Thursday, March 18, 2021

Overshoot or Omnicide?

Questions and Answers with Sam Carana


Above image shows a non-linear blue trend based on 1880-2020 NASA Land+Ocean data that are adjusted 0.78°C to reflect a pre-industrial base, to more fully reflect strong polar warming, and to reflect surface air temperatures over oceans. This blue trend highlights that the 1.5°C threshold was crossed in 2012 (inset), while the 2°C threshold looks set to be crossed next year and a 3°C rise could be reached at the end of 2026.

Overshoot?

The blue trend in the image at the top shows the temperature rise crossing 1.5°C in 2012. Could this have been a temporary overshoot? Could the trend be wrong and could temperatures come down in future, instead of continuing to rise, and could temperatures fall to such extent that this will bring the average temperature rise back to below 1.5°C?

To answer this question, let's apply the method followed by the IPCC and estimate the average temperature rise over a 30-year period that is centered around the start of 2012, i.e. from 1997 to the end of 2026. The IPPC used a 30-year period in its Special Report on Global Warming of 1.5 ºC, while assuming that, for future years, the current multi-decadal warming trend would continue (see image below).


As said, the image at the top shows the temperature rise crossing 1.5°C in 2012. For the average temperature over the 30-year period 1997-2026 to be below 1.5°C, temperatures would have to fall over the next few years. Even if the temperature for 2021 fell to a level as low as it was in 2018 and remained at that same lower level until end 2026, the 1997-2026 average would still be more than 1.5°C above pre-industrial. Furthermore, for temperatures to fall over the next few years, there would need to be a fall in concentrations of greenhouse gases over the next few years, among other things. Instead, greenhouse gas levels appear to be rising steadily, if not at accelerating pace.

What did the IPCC envisage? As the image below shows, the IPCC in AR5 did envisage carbon dioxide under RCP 2.6 to be 421 ppm in 2100, while the combined CO₂e for carbon dioxide, methane and nitrous oxide would be 475 ppm in 2100.


The image below, based on a study by Detlef van Vuuren et al. (2011), pictures pathways for concentrations of carbon dioxide, methane and nitrous oxide, for each of four Representative Concentration Pathways (RCPs).


Above image shows that, for RCP 2.6 to apply in the above study, there is little or no room for a rise in these greenhouse gases. In fact, the study shows that methane levels would have to be falling dramatically. At the moment, however, methane concentrations show no signs of falling and instead appear to be following if not exceeding RCP 8.5, as discussed in a recent post and as also illustrated by the images below.

Greenhouse gas levels are rising

As the image below shows, the carbon dioxide (CO₂) level recorded at Mauna Loa, Hawaii, was 421.21 parts per million (ppm) on April 3, 2021on April 3, 2021. 


The N20 satellite recorded a methane peak of 2862 ppb on the afterrnoon of March 29, 2021, at 487.2 mb, as the image below shows.


A similarly high methane peak was recorded by the MetOp-1 satellite at 469 mb on the morning of April 4, 2021. 

Below are the highest daily mean methane levels recorded by the MetOp-1 satellite at selected altitudes on March 10 or 12, for the years 2013-2021, showing that methane levels are rising, especially at the higher altitude associated with 293 mb. 


Similarly, nitrous oxide levels show no signs of falling, as illustrated by the image below.


Methane grew 15.85 ppb in 2020, how fast could CO₂e rise

Rising greenhouse gas levels and associated feedbacks threaten to cause temperatures to keep rising, in a runaway scenario that cannot be reverted even if emissions by people were cut to zero.

Peaks in greenhouse gas levels could suffice to trigger the clouds feedback, which occurs when a CO₂e threshold of around 1,200 ppm is crossed, and the stratocumulus decks abruptly become unstable and break up into scattered cumulus clouds.

Once the clouds tipping point is crossed, it will be impossible to undo its impact, in line with the nature of a tipping point. In theory, CO₂ levels could come down after the stratocumulus breakup, but the stratocumulus decks would only reform once the CO₂ levels drop below 300 ppm.

recent post repeated the warning that by 2026, there could be an 18°C rise when including the clouds feedback, while humans will likely go extinct with a 3°C rise and most life on Earth will disappear with a 5°C rise. In conclusion, once the clouds feedback gets triggered, it cannot be reverted by people, because by the time the clouds feedback starts kicking in, people would already have disappeared, so there won't be any people around to keep trying to revert it.

[ click on images to enlarge ]
Methane levels are rising rapidly. The image to the right shows a trend that is based on NOAA 2006-2020 annual gobal mean methane data and that points at a mean of 3893 ppb getting crossed by the end of 2026. 

Why is that value of 3893 ppb important? On April 8, 2021, carbon dioxide reached a peak of 421.36 ppm, i.e. 778.64 ppm away from the clouds tipping point at 1200 ppm, and 778.64 ppm CO₂e translates into 3893 ppb of methane at a 1-year GWP of 200. 

In other words, a methane mean of 3893 ppb alone could cause the clouds tipping point to get crossed, resulting in an abrupt 8°C temperature rise. 

Such a high mean by 2026 cannot be ruled out, given the rapid recent growth in mean annual methane levels (15.85 ppb in 2020, see inset on image). 

Additionally, there are further warming elements than just carbon dioxide and methane, e.g. nitrous oxide and water vapor haven't yet been included in the CO₂e total.

Moreover, it may not even be necessary for the global mean methane level to reach 3893 ppb. A high methane peak in one single spot may suffice and a peak of 3893 ppb of methane could be reached soon, given that methane just reached a peak of 2862 ppb, while even higher peaks were reached over the past few years, including a peak of 3369 ppb recorded on the afternoon of August 31, 2018

Abrupt stratocumulus cloud shattering 

[ click on images to enlarge ]
Catastrophic crack propagation is what makes a balloon pop. Could low-lying clouds similarly break up and vanish abruptly?

Could peak greenhouse gas concentrations in one spot break up droplets into water vapor, thus raising CO₂e and propagating break-up of more droplets, etc., to shatter entire clouds?

In other words, an extra burst of methane from the seafoor of the Arctic Ocean alone could suffice to trigger the clouds tipping point and abruptly push temperatures up by an additional 8°C.

Omnicide?

This brings the IPCC views and suggestions into question. As discussed above, for the average temperature to come down to below 1.5°C over the period 1997-2026, temperatures would need to fall over the next few years. What again would it take for temperatures to fall over the next few years?

Imagine that all emissions of greenhouse gases by people would end. Even if all emissions of greenhouse gases by people could magically end right now, there would still be little or no prospect for temperatures to fall over the next few years. Reasons for this are listed below, and it is not an exhaustive list since some things are hard to assess, such as whether oceans will be able to keep absorbing as much heat and carbon dioxide as they currently do.

By implication, there is no carbon budget left. Suggesting that there was a carbon budget left, to be divided among polluters and to be consumed over the next few years, that suggestion is irresponsible. Below are some reasons why the temperature is likely to rise over the next few years, rather than fall.

How likely is a rise of more than 3°C by 2026?

• The warming impact of carbon dioxide reaches its peak a decade after emission, while methane's impact over ten years is huge, so the warming impact of the greenhouse gases already in the atmosphere is likely to prevent temperatures from falling and could instead keep raising temperatures for some time to come.

• Temperatures are currently suppressed. We're in a La Niña period, as illustrated by the image below.


[ click on images to enlarge ]
As NASA describes, El Niño events occur roughly every two to seven years. As temperatures keep rising, ever more frequent strong El Niño events are likely to occur. NOAA anticipates La Niña to re-emerge during the fall or winter 2021/2022, so it's likely that a strong El Niño will occur between 2023 and 2025. 

• Rising temperatures can cause growth in sources of greenhouse gases and a decrease in sinks. The image below shows how El Niño/La Niña events and growth in CO₂ levels line up. 


• We're also at a low point in the sunspot cycle. As the image on the right shows, the number of sunspots can be expected to rise as we head toward 2026, and temperatures can be expected to rise accordingly. According to James Hansen et al., the variation of solar irradiance from solar minimum to solar maximum is of the order of 0.25 W/m⁻².

• Add to this the impact of a recent Sudden Stratospheric Warming event. We are currently experiencing the combined impact of three short-term variables that are suppressing the temperature rise, i.e. a Sudden Stratospheric Warming event, a La Niña event and a low in sunspots.

Over the next few years, in the absence of large volcano eruptions and in the absence of Sudden Stratospheric Warming events, a huge amount of heat could build up at surface level. As the temperature impact of the other two short-term variables reverses, i.e. as the sunspot cycle moves toward a peak and a El Niño develops, this could push up temperatures substantially. The world could be set up for a perfect storm by 2026, since sunspots are expected to reach a peak by then and since it takes a few years to move from a La Niña low to the peak of an El Niño period.

• Furthermore, temperatures are currently also suppressed by sulfate cooling. This impact is falling away as we progress with the necessary transition away from fossil fuel and biofuel, toward the use of more wind turbines and solar panels instead. Aerosols typically fall out of the atmosphere within a few weeks, so as the transition progresses, this will cause temperatures to rise over the next few years. Most sulfates are caused by large-scale industrial activity, such as coal-fired power plants and smelters. A significant part of sulphur emissions is also caused by volcanoes. Historically, some 20 volcanoes are actively erupting on any particular day. Of the 49 volcanoes that erupted during 2021, 45 volcanoes were still active with continuing (for at least 3 months) eruptions as at March 12, 2021.

• Also holding back the temperature rise at the moment is the buffer effect of thick sea ice in the Arctic that consumes heat as it melts. As Arctic sea ice thickness declines, more heat will instead warm up the Arctic, resulting in albedo changes, changes to the Jet Stream and possibly trigger huge releases of methane from the seafloor. The rise in ocean temperature on the Northern Hemisphere looks very threatening in this regard (see image on the right) and many of these developments are discussed at the extinction page. There are numerous further feedbacks that look set to start kicking in with growing ferocity as temperatures keep rising, such as releases of greenhouse gases resulting from permafrost thawing and the decline of the snow and ice cover. Some 30 feedbacks affecting the Arctic are discussed at the feedbacks page.

• The conclusion of study after study is that the situation is worse than expected and will get even worse as warming continues. Some examples: a recent study found that the Amazon rainforest is no longer a sink, but has become a source, contributing to warming the planet instead; another study found that soil bacteria release CO₂ that was previously thought to remain trapped by iron; another study found that forest soil carbon does not increase with higher CO₂ levels; another study found that forests' long-term capacity to store carbon is dropping in regions with extreme annual fires; a recent post discussed a study finding that at higher temperatures, respiration rates continue to rise in contrast to sharply declining rates of photosynthesis, which under business-as-usual emissions would nearly halve the land sink strength by as early as 2040; the post also mentions a study on oceans that finds that, with increased stratification, heat from climate warming less effectively penetrates into the deep ocean, which contributes to further surface warming, while it also reduces the capability of the ocean to store carbon, exacerbating global surface warming; finally, a recent study found that kelp off the Californian coast has collapsed. So, both land and ocean sinks look set to decrease as temperatures keep rising, while a 2020 study points out that the ocean sink will also immediately slow down as future fossil fuel emission cuts drive reduced growth of atmospheric CO₂. 

Where do we go from here?

[ image from earlier post ]
The same blue trend that's in the image at the top also shows up in the image on the right, from an earlier post, together with a purple trend and a red trend that picture even worse scenarios than the blue trend.

The purple trend is based on 15 recent years (2006-2020), so it can cover a 30-year period (2006-2035) that is centered around end December 2020. As the image shows, the purple trend points at a rise of 10°C by 2026, leaving little or no scope for the current acceleration to slow, let alone for the anomaly to return to below 2°C.

The red trend is based on a dozen recent years (2009-2020) and shows that the 2°C threshold could already have been crossed in 2020, while pointing at a rise of 18°C by 2025.

In conclusion, temperatures could rise by more than 3°C by the end of 2026, as indicated by the blue trend in the image at the top. At that point, humans will likely go extinct, making it in many respects rather futile to speculate about what will happen beyond 2026. On the other hand, the right thing to do is to help avoid the worst things from happening, through comprehensive and effective action as described in the Climate Plan.


Links

• Climate Plan

• NOAA Global Climate Report - February 2021 - Monthly Temperature Anomalies Versus El Niño

• NOAA Northern Hemisphere Ocean Temperature Anomaly

• NOAA Sunspots - solar cycle progression

• Smithsonian Institution - Volcanoes - current eruptions

• IPCC Special Report Global Warming of 1.5 ºC - Summary for Policy Makers

• IPCC AR5 WG1 Summary for Policymakers - Box SPM.1: Representative Concentration Pathways

• The representative concentration pathways: an overview - by Detlef van Vuuren et al. (2011)

• Young people's burden: requirement of negative CO₂ emissions - by James Hansen et al. (2017)

• 2020: Hottest Year On Record

• What Carbon Budget?

• Most Important Message Ever

• High Temperatures October 2020

• Temperature keep rising

• More Extreme Weather

• Extinction

• Feedbacks

• Sudden Stratospheric Warming

• Possible climate transitions from breakup of stratocumulus decks under greenhouse warming - by Tapio Schneider  et al.

• Iron mineral dissolution releases iron and associated organic carbon during permafrost thaw - by Monique Patzner et al.

• Global maps of twenty-first century forest carbon fluxes - by Nancy Harris et al.

• A trade-off between plant and soil carbon storage under elevated CO2 - by César Terrer et al.

• Forests' long-term capacity to store carbon is dropping in regions with extreme annual fires

• Decadal changes in fire frequencies shift tree communities and functional traits - by Adam Pellegrini et al.

• NOAA - Annual Mean Growth Rate for Mauna Loa, Hawaii

• NOAA - Trends in Atmospheric Methane
https://www.esrl.noaa.gov/gmd/ccgg/trends_ch4

• The Climate Data Guide: Nino SST Indices - by Kevin Trenberth & NCAR Staff (Eds)
https://climatedataguide.ucar.edu/climate-data/nino-sst-indices-nino-12-3-34-4-oni-and-tni

• Historical change of El Niño properties sheds light on future changes of extreme El Niño - by Bin Wang et al. 

• NOAA - ENSO: Recent Evolution, Current Status and Predictions, April 12, 2021
https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/lanina/enso_evolution-status-fcsts-web.pdf

• Upper Ocean Temperatures Hit Record High in 2020 - by Lijing Cheng et al.

• Large-scale shift in the structure of a kelp forest ecosystem co-occurs with an epizootic and marine heatwave - by Meredith McPherson et al.

• External Forcing Explains Recent Decadal Variability of the Ocean Carbon Sink - by Galen McKinley et al. (2020) 
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019AV000149

• Maximum warming occurs about one decade after a carbon dioxide emission - by Katharine Ricke et al.

• Blue Ocean Event

• Confirm Methane's Importance

• FAQs

Sunday, March 7, 2021

Confirm Methane's Importance

Agriculture, land use and forestry responsible for half of people's greenhouse gases emissions?

The image on the right updates an image from an earlier post, illustrating the difference between using a Gobal Warming Potential (GWP) for methane of 150 over a few years versus 28 over 100 years. The IPCC in its special report Climate Change and Land assessed the impact of AFOLU (agriculture, forestry, and other land use) versus the impact of fossil fuel, etc., by using a GWP for methane of 28 over 100 years, referring to AR5, an earlier IPCC report. 

Since AR5 was published, a study found methane's 100-year GWP to be 14% higher than the IPCC value. The image on the right therefore uses a short-term GWP for methane of 171 in the panel on the right-hand side, 14% higher than the 150 used earlier.

When using this 171 GWP for methane and when including pre- and post-production activities in the food system, AFOLU (agriculture, forestry, and other land use) causes about half of people's 2007-2016 emissions. 

The black bar for methane at a GWP of 171 in the panel on the right-hand side further shows a far greater impact caused by fossil fuel, etc., in particular by the use of natural gas for heating buildings, generating electricity, etc.

Methane's one-year GWP is 200

The image below shows a trendline that is based on IPCC AR5 data that were similarly updated by 14% and that indicates that methane's one-year GWP is 200. 


Methane Levels Rising Rapidly

NOAA data show that methane's global mean for November 2020 was 1891.9 ppb, i.e. 16.3 ppb above the 1875.6 ppb global mean for November 2019. 

Social Cost of Methane

In a January 2021 executive order, President Biden called - among other things - for an update of the 'social cost of methane', to take account of climate risk, of environmental justice, and of intergenerational equity, and to have a dollar figure for agencies to use when monetizing the value of changes in greenhouse gas emissions resulting from regulations and other relevant agency actions. 

Of course, it should be painfully clear by now that the unfolding climate collapse is an existential threat, making it obviously and vitally important to act on methane. We simply cannot afford to delay action, we cannot afford to do so financially nor in any other way. So, what can and should be done?

Above suggestion to take strong action was posted Nov. 9, 2020 at facebook

Even when issuing a mandate, e.g., for a rapid transition to clean, renewable energy, the question remains how this is best implemented. To what extent could bans help speed up the necessary transition to clean, renewable energy? Examples are banning cars from entering (parts of) cities, banning the construction of new coal-fired power plants, banning fracking and banning natural gas hookups in new construction.

Image from the 2014 post Biochar Builds Real Assets
The Climate Plan likes local communities to decide what works best in their area, while recommending local feebates as the preferred policy tool. Indeed, fees that are set high enough can effectively ban specific alternatives. Furthermore, instead of using money, local councils could add extra fees to rates for land where soil carbon falls, while using all the revenues for rebates on rates for land where soil carbon rises; that way, biochar effectively becomes a tool to lower rates, while it will also help improve the soil's fertility, its ability to retain water and to support more vegetation.
That way, real assets are built.

We cannot afford to delay action

Mean global carbon dioxide was 413.28 ppm in November 2020. Mean global methane was 1891.9 ppb in November 2020, which at a 1-year GWP of 200 is 378.38 ppm CO₂e. Together, CO₂ and methane add up to 791.66 ppm CO₂e, which is 408.34 ppm CO₂e away from the 1200 ppm CO₂e clouds tipping point.

This 408.34 ppm CO₂e translates into a methane equivalent of 2042 ppb of methane (again using a 1-year GWP of 200), in other words, it would add about 5 Gt of methane, an amount similar to the methane that is aready in the atmosphere now.

Such a methane burst of about 5 Gt alone could suffice to raise the CO₂e level to 1200 ppm and trigger a further 8°C global temperature rise due to the couds feedback.

How likely is a large methane burst? Remember the warnings by Natalia Shakhova et al., who more than a decade ago concluded abrupt release of ;up to 50 Gt from the vast amounts of methane stored in the form of hydrates and free gas to be highly possible at any time. A recent study found methane leaking from a large pool of deep, preformed methane, indicating a large potential for abrupt future releases.

Keep in mind that the clouds feedback could aso be triggered with a much smaller methane burst, since such an event would also come with a collapse in industrial activity and the associated fall in sulfate cooling, numerous additional feedbacks, and huge rises in greenhouse gas emissions, next to the temperature rise due to such a methane burst itself. The total potential rise in global air temperature at land-ocean surface level from 1750 to 2026 could be 18°C when including the clouds feedback. Also keep in mind that humans will likely go extinct with a 3°C rise and most life on Earth will disappear with a 5°C rise.


High peak levels

Ominously, some very high peak levels were recently recorded by the MetOp-1 satellite in the afternoon at 469 mb, i.e. 2930 ppb on March 3 and 2878 ppb on March 4.


As discussed in an earlier post, next to seafloor methane, there are further warming elements that could contribute to a rapid acceleration of the temperature rise.

Conclusion

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


Links

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

• IPCC special report Climate Change and Land
https://www.ipcc.ch/report/srccl

• IPCC Report Climate Change and Land
https://arctic-news.blogspot.com/2019/08/ipcc-report-climate-change-and-land.html

• Radiative forcing of carbon dioxide, methane, and nitrous oxide: A significant revision of the methane radiative forcing - by Maryam Etminan et al. (2018)
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2016GL071930

• IPCC keeps feeding the addiction
https://arctic-news.blogspot.com/2018/10/ipcc-keeps-feeding-the-addiction.html

• How much warming have humans caused?
https://arctic-news.blogspot.com/2016/05/how-much-warming-have-humans-caused.html

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

• January 2021 executive order by President Biden on Protecting Public Health and the Environment and Restoring Science to Tackle the Climate Crisis

• NOAA mean global carbon dioxide
https://www.esrl.noaa.gov/gmd/ccgg/trends/gl_data.html

• Why stronger winds over the North Atlantic are so dangerous
https://arctic-news.blogspot.com/2020/02/why-stronger-winds-over-north-atlantic-are-so-dangerous.html

• Feedbacks in the Arctic
https://arctic-news.blogspot.com/p/feedbacks.html

• When will we die?
https://arctic-news.blogspot.com/2019/06/when-will-we-die.html

• 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

• Methane Hydrates Tipping Point threatens to get crossed
https://arctic-news.blogspot.com/2020/08/methane-hydrates-tipping-point-threatens-to-get-crossed.html

• Arctic Hit By Ten Tipping Points
https://arctic-news.blogspot.com/2020/04/arctic-hit-by-ten-tipping-points.html

• Crossing the Paris Agreement thresholds
https://arctic-news.blogspot.com/p/crossing.html

• 2°C crossed
https://arctic-news.blogspot.com/2020/03/2c-crossed.html

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

• Blue Ocean Event
https://arctic-news.blogspot.com/2018/09/blue-ocean-event.html

• Record Arctic Warming
https://arctic-news.blogspot.com/2016/04/record-arctic-warming.html

• There is no time to lose
https://arctic-news.blogspot.com/2020/11/there-is-no-time-to-lose.html

• Warning of mass extinction of species, including humans, within one decade
https://arctic-news.blogspot.com/2017/02/warning-of-mass-extinction-of-species-including-humans-within-one-decade.html

• Extinction
https://arctic-news.blogspot.com/p/extinction.html

• Frequently Asked Questions: How much methane is stored in hydrates and how much of this could be released, say, within a few years?

• Source apportionment of methane escaping the subsea permafrost system in the outer Eurasian Arctic Shelf - by Julia Steinbach et al.

• 2020: Hottest Year On Record

Monday, February 22, 2021

Snowstorms, the breach of the Arctic vortex and the effects of ice meltwater on the oceans

by Andrew Glikson

Warnings by leading climate scientists regarding the high sensitivity of the atmosphere in response to abrupt compositional changes, such as near-doubling of greenhouse gas concentrations, are now manifest: According to Wallace Broecker, (the “father” of climate science) “The paleoclimate record shouts out to us that, far from being self-stabilizing, the Earth's climate system is an ornery beast which overreacts to even small nudges, and humans have already given the climate a substantial nudge”. As stated by James Zachos, “The Paleocene hot spell should serve as a reminder of the unpredictable nature of climate”.

As snowstorms such as the Beast from the East (2018) and Storm Darcy (2021) sweep the northern continents, reaching Britain and as far south as Texas and Greece, those who still question the reality and consequences of global climate change, including in governments, may rejoice as if they have a new argument to question global warming.

However, as indicated by the science, these fronts result from a weakened circum-Arctic jet stream boundary due to decreased temperature polarity between the Arctic Circle and high latitude zones in Europe, Russia and North America. The reduced contrast allows migration of masses of cold Arctic air southward and of tropical air northward across the weakened jet stream boundary, indicating a fundamental shift in the global climate pattern (Figure 1).

Figure 1. (A) Extensions from the Arctic polar zone into Europe and North America; (B) Extension into North America; (C) weakening and increasing undulation of the Arctic jet stream boundary (NOAA) allowing intrusion of air masses of contrasted temperature across the boundary.

The weakening of the Arctic boundary is a part of the overall shift of climate zones toward the poles in both hemispheres, documented in detail in Europe (Figure 2). Transient cooling pauses are projected as a result of the flow of cold ice meltwater from Greenland and Antarctica into the oceans, leading to stadial cooling intervals.

Figure 2. Migration of climate zones in Europe during 1981-2010 and under +2°C. Faint pink areas represent advanced warming. (A, left) Agro‐climate zonation of Europe based on growing season length (GSL) and active temperature sum (ATS) obtained as an ensemble median from five different climate model simulations during the baseline period (1981–2010). (B, right) Ensemble median spatial patterns of agro-climate zones migration under 2°C global surface warming according to model RCP8.5. Gray areas represent regions where no change with respect to the baseline period is simulated.

A combination of ice sheet melting and the flow of melt water into the oceans on the one hand, and ongoing warming of tropical continental zones on the other hand, are likely to lead to the following:
  • Storminess due to collisions of cold and warm air masses;
  • As the ice sheets continue to melt, the cold meltwater enhances lower temperatures at shallow ocean levels, as modelled by Hansen et al. (2016) and Bonselaer et al (2018) (Figure 3A), as contrasted with warming at deeper ocean levels over large parts of the oceans. This transiently counterbalances the effects of global warming over the continents arising from the greenhouse effect; 
  • The above processes herald chaotic climate effects, in particular along continental margins and island chains.
Figure 3. A. 2080–2100 meltwater-induced sea-air temperature anomalies relative to the standard RCP8.5 ensemble (Bronselaer et al., 2018), indicating marked cooling of parts of the southern oceans. Hatching indicates where the anomalies are not significant at the 95% level; B. Negative temperature anomalies through the 21st-22nd centuries signifying stadial cooling intervals (Hansen et al., 2016); C. A model of Global warming for 2096, where cold ice melt water occupies large parts of the North Atlantic and circum-Antarctica, raises sea level by about 5 meters and decreases global temperature by -0.33°C (Hansen et al., 2016).

The extreme rate at which the global warming and the shift of climate zones are taking place virtually within a period less than one generation-long, faster than major past warming events such as at the Paleocene-Eocene boundary 56 million years ago, renders the term “climate change” hardly appropriate, since what we are looking at is a sudden and abrupt event

According to Giger (2021) “Tipping points could fundamentally disrupt the planet and produce abrupt change in the climate. A mass methane release could put us on an irreversible path to full land-ice melt, causing sea levels to rise by up to 30 meters. We must take immediate action to reduce global warming and build resilience with these tipping points in mind.”

Computer modelling does not always capture the sensitivity, complexity and feedbacks of the atmosphere-ocean-land system as observed from paleoclimate studies. Many models portray gradual or linear responses of the atmosphere to compositional variations, overlooking self-amplifying effects and transient reversals associated with melting of the ice sheets and cooling of the oceans by the flow of ice melt.

According to Bonselaer et al. (2018) “The climate metrics that we consider lead to substantially different future climate projections when accounting for the effects of meltwater from the Antarctic Ice Sheet. These differences have consequences for climate policy and should be taken into account in future IPCC reports, given recent observational evidence of increasing mass loss from Antarctica” and “However, the effect on climate is not included (by the IPCC) and will not be in the upcoming CMIP6 experimental design. Similarly, the effects of meltwater from the Greenland Ice Sheet have so far not been considered, and could lead to further changes in simulated future climate”. Depending on future warming the effect of Antarctic ice meltwater may extend further, possibly becoming global.

By contrast to ocean cooling, further to NASA’s reported mean land-ocean temperature rise of +1.18°C in March 2020 above pre-industrial temperatures, relative to the 1951-1980 baseline, large parts of the continents, including central Asia, west Africa eastern South America and Australia are warming toward mean temperatures of +2°C and higher. The contrast between cooling of extensive ocean regions and warming of the continental tropics is likely to lead to extreme storminess, in particular along continent-ocean interfaces.

The late 20th century to early 21st century global greenhouse gas levels and regional warming rates have reached a large factor to an order of magnitude faster than warming events of past geological and mass extinction events, with major implications for the nature and speed of extreme weather events.

For these reasons the term “climate change” for the current extreme warming, which is reaching +1.5°C over the continents and more than +3°C over the Arctic over a period shorter than one century, no longer applies.

The world is looking at an extremely rapid shift in the climatic conditions that have allowed civilization to emerge.

Andrew Glikson
A/Prof. Andrew Glikson
Earth and Paleo-climate scientist
The University of New South Wales,
Kensington NSW 2052 Australia

Books:
The Asteroid Impact Connection of Planetary Evolution
The Archaean: Geological and Geochemical Windows into the Early Earth
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
Asteroids Impacts, Crustal Evolution and Related Mineral Systems with Special Reference to Australia







Friday, February 12, 2021

The extreme rate of global warming: IPCC Oversights of future climate trends

by Andrew Glikson

Intergovernmental Panel on Climate Change (IPCC) reports and comprehensive summaries of the peer-reviewed literature raise questions regarding the assumptions inherent in computer modelling of future climate changes, including the supposed linearity of future global temperature trends (Figure 1).

Figure 1. Global mean surface temperature increase as a function of cumulative total global carbon dioxide (CO2) emissions from various lines of evidence. IPCC

Computer modelling does not necessarily capture the sensitivity, complexity and feedbacks of the atmosphere-ocean-land system as observed from paleoclimate studies. Underlying published IPCC computer models appears to be an assumption of mostly gradual or linear responses of the atmosphere to compositional variations. This overlooks self-amplifying effects and transient reversals associated with melting of the ice sheets. 

Leading paleoclimate scientists have issued warnings regarding the high sensitivity of the atmosphere in response to extreme forcing, such as near-doubling of greenhouse gas concentrations: According to Wallace Broecker, “The paleoclimate record shouts out to us that, far from being self-stabilizing, the Earth's climate system is an ornery beast which overreacts to even small nudges, and humans have already given the climate a substantial nudge”. As stated by James Zachos, “The Paleocene hot spell should serve as a reminder of the unpredictable nature of climate”.

Holocene examples are abrupt stadial cooling events which followed peak warming episodes which trigger a flow of large volumes of ice melt water into the oceans, inducing stadial events. Stadial events can occur within very short time, as are the Younger dryas stadial (12.9-11.7 kyr) (Steffensen et al. 2008) (Figure 2) and the 8.2 kyr Laurentian cooling episode,

Despite the high rates of warming such stadial cooling intervals do not appear to be shown in IPCC models (Figure 1).

Figure 2. The younger dryas stadial cooling (Steffensen et al., 2008). Note the abrupt freeze and thaw boundaries of ~3 years and ~1 year.

Comparisons with paleoclimate warming rates follow: The CO₂ rise interval for the K-T impact is estimated to range from instantaneous to a few 10³ years or a few 10⁴ years (Beerling et al, 2002), or near-instantaneous (Figure 3A). An approximate CO₂ growth range of ~0.114 ppm/year applies to the Paleocene-Eocene Thermal Maximum (PETM) (Figure 3B) and ~0.0116 ppm/year to the Last Glacial Termination (LGT) during 17-11 kyr ago (Figure 3C). Thus the current warming rate of 2 to 3 ppm/year is about or more than 200 times the LGT rate (LGT: 17-11 kyr; ~0.0116 ppm/yr) and 20-30 times faster than the Paleocene-Eocene Thermal Maximum (PETM) rate of ~0.114 ppm/year.

Therefore the term “climate change” for the extreme warming reaching +1.5°C over the continents and more than +3°C over the Arctic over a period of less than 100 years, requires reconsideration.

However, comparisons between the PETM and current global warming may be misleading since, by distinction from the current existence of large ice sheets on Earth, no ice was present about 55 million years ago.

Figure 3. (A) Reconstructed atmospheric CO₂ variations during the Late Cretaceous–early Tertiary, based on -
Stomata indices of fossil leaf cuticles calibrated using inverse regression and stomatal ratios (Beerling et al. 2002);
(B) Simulated atmospheric CO₂ at and after the Palaeocene-Eocene boundary (after Zeebe et al., 2009);
(C) Global CO₂ and temperature during the last glacial termination (After Shakun et al., 2012) (LGM - Last Glacial Maximum; OD – Older dryas; BA - Bølling–Alerød; YD - Younger dryas)

Observed climate complexities leading to the disturbance of linear temperature variations include:
  1. The weakening of climate zone boundaries, such as the circum-Arctic jet stream, allowing cold air and water masses to shift from polar to mid-latitude zones and tropical air masses to penetrate polar zones (Figure 4), induce collisions between air masses of contrasted temperatures and storminess, with major effects on continental margins and island chains.

  2. Amplifying feedbacks, including release of carbon from warming oceans due to reduced CO₂ solubility and therefore reduced intake from the atmosphere, release of methane from permafrost and from marine sediments, desiccated vegetation and extensive bush fires release of CO₂.

  3. The flow of cold ice melt water into the oceans from melting ice sheets—Greenland (Rahmstorf et al., 2015) and Antarctica (Bonselaer et al., 2018)—ensuing in stadial cooling effects, such as the Younger dryas and following peak interglacial phases during the last 800,000 years (Cortese et al., 2007; Glikson, 2019).
Figure 4. Weakening and undulation of the jet stream, shifts of climate zones and penetration of air masses across the weakened climate boundary. NOAA.

In the shorter term such international targets as “zero emissions by 2050” apparently do not include the export of petroleum, coal and gas, thus allowing nations to circumvent domestic emission limits. Australia, the fifth biggest miner and third biggest exporter of fossil fuels, is responsible for about 5% of global greenhouse gas emissions.

At present the total CO₂+CH₄+N₂O level (mixing ratio) is near 500 ppm CO₂-equivalent (Figure 5). From the current atmospheric CO₂ level of above ~415 ppm, at the rise rate of 2 - 3 ppm/year, by 2050 the global CO₂ level would reach about 500 ppm and the CO₂-equivalent near 600 ppm, raising mean temperatures to near-2°C above preindustrial level, enhancing further breakdown of the large ice sheets and a further rise of sea levels.

Figure 5. Evolution of the CO₂+CH₄+N₂O level (mixing ratio)


Andrew Glikson

Dr Andrew Glikson
Earth and Paleo-climate scientist
ANU Climate Science Institute
ANU Planetary Science Institute
Canberra, Australia



Books:
The Asteroid Impact Connection of Planetary Evolution
http://www.springer.com/gp/book/9789400763272
The Archaean: Geological and Geochemical Windows into the Early Earth
http://www.springer.com/gp/book/9783319079073
Climate, Fire and Human Evolution: The Deep Time Dimensions of the Anthropocene
http://www.springer.com/gp/book/9783319225111
The Plutocene: Blueprints for a Post-Anthropocene Greenhouse Earth
http://www.springer.com/gp/book/9783319572369
Evolution of the Atmosphere, Fire and the Anthropocene Climate Event Horizon
http://www.springer.com/gp/book/9789400773318
From Stars to Brains: Milestones in the Planetary Evolution of Life and Intelligence
https://www.springer.com/us/book/9783030106027
Asteroids Impacts, Crustal Evolution and Related Mineral Systems with Special Reference to Australia
http://www.springer.com/us/book/9783319745442