Sea Ice Update: Arctic Stable, Antarctic Recovering

The climate doomsday machine constantly insists that sea ice at the two poles is shrinking inexorably and that the Arctic will soon be ice-free in the summer. But the latest data puts the kibosh on those predictions. The maximum winter Arctic ice extent last month was no different from 2023, and the minimum summer 2024 extent in the Antarctic, although lower than the long-term average, was higher than last year.

Satellite images of Arctic sea ice extent in February 2024, one month before its winter peak (left image), and Antarctic extent at its summer minimum the same month (right image), are shown in the figure below. Sea ice shrinks during summer months and expands to its maximum extent during the winter. The red lines in the figure denote the median ice extent from 1981 to 2010.

Arctic summer ice extent decreased by approximately 39% over the interval from 1979 to 2023, but was essentially the same in 2023 as it was in 2007. Arctic winter ice extent on March 3, 2024 was 11% lower than in 1979, when satellite measurements began, but slightly higher than in 2023, as indicated by the inset in the figure below.

Arctic winter maximum extent fluctuates less than its summer minimum extent, as can be seen in the right panel of the figure which compares the annual trend by month for various intervals during the satellite era, as well as for the low-summer-ice years of 2007 and 2012. The left panel shows the annual trend by month for all years from 2013 through 2024.

What is noticeable about this year’s winter maximum is that it was not unduly low, despite the Arctic being warmer than usual. According to the U.S. NSIDC (National Snow & Ice Data Center), February air temperatures in the Arctic troposphere, about 760 meters (2,500 feet) above sea level, were up to 10 degrees Celsius (18 degrees Fahrenheit) above average.

The NSIDC attributes the unusual warmth to a strong pressure gradient that forced relatively warm air over western Eurasia to flow into the Arctic. However, other explanations have been put forward for enhanced winter warming, such as the formation during non-summer seasons of more low-level clouds due to the increased area of open water compared to sea ice. The next figure illustrates this effect between 2008 and 2022.

Despite the long-term loss of ice in the Arctic, the sea ice around Antarctica had been expanding steadily during the satellite era 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.

Note that this figure shows “anomalies,” or departures from the February mean ice extent for the period from 1981 to 2010, rather than the minimum extent of summer ice in square km. The anomaly trend is plotted as the percent difference between the February extent for that year and the February mean from 1981 to 2010.

As can be seen, the summer ice minimum recovered briefly in 2020 and 2021, only to fall once more and pick up again this year. The left panel in the next figure shows the annual Antarctic trend by month for all years from 2013 through 2024, along with the summer minimum (in square km) in the inset. As for the Arctic previously, the right panel compares the annual trend by month for various intervals during the satellite era, as well as for the high-summer-ice years of 2012 and 2014.

Antarctic sea ice at its summer minimum this year was especially low in the Ross, Amundsen, and Bellingshausen Seas, all of which are on the West Antarctica coast, while the ice cover in the Weddell Sea to the north and along the East Antarctic coast was at average levels. Such a pattern is thought to be associated with the current El Niño.

A slightly different representation of the Antarctic sea ice trend is presented in the following figure, in which the February anomaly is shown directly in square km rather than as a difference percentage. This representation illustrates more clearly how the decline in summer sea ice extent has now persisted for seven years.

The overall trend from 1979 to 2023 is an insignificant 0.1% per decade relative to the 1981 to 2010 mean. Yet a prolonged increase above the mean occurred from 2008 to 2017, followed by the seven-year decline since then. The current downward trend has sparked debate and several possible reasons 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.

Next: The Deceptive Catastrophizing of Weather Extremes: (1) The Science

Challenges to the CO2 Global Warming Hypothesis: (11) Global Warming Driven by Oceanic Seismic Activity, Not CO2

Although undersea volcanic eruptions can’t cause global warming directly, as I discussed in a previous post, they can contribute indirectly by altering the deep-ocean thermohaline circulation. According to a recent lecture, submarine volcanic activity is currently intensifying the thermohaline circulation sufficiently to be the principal driver of global warming.

The lecture was delivered by Arthur Viterito, a renowned physical geographer and retired professor at the College of Southern Maryland. His provocative hypothesis links an upsurge in seismic activity at mid-ocean ridges to recent global warming, via a strengthening of the ocean conveyor belt that redistributes seawater and heat around the globe.

Viterito’s starting point is the observation that satellite measurements of global warming since 1979 show distinct step increases following major El Niño events in 1997-98 and 2014-16, as demonstrated in the following figure. The figure depicts the satellite-based global temperature of the lower atmosphere in degrees Celsius, as compiled by scientists at the University of Alabama in Huntsville; temperatures are annual averages and the zero baseline represents the mean tropospheric temperature from 1991 to 2020.

Viterito links these apparent jumps in warming to geothermal heat emitted by volcanoes and hydrothermal vents in the middle of the world’s ocean basins – heat that shows similar step increases over the same time period, as measured by seismic activity. The submarine volcanoes and hydrothermal vents lie along the earth’s mid-ocean ridges, which divide the major oceans roughly in half and are illustrated in the next figure. The different colors denote the geothermal heat output (in milliwatts per square meter), which is highest along the ridges.

The total mid-ocean seismic activity along the ridges is shown in the figure below, in which the global tropospheric temperature, graphed in the first figure above, is plotted in blue against the annual number of mid-ocean earthquakes (EQ) in orange. The best fit between the two sets of data occurs when the temperature readings are lagged by two years: that is, the 1979 temperature reading is paired with the 1977 seismic reading, and so on. As already mentioned, seismic activity since 1979 shows step increases similar to the temperature.

A regression analysis yields a correlation coefficient of 0.74 between seismic activity and the two-year lagged temperatures, which implies that mid-ocean geothermal heat accounts for 55% of current global warming, says Viterito. However, a correlation coefficient of 0.74 is not as high as some estimates of the correlation between rising CO₂ and temperature.

In support of his hypothesis, Viterito states that multiple modeling studies have demonstrated how geothermal heating can significantly strengthen the thermohaline circulation, shown below. He then links the recently enhanced undersea seismic activity to global warming of the atmosphere by examining thermohaline heat transport to the North Atlantic-Arctic and western Pacific oceans.

In the Arctic, Viterito points to several phenomena that he believes are a direct result of a rapid intensification of North Atlantic currents which began around 1995 – the same year that mid-ocean seismic activity started to rise. The phenomena include the expansion of a phytoplankton bloom toward the North Pole due to incursion of North Atlantic currents into the Arctic; enhanced Arctic warming; a decline in Arctic sea ice; and rapid warming of the Subpolar Gyre, a circular current south of Greenland.

In the western Pacific, he cites the increase since 1993 in heat content of the Indo-Pacific Warm Pool near Indonesia; a deepening of the Indo-Pacific Warm Pool thermocline, which divides warmer surface water from cooler water below; strengthening of the Kuroshio Current near Japan; and recently enhanced El Niños.

But, while all these observations are accurate, they do not necessarily verify Viterito’s hypothesis that submarine earthquakes are driving current global warming. For instance, he cites as evidence the switch of the AMO (Atlantic Multidecadal Oscillation) to its positive or warm phase in 1995, when mid-ocean seismic activity began to increase. However, his assertion begs the question: Isn’t the present warm phase of the AMO just the same as the hundreds of warm cycles that preceded it?

In fact, perhaps the AMO warm phase has always been triggered by an upturn in mid-ocean earthquakes, and has nothing to do with global warming.

There are other weaknesses in Viterito’s argument too. One example is his association of the decline in Arctic sea ice, which also began around 1995, with the current warming surge. What he overlooks is that the sea ice extent stopped shrinking on average in 2007 or 2008, but warming has continued.

And while he dismisses CO₂ as a global warming driver because the rising CO₂ level doesn’t show the same step increases as the tropospheric temperature, a correlation coefficient between CO₂ and temperature as high as 0.8 means that any CO₂ contribution is not negligible.

It’s worth noting here that a strengthened thermohaline circulation is the exact opposite of the slowdown postulated by retired meteorologist William Kininmonth as the cause of global warming, a possibility I described in an earlier post in this Challenges series (#7). From an analysis of longwave radiation from greenhouse gases absorbed at the tropical surface, Kininmonth concluded that a slowdown in the thermohaline circulation is the only plausible explanation for warming of the tropical ocean.

Next: Foundations of Science Under Attack in U.S. K-12 Education

Rapid Climate Change Is Not Unique to the Present

Rapid climate change, such as the accelerated warming of the past 40 years, is not a new phenomenon. During the last ice age, which spanned the period from about 115,000 to 11,000 years ago, temperatures in Greenland rose abruptly and fell again at least 25 times. 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. What they found was a series of rapid climate fluctuations, when the icebound earth suddenly warmed to near-interglacial conditions over just a few decades, only to gradually cool back down to frigid ice-age temperatures.

Ice-core data from Greenland and Antarctica are depicted in the figure below; 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.

Multiple D-O events can be seen in the four sets of data, stronger in Greenland than Antarctica. The periodicity of successive events averages 1,470 years, which has led to the suggestion of a 1,500-year cycle of climate change associated with the sun.

Somewhat similar cyclicity has been observed during the present interglacial period or Holocene, with eight sudden temperature drops and recoveries, mirroring D-O temperature spurts, as illustrated by the thick black line in the next figure. Note that the horizontal timescale runs forward, compared to backward in the previous (and following) figure.

These so-called Bond events were identified by geologist Gerard Bond and his colleagues, who used drift ice measured in deep-sea sediment cores, and δ¹⁸O as a temperature proxy, to study ancient climate change. The deep-sea cores contain glacial debris rafted into the oceans by icebergs, and then dropped onto the sea floor as the icebergs melted. The volume of glacial debris was largest, and it was carried farthest out to sea, when temperatures were lowest.

Another set of distinctive, abrupt events during the latter part of the last ice age were Heinrich events, which are related to both D-O events and Bond cycles. Five of the six or more Heinrich events are shown in the following figure, where the red line represents Greenland ice-core δ¹⁸O data, and some of the many D-O events are marked; the figure also includes Antarctic δ¹⁸O data, together with ice-age CO₂ and CH₄ levels.

As you can see, Heinrich events represent the cooling portion of certain D-O events. Although the origins of both are debated, they are thought likely to be associated with an increase in icebergs discharged from the massive Laurentide ice sheet which covered most of Canada and the northern U.S. Just as with Bond events, Heinrich and D-O events left a signature on the ocean floor, in this case in the form of large rocks eroded by glaciers and dropped by melting icebergs.

The melting icebergs would have also disgorged enormous quantities of freshwater into the Labrador Sea. One hypothesis is that this vast influx of freshwater disrupted the deep-ocean thermohaline circulation (shown below) by lowering ocean salinity, which in turn suppressed deepwater formation and reduced the thermohaline circulation.

Since the thermohaline circulation plays an important role in transporting heat northward, a slowdown would have caused the North Atlantic to cool, leading to a Heinrich event. Later, as the supply of freshwater decreased, ocean salinity and deepwater formation would have increased again, resulting in the rapid warming of a D-O event.

However, this is but one of several possible explanations. The proposed freshwater increase and reduced deepwater formation during D-O events could have resulted from changes in wind and rainfall patterns in the Northern Hemisphere, or the expansion of Arctic sea ice, rather than melting icebergs.

In 2021, an international team of climate researchers concluded that when certain parts of the ice-age climate system changed abruptly, other parts of the system followed like a series of dominoes toppling in succession. But to their surprise, neither the rate of change nor the order of the processes were the same from one event to the other.

Using data from two Greenland ice cores, the researchers discovered that changes in ocean currents, sea ice and wind patterns were so closely intertwined that they likely triggered and reinforced each other in bringing about the abrupt climate changes of D-O and Heinrich events.

While there’s clearly no connection between ice-age D-O events and today’s accelerated warming, this research and the very existence of such events show that the underlying causes of rapid climate change can be elusive.

Next: Challenges to the CO2 Global Warming Hypothesis: (11) Global Warming Is Driven by Oceanic Seismic Activity, Not CO2

Challenges to the CO2 Global Warming Hypothesis: (10) Global Warming Comes from Water Vapor, Not CO2

In something of a twist to my series on challenges to the CO₂ global warming hypothesis, this post describes a new paper that attributes modern global warming entirely to water vapor, not CO₂.

Water vapor (H₂O) is in fact the major greenhouse gas in the earth’s atmosphere and accounts for about 70% of the Earth’s natural greenhouse effect. Water droplets in clouds account for another 20%, while CO₂ contributes only a small percentage, between 4 and 8%, of the total. The natural greenhouse effect keeps the planet at a comfortable enough temperature for living organisms to survive, rather than 33 degrees Celsius (59 degrees Fahrenheit) cooler.

According to the CO₂ hypothesis, it’s the additional greenhouse effect of CO₂ and other gases from human activities that is responsible for the current warming (ignoring El Niño) of about 1.0 degrees Celsius (1.8 degrees Fahrenheit) since the preindustrial era. Because elevated CO₂ on its own causes only a tiny increase in temperature, the hypothesis postulates that the increase from CO₂ is amplified by water vapor in the atmosphere and by clouds – a positive feedback effect.

The paper’s authors, Canadian researchers H. Douglas Lightfoot and Gerald Ratzer, don’t dispute that the natural greenhouse effect exists, as do other, heretical challenges described previously in this series. But the authors ignore the postulated water vapor amplification of CO₂ greenhouse warming, and claim that increased water vapor alone accounts for today’s warmer world. It’s well known that extra water vapor is produced by the sun’s evaporation of seawater.

The basis of Lightfoot and Ratzer’s conclusion is something called the psychrometric chart, which is a rather intimidating tool used by architects and engineers in designing heating and cooling systems for buildings. The chart, illustrated below, is a mathematical model of the atmosphere’s thermodynamic properties, including heat content (enthalpy), temperature and relative humidity.

As inputs to their psychrometric model, the researchers used temperature and relative humidity measurements recorded on the 21st of the month over a 12-month period at 20 different locations: four north of the Arctic Circle, six in north mid-latitudes, three on the equator, one in the Sahara Desert, five in south mid-latitudes and one in Antarctica.

As indicated in the figure above, one output of the model from these inputs is the mass of water vapor in grams per kilogram of dry air. The corresponding mass of CO₂ per kilogram of dry air at each location was calculated from Mauna Loa CO₂ data in ppm (parts per million).

Their results revealed that the ratio of water vapor molecules to CO₂ molecules ranges from 0.3 in polar regions to 108 in the tropics. Then, in a somewhat obscure argument, Lightfoot and Ratzer compared these ratios to calculated spectra for outgoing radiation at the top of the atmosphere. Three spectra – for the Sahara Desert, the Mediterranean, and Antarctica – are shown in the next figure.

The significant dip in the Sahara Desert spectrum arises from absorption by CO₂ of outgoing radiation whose emission would otherwise cool the earth. You can see that in Antarctica, the dip is absent and replaced by a bulge. This bulge has been explained by William Happer and William van Wijngaarden as being a result of the radiation to space by greenhouse gases over wintertime Antarctica exceeding radiation by the cold ice surface.

Yet Lightfoot and Ratzer assert that the dip must be unrelated to CO₂ because their psychrometric model shows there are 0.3 to 40 molecules of water vapor per CO₂ molecule in Antarctica, compared with a much higher 84 to 108 in the tropical Sahara where the dip is substantial. Therefore, they say, the warming effect of CO₂ must be negligible.

As I see it, however, there are at least two fallacies in the researchers’ arguments, First, the psychrometric model is an inadequate representation of the earth’s climate. Although the model takes account of both convective heat and latent heat (from evaporation of H₂O) in the atmosphere, it ignores multiple feedback processes, including the all-important water vapor feedback mentioned above. Other feedbacks include the temperature/altitude (lapse rate) feedback, high- and low-cloud feedback, and the carbon cycle feedback.

A more important objection is that the assertion about water vapor causing global warming represents a circular argument.

According to Lightfoot and Ratzer’s paper, any warming above that provided by the natural greenhouse effect comes solely from the sun. On average, they correctly state, about 26% of the sun’s incoming energy goes into evaporation of water (mostly seawater) to water vapor. The psychrometric model links the increase in water vapor to a gain in temperature.

But the Clausius-Clapeyron equation tells us that warmer air holds more moisture, about 7% more for each degree Celsius of temperature rise. So an increase in temperature raises the water vapor level in the atmosphere – not the other way around. Lightfoot and Ratzer’s claim is circular reasoning.

Next: Rapid Climate Change Is Not Unique to the Present

Antarctica Sending Mixed Climate Messages

Antarctica, the earth’s coldest and least-populated continent, is an enigma when it comes to global warming.

While the huge Antarctic ice sheet is known to be shedding ice around its edges, it may be growing in East Antarctica. Antarctic sea ice, after expanding slightly for at least 37 years, took a tumble in 2017 and reached a record low in 2023. And recent Antarctic temperatures have swung from record highs to record lows. No one is sure what’s going on.

The influence of global warming on Antarctica’s temperatures is uncertain. A 2021 study concluded that both East Antarctica and West Antarctica have cooled since the beginning of the satellite era in 1979, at rates of 0.70 degrees Celsius (1.3 degrees Fahrenheit) per decade and 0.42 degrees Celsius (0.76 degrees Fahrenheit) per decade, respectively. But over the same period, the Antarctic Peninsula (on the left in the adjacent figure) has warmed at a rate of 0.18 degrees Celsius (0.32 degrees Fahrenheit) per decade.

During the southern summer, two locations in East Antarctica recorded record low temperatures early this year. At the Concordia weather station, located at the 4 o’clock position from the South Pole, 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, 2023, 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. Vostok has the distinction of reporting the lowest temperature ever recorded in Antarctica, and also the world record low, of -89.2 degrees Celsius (-128.6 degrees Fahrenheit) on July 21, 1984.

Barely a year before, however, East Antarctica had experienced a heat wave, when the temperature soared to -10.1 degrees Celsius (13.8 degrees Fahrenheit) at the Concordia station on March 18, 2022. This balmy reading was the highest recorded hourly temperature at that weather 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 the previous March record for three consecutive days, including nighttime.

Antarctic sea ice largely disappears during the southern summer and reaches its maximum extent in September, at the end of winter. The two figures below illustrate the winter maximum extent in 2023 (left) and the monthly variation of Antarctic sea ice extent this year from its March minimum to the September maximum (right).

The black curve on the right depicts the median extent from 1981 to 2010, while the dashed red and blue curves represent 2022 and 2023, respectively. It's clear that Antarctic sea ice in 2023 has lagged the median and even 2022 by a wide margin throughout the year. The decline in summer sea ice extent has now persisted for six years, as seen in the following figure which shows the average monthly extent since satellite measurements began, as an anomaly from the median value.

The overall trend from 1979 to 2023 is an insignificant 0.1% per decade relative to the 1981 to 2010 median. Yet a prolonged  increase above the median occurred from 2008 to 2017, followed by the six-year decline since then. The current downward trend has sparked much debate and several possible reasons have been put forward, 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.

Melting of the Antarctic ice sheet is currently causing sea levels to rise by 0.4 mm (16 thousandths of an inch) per year, contributing about 10% of the global total. But the ice loss is not uniform across the continent, as seen in the next figure showing changes in Antarctic ice sheet mass since 2002.

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.

You can see that East Antarctica has experienced modest amounts of ice gain, which is due to warming-enhanced snowfall. Nevertheless, this gain has been offset by significant loss of ice in West Antarctica over the same period, largely from melting of glaciers – which is partly caused by active volcanoes underneath the continent. While the ice sheet mass declined at a fairly constant rate of 133 gigatonnes (147 gigatons) per year from 2002 to 2020, it appears that the total mass may have reached a minimum and is now on the rise again.

Despite the hullabaloo about its melting ice sheet and shrinking sea ice, what happens next in Antarctica continues to be a scientific mystery.

Next: Two Statistical Studies Attempt to Cast Doubt on the CO2 Narrative

Hottest in 125,000 Years? Dishonest Claim Contradicts the Evidence

Amidst the hysterical hype in the mainstream media about recent heat waves all over the Northern Hemisphere, especially in the U.S., the Mediterranean and Asia, one claim stands out as utterly ridiculous – which is that temperatures were the highest the world has seen in 125,000 years, since the interglacial period between the last two ice ages.

But the claim, repeated mindlessly by newspapers, magazines and TV networks in lockstep, is blatantly wrong. Aside from the media confusing the temperature of the hotter ground with that of the air above, there is ample evidence that the earth’s climate has been as warm or warmer than today’s – and comparable to that 125,000 years ago – several times during the past 11,000 years after the last ice age ended.

Underlying the preposterous claim is an erroneous temperature graph featured in the 2021 Sixth Assessment Report of the IPCC (Intergovernmental Panel on Climate Change). The report revives the infamous “hockey stick” – a reconstructed temperature graph for the past 2020 years resembling the shaft and blade of a hockey stick on its side, with no change or a slight decline in temperature for the first 1900 years, followed by a sudden, rapid upturn during the most recent 120 years.

Prominently displayed near the beginning of the report, the IPCC’s latest version of the hockey stick is shown in the figure above. The solid grey line from 1 to 2000 is a reconstruction of global surface temperature from paleoclimate archives, while the solid black line from 1850 to 2020 represents direct observations. Both are relative to the 1850–1900 mean and averaged by decade.

But what is missing from the spurious hockey stick are two previously well-documented features of our past climate: the MWP (Medieval Warm Period) around the year 1000, a time when warmer than normal conditions were reported in many parts of the world, and the cool period centered around 1650 known as the LIA (Little Ice Age).

The two features are clearly visible in a different reconstruction of past temperatures by Fredrik Ljungqvist, who is a professor of geography at Stockholm University in Sweden. Ljungqvist’s 2010 reconstruction, for extra-tropical latitudes (30–90°N) in the Northern Hemisphere only, is depicted in the next figure; temperatures are averaged by decade. Not only do the MWP and LIA stand out, but the end of the Roman Warm Period at the beginning of the previous millennium can also be seen on the left.

Both this reconstruction and the IPCC’s are based on paleoclimate proxies such as tree rings, marine sediments, ice cores, boreholes and leaf fossils. Although other reconstructions have supported the IPCC position that the MWP and LIA did not exist, a large number also provide strong evidence that they were real.

A 2016 summary paper by Ljungqvist and a co-author found that of the 16 large-scale reconstructions they studied, 7 had their warmest year during the MWP and 9 in the 20th century. The overall choice of research papers that the IPCC’s report drew from is strongly biased toward the lack of both the MWP and LIA, and many of the temperature reconstructions cited in the report are faulty because they rely on cherry-picked or incomplete proxy data.

A Southern Hemisphere example is shown in the figure below, depicting reconstructed temperatures for the continent of Antarctica back to the year 500. This also reveals a distinct LIA and what appears to be an extended MWP at the South Pole.

The hockey stick, the creation of climate scientist and IPCC author Michael Mann, first appeared in the IPCC’s Third Assessment Report in 2001, but was conspicuously absent from the fourth and fifth reports. It disappeared after its 2003 debunking by mining analyst Stephen McIntyre and economist Ross McKitrick, who found that the graph was based on faulty statistical analysis, as well as preferential data selection (see here and here). The hockey stick was also discredited by a team of scientists and statisticians assembled by the U.S. National Academy of Sciences.

Plenty of evidence, including that presented here, shows that global temperatures were not relatively constant for centuries as the hockey stick would have one believe. Maximum temperatures were actually higher than now during the MWP, when Scandinavian Vikings farmed in Greenland and wine was grown in the UK, and then much lower during the LIA, when frost fairs on the UK’s frozen Thames River became a common sight.

In a previous post, I presented evidence for a period even warmer than the MWP immediately following the last ice age, a period known as the Holocene Thermal Maximum.

Next: Record Heat May Be from Natural Sources: El Niño and Water Vapor from 2022 Tonga Eruption

Challenges to the CO2 Global Warming Hypothesis: (8) The Antarctic Centennial Oscillation as the Source of Global Warming

Possibly overlooked at the time it was published, a 2018 paper on Antarctica presents an unusual challenge to the CO₂ global warming hypothesis, which postulates that observed global warming – currently about 0.9 degrees Celsius (1.6 degrees Fahrenheit) since the preindustrial era – has been caused primarily by human emissions of CO₂ and other greenhouse gases into the atmosphere.

The proposed challenge is that current global warming can be explained by a natural ocean cycle known as the ACO (Antarctic Centennial Oscillation), the evolutionary precursor of today’s AAO (Antarctic Oscillation), also called the SAM (Southern Annular Mode). This unconventional idea comes from a group of researchers at the Environmental Studies Institute in Santa Cruz, California.

The Santa Cruz group points out that global temperatures have oscillated for at least the last 542 million years, since the beginning of the current Phanerozoic Eon. Superimposed on multi-millennial climate cycles are numerous shorter global and regional cycles ranging in period from millennia down to a few weeks. Among these are numerous present-day ocean cycles, including the above AAO, ENSO (the El Niño – Southern Oscillation) and the AMO (Atlantic Multidecadal Oscillation).

In their 2018 paper the researchers report on the previously unexplored ACO, the record of which is entrained in stable isotopes frozen in ice cores at Vostok in Antarctica and three additional Antarctic drill sites widely distributed on the East Antarctic Plateau, namely, EPICA (European Project for Ice Coring in Antarctica) Dronning Maud Land, EPICA Dome C and Talos Dome.

Past surface temperatures were calculated from the ice cores by measuring either the oxygen ¹⁸O to ¹⁶O, or hydrogen ²H to ¹H, isotopic ratios. Precise ice-core chronology enabled the paleoclimate records from the four drill sites to be synchronized in time.

In analyzing the ice-core data, the paper’s authors found a prominent cycle with a mean repetition period of 352 years over the time interval they evaluated, from 226,400 years before 1950 to the year 1801. Identified as the ACO, the cycle time series nevertheless shows a progressive increase in both frequency and amplitude or temperature swing, the period shortening as the amplitude increases proportionally.

The figure below illustrates the cycle’s temperature oscillations, as measured at Vostok for the last 20,000 years. LGM is the Last Glacial Maximum, LGT the subsequent Last Glacial Termination, and the time scale is measured in thousands of years before 1950 (Kyb1950). The top panel shows temperatures from the LGM to the present, while the lower four panels show the record on an expanded time and temperature scale, with every identified ACO cycle labeled. The small blue and red numbers designate smaller-amplitude oscillations (approximately 10% of all cycles identified), which were found at all four drill sites.

The steady decline of the ACO period over 226 millennia, and the corresponding rise in temperature swing, are depicted in the next figure for the Vostok record. Here individual records have been averaged over 5,000-year intervals. Without averaging, the period ranges from 63 to 1,174 years, and the cycle temperature swing varies from 0.05 degrees Celsius (0.09 degrees Fahrenheit) to as much as 3.2 degrees Celsius (5.8 degrees Fahrenheit).

Because of the variation in period (frequency) and amplitude, the null hypothesis that the observed cycles represent random fluctuations in cycle structure was tested by the researchers, using the statistical concept of autocorrelation. This confirmed that the cycle structure was indeed nonrandom. However, the data for the whole 226,400 years did reveal evidence for other, lower-frequency cycles, including ones with periods of 1,096 and 1,470 years.

So how is all this connected to global warming?

The variable ACO cycles show that temperature fluctuations of several degrees Celsius have occurred many times in the past 226 millennia, including our present Holocene (c and d in the first figure above) – at least in Antarctica. That these Antarctic cycles extend globally was inferred by the researchers from the correspondence between the 1,096- and 1,470-year ACO cycles mentioned above and so-called Bond events in the Northern Hemisphere, which are thought to have the same periodicity but occur up to 3 millennia later.

Bond events refer to glacial debris rafted into the North Atlantic Ocean by icebergs and then dropped onto the sea floor as the icebergs melt.  The volume of glacial debris, which is measured in deep-sea sediment cores, fluctuates as global temperatures rise and fall.

1,096 and 1,470 years are also approximate multiples of the mean ACO period of 352 years. This finding, together with the observation about Bond events, is considered by the researchers to be strong evidence that the ACO is a natural climate cycle that arises in Antarctica and then propagates northward, influencing global temperatures. It’s feasible that our current global warming – during which temperatures have already risen by close to 1 degree Celsius (1.8 degrees Fahrenheit) – is simply part of the latest ACO (or AAO/SAM) cycle.

Such speculation, however, needs to be reinforced by solid scientific evidence before it can be considered a serious challenge to the CO₂ hypothesis.

Next: No Evidence That Extreme Weather on the Rise: A Look at the Past - (1) Hurricanes

No Evidence That Cold Extremes Are Becoming Less Frequent

The IPCC (Intergovernmental Panel on Climate Change), whose assessment reports are the voice of authority for climate science, errs badly in its Sixth Assessment Report (AR6) by claiming that cold weather extremes have become less frequent and severe. While that may be expected in a warming world, observational evidence shows that in fact, cold extremes are on the rise and may actually have become more severe.

Cold extremes include abnormally low temperatures, prolonged cold spells, unusually heavy snowfalls and longer winter sea­sons. That cold extremes are indeed increasing has been chronicled in detail by environmental scientist Madhav Khandekar in several recent research papers (here, here and here). While the emphasis of Khandekar’s publications has been on harsh winters in North America, he has catalogued cold extremes in South America, Europe and Asia as well.

The figure below shows the locations of 4,145 daily low-temperature records broken or tied in the northeastern U.S. during the ice-cold February of 2015; that year tied with 1904 for the coldest Janu­ary to March period in the northeast, in records extending back to 1895. Of the 4,145 records, 3,573 were new record lows and the other 572 tied previous records.

Examples of cold extremes in recent years abound (see here and here). During the 2020 southern winter and northern summer, the Australian island state of Tasmania recorded its most frigid winter minimum ever, exceeding the previous low of −13.0 degrees Celsius (8.6 degrees Fahrenheit) by 1.2 degrees Celsius (2.2 degrees Fahrenheit); Norway endured its chilliest July in 50 years; neighboring Sweden shivered through its coldest sum­mer since 1962; and Russia was also bone-chilling cold.

In the northern autumn of 2020, bitterly cold temperatures afflicted many communities in the U.S. and Canada. The north­ern U.S state of Minnesota experienced its largest early-season snowstorm in recorded history, going back about 140 years. And in late December, the subfreezing polar vortex began to expand out of the Arctic.

Earlier in 2020, massive snowstorms covered much of Patagonia in more than 150 cm (60 inches) of snow, and buried alive at least 100,000 sheep and 5,000 cattle. Snowfalls not seen for decades occurred in other parts of South America, and in South Africa, southeastern Australia and New Zealand.

A 2021 example of a cold extreme was the North American cold wave in February, which brought record-breaking subfreez­ing temperatures to much of the central U.S., as well as Canada and northern Mexico. Texas experienced its coldest February in 43 years; the frigid conditions lasted several days and resulted in widespread power outages and damage to infrastructure. Curiously, the Texan deep freeze was ascribed to global warming by a team of climate scien­tists, who linked it to stretching of the Arctic polar vortex.

Other exceptional cold extremes in 2021 included the lowest average UK minimum temperature for April since 1922; record low temperatures in both Switzerland and Slove­nia the same month; the coldest winter on record at the South Pole; and an all-time high April snowfall in Belgrade, in record books dating back to 1888.

In 2022, Australia and South America saw some of their coldest weather in a century. In May, Australia experienced the heaviest early-season mountain snow in more than 50 years. In June, Brisbane in normally temperate Queensland had its coldest start to winter since 1904. And in December, the state of Victoria set its coldest summer temperature record ever.

South America also suffered icy conditions in 2022, after an historically cold winter in 2021 which decimated crops. The same Antarctic cold front that froze Australia in May brought bone-numbing cold to northern Argentina, Paraguay and southern Brazil; Brazil’s capital Brasilia logged its lowest temperature in recorded history.

In December 2022, the U.S. set 126 monthly low-temperature records, while century-old low-temperature records tumbled in neighboring Canada. This followed all-time record-breaking snow in Japan, extra-heavy snow in the Himalayas which thwarted mountain climbers there, and heavy snow across China and South Korea.

Clearly, cold extremes are not going away or becoming less severe. And frequent statements by the mainstream media linking cold extremes to global warming are absurd, although such statements may fit the popular belief that global warming causes weather extremes in general. As I have explained in numerous blog posts and reports, this belief is mistaken and there is no evidence that weather extremes are worsening because of climate change.

Extreme weather conditions are produced by natural patterns in the climate system, not global warming. Khandekar links cold extremes to the North Atlantic and Pacific Decadal Oscil­lations, and possibly to solar activity.

Next: Global Warming from Food Production and Consumption Grossly Overestimated

Are Ocean Surface Temperatures, Not CO2, the Climate Control Knob?

According to the climate change narrative, modern global warming is largely the result of human emissions of CO₂ into the atmosphere. But a recent lecture questioned that assertion with an important observation suggesting that ocean surface temperatures, not CO₂, are the planet’s climate control knob.

The lecture was delivered by Norwegian Ole Humlum, who was formerly a full professor in physical geography at both the University Centre in Svalbard, Norway and the University of Oslo, in addition to holding visiting positions in Scotland and the Faroe Islands. He currently publishes regular updates on the state of the global climate.

In his lecture, Humlum dwelt on temperature measurements of the world’s oceans. Since 2004, ocean temperatures have been studied in detail at depths of up to 2 km (1.2 miles), by means of a global array of almost 3,900 Argo profiling floats. These free-drifting robotic floats patrol the oceans, taking a deep dive every 10 days to probe the temperature and salinity of the watery depths, and transmitting the data to a satellite within hours of reaching the surface again. A 2018 map of the Argo array is shown below.

The next figure illustrates how the oceans have warmed during the period that the floats have been in operation, up to August 2020. The vertical scale is the global ocean temperature change in degrees Celsius averaged from 65^oS to 65^oN (excluding the polar regions), while the horizontal scale gives the depth up to 1,900 meters (6,200 feet).

You can see that warming has been most prominent at the surface, where the average sea surface temperature has gone up since 2004 by about 0.27 degrees Celsius (0.49 degrees Fahrenheit). The temperature increase deep down is an order of magnitude smaller. Most of the temperature rise at shallow depths comes from the tropics (30^oS to 30^oN) and the Antarctic (65^oS to 55^oS), although the Arctic (55^oN to 65^oN) measurements reveal considerable cooling down to about 1,400 meters (4,600 feet) in that region.

But Humlum’s most profound observation is of the timeline for Argo temperature measurements as a function of depth. These are depicted in the following figure showing global depth profiles for the tropical oceans in degrees Celsius, from 2004 to 2014. The tropics cover almost 40% of the earth’s surface; the oceans in total cover 71%.

The fluctuations in each Argo depth profile arise from seasonal variations in temperature from summer to winter, which are more pronounced at the surface than at greater depths. If you focus your attention on any yearly summer peak at zero depth, you will notice that it moves to the right – that is, to later times – as the depth increases. In other words, there is a time delay of any temperature change with depth.

From a correlation analysis of the Argo data, Humlum finds that the time delay at a depth of 200 meters (650 feet) is a substantial 20 months, so that it takes 20 months for a temperature increase or decrease at the tropical surface to propagate down to that depth. A similar, though smaller, delay exists between any change in sea surface temperature (SST) and corresponding temperature changes in the atmosphere and on land, as shown in the figure below.

At an altitude of 200 meters (650 feet) in the atmosphere, changes in the SST show up slightly less than half a month later. But in the lower troposphere, where satellite temperature measurements are made, the delay is 2 months, as it is also for land surface temperatures. Humlum’s crucial argument is that sea surface temperatures lead all other global temperature observations – that is, the global temperature signal originates at the ocean surface.

However, according to the CO₂ global warming hypothesis, the CO₂ signal originates at an altitude of about 9 km (5.6 miles) in the upper troposphere and is seen at the sea surface some time later. So the CO₂ hypothesis predicts that the sea surface is a lagging, not a leading indicator – exactly the opposite of what actual observations are telling us.

Humlum concludes that CO₂ cannot be the earth’s climate control knob and that our global climate is apparently controlled by the SST. The climate control knob must instead be whatever natural system controls sea surface temperatures. Potential candidates, he says, include the sun, cloud cover, sediments and organic life in the oceans, and the action of winds. Further research is needed to identify which of these possibilities truly powers the global climate.

Next: Mainstream Media Jumps on Extreme Weather Caused by Climate Change Bandwagon

Arctic Sea Ice Refuses to Disappear, despite Ever Rising Arctic Temperatures

The loss of sea ice in the Arctic due to global warming has long been held up by the mainstream media and climate activists as cause for alarm. The ice would be completely gone in summer, they predicted, by 2013, then 2016, then 2030. But the evidence shows that Arctic ice is not cooperating, and in fact its summer extent in 2022 was the same as in 2008. And this stasis has occurred even as Arctic temperatures continue to soar.

The minimum summer Arctic ice extent this month was about 67% of its coverage in 1979, which is when satellite measurements of sea ice in the Arctic and Antarctic began. The figure to the left shows satellite-derived images of Arctic sea ice extent in the summer of 2022 (September 18) and the winter of 2021 (March 7) , which was similar to 2022. Sea ice shrinks during summer months and expands to its maximum extent during the winter.

Over the interval from 1979 to 2022, Arctic summer ice detached from the Russian coast, although it still encases northern Greenland as can be seen. The figure below compares the monthly variation of Arctic ice extent from its March maximum to the September minimum, for the years 2022 (blue curve) and 2008 (red curve). The 2022 summer minimum is seen to be almost identical to that in 2008, as was the 2021 minimum, with the black curve depicting the median extent over the period from 1981 to 2010.

The next figure illustrates the estimated Arctic ice thickness and volume at the 2022 minimum. 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.

The thickest, and oldest, winter ice currently lies along the northern coasts of the Canadian Arctic Archipelago and Greenland. According to a trio of Danish research institutions, just 20% of the Arctic ice pack today consists of thick ice more than one to two years old, compared to 40% in 1983. Thick, multi-year ice doesn’t melt away in the summer, but much of the ice cover currently formed during winter consists of thin, first-year ice. 

What is surprising, however, is that the lack of any further loss in summer ice extent since 2008 has been accompanied by a considerable increase in Arctic temperature. The left panel of the next figure, from a dataset compiled by the European Union’s Copernicus Climate Change Service, shows the mean surface temperature in the Arctic since 1979.

You can see that the Arctic has been warming steadily since at least 1979, when the first satellite measurements were made. As shown in the figure, the mean temperature there shot up by 3 degrees Celsius (5.4 degrees Fahrenheit), compared to global warming over the same interval of only 0.68 degrees Celsius (1.2 degrees Fahrenheit). That’s an Arctic warming rate 4 times faster than the globe as a whole. From 2008 to 2022, during which the summer ice extent remained unchanged on average, the Arctic nevertheless warmed by about 1.3 degrees Celsius (2.3 degrees Fahrenheit).

This phenomenon of excessive warming at the North Pole is known as Arctic amplification, depicted numerically in the right panel of the figure above. The effect shows strong regional variability, with some areas – such as the Taymyr Peninsula region in Siberia and the sea near Novaya Zemlya Island – warming by as much as seven times the global average. The principal reason for the high amplification ratio in these areas is exceptionally low winter ice cover, which is most pronounced in the Barents Sea near Novaya Zemlya.

The amplification is a result of so-called albedo (reflectivity) feedback. Sea ice is covered by a layer of white snow that reflects around 85% of incoming sunlight back out to space. As the highly reflective ice melts from global warming, it exposes more of the darker seawater underneath. The less reflective seawater absorbs more incoming solar radiation than sea ice, pushing the temperature higher. This in turn melts more ice and exposes more seawater, amplifying the warming in a feedback loop.

Interestingly, computer climate models, most of which exaggerate the impact of global warming, underestimate Arctic warming. The models typically estimate an average Arctic amplification ratio of about 2.5, much lower than the average ratio of 4 deduced from actual observations. A recent research study attributes this difference to possible errors in the modeled sensitivity to greenhouse gas forcing, and in the distribution of heating from the forcing between the atmosphere, cryosphere and ocean.

They also suggest that climate models underestimate multi-decadal internal variability, especially of atmospheric circulation in mid-latitudes (30^o to 60^o from the equator), which influences temperature variability in the Arctic as well.

Next: Climate-Related Disasters Wrongly Linked to Global Warming by Two International Agencies

No Evidence That Thwaites Glacier in Antarctica Is about to Collapse

Contrary to recent widespread media reports and dire predictions by a team of earth scientists, Antarctica’s Thwaites Glacier – the second fastest melting glacier on the continent – is not on the brink of collapse. The notion that catastrophe is imminent stems from a basic misunderstanding of ice sheet dynamics in West Antarctica.

The hoopla began with publication of a research study in November 2021 and a subsequent invited presentation to the AGU (American Geophysical Union). Both postulated that giant cracks recently observed in the Thwaites Eastern Ice Shelf (pictured to the left) may cause the whole ice shelf to shatter within as little as five years. The cracks result from detachment of the ice shelf’s seaward edge from an underwater mountain about 40 kilometers (25 miles) offshore that pins the shelf in place like a cork in a bottle.

Because the ice shelf already floats on the ocean, collapse of the shelf itself and release of a flotilla of icebergs wouldn’t cause global sea levels to rise. But the researchers argue that loss of the ice shelf would speed up glacier flow, increasing the contribution to sea level rise of the Thwaites Glacier – often dubbed the “doomsday glacier” – from 4% to 25%. A sudden increase of this magnitude would have a devastating impact on coastal communities worldwide. The glacier’s location is indicated by the lower red dot in the figure below.  

But such a drastic scenario is highly unlikely, says geologist and UN IPCC expert reviewer Don Easterbrook. The misconception is about the submarine “grounding” of the glacier terminus, the boundary between the glacier and its ice shelf extending out over the surrounding ocean, as illustrated in the next figure.

The grounding line of the Thwaites Glacier, shown in red in the left figure below, has been retreating since 2000. According to the study authors, this spells future disaster: the retreat, they say, will lead to dynamic instability and greatly accelerated discharge of glacier ice into the ocean, by as much as three times.

As evidence, the researchers point to propagating rifts on the top of the ice shelf and basal crevasses beneath it, both of which are visible in the satellite image above, the rifts as diagonal lines and the crevasses as nearly vertical ones. The crevasses arise from basal melting produced by active volcanoes underneath West Antarctica combined with so-called circumpolar deep water warmed by climate change.

However, as Easterbrook explained in response to a 2014 scare about the adjacent Pine Island glacier, this reasoning is badly flawed since a glacier is not restrained by ice at its terminus. Rather, the terminus is established by a balance between ice gains from snow accumulation and losses from melting and iceberg calving. The removal of ice beyond the terminus will not cause unstoppable collapse of either the glacier or the ice sheet behind it.

Other factors are important too, one of which is the source area of Antarctic glaciers. Ice draining into the Thwaites Glacier is shown in the right figure above in dark green, while ice draining into the Pine Island glacier is shown in light green; light and dark blue represent ice draining into the Ross Sea to the south of the two glaciers. The two glaciers between them drain only a relatively small portion of the West Antarctic ice sheet, and the total width of the Thwaites and Pine Island glaciers constitutes only about 170 kilometers (100 miles) of the 4,000 kilometers (2,500) miles of West Antarctic coastline.

Of more importance are possible grounding lines for the glacier terminus. The retreat of the present grounding line doesn’t mean an impending calamity because, as Easterbrook points out, multiple other grounding lines exist. Although the base of much of the West Antarctic ice sheet, including the Thwaites glacier, lies below sea level, there are at least six potential grounding lines above sea level, as depicted in the following figure showing the ice sheet profile. A receding glacier could stabilize at any of these lines, contrary to the claims of the recent research study.

As can be seen, the deepest parts of the subglacial basin lie beneath the central portion of the ice sheet where the ice is thickest. What is significant is the ice thickness relative to its depth below sea level. While the subglacial floor at its deepest is 2,000 meters (6,600 feet) below sea level, almost all the subglacial floor in the above profile is less than 1,000 meters (3,300 feet) below the sea. Since the ice is mostly more than 2,500 meters (8,200 ft) thick, it couldn’t float in 1,000 meters (3,300 feet) of water anyway.

Next: Science Under Renewed Attack: New Zealand Proposal to Equate Maori Mythology with Science

Sudden Changes in Ocean Currents Warmed Arctic, Cooled Antarctic in Past

Abrupt changes in ocean currents – and not greenhouse gases – were responsible for sudden warming of the Arctic and for sudden cooling in the Antarctic at different times in the past, according to two recent research studies. The Antarctic cooling marked the genesis of the now massive Antarctic ice sheet.

The first study, by a team of European scientists, discovered that the expansion of warm Atlantic Ocean water flowing into the Arctic caused sea surface temperatures in the Fram Strait east of Greenland to rise by about 2 degrees Celsius (3.6 degrees Fahrenheit) as early as 1900. The phenomenon, known as “Atlantification” of the Arctic, is important because it precedes instrumental measurements of the effect by several decades and is not simulated by computer climate models.

The conclusion is based on an 800-year reconstruction of Atlantification along the Fram Strait, which separates Atlantic waters from the Arctic Ocean. The researchers used marine sediment cores as what they call a “natural archive” of past climate variability, deriving the chronological record from radionuclide dating.

Shown in the figure below is the sea surface temperature and Arctic sea ice extent from 1200 to 2000. The blue curve represents the reconstructed mean summer temperature (in degrees Celsius) of Atlantic waters in the eastern Fram strait, while the red curve indicates the April retreat (in kilometers) of the sea ice edge toward the Arctic. You can see clearly that the seawater temperature increased abruptly around 1900, after centuries of remaining constant, and that sea ice began to retreat at the same time, after at least a century of extending about 200 kilometers farther into the strait.

Along with temperature, the salinity of Atlantic waters in the strait suddenly increased also. The researchers suggest that this Atlantification phenomenon could have been due to weakening of two ocean currents – the AMOC (Atlantic Meridional Overturning Circulation) and the SPG (Subpolar Gyre), a circular current south of Greenland – at the end of the Little Ice Age. The AMOC forms part of the ocean conveyor belt that redistributes seawater and heat around the globe.

This abrupt change in ocean currents is thought to have redistributed nutrients, heat and salt in the northeast Atlantic, say the study authors, but is unlikely to be associated with greenhouse gases. The change caused subtropical Atlantic waters to flow northward through the Fram Strait, as illustrated schematically in the figure below; the halocline is the subsurface layer in which salinity changes sharply from low (at the surface) to high. The WSC (West Spitsbergen Current) carries heat and salt to the Arctic and keeps the eastern Fram Strait ice-free.

Sudden cooling occurred in the Antarctic but millions of years earlier, a second study has found. Approximately 34 million years ago, a major reorganization of ocean currents in the Southern Ocean resulted in Antarctic seawater temperatures abruptly falling by as much as 5 degrees Celsius (9 degrees Fahrenheit). The temperature drop initiated growth of the Antarctic ice sheet, at the same time that the earth underwent a drastic transition from warm Greenhouse to cold Icehouse conditions.

This dramatic cooling was caused by tectonic events that opened up two underwater gateways around Antarctica, the international team of researchers says. The gateways are the Tasmanian Gateway, formerly a land bridge between Antarctica and Tasmania, and Drake Passage, once a land bridge from Antarctica to South America. The scientists studied the effect of tectonics using a high-resolution ocean model that includes details such as ocean eddies and small-scale seafloor roughness.

After tectonic forces caused the two land bridges to submerge, the present-day ACC (Antarctic Circumpolar Current) began to flow. This circumpolar current, although initially less strong than today, acted to weaken the flow of warm waters to the Antarctic coast. As the two gateways slowly deepened, the warm-water flow weakened even further, causing the relatively sudden cooling event.

Little cooling occurred before one or both gateways subsided to a depth of more than 300 meters (1,000 feet). After the second gateway had subsided from 300 meters (1,000 feet) to 600 meters (2,000 feet), surface waters along the entire Antarctic coast cooled by 2 to 3.5 degrees Celsius (3.6 to 6.3 degrees Fahrenheit). And once the second gateway had subsided below 600 meters (2,000 feet), the temperature of Antarctic coastal waters decreased another 0.5 to 2 degrees Celsius (0.9 to 3.6 degrees Fahrenheit). The next figure depicts the gradual opening of the two gateways.

Although declining CO₂ levels in the atmosphere may have played a minor role, the study authors conclude that undersea tectonic changes were the key factor in altering Southern Ocean currents and in creating our modern-day Icehouse world.

Next: No Evidence That Thwaites Glacier in Antarctica Is about to Collapse

Challenges to the CO2 Global Warming Hypothesis: (5) Peer Review Abused to Axe Skeptical Paper

A climate research paper featured in a previous post of mine has recently been removed by the publisher, following a post-publication review by seven new reviewers who all recommended rejection of the paper. This drastic action represents an abuse of the peer review process in my opinion, as the reviews are based on dubious science.

The paper in question was a challenge to the CO₂ global warming hypothesis by French geologist Pascal Richet. From analysis of an Antarctic ice core, Richet postulates that greenhouse gases such as CO₂ had only a minor effect on the earth’s climate over the past 423,000 years, and that any assumed forcing of climate by CO₂ is incompatible with ice-core data.

Past atmospheric CO₂ levels and surface temperatures are calculated from ice cores by measuring the air composition and the oxygen ¹⁸O to ¹⁶O isotopic ratio, respectively, in air bubbles trapped by the ice. Data from the core, drilled at the Russian Vostok station in East Antarctica, is depicted in the figure below. The CO₂ level is represented by the upper graphs (below the insolation data) that show the substantial drop in CO₂ during an ice age; the associated drop in temperature ΔT is represented by the lower graphs.

It’s well known that the CO₂ level during the ice ages closely mimicked changes in temperature, but the CO₂ concentration lagged behind. What Richet observed is that the temperature peaks in the Vostok record are much narrower than the corresponding CO₂ peaks. From this observation, he argued that CO₂ can’t drive temperature since an effect can’t last for a shorter period than its cause.

The seven negative reviews focused on two main criticisms. The first is that Richet supposedly fails to understand that CO₂ can act both as a temperature driver, when CO₂ leads, and as an amplifying feedback, when CO₂ lags.

At the end of ice ages, it’s thought that a subtle change in the earth’s orbit around the sun initiated a sudden upward turn of the temperature. This slight warming was then amplified by feedbacks, including CO₂ feedback triggered by a surge in atmospheric CO₂ as it escaped from the oceans; CO₂ is less soluble in warmer water. A similar but opposite chain of events is believed to have enhanced global cooling as the temperature fell at the beginning of an ice age. In both cases – deglaciation and glaciation – CO₂ as a feedback lagged temperature.

However, several of Richet’s reviewers base their criticism on a 2012 paper, by paleoclimatologist Jeremy Shakun and coauthors, which proposes the somewhat preposterous notion that CO₂ lagged temperature during the most recent glaciation, all through the subsequent ice age, and during 0.3 degrees Celsius (0.5 degrees Fahrenheit) of the initial warming as the ice age ended – but then switched roles from feedback to driver and led temperature during the remaining deglaciation.

Shakun’s proposal is illustrated in the left graph below, in which the blue curve shows the mean global temperature during deglaciation, the red curve represents the temperature in Antarctica and the yellow dots are the atmospheric CO₂ concentration. The CO₂ levels and Antarctic temperatures are derived from an ice core, as in Richet’s paper but using the so-called Dome C core, while global temperatures are calculated from proxy data obtained from ocean and lake sediments.

The apparent switch of CO₂ from feedback to driver is clearly visible in the figure above about 17,500 years ago, when the temperature escalated sharply. Although the authors attempt to explain the sudden change as resulting from variability of the AMOC (Atlantic Meridional Overturning Circulation), their argument is only hand-waving at best and does nothing to bolster their postulated dual role for CO₂.

In any case, a detailed, independent analysis of the same proxy data has found there is so much data scatter that whether CO₂ leads or lags the warming can’t even be established. This analysis is shown in the right graph above, where the green dots represent the temperature data and the black circles are the CO₂ level.

All this invalidates the reviewers’ first main criticism of Richet’s paper. The second criticism is that Richet dismisses computer climate models as an unreliable tool for studying the effect of CO₂ on climate, past or present. But, as frequently pointed out in these pages, climate models indeed have many weaknesses. These include the omission of many types of natural variability, exaggeration of predicted temperatures and the inability to reproduce the past climate accurately. Repudiation of climate models is therefore no reason to reject a paper.

Some of the reviewers’ lesser criticisms of Richet’s paper are justified, such as his analysis of only one Antarctic ice core when several are available, and his inappropriate philosophical and political comments in a scientific paper. But outright rejection of the paper smacks of bias against climate change skeptics and is an abuse of the time-honored tradition of peer review.

Next: The Crucial Role of Water Feedbacks in Global Warming

Ice Sheet Update (1): Evidence That Antarctica Is Cooling, Not Warming

Melting due to climate change of the Antarctic and Greenland ice sheets has led to widespread panic about the future impact of global warming. But, as we’ll see in this and a subsequent post, Antarctica may not be warming overall, while the rate of ice loss in Greenland has slowed recently.

The kilometers-thick Antarctic ice sheet contains about 90% of the world’s freshwater ice and would raise global sea levels by about 60 meters (200 feet) were it to melt completely. The Sixth Assessment Report of the UN’s IPCC (Intergovernmental Panel on Climate Change) maintains with high confidence that, between 2006 and 2018, melting of the Antarctic ice sheet was causing sea levels to rise by 0.37 mm (15 thousandths of an inch) per year, contributing about 10% of the global total.

By far the largest region is East Antarctica, which covers two thirds of the continent as seen in the figure below and holds nine times as much ice by volume as West Antarctica. The hype about imminent collapse of the Antarctic ice sheet is based on rapid melting of the glaciers in West Antarctica; the glaciers contribute an estimated 63% (see here) to 73% (here) of the annual Antarctic ice loss. East Antarctica, on the other hand, may not have shed any mass at all – and may even have gained slightly – over the last three decades, due to the formation of new ice resulting from enhanced snowfall.  

The influence of global warming on Antarctica is uncertain. In an earlier post, I reported the results of a 2014 research study that concluded West Antarctica and the small Antarctic Peninsula, which points toward Argentina, had warmed appreciably from 1958 to 2012, but East Antarctica had barely heated up at all over the same period. The warming rates were 0.22 degrees Celsius (0.40 degrees Fahrenheit) and 0.33 degrees Celsius (0.59 degrees Fahrenheit) per decade, for West Antarctica and the Antarctic Peninsula respectively – both faster than the global average.

But a 2021 study reaches very different conclusions, namely that both West Antarctica and East Antarctica cooled between 1979 and 2018, while the Antarctic Peninsula warmed but at a much lower rate than found in the 2014 study. Both studies are based on reanalyses of limited Antarctic temperature data from mostly coastal meteorological stations, in an attempt to interpolate temperatures in the more inaccessible interior regions of the continent.

This later study appears to carry more weight as it incorporates data from 41 stations, whereas the 2014 study includes only 15 stations. The 2021 study concludes that East Antarctica and West Antarctica have cooled since 1979 at rates of 0.70 degrees Celsius (1.3 degrees Fahrenheit) per decade and 0.42 degrees Celsius (0.76 degrees Fahrenheit) per decade, respectively, with the Antarctic Peninsula having warmed at 0.18 degrees Celsius (0.32 degrees Fahrenheit) per decade.

It’s the possible cooling of West Antarctica that’s most significant, because of ice loss from thinning glaciers. Ice loss and gain rates from Antarctica since 2003, measured by NASA’s ICESat satellite, are illustrated in the next figure, in which dark reds and purples show ice loss and blues show gain.

The high loss rates along the coast of West Antarctica have been linked to thinning of the floating ice shelves that terminate glaciers, by so-called circumpolar deep water warmed by climate change. Although disintegration of an ice shelf already floating on the ocean doesn’t raise sea levels, a retreating ice shelf can accelerate the downhill flow of glaciers that feed the shelf. It’s thought this can destabilize the glaciers and the ice sheets behind them.

However, not all the melting of West Antarctic glaciers is due to global warming and the erosion of ice shelves by circumpolar deep water. As I’ve discussed in a previous post, active volcanoes underneath West Antarctica are melting the ice sheet from below. One of these volcanoes is making a major contribution to melting of the Pine Island Glacier, which is adjacent to the Thwaites Glacier in the first figure above and is responsible for about 25% of the continent’s ice loss.

If the Antarctic Peninsula were to cool along with East Antarctica and West Antarctica, the naturally occurring SAM (Southern Annular Mode) – the north-south movement of a belt of strong southern westerly winds surrounding Antarctica – could switch from its present positive phase to negative. A negative SAM would result in less upwelling of circumpolar deep water, thus reducing ice shelf thinning and the associated melting of glaciers.

As seen in the following figure, the 2021 study’s reanalysis of Antarctic temperatures shows an essentially flat trend for the Antarctic Peninsula since the late 1990s (red curve); warming occurred only before that time. The same behavior is even evident in the earlier 2014 study, which goes back to 1958. So future cooling of the Antarctic Peninsula is not out of the question. The South Pole in East Antarctica this year experienced its coldest winter on record.

Next: Ice Sheet Update (2): Evidence That Greenland Melting May Have Slowed Down

Sea Ice Update: No Evidence for Recent Ice Loss

Climate activists have long lamented the supposedly impending demise of Arctic sea ice due to global warming. But, despite the constant drumbeat of apocalyptic predictions, the recently reached minimum extent of Arctic ice in 2021 is no smaller than it was back in 2008.  And at the other end of the globe, the sea ice around Antarctica has been expanding for at least 42 years.

Scientific observations of sea ice in the Arctic and Antarctic have only been possible since satellite measurements began in 1979. The figure below shows satellite-derived images of Arctic sea ice extent in the summer of 1979 (left image), and the summer (September) and winter (March) of 2021 (right image, with September on the left). Sea ice shrinks during summer months and expands to its maximum extent during the winter.

Over the interval from 1979 to 2021, Arctic summer ice extent decreased by approximately 30%; while it still embraces northern Greenland, it no longer reaches the Russian coast. The left graph in the next figure compares the monthly variation of Arctic ice extent from its March maximum to the September minimum, for the years 2021 (blue curve) and 2008 (green curve). The 2021 summer minimum is seen to be almost identical to that in 2008, with the black curve depicting the median extent over the period from 1981 to 2010.

The right graph in the figure shows the estimated month-by-month variation of Arctic ice volume in recent years. The volume depends on both ice extent and its thickness, which varies with location as well as season – the thickest, and oldest, winter ice currently lying along the northern coasts of the Canadian Arctic Archipelago and Greenland.

Arctic ice thickness is notoriously difficult to measure, the best data coming from limited submarine observations. According to one account based on satellite data, more than 75% of the Arctic winter ice pack today consists of thin ice just a few months old, whereas in the past it was only 50%. However, these estimates are unreliable and a trio of Danish research institutions that monitor the Arctic estimate that the ice volume has changed very little over the last 17 years, as seen in the figure above.

Another indication that Arctic ice is not melting as fast as climate activists claim is the state of the Northwest Passage – the waterway between the Atlantic and Pacific Oceans through the Arctic Ocean, along the coast of North America. Although both the southern and northern routes of the Northwest Passage have been open intermittently since 2007, ice conditions this year are relatively severe compared to the past two decades: thicker multiyear ice is the main hazard. The northern deep-water route is already choked with ice and will not open until at least next year.

In the Antarctic, sea ice almost disappears completely during the southern summer and reaches its maximum extent in September, at the end of winter. This is illustrated in the satellite-derived images below, showing the summer minimum (left image) and winter maximum extent (right image) in 2021. The Antarctic winter sea ice extent is presently well above its long-term average.

In fact, despite the long-term loss of ice in the Arctic, the sea ice around Antarctica has expanded slightly during the satellite era, as shown in the following figure up to 2020. Although the maximum Antarctic ice extent (shown in red) fluctuates greatly from year to year, and took a tumble in 2017, it has grown at an average rate between 1% and 2% per decade (dashed red line) since 1979.

Note that the ice losses shown in this figure are “anomalies,” or departures from the monthly mean ice extent for the period from 1981 to 2010, rather than the minimum extent of summer ice. So the Arctic data don’t reveal how the 2021 minimum was almost identical to 2008, as illustrated in the earlier figures.

Several possible reasons have been put forward for the greater fluctuations in Antarctic winter sea ice compared to that in the Arctic. One analysis links the Antarctic oscillations to ENSO (the El Niño – Southern Oscillation), a natural cycle that causes variations in mean temperature and other climatic effects in tropical regions of the Pacific Ocean. The Pacific impinges on a substantial portion of the Southern Ocean that surrounds Antarctica.

The analysis suggests that the very large winter ice extents of 2012, 2013 and 2014 were a consequence of the 2012 La Niña, which is the cool phase of ENSO. Reinforcing that idea is the fact that this year’s surge in ice extent follows another La Niña earlier in 2021; the big loss of sea ice in 2017 could be associated with 2016’s strong El Niño, the warm phase of ENSO. The natural Pacific Decadal Oscillation may also play a role.

Next: Ice Sheet Update (1): Evidence That Antarctica Is Cooling, Not Warming

Challenges to the CO2 Global Warming Hypothesis: (4) A Minimal Ice-Age Greenhouse Effect

As an addendum to my 2020 series of posts on the CO₂ global warming hypothesis (here, here and here), this post presents a further challenge to the hypothesis central to the belief that humans make a substantial contribution to climate change. The hypothesis is that observed global warming – currently about 1 degree Celsius (1.8 degrees Fahrenheit) since the preindustrial era – has been caused primarily by human emissions of CO₂ and other greenhouse gases into the atmosphere.

The new challenge to the CO₂ hypothesis is set out in a recent research paper by French geologist Pascal Richet. Richet claims, by reexamining previous analyses of an Antarctic ice core, that greenhouse gases such as CO₂ and methane had only a minor effect on the earth’s climate over the past 423,000 years, and that the assumed forcing of climate by CO₂ is incompatible with ice-core data. The paper is controversial, however, and the publisher has subjected it to a post-publication review, as a result of which the paper has since been removed.

The much-analyzed ice core in question was drilled at the Russian Vostok station in East Antarctica. Past atmospheric CO₂ levels and surface temperatures are calculated from ice cores by measuring the air composition and the oxygen ¹⁸O to ¹⁶O isotopic ratio, respectively, in air bubbles trapped by the ice. The Vostok record, which covers the four most recent ice ages or glaciations as well as the current interglacial (Holocene), is depicted in the figure below. The CO₂ level is represented by the upper set of graphs (below the insolation data), and shows the substantial drop in CO₂ during an ice age; the associated drop in temperature ΔT is represented by the lower set of graphs.

It is seen that transitions from glacial to interglacial conditions are relatively sharp, while the ice ages themselves are punctuated by smaller warming and cooling episodes. And, though it’s hardly visible in the figure, the ice-age CO₂ level closely mimics changes in temperature, but the CO₂ concentration lags behind – with CO₂ going up or down after the corresponding temperature shift occurs. The lag is more pronounced for temperature declines than increases.

The oceans, which are where the bulk of the CO₂ on our planet is stored, can hold much more CO₂ (and heat) than the atmosphere. Warm water holds less CO₂ than cooler water, so the oceans release CO₂ when the temperature rises, but take it in when the earth cools.

Richet noticed that the temperature peaks in the Vostok record are much narrower than the corresponding CO₂ peaks. The full widths at half maximum, marked by thick horizontal bars in the figure above, range from about 7,000 to 16,000 years for the initial temperature peak in cycles II, III and IV, but from 14,000 to 23,000 years for the initial CO₂ peak; cycle V can’t be analyzed because its start is missing from the data. All other peaks are also narrower for temperature than for CO₂.

The author argues that CO₂ can’t drive temperature since an effect can’t last for a shorter period of time than its cause. The fact that the peaks are systematically wider for CO₂ than for temperature implies that the CO₂ level responds to temperature changes, not the other way round. And for most of cycles II, III and IV, CO₂ increases correspond to temperature decreases and vice versa.

Richet’s conclusion, if correct, would deal a deathblow to the CO₂ global warming hypothesis. The reason has to do with the behavior of the temperature and CO₂ level at the commencement and termination of ice ages.

Ice ages are believed to have ended (and begun) because of changes in the Earth’s orbit around the sun. After tens of thousands of years of bitter cold, the temperature suddenly took an upward turn. But according to the CO₂ hypothesis, the melting of ice sheets and glaciers caused by the slight initial warming could not have continued, unless this temperature rise was amplified by positive feedbacks. These include CO₂ feedback, triggered by a surge in atmospheric CO₂ as it escaped from the oceans.

The problem with this explanation is that it requires a similar chain of events, based on CO₂ and other feedbacks, to have enhanced global cooling as the temperature fell at the beginning of an ice age. But, says Richet, “From the dual way in which feedback would work, temperature decreases and increases should be similar for the same concentrations of greenhouse gases, regardless of the residence times of these gases in the atmosphere.” The fact that temperature decreases don’t depend in any straightforward way on CO₂ concentration in the figure above demonstrates that the synchronicity required by the feedback mechanism is absent.

Next: Fishy Business: Alleged Fraud over Ocean Acidification Research, Reversal on Coral Extinction

Growing Antarctic Sea Ice Defies Climate Models

We saw in the previous post how computer climate models greatly exaggerate short-term warming. Something else they get wrong is the behavior of Antarctic sea ice. According to the models, sea ice at both the North and South Poles should shrink as global temperatures rise. It’s certainly contracting in the Arctic, faster in fact than most models predict, but contrary to expectations, sea ice in the Antarctic is actually expanding.

Scientific observations of sea ice in the Arctic and Antarctic have only been possible since satellite measurements began in 1979. The figure below shows satellite-derived images of Antarctic sea ice extent at its summer minimum in 2020 (left image), and its previous winter maximum in 2019 (right image). Sea ice expands to its maximum extent during the winter and contracts during summer months.

But in contrast to the increase in the maximum extent of sea ice around Antarctica shown by observations during the satellite era, the computer models all simulate a decrease. Two research groups have investigated this decrease in detail for the previous generation of CMIP5 models.

One of the groups is the BAS (British Antarctic Survey), which has a long history of scientific studies of Antarctica dating back to World War II and before. Their 2013 assessment of 18 CMIP5 climate models found marked differences in the modeled trend in month-to-month Antarctic sea ice extent from that observed over the previous 30 years, as illustrated in the next figure. The thick blue line at the top indicates the trend in average monthly ice extent measured over the period from 1979 to 2005, and the colored lines are the monthly trends simulated by the various models; the black line is the model mean.

It’s seen that almost all models exhibit an incorrect negative trend for every month of the year. The mean monthly trend for all models is a decline of -3.2% per decade between 1979 and 2005, with the largest mean monthly decline being -13.6% per decade in February. But the actual observed gain in Antarctic sea ice extent is (+)1.1% per decade from 1979 to 2005 according to the BAS, or a somewhat higher 1.8% per decade from 1979 to 2019, as estimated by the U.S. NSIDC (National Snow and Ice Data Center) and depicted below.

For actual sea ice extent, the majority of models simulate too meager an extent at the February minimum, while several models estimate less than two thirds of the real-world extent at the September maximum. Similar results were obtained in a study by a Chinese research group, as well as other studies.

The discrepancy in sea ice extent between the empirical satellite observations and the climate models is particularly pronounced on a regional basis. At the February minimum, the satellite data indicate substantial residual ice in the Weddell Sea to the east of the Antarctic Peninsula (see the first figure above), whereas most models show very little. And the few models that simulate a realistic amount of February sea ice fail to reproduce the loss of ice in the Ross Sea adjoining West Antarctica.

All these differences indicate that computer models are not properly simulating the physical processes that govern Antarctic sea ice. Various possible processes not incorporated in the models have been suggested to explain the model deficiencies. These include freshening of seawater by melting ice shelves attached to the Antarctic ice sheet; meltwater from rain; and atmospheric processes involving clouds or wind.

BAS climate modeler Paul Holland thinks the seasons may hold the key to the conundrum, having noticed that trends in sea ice growth or shrinkage vary in strength in the different seasons. Holland surmised that it was more important to look at how fast the ice was growing or shrinking from season to season than focusing on changes in ice extent. His calculations of the rate of growth led him to conclude that seasonal wind trends play a role.

The researcher found that winds are spreading sea ice out in some regions of Antarctica, while compressing or keeping it intact in others, and that these effects begin in the spring. “I always thought, and as far as I can tell everyone else thought, that the biggest changes must be in autumn, Holland said. “But the big result for me now is we need to look at spring. The trend is bigger in the autumn, but it seems to be created in spring.”

That’s where Holland’s research stands for now. More detailed work is required to check out his novel idea.

Next: Good Gene – Bad Gene: When GMOs Succeed and When They Don’t

Both Greenland and Antarctic Ice Sheets Melting from Below

Amidst all the hype over melting from above of the Antarctic and Greenland ice sheets due to global warming, little attention has been paid to melting from below due to the earth’s volcanic activity. But the two major ice sheets are in fact melting on both top and bottom, meaning that the contribution of global warming isn’t as large as climate activists proclaim.

In central Greenland, Japanese researchers recently discovered a flow of molten rocks, known as a mantle plume, rising up beneath the island. The previously unknown plume emanates from the boundary between the earth’s core and mantle (labeled CMB in the following figure) at a depth of 2,889 km (1,795 miles), and melts Greenland’s ice from below.

As the figure shows, the Greenland plume has two branches. One of the branches feeds into the similar Iceland plume that arises underneath Iceland and supplies heat to an active volcano there. The Greenland plume provides heat to an active volcano on the island of Jan Mayen in the Arctic Ocean, as well as a geothermal area in the Svalbard archipelago in the same ocean.

To study the plume, the research team used seismic topography – a technique, similar to a CT scan of the human body, that constructs a three-dimensional image of subterranean structures from differences in the speed of earthquake sound waves traveling through the earth. Sound waves pass more slowly through rocks that are hotter, less dense or hydrated, but more quickly through rocks that are colder, denser or drier. The researchers took advantage of seismographs forming part of the Greenland Ice Sheet Monitoring Network, set up in 2009, to analyze data from 16,257 earthquakes recorded around the world.

The existence of a mantle plume underneath Antarctica, originating at a depth of approximately 2,300 km (1,400 miles), was confirmed by a Caltech (California Institute of Technology) study in 2017. Located under West Antarctica (labeled WA in the next figure), the plume generates as much as 150 milliwatts of heat per square meter – heat that feeds several active volcanoes and also melts the overlying ice sheet from below. For comparison, the earth’s geothermal heat is 40-60 milliwatts per square meter on average, but reaches about 200 milliwatts per square meter beneath geothermally active Yellowstone National Park in the U.S.

A team of U.S. and UK researchers found in 2018 that one of the active volcanoes drawing heat from the mantle plume in West Antarctica is making a major contribution to the melting of the Pine Island Glacier. The Pine Island Glacier, situated adjacent to the Thwaites Glacier in the figure above, is the fastest melting glacier in Antarctica, responsible for about 25% of the continent’s ice loss.   

The researchers’ discovery was serendipitous. Originally part of an expedition to study ice melting patterns in seawater close to West Antarctica, the team was surprised to find high concentrations of the gaseous helium isotope ³He near the Pine Island Glacier. Because ³He is found almost exclusively in the earth’s mantle, where it’s given off by hot magma, the gas is a telltale sign of volcanism.

The study authors calculated that the volcano buried underneath the Pine Island Glacier released at least 2,500 megawatts of heat to the glacier in 2014, which is about 60% of the heat released annually by Iceland’s most active volcano and roughly 25 times greater than the annual heating caused by any one of over 100 dormant Antarctic volcanoes.

A more recent study by the British Antarctic Survey found evidence for a hidden source of heat beneath the ice sheet in East Antarctica (labeled EA in the figure above). From ice-penetrating radar data, the scientists concluded that the heat source is a combination of unusually radioactive rocks and hot water coming from deep underground. The heat melts the base of the ice sheet, producing meltwater which drains away under the ice to fill subglacial lakes. The estimated geothermal heat flux is 120 milliwatts per square meter, comparable to the 150 milliwatts per square meter from the mantle plume underneath West Antarctica that was discussed above.

All these hitherto unknown subterranean heat sources in Antarctica and Greenland, just like global warming, melt ice and contribute to sea level rise. However, as I’ve discussed in previous posts (see here and here), the giant Antarctic ice sheet may not be melting at all overall, and the Greenland ice sheet is only losing ice slowly.

Next: Science on the Attack: The Vaccine Revolution Spurred by Messenger RNA

No Convincing Evidence That Antarctic Ice Sheet Is Melting

Of all the observations behind mass hysteria over our climate, none induces as much panic as melting of the earth’s two biggest ice sheets, covering the polar landmasses of Antarctica and Greenland. As long ago as 2006, Al Gore’s environmental documentary “An Inconvenient Truth” proclaimed that global warming would melt enough ice to cause a 6-meter (20-foot) rise in sea level “in the near future.” Today, every calving of a large iceberg from an ice shelf or glacier whips the mainstream media into a frenzy.

The huge Antarctic ice sheet alone would raise global sea levels by about 60 meters (200 feet) were it to melt completely. But there’s little evidence that the kilometers-thick ice sheet, which contains about 90% of the world’s freshwater ice, is melting at all.

Any calving of large icebergs – a natural process unrelated to warming – from an ice shelf, or even disintegration into small icebergs, barely affects sea level. This is because the ice that breaks off was already floating on the ocean. Although a retreating ice shelf can contribute to sea level rise by accelerating the downhill flow of glaciers that feed the shelf, current breakups of Antarctic ice shelves are adding no more than about 0.1 mm (about 4/1000ths of an inch) per year to global sea levels, according to NOAA (the U.S. National Oceanic and Atmospheric Administration).

Global warming has certainly affected Antarctica, though not by as much as the Arctic. East Antarctica, by far the largest region that covers two thirds of the continent, heated up by only 0.06 degrees Celsius (0.11 degrees Fahrenheit) per decade between 1958 and 2012. At the South Pole, which is located in East Antarctica, temperatures actually fell in recent decades.

For comparison, global temperatures over this period rose by 0.11 degrees Celsius (0.20 degrees Fahrenheit) per decade, and Arctic temperatures shot up at an even higher rate. Antarctic warming from 1958 to 2012 is illustrated in the figure below, based on NOAA data. East Antarctica is to the right, West Antarctica to the left of the figure.

You can see, however, that temperatures in West Antarctica and the small Antarctic Peninsula, which points toward Argentina, increased more rapidly than in East Antarctica, by 0.22 degrees Celsius (0.40 degrees Fahrenheit) and 0.33 degrees Celsius (0.59 degrees Fahrenheit) per decade, respectively – faster than the global average. Still, the Peninsula has cooled since 2000.

It’s not surprising, therefore, that all the hype about imminent collapse of the Antarctic ice sheet centers on events in West Antarctica, such as glaciers melting at rapid rates. The Fifth Assessment Report of the UN’s IPCC (Intergovernmental Panel on Climate Change) maintained with high confidence that, between 2005 and 2010, the ice sheet was shedding mass and causing sea levels to rise by 0.41 mm per year, contributing about 24% of the measured rate of 1.7 mm (1/16th of an inch) per year between 1900 and 2010.

On the other hand, a 2015 NASA study reported that the Antarctic ice sheet was actually gaining rather than losing ice in 2008, and that ice thickening was making sea levels fall by 0.23 mm per year. The study authors found that the ice loss from thinning glaciers in West Antarctica and the Antarctic Peninsula was currently outweighed by new ice formation in East Antarctica resulting from warming-enhanced snowfall. Across the continent, Antarctica averages roughly  5 cm (2 inches) of precipitation per year. The same authors say that the trend has continued until at least 2018, despite a recent research paper by an international group of polar scientists endorsing the IPCC human-caused global warming narrative of diminishing Antarctic ice.

The two studies are both based on satellite altimetry – the same method used to measure sea levels, but in this case measuring the height of the ice sheet. Both studies also depend on models to correct the raw data for factors such as snowdrift, ice compaction and motion of the underlying bedrock. It’s differences in the models that give rise to the diametrically opposite results of the studies, one finding that Antarctic ice is melting away but the other concluding that it’s really growing.

Such uncertainty, even in the satellite era, shouldn’t be surprising. Despite the insistence of many climate scientists that theirs is a mature field of research, much of today’s climate science is dependent on models to interpret the empirical observations. The models, just like computer climate models, aren’t always good representations of reality.

Al Gore’s 6-meter (20-foot) rise hasn’t happened yet, and isn’t likely to happen even by the end of this century. Global panic over the impending meltdown of Antarctica is totally unwarranted.

(This post has also been kindly reproduced in full on the Climate Depot blog.)

Next: No Convincing Evidence That Greenland Ice Sheet Is Melting Rapidly

Shrinking Sea Ice: Evaluation of the Evidence

Most of us know about the loss of sea ice in the Arctic due to global warming. The dramatic reduction in summer ice cover, which has continued for almost 40 years, is frequently hyped by the mainstream media and climate activists as an example of what we’re supposedly doing to the planet.

But the loss is nowhere near as much as predicted, and in fact was no more in the summer of 2019 than in 2007. Also, it’s little known that Arctic sea ice has melted before during the record heat of the 1930s. And the sea ice around Antarctica, at the other end of the globe, has been expanding since at least 1979.

Actual scientific observations of sea ice in the Arctic and Antarctic have only been possible since satellite measurements began in 1979. The figure below shows satellite-derived images of Arctic sea ice extent in the summer of 1979 (left image), and the summer (September) and winter (March) of 2018 (right image). Sea ice expands to its maximum extent during the winter and shrinks during summer months.   

Arctic summer ice extent decreased by approximately 33% over the interval from 1979 to 2018; while it still encases northern Greenland, it no longer reaches the Russian coast.

However, there has been no net ice loss since 2007, with the year-to-year minimum extents fluctuating around a plateau. An exception was 2012, when a powerful August storm known as the Great Arctic Cyclone tore off a large chunk of ice from the main sea ice pack. Clearly, the evidence refutes numerous prognostications by advocates of catastrophic human-caused warming that Arctic ice would be completely gone by 2016. 

Before 1979, the only data available on Arctic sea ice are scattered observations from sources such as ship reports, aircraft reconnaissance and drifting buoys – observations recorded and synthesized by the Danish Meteorological Institute and the Russian Arctic and Antarctic Research Institute. Analyses of this spotty data have resulted in numerous reconstructions of Arctic sea ice extent in the pre-satellite era.

One such recent reconstruction is shown in the next figure, depicting reconstructed Arctic summer ice area, in millions of square kilometers, from 1900 to 2013. The reconstruction was based on the strong correlation of Arctic sea ice extent with Arctic air temperatures during the satellite era, especially in the summer, a correlation assumed to be the same in earlier years as well. This assumption then enabled the researchers to reconstruct the sea ice area before 1979 from observed temperatures in that era.  

What this graph reveals is that summer ice cover in the Arctic, apart from its present decline since about 1979, contracted previously in the 1920s and 1930s. According to the researchers, the biggest single-year decrease in area, which occurred in 1936, was about 26% – not much less than the 33% drop by 2018. Although this suggests that the relatively low sea ice extents in recent years are comparable to the 1930s, the reconstruction doesn’t incorporate any actual pre-satellite observations. Other reconstructions that do incorporate the earlier data show a smaller difference between the 1930s and today.

It’s the opposite story for sea ice in the Antarctic, which is at its lowest extent during the southern summer in February, as shown in the satellite-derived image below for 2018-19.

Despite the contraction in the Arctic, the sea ice around Antarctica has been expanding during the satellite era. As can be seen from the following figure, Antarctic sea ice has gained in extent by an average of 1.8% per decade (the dashed line represents the trend), though the ice extent fluctuates greatly from year to year. Antarctic sea ice covers a larger area than Arctic ice but occupies a smaller overall volume, because it’s only about half as thick.

Another fallacious claim about disappearing sea ice in the Arctic, one that has captured the public imagination like no other, is that the polar bear population is diminishing along with the ice. But, while this may yet happen in the future, current evidence shows that the bear population has been stable for the whole period that the ice has been decreasing and may even be growing, according to the native Inuit.

In summary, Arctic sea ice shrank from about 1979 to 2007 because of global warming, but has remained at the same extent on average in the 12 years since then, while Antarctic sea ice has expanded slightly over the whole period. So there’s certainly no cause for alarm.

Next: No Convincing Evidence That Antarctic Ice Sheet is Melting