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

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

The record heat worldwide over the last few months – simultaneous heat waves in both the Northern and Southern Hemispheres, and abnormally warm oceans – has led to the hysterical declaration of “global boiling” by the UN Secretary General, the media and even some climate scientists. But a rational look at the data reveals that the cause may be natural sources, not human CO₂.

The primary source is undoubtedly the warming El Niño ocean cycle, a natural event that recurs at irregular intervals from two to seven years. The last strong El Niño, which temporarily raised global temperatures by about 0.14 degrees Celsius (0.25 degrees Fahrenheit), was in 2016. For comparison, it takes a full decade for current global warming to increase temperatures by that much. 

However, on top of the 2023 El Niño has been an unexpected natural source of warming – water vapor in the upper atmosphere, resulting from a massive underwater volcanic eruption in the South Pacific kingdom of Tonga in January 2022.

Normally, erupting volcanoes cause significant global cooling, from shielding of sunlight by sulfate aerosol particles in the eruption plume that linger in the atmosphere. Following the 1991 eruption of Mount Pinatubo in the Philippines, for example, the global average temperature fell by 0.6 degrees Celsius (1.1 degrees Fahrenheit) for more than a year.

But the eruption of the Hunga Tonga–Hunga Haʻapai volcano did more than just launch a destructive tsunami and shoot a plume of ash, gas, and pulverized rock 55 kilometers (34 miles) into the sky. It also injected 146 megatonnes (161 megatons) of water vapor into the stratosphere (the layer of the atmosphere above the troposphere) like a geyser. Because it occurred only about 150 meters (500 feet) underwater, the eruption immediately superheated the shallow seawater above and converted it explosively into steam.

Although the excess water vapor – enough to fill more than 58,000 Olympic-size swimming pools – was originally localized to the South Pacific, it quickly diffused over the whole globe. According to a recent study by a group of atmospheric physicists at the University of Oxford and elsewhere, the eruption boosted the water vapor content of the stratosphere worldwide by as much as 10% to 15%. 

Water vapor is a powerful greenhouse gas, the dominant greenhouse gas in the atmosphere in fact; it is responsible for about 70% of the earth’s natural greenhouse effect, which keeps the planet at a comfortable enough temperature for living organisms to survive, rather than 33 degrees Celsius (59 degrees Fahrenheit) cooler. So even 10–15% extra water vapor in the stratosphere makes the earth warmer.

The study authors estimated the additional warming from the Hunga Tonga eruption using a simple climate model combined with a widely available radiative transfer model. Their estimate was a maximum global warming of 0.035 degrees Celsius (0.063 degrees Fahrenheit) in the year following the eruption, diminishing over the next five years. The cooling effect of the small amount of sulfur dioxide (SO₂) from the eruption was found to be minimal.

As I explained in an earlier post, any increase in ocean surface temperatures from the Hunga Tonga eruption would have been imperceptible, at a minuscule 14 billionths of a degree Celsius or less. That’s because the oceans, which cover 71% of the earth’s surface, are vast and can hold 1,000 times more heat than the atmosphere. Undersea volcanic eruptions can, however, cause localized marine heat waves, as I discussed in another post.

Although 0.035 degrees Celsius (0.063 degrees Fahrenheit) of warming from the Hunga Tonga eruption pales in comparison with 2016’s El Niño boost of 0.14 degrees Celsius (0.25 degrees Fahrenheit), it’s nevertheless more than double the average yearly increase of 0.014 degrees Celsius (0.025 degrees Fahrenheit) of global warming from other sources such as greenhouse gases.

El Niño is the warm phase of ENSO (the El Niño – Southern Oscillation), a natural cycle that causes drastic temperature fluctuations and other climatic effects in tropical regions of the Pacific, as well as raising temperatures globally. Its effect on sea surface temperatures in the central Pacific is illustrated in the figure below. It can be seen that the strongest El Niños, such as those in 1998 and 2016, can make Pacific surface waters more than 2 degrees Celsius (3.6 degrees Fahrenheit) hotter for a whole year or so. 

Exactly how strong the present El Niño will be is unknown, but the heat waves of July suggest that this El Niño – augmented by the Hunga Tonga water vapor warming – may be super-strong. Satellite measurements showed that, in July 2023 alone, the temperature of the lower troposphere rose from 0.38 degrees Celsius (0.68 degrees Fahrenheit) to 0.64 degrees Celsius (1.2 degrees Fahrenheit) above the 1991-2020 mean.

If this El Niño turns out to be no stronger than in the past, then the source of the current “boiling” heat will remain a mystery. Perhaps the Hunga Tonga water vapor warming is larger than the Oxford group estimates. The source certainly isn’t any warming from human CO₂, which raises global temperatures gradually and not abruptly as we’ve seen in 2023.

Next: Has the Mainstream Media Suddenly Become Honest in Climate Reporting?

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

Recent Marine Heat Waves Caused by Undersea Volcanic Eruptions, Not Human CO2

In a previous post, I showed how submarine volcanic eruptions don’t contribute to global warming, despite the release of enormous amounts of explosive energy. But they do contribute to regional climate change in the oceans, such as marine heat waves and shrinkage of polar sea ice, explained a retired geologist in a recent lecture.

Wyss Yim, who holds positions at several universities in Hong Kong, says that undersea volcanic eruptions – rather than CO₂ – are an important driver of regional climate variability. The release of geothermal heat from these eruptions can explain oceanic heat waves, polar sea-ice changes and stronger-than-normal cycles of ENSO (the El Niño – Southern Oscillation), which causes temperature fluctuations and other climatic effects in the Pacific.

Submarine eruptions can eject basaltic lava at temperatures as high as 1,200 degrees Celsius (2,200 degrees Fahrenheit), often from multiple vents over a large area. Even though the hot lava is quickly quenched by the surrounding seawater, the heat absorbed by the ocean can have local, regional impacts that last for years.

The Pacific Ocean in particular is a major source of active terrestrial and submarine volcanoes, especially around the Ring of Fire bounding the Pacific tectonic plate, as illustrated in the figure below. Yim has identified eight underwater eruptions in the Pacific from 2011 to 2022 that had long-lasting effects on the climate, six of which emanated from the Ring of Fire.

One of these eruptions was from the Nishino-shima volcano south of Tokyo, which underwent a massive blow-out, initially undersea, that persisted from March 2013 to August 2015. Yim says the event was the principal cause of the so-called North Pacific Blob, a massive pool of warm seawater that formed in the northeast Pacific from 2013 to 2015, extending all the way from Alaska to the Baja Peninsula in Mexico and up to 400 meters (1,300 feet) deep. Climate scientists at the time, however, attributed the Blob to global warming.

The Nishino-shima eruption, together with other submarine eruptions in the Pacific during 2014 and 2015, was a major factor in prolonging and strengthening the massive 2014-2017 El Niño. A map depicting sea surface temperatures in January 2014, at the onset of El Niño and almost a year after the emergence of the Blob, is shown in the next figure. At that time, surface temperatures across the Blob were about 2.5 degrees Celsius (4.5 degrees Fahrenheit) above normal.

By mid-2014, the Blob covered an area approximately 1,600 km (1,000 miles) square. Its vast extent, states Yim, contributed to the gradual decline of Arctic sea ice between 2014 and 2016, especially in the vicinity of the Bering Strait. The Blob also led to two successive years without winter along the northeast Pacific coast.

Biodiversity in the region suffered too, with sustained toxic algal blooms. Yet none of this was caused by climate change.

The 2014-2017 El Niño was further exacerbated by the eruption from May to June 2015 of the Wolf volcano on the Galapagos Islands in the eastern Pacific. Although the Wolf volcano is on land, its lava flows entered the ocean. The figure below shows the location of the Wolf eruption, along with submarine eruptions of both the Axial Seamount close to the Blob and the Hunga volcano in Tonga in the South Pacific.

According to Yim, the most significant drivers of the global climate are changes in the earth’s orbit and the sun, followed by geothermal heat, and – only in third place – human-induced changes such as increased greenhouse gases. Geothermal heat from submarine volcanic eruptions causes not only marine heat waves and contraction of polar sea ice, but also local changes in ocean currents, sea levels and surface winds.

Detailed measurements of oceanic variables such as temperature, pressure, salinity and chemistry are made today by the worldwide network of 3,900 Argo profiling floats. The floats are battery-powered robotic buoys that patrol the oceans, sinking 1-2 km (0.6-1.2 miles) deep once every 10 days and then bobbing up to the surface, recording the properties of the water as they ascend. When the floats eventually reach the surface, the data is transmitted to a satellite.

Yim says his studies show that the role played by submarine volcanoes in governing the planet’s climate has been underrated. Eruptions of any of the several thousand active underwater volcanoes can have substantial regional effects on climate, as just discussed.

He suggests that the influence of volcanic eruptions on atmospheric and oceanic circulation should be included in climate models. The only volcanic effect in current models is the atmospheric cooling produced by eruption plumes.

Next: Climate Heresy: To Avoid Extinction We Need More, Not Less CO2

Are Current Hot and Cold Extremes Climate Change or Natural Variability?

While sizzling temperatures in Europe have captured the attention of the mainstream media, recent prolonged bouts of cold in the Southern Hemisphere have gone almost unnoticed. Can these simultaneous weather extremes be ascribed to climate change, or is natural variability playing a major role?

It’s difficult to answer the question because a single year is a short time in the climate record. Formally, climate is the average of weather, or short-term changes in atmospheric conditions, over a 30-year period. But it is possible to compare the current heat and cold in different parts of the globe with their historical trends.

The recent heat wave in western and southern Europe is only one of several that have afflicted the continent recently. The July scorcher this year, labeled unprecedented by the media, was in fact less severe than back-to-back European heat waves in the summer of 2019.

In the second 2019 wave, which also occurred in July, the mercury in Paris reached a new record high of 42.6 degrees Celsius (108.7 degrees Fahrenheit), besting the previous record of 40.4 degrees Celsius (104.7 degrees Fahrenheit) set back in July 1947. A month earlier, during the first heat wave, temperatures in southern France hit a blistering 46.0 degrees Celsius (114.8 degrees Fahrenheit). Both readings exceed the highest temperatures reported in France during the July 2022 heat wave.

Yet back in 1930, the temperature purportedly soared to a staggering 50 degrees Celsius (122 degrees Fahrenheit) in the Loire valley during an earlier French heat wave, according to Australian and New Zealand newspapers. The same newspapers reported that in 1870, the ther­mometer had reached an even higher, unspecified level in that region. Europe’s official all-time high-temperature record is 48.0 degrees Celsius (118.4 degrees Fahrenheit) set in 1977.

Although the UK, Portugal and Spain have also suffered from searing heat this year, Europe experienced an unseasonably chilly spring. On April 4, France experienced its coldest April night since records began in 1947, with no less than 80 new low-temperature records being established across the nation. Fruit growers all across western Europe resorted to drastic measures to save their crops, including the use of pellet stoves for heating and spraying the fruit with water to create an insulating layer of ice.

South of the Equator, Australia and South America have seen some of their coldest weather in a century. Australia’s misery began with frigid Antarctic air enveloping the continent in May, bringing with it 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 Alice Springs, which usually enjoys a balmy winter in the center of the country, has just endured 12 consecutive mornings of sub-freezing temperatures, surpassing the previous longest streak set in 1976.

South America too is experiencing icy conditions this year, 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. Later in the month the cold expanded north into Bolivia and Peru.

Based on history alone then, there’s nothing particularly unusual about the 2022 heat wave in Europe or the shivery winter down under, which included the coldest temperatures on record at the South Pole. Although both events have been attributed to climate change by activists and some climate scientists, natural explanations have also been put forward.

A recent study links the recent uptick in European heat waves to changes in the northern polar and subtropical jet streams. The study authors state that an increasingly persistent double jet stream pattern and its associated heat dome can explain "almost all of the accelerated trend" in heat waves across western Europe. Existence of a stable double-jet pattern is related to the blocking phenomenon, an example of which is shown in the figure below.

Blocking refers to a jet stream buckling that produces alternating, stationary highs and lows in pressure. Normally, highs and lows move on quickly, but the locking in place of a jet stream for several days or weeks can produce a heat dome. The authors say double jets and blocking are closely connected, but further research is needed to ascertain whether the observed increase in European double jets is part of internal natural variability of the climate system, or a response to climate change.

Likewise, it has been suggested that the frigid Southern Hemisphere winter may have a purely natural explanation, namely cooling caused by the January eruption of an undersea volcano in the South Pacific kingdom of Tonga. Although I previously showed how the massive submarine blast could not have contributed to global warming, it’s well known that such eruptions pour vast quantities of ash into the upper atmosphere, where it lingers and causes subsequent cooling by reflecting sunlight.

Next: Evidence for More Frequent and Longer Heat Waves Is Questionable

Can Undersea Volcanoes Cause Global Warming?

It’s well known that active volcanoes on land can cause significant global cooling when they erupt, from shielding of sunlight by sulfate aerosol particles in the eruption plume which linger in the atmosphere. But what is the effect on climate of undersea volcanic eruptions such as the massive submarine blast that blanketed the nearby South Pacific kingdom of Tonga with ash in January?

Submarine volcanoes are relatively unexplored but are thought to number over a million, of which several thousand may be currently active. Many lie along tectonic plate boundaries, where plates are pulling apart or colliding with each other. The Tonga volcano sits above a geological pileup, where the western edge of the Pacific plate dives under the Indian–Australian plate.

The eruption of any volcano releases a huge amount of energy. In the case of a submarine volcano that may be thousands of meters deep, the plume may not even reach the surface and all the energy is absorbed by the ocean. The Tonga eruption was from a shallow depth, so much of the energy was dissipated at the ocean surface – launching a destructive tsunami – and in the atmosphere – generating a plume of ash that reached a record altitude of 55 kilometers (34 miles), a shockwave that traveled around the globe, and nearly 400,000 lightning strikes.

You might think all that energy could contribute to global warming, had the volcano erupted in deeper water that would have converted all the energy to heat. However, the oceans, which cover 71% of the earth’s surface, are vast and can hold 1,000 times more heat than the atmosphere. Any change in sea surface temperatures from even multiple underwater volcanic eruptions would be imperceptible.

This can be seen from a simple calculation. According to NASA scientists, the energy released by the undersea Tonga eruption was equivalent to the explosive power of 3.6 to 16 megatonnes (4 to 18 megatons) of TNT. For comparison, the 1980 eruption on land of Mount Saint Helens in Washington state released about 22 megatonnes of TNT equivalent, and the famous 1883 explosion of Indonesia's Krakatoa unleashed 180 megatonnes; the atomic bomb that the U.S. dropped on Hiroshima in Japan in 1945 released roughly 14 kilotonnes of TNT equivalent.

The upper Tonga limit of 16 megatonnes is equal to 7.5 x 10¹⁶ Joules of energy. Assuming the heat capacity of seawater to be 3,900 Joules per kilogram per degree Celsius and the total mass of the oceans to be 1.4 × 10²¹ kilograms, it would take 5.5 × 10²⁴ Joules (5.5 trillion trillion Joules) to warm the entire ocean by 1 degree Celsius (1.8 degrees Fahrenheit).

So if all 16 megatonnes had gone into the ocean, ocean temperatures would have risen by (7.5 x 10¹⁶)/( 5.5 × 10²⁴) or a minuscule 1.4 x 10^-8 (14 billionths) of a degree Celsius. The Krakatoa above-water eruption, on the other hand, decreased global air temperatures by as much as 1.2 degrees Celsius (2.2 degrees Fahrenheit) for several years and may have cooled the oceans as well.

But there’s another potential source of warming from submarine volcanoes, and that is the CO₂ emitted along with the sulfur dioxide (SO₂) that causes cooling through formation of sulfate aerosols. If the underwater plume reaches the ocean surface, both gases are released into the atmosphere. In the case of Tonga, while the amount of SO₂ emitted was too small to have any cooling effect, the emitted CO₂ could in theory contribute to global warming.

However, the yearly average of CO₂ emissions from all volcanoes, both on land and submarine, is only 1 to 2% of current human emissions that have raised global temperatures by 1 degree Celsius (1.8 degrees Fahrenheit) at most. So any CO₂ warming effect from an underwater eruption is unlikely to be much larger than the above calculation for energy release. Interestingly though, Chinese researchers recently reported that the atmospheric concentration of CO₂ near Tonga after the eruption jumped by 2 parts per million, which is as much as the global concentration normally increases in a whole year from human sources. But this is most probably a temporary local effect that won’t affect the global CO₂ increase expected in 2022.

Despite the inability of undersea eruptions to affect our present climate, it was suggested in a 2015 research paper that CO₂ from submarine volcanoes may have triggered the warming that pulled the earth out of the last ice age about 15,000 years ago.

The basic idea is that lower sea levels during glaciation relieved the hydrostatic pressure on submarine volcanoes that suppressed eruptions during warmer times. This caused them to erupt more. After a lengthy ice age, the buildup of CO₂ from undersea eruptions initiated warming that then began to melt the ice sheets covering volcanoes on land, causing them in turn to belch CO₂ that enhanced the warming, melting more ice in a feedback effect.

Next: New Projections of Sea Level Rise Are Overblown

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

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.

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