfall, before losing mass over the warmer spring/summer months.

The extent of annual ice melting is illustrated in the next figure. Part (a) portrays the melt extent as a percentage of total ice sheet area for the 2023-24 melt season; part (b) shows the number of surface melt days from April 1 to August 31, 2024, expressed as an anomaly relative to the 1991-2020 mean.

The melt pattern in (a) hovers around the mean melt percentage from 1991 to 2020, indicated by the black line. This result on its own means that losses from the ice sheet are not accelerating, as is sometimes claimed. And (b) reveals that, while Greenland as a whole was still losing ice in 2024, the losses occurred primarily on the east coast of the island, with some ice buildup on the west coast. The report authors attribute this to persistent summertime low pressure over southern Greenland in 2024.

In addition to spring/summer melting, the ice sheet loses ice at its edges from calving or breaking off of icebergs, and from submarine melting by warm seawater. The report authors have estimated the rate of Greenland ice sheet discharge, which typically peaks in July and reaches a minimum in the fall. The figure below shows the annual rate of solid ice discharge from 1991 to 2024 in (a), and the monthly rate in (b).

It can be seen that the discharge rate sped up in the early 2000s, but has since leveled off. The mean discharge rate from 1991 to 2020 was 458 gigatonnes (505 gigatons) per year. Although the solid ice discharge rate during 2023-24 (thick blue line in (b)) exceeded the long-term mean (thin black line), it was not the highest in the record.

The next figure shows the average annual gain or loss of both the surface mass balance (in blue) and the total ice sheet mass (in black), going all the way back to 1840. The surface mass balance includes gains from snowfall and losses from melt runoff, but not sheet edge losses from calving glaciers. Most of the data comes from meteorological stations across Greenland.

The total mass in this graph includes the surface mass balance, iceberg calving and submarine melting (combined in the gray dashed line), and melting from basal sources underneath the ice sheet, but not peripheral glaciers – glaciers that contribute 15 to 20% of Greenland’s total mass loss.

You can see that the rate of ice loss increased temporarily in the early 2000s, as noted previously. But it’s also clear from the graph that high short-term loss rates have occurred more than once in the past, notably in the 1930s and the 1950s – so the current shrinking of the Greenland ice sheet is nothing remarkable. There’s no obvious correlation with global temperatures, since the planet warmed from 1910 to 1940 but cooled from 1940 to 1970.

The Greenland ice sheet is currently the second largest contributor to sea level rise, after thermal expansion of ocean water due to warming. If the rate of ice loss were to remain at its 2002 to 2023 average of 266 gigatonnes (293 gigatons) per year, which is an annual loss of about 0.01% of the total mass of the ice sheet, it would take another 10,000 years for all Greenland’s ice to melt.

Next: A Novel Geoengineering Strategy to Combat Sea Level Rise (1)

How Consensus Can Impede Scientific Progress

As I wrote several years ago (see here), a commonly misunderstood concept in science is the role of consensus. A scientific consensus is built by the slow accumulation of unambiguous pieces of empirical evidence, until the collective evidence is strong enough to become a theory.

Scientific consensus, however, is never reached by taking a poll of scientists. And a consensus isn’t necessarily the last word. A consensus, whether newly proposed or well-established, can be wrong. Failure to recognize this possibility has often held up progress in science.

A recent example comes from the field of archaeology. Throughout the 20th century, the predominant hypothesis was that humans first reached the Americas at the end of the last ice age about 13,000 years ago, when melting ice created a now submerged landmass known as Beringia, shown in the figure below. Asian hunters crossed from Siberia to Alaska, these so-called Clovis people (named after a unique type of spear point they used) subsequently migrating south along the edges of melting ice sheets to warmer climes. 

But despite evidence that the Clovis were not the first arrivals in the Americas, archaeologists who disputed the conventional wisdom were all but ignored and the sites they investigated were disregarded. Prominent among these naysayers was Canadian archaeologist Jacques Cinq-Mars, who carried out excavations at the Bluefish Caves in northwestern Yukon from 1977 to 1987.

Cinq-Mars and his team made an important discovery – bones of horses and woolly mammoths that exhibited cut marks from human butchering and toolmaking. Depicted on the left is a fragment from a horse’s jawbone showing deep thin cuts with a V-shaped profile, typical of butchery to remove muscle. Even more remarkably, radiocarbon testing dated the oldest finds to around 24,000 years ago, thousands of years before the Clovis people were thought to have been in the vicinity.

Reinforcement for Cinq-Mars’ new hypothesis about the first inhabitants of both North (and South) America came from another archaeological study in Washington state, where evidence was found for slaughtering and butchering of mastodons using all-purpose stone tools that resembled Exacto blades, during the same time period as the Bluefish Caves discoveries.

Another significant piece of evidence against the Clovis-first hypothesis was the discovery in Chile of “stone tools, remains of a large hide-covered shelter that may have housed 30 people, communal hearths, chunks of mastodon meat, and three human footprints,” the oldest of which was dated to 14,500 years in the past – again, before the Clovis even crossed Beringia.

Nevertheless, Cinq-Mars’ discovery was met with often acrimonious skepticism at the time, because the renegade archaeologist had dared to contest the prevailing consensus. His competence and sanity were constantly ridiculed and his conference presentations laughed at, experiences that he likened to questioning by the Inquisition. Eventually, even funding for his fieldwork dried up. Only now, some 40 years later, has the Clovis-first model become outmoded among most archaeologists and Cinq-Mars finally vindicated.

These ad hominem attacks on Cinq-Mars were no more virulent, however, than those directed earlier in the century at Alfred Wegener, the German meteorologist who proposed the revolutionary theory of continental drift.

Wegener was vehemently criticized by his peers because his theory threatened the geology establishment, which clung to the old consensus of rigidly fixed continents. One critic harshly dismissed his hypothesis as “footloose,” and geologists scorned what they called Wegener’s “delirious ravings” and other symptoms of “moving crust disease.” It wasn’t for almost 60 years that continental drift theory was accepted by mainstream geologists, after compelling evidence for the theory emerged.

These are not isolated examples in scientific history. Another, from the 19th century in the field of medicine, was the discovery of the now unquestioned importance of handwashing to prevent infection in hospitals. At that time, up to 10% of women who had their babies delivered by obstetricians used to die from so-called childbed fever shortly after childbirth.  In deliveries performed by midwives or at home, the death rate was several times lower.

A combative Hungarian obstetrician named Ignaz Semmelweis came up with the brilliant realization that hospital obstetricians weren’t washing their hands after carrying out barehanded autopsies on the pus-ridden bodies of women who had suffered an anguished death from the same disease only the day before. Once Semmelweis proposed that doctors wash their hands vigorously in a chlorinated lime solution after conducting autopsies, the mortality rate in obstetric wards plummeted.

But the discovery was widely rejected by the medical establishment of the day, whose consensus about disease was that it came from an imbalance in the four bodily humors of Hippocratic medical theory. Not until 20 years later, after Semmelweis had been beaten to death in an asylum, was his infection hypothesis vindicated by the newly accepted germ theory of disease. 

I’ve documented further examples of scientific progress being impeded by a mistaken mainstream consensus here.

Next: Ice Sheet Update (2): Greenland Ice Sheet Loss Slows Down

Ice Sheet Update (1): Reversal of Fortune for Antarctic Ice Sheet

The massive Antarctic ice sheet has long been a puzzle when it comes to global warming. Although the ice sheet is known to be shedding ice around its edges, past evidence has suggested that it may be growing in East Antarctica. Yet overall, the Antarctic ice sheet has melted enough to raise global sea levels by as much as 0.44 mm (17 thousandths of an inch) per year – until recently.

Now, a new study by Chinese earth scientists reveals what the researchers call an “astonishing rebound,” with the ice sheet growing – and no longer melting – for the first time in decades. The study was reported in a separate April news release.

The upper panel in the figure below shows changes in Antarctic ice sheet mass from April 2002 to December 2023, measured in billions of tonnes (gigatonnes, Gt where 1 gigatonne = 1.102 U.S. gigatons). The colored ovals indicate the rate of mass change for specific periods. You can see that while the loss rate accelerated during the two decades after 2002, the losses switched to an abrupt gain (positive rate of change) between 2021 and 2023. The data are based on satellite gravimetry, which measures the gravitational field across the earth’s surface.

The lower panel in the above figure shows the same data, but only until April 2023. In the image on the right, light blue shades indicate ice gain while orange and red shades indicate ice loss. White denotes areas where there has been very little or no change in ice mass since 2002; gray areas are floating ice shelves whose mass change is not measured by this satellite method.

Clearly, the ice loss was not uniform but was concentrated in West Antarctica, where melting of glaciers is significant and partly caused by active volcanoes underneath the continent. East Antarctica, on the other hand, had experienced modest amounts of ice gain, due to warming-enhanced snowfall, even before the recent abrupt gain for the continent as a whole.

To the surprise of the Chinese researchers, not only did the Antarctic ice sheet overall build up ice from 2021 to 2023 and possibly beyond, but so did four major glaciers in East Antarctica that were previously of concern because of their accelerating contributions to ice sheet loss. The large drainage areas of the four glaciers, which are in the Wilkes Land–Queen Mary Land region, are depicted by colored dots in the figure to the left above; the glaciers drain into the south eastern Antarctic coast.

Earlier reports had indicated that more glaciers in East Antarctica were starting to thaw and losing ice faster than anyone thought, say the study authors. In particular, the four glaciers just mentioned had exhibited increasing instability, with signs of ice thinning and extensive grounding line retreat, over the past two decades. Yet this pattern reversed and the four glaciers instead showed a significant gain in mass during the 2021 to 2023 period, as illustrated in the next figure.

The rate of total mass loss for the four glacier basins studied was 3.06 Gt per year for the period 2002–10, increasing dramatically to a loss rate of 50.70 Gt per year for the period 2011–20 – a loss rate acceleration far larger than that for the Antarctic ice sheet as a whole, shown in the upper panel of the first figure above.

This intensification of mass loss from the four glaciers is attributed by the researchers to a 27% increase in glacier ice discharge at the grounding line, combined with a 73% decrease in precipitation and sublimation from 2011 to 2020 in the Wilkes Land–Queen Mary Land region.

As for the contribution of Antarctic ice sheet mass change to global sea levels, the loss of 73.8 Gt per year during 2002–10 caused a sea level rise of 0.20 mm (8 thousandths of an inch) annually, while the increased loss of 142 Gt per year during 2011–20 caused a rise of 0.39 mm (15 thousandths of an inch) annually. In contrast, the annual ice gain of 108 Gt from 2021 to 2023 contributed a fall of 0.30 mm (12 thousandths of an inch) annually to global sea levels during those years.

In conclusion, it’s worth noting that the effect of global warming on Antarctic temperatures has been largely nonexistent. A 2019 study found that the average temperature in East Antarctica had shown no trend in 60 years, while the small Antarctic Peninsula - on the far west of the continent as shown in the figure below – had both warmed and cooled over the same period.

Next: How Consensus Can Impede Scientific Progress

Climate Model Track Record Improves Slightly: Paused Arctic Sea Ice Loss Predicted Correctly

As readers will know, I’ve been highly critical of computer climate models in these pages (see, for example, here and here). Some models greatly exaggerate future warming, or overestimate low cloud feedback, or are unable to reproduce observed sea surface temperature trends.

But a new study exonerates the models when it comes to predictions of sea ice loss in the Arctic, in particular the pause in loss of Arctic sea ice during the past two decades. Despite rising global temperatures, and contrary to alarmist projections of an ice-free summer by 2020, no statistically significant decline in Arctic summer minimum sea ice extent occurred between 2005 and 2024. Sea ice expands to its maximum extent during the winter and shrinks during summer months.

In correctly predicting this 20-year pause, the UK – U.S. collaboration partially redeems the same CMIP5 and CMIP6 models that have previously been shown incapable of accurately hindcasting the observed Arctic sea ice decline during the warming period of the early 20th century.

The present study also finds that periods with no sea ice loss while greenhouse gas emissions continue to increase are not at all unusual in large-ensemble CMIP5 and CMIP6 simulations. The modeling results suggest that internal climate variability – due to natural ocean cycles such as the AMO (Atlantic Multidecadal Oscillation), the PDO (Pacific Decadal Oscillation) or the NAO (North Atlantic Oscillation) – has offset any possible loss of Arctic sea ice due to human emissions.

The figure below illustrates the current robust and prolonged pause in Arctic sea ice loss, based on U.S. NSIDC (National Snow and Ice Data Center) data from satellite measurements, one of two key sea ice indices. The top panel shows the minimum summer ice extent in September over the satellite era from 1979 to 2024.

The center panel depicts 20-year trends during that time, the mean trend being a loss of 0.30 square km per decade, an amount that is not statistically significant despite the strong minimum in 2012; the red shaded envelope represents the 95% confidence level for statistical significance. The insignificant trend is approximately four times smaller than the peak 20-year sea ice trend recorded from 1993 to 2012. The bottom panel demonstrates how the current pause in Arctic sea ice loss shows up in every single month of the year, not just September.

The same effect of a drastic slowdown in Arctic sea ice decline is also evident in sea ice volume. The volume depends on both ice extent and thickness, which varies with location as well as season. Arctic ice thickness is notoriously difficult to measure, the best data coming from limited submarine observations.

According to the study authors, the loss of Arctic sea ice volume has stalled for at least the past 15 years, as shown by the shaded band on the left of the next figure. For the period 2010 to 2024, the simulated annual mean Arctic sea ice volume decreased by only 0.4 million cubic km per decade, a value that is seven times smaller than the long-term simulated loss from 1979 to 2024 of 2.9 million cubic km per decade, and again is not statistically significant.

Geographically, the sea ice volume loss is mostly evident in the Barents Sea, while the slowdown in September sea ice extent occurs mainly in the Pacific and Eurasian sectors. A satellite-derived image of total minimum Arctic sea ice extent is shown on the right of the above figure; the blue contour represents the median extent for 1991-2020.

As mentioned above, the new study has discovered that CMIP5 and CMIP6 climate models frequently simulate pauses in Arctic sea ice loss like the present one, rather than the past 20 years being an unexpected, rare event. Analysis of ensemble members that simulate the observed pause indicates that the current slowdown could possibly persist for a further five to ten years, say the study authors.

The following figure shows the percentage of ensemble members in various ensembles that have 2005-2024 September sea ice loss trends less than the observed value (note that the vertical label refers incorrectly to greater than). As can be seen, the multimodel average indicates that the chance of the ongoing pause in Arctic sea ice loss occurring at all is approximately 20%.

Although 20% is not 100%, the fact that climate models can make such a prediction is remarkable. Furthermore, the authors infer from the multimodel average that the present pause in September Arctic sea ice loss has a 1 in 2 chance of persisting for a further five years, and a 1 in 3 chance of persisting for another ten years.

In conclusion, the authors comment that their study is “a reminder that we should be humble about multidecadal predictions of the climate system, especially in highly variable regions such as the Arctic.”

Next: Ice Sheet Update (1): Reversal of Fortune for Antarctic Ice Sheet