Arctic News

Wednesday, December 11, 2019

The portent of runaway greenhouse warming

by Andrew Glikson
Earth and climate scientist
Australian National University

Figure 1. Relations between CO₂ levels in the atmosphere and mass extinctions of genera.

Data cited from D. Royer et al. (2002), from G. Keller (2016) and P. Wignall et al. (2002).

Carbon, the essential element underpinning photosynthesis and life, is transformed into toxic substances in the remnants of plants and organisms buried in sediments. Once released to the atmosphere in the form of CO₂, CO and methane, in large quantities these gases become lethal and have been responsible for mass extinctions of species (Fig. 1).

Figure 2. Potential heating, Carana (2019)

Given amplifying feedbacks from land and oceans triggered by rising temperatures, the concept of an upper limit of warming determined by limitation on carbon emissions alone is unlikely, since, under a rising high greenhouse gas concentration, amplifying feedbacks triggered by methane release, bushfires, warming oceans and loss of reflectivity of melting ice, temperatures would keep rising. As an example, findings show that warmer ocean water is melting hydrates and releasing methane into the sediment and waters off the coast of Washington state, at levels that reach the same amount of methane from the Deepwater Horizon blowout. Carana (2019) finds a potential for abrupt warming of 18°C or 32.4°F (Fig. 2).

Attempts at CO₂ drawdown (sequestration), if urgently applied on a global scale, may conceivably be able to slow down further warming. This article refers to natural methane reservoirs and human-induced methane emissions, indicating that, once temperatures supersede a critical level, a further rise in methane release would result regardless of restrictions of emissions.

According to Kelley (2003) a planetary “runaway greenhouse event” may be triggered when a planet overheats due to absorption of more solar energy than it can give off to retain equilibrium. As a result, the oceans may boil filling its atmosphere with steam, which leaves the planet uninhabitable, as Venus is now. Planetary geologists think there is good evidence that Venus was the victim of a runaway greenhouse effect which turned the planet into the boiling hell we see today. According to Hansen (2010): “If we burn all fossil fuels, the forcing will be at least comparable to that of the PETM, but it will have been introduced at least ten times faster. [. .] The warming ocean can be expected to affect methane hydrate stability at a rate that could exceed that in the PETM, where the rate of change was driven by the speed of the methane hydrate climate feedback, not by the nearly instantaneous introduction of all fossil fuel carbon.” In a critical review of the theory of runaway greenhouse warming, Goldblatt and Watson (2012) state: “We cannot therefore completely rule out the possibility that human actions might cause a transition, if not to full runaway, then at least to a much warmer climate state than the present one.”

The concentration of fossil carbon deposits in the form of coal, oil, natural gas, coal seam gas, permafrost methane, ice clathrates, shale oil, and oil sands, once released to the atmosphere in large quantities, generates powerful feedbacks from land, ocean, atmosphere and cryosphere. This includes further release of greenhouse gases, warming oceans, loss of reflectivity of melting ice, and bushfires, pushing temperatures further upward. With carbon dioxide concentrations rising at a rate of 2–3 parts per million (ppm) per year (October 2018: 406.00 ppm; October 2019: 408.53 ppm) and the Earth heating-up by 0.98°C since 1951-1980, the ultimate consequences of this trend belong to the unthinkable.

Through 2012, total accumulated emissions are estimated to have reached 384 GtC, with an annual amount of 43.1 billion tonnes of carbon dioxide expected to be added in 2019.

A 2016 IPCC analysis found that no more than 275 GtC of the world’s reserves of fossil fuels of 746 GtC could be emitted, if the global temperature rise is to be restricted to 2°C above pre-industrial temperatures, an impossible target since amplifying carbon feedbacks would push temperatures upwards.

According to Heede and Oreskes (2016), global reserves of oil (~171 GtC), natural gas (~95) and coal (479 GtC) add up to a total of 746 GtC. Hansen et al. (2013) estimates that recoverable fossil fuel reserves include ~120 GtC gas, ~80 GtC oil, >10,000 GtC coal, >2000 GtC unconventional gas, and ~700 GtC unconventional oil, adding up to a total of ~13,000 GtC (Fig. 3).

Figure 4. Vulnerable carbon pools. (A) Land: Permafrost ~900 GtC; High-latitude peatlands ~400 GtC;
Tropical peatlands ~100 GtC; Vegetation subject to fire and/or deforestation ~650 GtC;
(B) Oceans: Methane hydrates ~10,000 GtC; Solubility pump ~2700 GtC; Biological pump ~3300 GtC;
Total (A) + (B): ~18,050 GtC (Canadell 2007)

The amount of unstable methane deposits in permafrost and methane hydrates (clathrates) in ocean sediments is of a similar order of magnitude as the amount of fossil fuel reserves. Vulnerable carbon pools include methane hydrates in sediments (~10,000 GtC), solubility and biological pump (~6000 GtC), permafrost methane (~900 GtC), and peatlands and vulnerable vegetation (~1150 GtC), adding up to a total of ~18,050 GtC (Fig. 4).

Unoxidized metastable deposits of methane and methane hydrates, accumulated during the Pleistocene glacial-interglacial cycles and vulnerable to temperature rise, are already leaking as indicated by atmospheric concentrations which have risen from 1988 (~1700 ppb CH₄) to 2019 (~1860 ppb CH₄) at a rate of ~5.2 ppb/year, a rise of more than 4 ppm CO₂-equivalent at GWP25xCO₂ or 24 ppm CO₂-e at GWP150xCO₂.

Meinshausen et al. (2011) estimated global-mean surface temperature increases, applying a climate sensitivity of 3°C per doubling of CO₂, resulting by 2100 in a temperature rise of between 1.5°C to 4.5°C relative to pre-industrial levels. By 2300, under constant emissions, CO₂ concentrations would rise to ~2000 ppm, methane to 3.5 ppm and nitrous oxide to 0.52 ppm (Fig. 5). Amplifying feedbacks are taken into account, but the effects of tipping points and of cold ice-melt pools formed in the oceans near Greenland and Antarctica ice sheets are unclear.

Given the estimated total of exploitable hydrocarbon resources (~13.000 GtC) and of vulnerable carbon pools (~18,050 GtC), the amount released under different future climate conditions is subject to estimates:

Assuming mean global temperature of +2°C (above pre-industrial), with allowance made for the masking effects of sulphur aerosols, the combustion of ~2% of the fossil fuel reserves (13,000 GtC), i.e. ~260 GtC, would raise CO₂ concentration by ~130 ppm (100 GtC = 50 ppm CO₂) (Fig. 3). Combustion of ~5% of the fossil fuel reserve would raise CO₂ concentration by ~325 ppm.
Under +2°C above pre-industrial, release of CO₂ from fires and other feedback effects such as melting of permafrost and release of methane would raise atmospheric carbon by at least 1 percent of vulnerable carbon pools (~18,050 GtC).
The flow of ice melt water from Greenland and Antarctica into the oceans would create large regions of cold water capable of absorption of atmospheric CO₂.

Hansen (2010) concludes: “if we burn all reserves of oil, gas, and coal, there's a substantial chance that we will initiate the runaway greenhouse. If we also burn the tar sands and tar shale, I believe the Venus syndrome [runaway greenhouse warming] is a dead certainty”. Stephen Hawking (2017) appears to agree with Hansen’s warning, stating: “if the US pulls out of the Paris climate agreement it may lead to runaway global warming, eventually turning Earth's atmosphere into something resembling Venus”. Goldblatt and Watson (2012) wrote: “The ultimate climate emergency is a ‘runaway greenhouse’: a hot and water-vapor-rich atmosphere limits the emission of thermal radiation to space, causing runaway warming … This would evaporate the entire ocean and exterminate all planetary life … We cannot therefore completely rule out the possibility that human actions might cause a transition, if not to full runaway, then at least to a much warmer climate state than the present one … However, our understanding of the dynamics, thermodynamics, radiative transfer and cloud physics of hot and steamy atmospheres is weak.”

An analysis by Carana (2013) suggests that accelerated release of methane from permafrost and methane hydrates (clathrates) could trigger runaway global warming (Fig. 6). A polynomial trend for the Arctic shows temperature anomalies of +4°C by 2020, +7°C by 2030 and +11°C by 2040, threatening major feedbacks, further albedo changes and methane releases leading to global temperature anomalies of 20°C+ by 2050.

Figure 6. A polynomial 2 trend line points at global temperature anomalies (Carana 2013). A polynomial function is a function such as a quadratic, a cubic, a quartic, and so on, involving only non-negative integer powers of x.

The magnitude of the runaway greenhouse effect that now threatens to eventuate becomes evident when looking at the geological record. For example, the 55 million years-old PETM event (Paleocene-Eocene Thermal Maximum), lasting for about 100,000 years, driven by CO₂ levels as hugh as 1700 ppm, does not appear to have triggered a runaway greenhouse process. The PETM is attributed to ¹³C-depleted methane (Zeebe et al. 2009), reaching 5 - 8°C and leading to a mass extinction of 35-50% of benthic foraminifera. By sharp contrast, the current Anthropocene hyperthermal event, commencing with the industrial age and re-accelerating since about 1975, constitutes a temporally abrupt development exceeding the rate of geological hyperthermal events (Fig. 7), a rate which does not allow biological adaptation and thereby enhances a mass extinction of species (Barnosky et al. 2011).

Figure 7. A comparison of Cenozoic CO₂ rise rates and temperature rise rates,
highlighting the extreme rise rates in the Anthropocene. From an earlier post.

As Australia burns, the IPCC maintains there is time left to consume a carbon budget and to keep handing out offsets and carbon credits; at the 25th meeting of the Conference of the Parties to the United Nations Convention on Climate Change in Madrid, Australia is seeking to use "carry-over credits" to meet its pledged emissions reductions. The situation is illustrated by Sam Carana in the image below.

Andrew Glikson

Dr Andrew Glikson
Earth and climate scientist
Australian National University

Books:
- The Archaean: Geological and Geochemical Windows into the Early Earth
- The Asteroid Impact Connection of Planetary Evolution
- Asteroids Impacts, Crustal Evolution and Related Mineral Systems with Special Reference to Australia
- Climate, Fire and Human Evolution: The Deep Time Dimensions of the Anthropocene
- The Plutocene: Blueprints for a Post-Anthropocene Greenhouse Earth
- Evolution of the Atmosphere, Fire and the Anthropocene Climate Event Horizon
- From Stars to Brains: Milestones in the Planetary Evolution of Life and Intelligence

Links

• The RCP greenhouse gas concentrations and their extensions from 1765 to 2300, by Malte Meinshausen et al. (2011)
https://link.springer.com/article/10.1007/s10584-011-0156-z

• Contributions to accelerating atmospheric CO₂ growth from economic activity, carbon intensity, and efficiency of natural sinks, by J. Canadell et al. (2007)
https://www.pnas.org/content/104/47/18866

• Planetary ‘Runaway Greenhouse’ Climates More Easily Triggered than Previously Thought, by Peter Kelley (2013)
https://scitechdaily.com/planetary-runaway-greenhouse-climates-more-easily-triggered-than-previously-thought

• How Likely Is a Runaway Greenhouse Effect on Earth? MIT Technology Review (2012)
https://www.technologyreview.com/s/426608/how-likely-is-a-runaway-greenhouse-effect-on-earth/

• Storms of my grandchildren: the truth about the coming climate catastrophe and our last chance to save humanity, by James Hansen (2010)
https://www.bloomsbury.com/us/storms-of-my-grandchildren-9781608195022

• The runaway greenhouse: implications for future climate change, geoengineering and planetary atmospheres, by Colin Goldblatt and Andrew Watson (2012)
https://royalsocietypublishing.org/doi/full/10.1098/rsta.2012.0004

• Low simulated radiation limit for runaway greenhouse climates, by Colin Goldblatt, et al. (2013)
https://www.nature.com/articles/ngeo1892

• Assessing “Dangerous Climate Change”: Required Reduction of Carbon Emissions to Protect Young People, Future Generations and Nature, by James Hansen et al. (2013)
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0081648

• Towards the Sixth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC), by Valérie Masson-Delmotte, Panmao Zhai, Wilfran Moufouma-Okia, Anna Pirani, Jan Fuglestvedt
https://wg1.ipcc.ch/presentations/201612_Fuglestvedt_AGU_IPCC.pdf

• Global Carbon Project, Carbon Budget 2019, press release
https://www.globalcarbonproject.org/carbonbudget/19/files/Norway_CICERO_GCB2019.pdf

• Potential emissions of CO₂ and methane from proved reserves of fossil fuels: An alternative analysis, by Richard Heede and Naomi Oreskes
https://www.sciencedirect.com/science/article/pii/S0959378015300637

• A rise of 18°C or 32.4°F by 2026?
https://arctic-news.blogspot.com/2019/02/a-rise-of-18c-or-324f-by-2026.html

• Arctic Methane Impact
https://arctic-news.blogspot.com/2013/11/arctic-methane-impact.html

• A record CO2 rise rate since the KT dinosaur extinction 66 million years ago
http://arctic-news.blogspot.com/2019/11/a-record-co2-rise-rate-since-kt-dinosaur-extinction-66-million-years-ago.html

• Another link between CO2 and mass extinctions of species, by Andrew Glikson
https://theconversation.com/another-link-between-co2-and-mass-extinctions-of-species-12906

Wednesday, November 27, 2019

Accelerating greenhouse gas levels

The United Nations Environment Programme (UNEP) just released its annual Emissions Gap Report, warning that even if all current unconditional commitments under the Paris Agreement are implemented, temperatures are expected to rise by 3.2°C, bringing even wider-ranging and more destructive climate impacts.

The report adds that a continuation of current policies would lead to a global mean temperature rise of 3.5°C by 2100 (range of 3.4–3.9°C, 66% probability) and concludes that current policies will clearly not keep the temperature rise below 3°C and that temperatures may rise by much more than that.

Below is the UNEP video On the brink: Emissions Gap Report findings in 60 seconds.

[ image from earlier post ]

Indeed, the rise in greenhouse gas levels appears to be accelerating, despite pledges made under the Paris Agreement to holding the increase in the global average temperature to well below 2°C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5°C above pre-industrial levels.

The World Meteorological Organization (WMO) recently reported carbon dioxide (CO₂) concentrations for 2018 of 407.8 ppm (parts per million), as illustrated by the image on the right. The WMO adds that CO₂ levels, as well as methane and nitrous oxide levels, had all surged by higher amounts than during the past decade.

In energy, fossil fuel consumption for heating and transport increased. While renewables grew strongly in 2018, an even larger part of the growth in electricity was generated by fossil fuel, particularly by coal and natural gas.

As the image below shows, a trend based on NOAA March 1958 through October 2019 monthly mean CO₂ data at Mauna Loa points at CO₂ levels crossing the 415 ppm mark in 2020, when an El Niño is forecast to come, as discussed in an earlier post.

The added trend in the image points at CO₂ levels crossing 1200 ppm before the end of the century, triggering the cloud feedback tipping point that by itself could push up global temperatures by 8°C, within a few years. Importantly, the clouds feedback starts at 1200 ppm CO₂-equivalent. Besides a CO₂ rise, further elements could contribute to the 1200 ppm CO₂e tipping point getting reached, such as albedo changes due to disappearing Arctic sea ice and seafloor methane releases from a rapidly-warming Arctic Ocean.

In conclusion, a huge temperature rise could eventuate much earlier than by the end of the century. The image below illustrates the potential for a rise of 18°C or 32.4°F by 2026.

[ from an earlier post ]

As discussed in a recent post, a 2020 El Niño could be the catalyst triggering huge methane releases from the Arctic Ocean seafloor starting in 2020 and resulting in such a 18°C (or 32.4°F) temperature rise within a few years time. To put this into perspective, an earlier post concluded that humans will likely go extinct at a 3°C rise, as such an abrupt rise will make habitat for humans (and many other species) disappear.

In the video below, John Davis describes some of the extreme weather events that he experienced recently. “Disasters like this are man-made now”, John says, “they're not natural disasters. This is caused by climate change.”

Meanwhile, a recent study found that the consensus among research scientists on anthropogenic global warming has grown to 100%, based on a review of 11,602 peer-reviewed articles on “climate change” and “global warming” published in the first 7 months of 2019.

This further confirms the probability or likelihood that emissions by people are causing global warming, from a likely danger to certain danger. Furthermore, as discussed in many earlier posts, there are two additional dimensions to the danger of climate change; the severity of the impact makes it not merely a catastrophic danger, it is an existential threat; finally, regarding timescale, the danger is not just near, the danger is imminent and in many respects we're already too late.

Above image expresses this visually, with the red area depicting where we are now. There were readability problems with the text on the sides of the cube, reason why a version without text and the color on the sides was posted in an earlier post.

The situation is dire and calls for comprehensive and effective action, as described in the Climate Plan.

Links

• UN news release
https://www.unenvironment.org/news-and-stories/press-release/cut-global-emissions-76-percent-every-year-next-decade-meet-15degc

• Paris Agreement
https://unfccc.int/process-and-meetings/the-paris-agreement/the-paris-agreement

• United Nations Environment Programme (UNEP) - Emissions Gap Report
https://www.unenvironment.org/resources/emissions-gap-report-2019

• UNEP video: On the brink: Emissions Gap Report findings in 60 seconds
https://www.unenvironment.org/news-and-stories/video/brink-emissions-gap-report-findings-60-seconds

• WMO - Greenhouse gas concentrations in atmosphere reach yet another high
https://public.wmo.int/en/media/press-release/greenhouse-gas-concentrations-atmosphere-reach-yet-another-high

• NOAA Trends in Atmospheric Carbon Dioxide
https://www.esrl.noaa.gov/gmd/ccgg/trends/data.html

• Most Important Message Ever
https://arctic-news.blogspot.com/2019/07/most-important-message-ever.html

• 2020 El Nino could start 18°C temperature rise
https://arctic-news.blogspot.com/2019/11/2020-el-nino-could-start-18-degree-temperature-rise.html

• Scientists Reach 100% Consensus on Anthropogenic Global Warming
https://journals.sagepub.com/doi/full/10.1177/0270467619886266

• The Threat Of Arctic Albedo Change
https://arctic-news.blogspot.com/2016/09/the-threat-of-arctic-albedo-change.html

• Climate Plan
https://arctic-news.blogspot.com/p/climateplan.html

Sunday, November 24, 2019

The breach of the Paris Agreement

By Andrew Glikson
Earth and climate scientist
Australian National University

Since its inception the Paris Agreement has been in question due to, among other:

its broad definition, specifically holding the increase in the global average temperature to well below 2°C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5°C above pre-industrial levels;
its non-binding nature; and
accounting tricks by vested interests.

The goal assumes pre-determined limits can be placed on greenhouse gas levels and temperatures beyond which they would not continue to rise. Unfortunately these targets do not appear to take account of the amplifying positive feedback effects from land and oceans under the high cumulative greenhouse gas levels and their warming effects. Thus unfortunately the current high CO₂ levels of about 408 ppm and near-500ppm CO₂-equivalent (CO₂+methane+nitrous oxide) would likely continue to push temperatures upwards.

Significant climate science evidence appears to have been left out of the equation. The accord hinges on the need to reduce emissions, which is essential, but it does not indicate how further temperature rise can be avoided under the conditions of a high-CO₂ atmosphere, which triggers carbon release, unless massive efforts at sequestration (drawdown) of greenhouse gases are undertaken. Inherent in global warming are amplifying positive feedbacks, including albedo (reflection) decline due to the melting of ice and the opening of dark water surfaces, increased water vapor contents of the atmosphere in tropical regions which enhances the greenhouse effect, reduced sequestration of CO₂ by the warming oceans, desiccation of vegetation, fires, release of methane from permafrost and other processes. This means that even abrupt reductions in emissions may not be sufficient to stem global warming, unless accompanied by sequestration of greenhouse gases from the atmosphere to a lower level, recommended as below 350 ppm CO₂ by James Hansen, the leading climate scientist.

The world is on track to produce 50% more fossil fuels than can be burned before reaching the limit prescribed by the Paris Agreement, with currently planned coal, oil and gas outputs making the Paris Agreement goal impossible. Projected fossil fuel production in 2030 being more than is consistent with 2°C, and 120% more than that for 1.5°C.

Unbelievably, according to the International Monetary Fund, “In 2017 the world subsidized fossil fuels by $5.2 trillion, equal to roughly 6.5% of global GDP”, which is more than the total the world spends on human health. Such subsidies cannot possibly be consistent with the Paris Agreement. The pledge to end fossil fuel subsidies by 2025 by the G7 nations, with exceptions by the UK and Japan, may come too late as global CO₂ concentrations, already intersecting the stability limits of the Greenland and Antarctic ice sheets, are rising at a rate of 2 to 3 ppm per year, the highest in many millions of years.

Despite the scientific consensus regarding the anthropogenic origin of global warming, the world’s biggest fossil fuel corporations are taking a defiant stance against warnings that reserves of coal, oil and gas are already several times larger than can be burned if the world’s governments are to meet their pledge to tackle climate change. ExxonMobil said new reserves in the Arctic and Canadian tar sands must be exploited. Peabody Energy, the world’s largest private coal company, said global warming was “an environmental crisis predicted by flawed computer models”. Glencore Xstrata said that governments would fail to implement measures to cut carbon emissions. The World Bank and Bank of England have already warned of the “serious risk” climate action poses to trillions of dollars of fossil fuel assets.

Not to mention the risks to the living Earth and its billions of inhabitants!

The apparent neglect of scientific advice is not an isolated instance. It is not uncommon that climate reports are dominated by the views of economists, lawyers, bureaucrats and politicians, often overlooking the evidence presented by some of the world’s highest climate science authorities. Whereas the IPCC reports include excellent and comprehensive summaries of the peer-reviewed literature, the summaries for policy makers only partly represent the evidence and views of scientific authorities in the field, including those who have identified global warming in the first place.

Figure 2. from: James Hansen, data through June 2019

There exists a tendency in the media to report averages, such as average global temperature values, rather than the increasingly-common high zonal, regional and local anomalies.

For example, the annual mean global temperature rise of for 2018 is about one third the Arctic mean temperature rise (Fig. 2). Given that developments in the Arctic bear major consequences for climate change, the global mean does not represent the seriousness of the climate crisis.

Another example is the way extremes weather events are reported as isolated instances, neglecting the rising frequency and intensity of hurricanes, storms, fires and droughts, indicated in frequency plots (Fig 3.).

Figure 3. Rise in geophysical, meteorological, hydrologocal and climatological events. Munich RE.

It is not until international and national institutions take full account of what climate science is indicating that a true picture of the climate crisis will be communicated to the public.

Andrew Glikson

Dr Andrew Glikson
Earth and climate scientist
Australian National University

Books:
- The Archaean: Geological and Geochemical Windows into the Early Earth
- The Asteroid Impact Connection of Planetary Evolution
- Asteroids Impacts, Crustal Evolution and Related Mineral Systems with Special Reference to Australia
- Climate, Fire and Human Evolution: The Deep Time Dimensions of the Anthropocene
- The Plutocene: Blueprints for a Post-Anthropocene Greenhouse Earth
- Evolution of the Atmosphere, Fire and the Anthropocene Climate Event Horizon
- From Stars to Brains: Milestones in the Planetary Evolution of Life and Intelligence

Sunday, November 17, 2019

Arctic Ocean November 2019

On November 16, 2019, there was little sea ice between Greenland and Svalbard. For reference, the image below has been added, showing coastlines for the same area.

The image on the right shows that the average air temperature (2 m) on November 15, 2019, was 4°C higher over the Arctic than during 1979-2000.
Ocean heat is rising up from the Arctic Ocean, while a wavy jet stream enables cold air to leave the Arctic and descend over North America and Eurasia. On November 13, 2019, it was warmer in Alaska than in Alabama.

The image below shows temperatures north of 80°N. The red line on the image shows the 2019 daily mean temperature up to November 16, 2019. The temperature is now well above the 1958-2002 mean (green line). The image also shows the freezing point of fresh water (273.15K, 0°C or 32°F, blue line).

The freezing point for salt water is lower, at around -2°C, or 28.4°F, or 271.2°K. In other words, a rise in the salt content of the water alone can make ice melt, i.e. even when the temperature of the water doesn't rise.

The image below shows that Arctic sea ice volume has been at record low levels for the time of year for some time.

As the image below shows, Arctic sea ice extent in the Chukchi Sea is currently very low.

[ image by Zack Labe, uploaded November 13, 2019 ]

Oceans are absorbing more than 90% of global heating, as illustrated by the image below.

Arctic sea ice used to absorb 0.8% of global heating (in 1993 to 2003). Ocean heat keeps flowing into the Arctic Ocean, carried by ocean currents, as illustrated by the image below.

As peak heat arrives in the Arctic Ocean, it melts sea ice from below. In Summer 2019, a critical tipping point was crossed; ocean heat could no longer find further sea ice to melt, as the thick sea ice that hangs underneath the surface had disappeared. A thin layer of sea ice at the surface was all that remained, as air temperatures remained low enough to prevent it from melting from above.

This indicates that the buffer has gone that has until now been consuming ocean heat as part of the melting process. As long as there is sea ice in the water, this sea ice will keep absorbing heat as it melts, so the temperature will not rise at the sea surface. The amount of energy absorbed by melting ice is as much as it takes to heat an equivalent mass of water from zero to 80°C.

The images above and below shows very high sea surface temperature anomalies on the Northern Hemisphere for October 2015 and October 2019. In both cases, anomalies of 1.09°C or 1.96°F above the 20th century average were recorded.

The October 2015 anomaly occurred under El Niño conditions, whereas the equally-high anomaly in October 2019 occurred under El Niño/La Niña-neutral conditions, while another El Niño is likely to come in 2020. In other words, the threat is that even more ocean heat is likely to arrive in the Arctic Ocean in 2020.

The danger is particularly high in October, as Arctic sea ice starts growing in extent at the end of September, thus sealing off the water, meaning that less ocean heat will be able to escape to the atmosphere. This increases the danger that hot water will reach sediments at the Arctic Ocean seafloor and trigger massive methane eruptions.

Concentrations of carbon dioxide (CO₂, 407.8 ppm), methane (CH₄, 1869 ppb) and nitrous oxide (N₂O, 331.1 ppb) in 2018 surged by higher amounts than during the past decade, the WMO said in a recent news release and as illustrated by the image on the right, which shows that CH₄, CO₂ and N₂O levels in the atmosphere in 2018 were, respectively, 259%, 147% and 123% of their pre-industrial (before 1750) levels.

“There is no sign of a slowdown, let alone a decline, in greenhouse gases concentration in the atmosphere despite all the commitments under the Paris Agreement on Climate Change,” said WMO Secretary-General Petteri Taalas.

“It is worth recalling that the last time the Earth experienced a comparable concentration of CO2 was 3-5 million years ago. Back then, the temperature was 2-3°C warmer, sea level was 10-20 meters higher than now,” said Mr Taalas.

Global methane levels are very high. Mean global methane levels were as high as 1914 parts per billion on September 3, 2019, as discussed in a recent post. Peak methane levels as high as 2961 parts per billion were recorded by the MetOp-2 satellite on October 24, 2019, in the afternoon at 469 mb.

The situation is dire and calls for comprehensive and effective action, as described in the Climate Plan.

In the video below, Paul Beckwith discusses Arctic sea ice.