Climate Tipping Points

Paleoclimate perspectives of 21st-23rd centuries, IPCC projections and tipping points

by Andrew Glikson
Earth and paleo-climate scientist
Australian National University

Abstract

IPCC models of future climate trends contain a number of departures from patterns deduced from the paleoclimate evidence. With CO₂ levels reaching 411.8 ppm in January 2019 and CH₄ levels reaching 1.867 ppm in October 2018, for a greenhouse radiative forcing factor of CH₄=25 CO₂ equivalents, the total CO₂-equivalent of 457.5 ppm¹ approaches the stability limit of the Greenland ice sheet, estimated at a greenhouse gas forcing of approximately 500 ppm CO₂ although ephemeral ice may have existed as far back as the middle Eocene. As the concentration of greenhouse gases is rising and amplifying feedbacks from land, oceans and ice sheet melting increase, transient temperature reversals (stadials) accentuate temperature polarities between warming land masses and oceanic regions cooled by the flow of cold ice melt water from the ice sheets, leading to extreme weather events. The rise in Arctic temperatures, at a rate twice as fast as that of lower latitudes, weakens the polar boundary and results in undulation of the jet stream, allowing warm air masses to shift north across the boundary, further heating the polar region. The weakened boundary further allows cold air masses to breach the boundary shifting away from the Arctic. Combined with the flow of ice melt water from Greenland, these developments are leading to a cooling of sub-polar oceans and adjacent land. Similar growth of cold water pools occur along the fringes of Western Antarctica. The cold water pools cover deeper warmer salt water layers which melt the frontal glaciers. The slow-down of the AMOC is analogous to Pleistocene (2.6-0.01 Ma) and early Holocene stadial freeze events such as the Younger Dryas (12.9 – 11.7 kyr) and the 8.5 kyr Laurentide ice melt, where peak temperatures were followed closely by sharp cooling. Climate projections by Hansen et al. (2016) suggest a stadial event associated with significant sea level rise and involving sharp cooling of approximately -2°C, lasting several decades between the mid-21 st century and the mid-22nd century, a time dependent on the rate of Greenland and Antarctic ice melt. Accelerating ice melt and nonlinear sea level rise would reach multi-meters levels over a timescale of 50–150 years.

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¹ January 2019: CO₂ = 410.8 ppm https://www.esrl.noaa.gov/gmd/ccgg/trends/ ; October 2018: CH₄ 1.8676 ppm (CO₂ equivalent x25 = 46.7 CO₂e) https://www.esrl.noaa.gov/gmd/ccgg/trends_ch4/

Paleoclimate records

Pleistocene paleo-climate records are marked by abrupt warming and cooling events during both glacial periods (Dansgaard-Oeschger (D-O) cycles; Ganopolski and Rahmstorf 2001; Camille and Born, 2019) and stadial interglacial periods, the latter defined as stadial freeze events (Figure 1). The paleo-climate record indicates that during the last ~450,000 years peak interglacial temperatures were repeatedly succeeded by temporary freeze events, attributed to the flow of cold ice melt water flow into the North Atlantic Ocean (Cortese et al. 2007) (Figure 1), associated with rapid rises in sea level, as during the last glacial termination (Figure 2). The rise in extreme weather events associated with current global warming to ~0.9°C above 1884 level (NASA, 2018) compares with temperatures and extreme weather events associated with the early Holocene Period (~11.6 –7.0 kyr), a period of major sea level rise of ~60 meters (Smith et al. 2011) and with the Eemian interglacial (128-116 kyr). During the Eemian tropical and extratropical North Atlantic cyclones may have been more intense than at present, and may have produced waves larger than those observed historically, as evidenced by large boulders transported by waves generated by intense storms and cliff erosion (Roverea et al. 2017). Sea levels during the Eemian, when temperatures were about +1°C or and sea levels were +6 to +9 m higher than during the late Holocene, offer analogies with current developments (Roverea A et al. 2017; Kaspar et al. 2007).

Figure 1. (A) Evolution of sea surface temperatures in 5 glacial-interglacial transitions recorded in ODP
1089 at the sub-Antarctic Atlantic Ocean. Lower grey lines – δ¹⁸O measured on Cibicidoides plankton;
Black lines – sea surface temperature. Marine isotope stage numbers are indicated on top of diagrams.
Note the stadial temperature drop events following interglacial peak temperatures, analogous
to the Younger Dryas preceding the onset of the Holocene (Cortese et al. 2007⁽²⁵⁾).
(B) Mean temperatures for the late Pleistocene and early Holocene.

With CO₂ levels reaching 411.8 ppm in January 2019 and CH₄ reaching 1.867 ppm in October 2018, for a greenhouse radiative forcing factor of CH₄=25 CO₂e, the total CO₂-equivalent of 457.5 ppm¹ approaches Miocene levels (Gasson et al. 2016). Levy et al. (2016), Tripati and Darby (2018) and other considered the implications of the rise of greenhouse levels above about 500 ppm CO₂ for the future of the Greenland ice sheet. Whereas due to hysteresis² of the ice sheets may delay complete melting, the extreme rate of warming (Figure 3) may in part override this effect.

Anthropocene tipping points

During the late Anthropocene³, accelerating since about 1960, the rise of radiative forcing due mainly to increasing greenhouse gas concentration above >457 ppm CO₂-equivalent, accounts for a rise of mean global temperatures by 0.98°C since 1880 (NASA (2018) A further rise by more than >0.5°C is masked by aerosols, mainly sulphur dioxide and sulfuric acid (Hansen et al., 2011).

The temperature rise is potentially further enhanced by amplifying feedbacks from land and oceans, including infrared absorption by water surfaces following sea ice melting, reduction of CO₂ concentration in warming water, release of methane and fires. However, climate change trajectories are likely to be highly irregular as a result of stadial ocean cooling events affected by flow of ice melt. Whereas similar temperature fluctuations including stadial events have occurred during past interglacial periods (Cortese et al. 2007; figure 1), with a further rise in atmospheric greenhouse gases the intensity and frequency of extreme weather events would enter uncharted territory unlike any recorded during the Pleistocene, potentially rendering large parts of the continents uninhabitable (Wallace-Wells, 2019).

Figure 2. Tipping points in the Earth system (Lenton et al., 2008)
https://www.pik-potsdam.de/services/infodesk/tipping-elements/kippelemente
Creative Commons BY-ND 3.0 DE license.

Expressions of climate tipping points include intensifying climate feedbacks such ice sheet and sea ice melting, declining Atlantic circulation, intensifying monsoons, increasing El-Nino events, heatwaves and fires, rainforest dieback, melting permafrost and breakdown of methane clathrates (Figure 2) (Lenton et al., 2008). According to the Potsdam Climate Impacts Institute (PIK), tipping points include transformation of the Amazon Rainforest, retreat of the Northern Boreal Forests, destruction of Coral Reefs and weakening of the Marine Carbon Pump, melting of the Arctic Sea Ice, loss of the Greenland Ice Sheet, collapse of the West Antarctic Ice Sheet, partial Collapse in East Antarctica, melting of the Yedoma Permafrost and methane Emissions from the Ocean (Schellnhuber, 2009).

Figure 3. Atmospheric carbon dioxide rise rates and global warming events: a comparison between current
global warming, the Paleocene-Eocene Thermal Event (PETM) and the last Glacial Termination. 

The rate at which atmospheric greenhouse gases and temperatures are rising exceeds global warming rates of the PETM and of last glacial termination and is the fastest recorded in Cenozoic record, excepting that associated with asteroid impacts (Figure 3). Ice mass loss would raise sea level by several meters in an exponential rather than linear response, with doubling time of ice loss yielding multi-meter sea level rise. Modelled 2055-2100 AIB model forcing of +1.19°C above 1880-1920 leads to a projected global warming trend which includes a transient drop in temperature, reflecting stadial freezing events in the Atlantic Ocean and the sub-Antarctic Ocean, reaching -2°C over several decades (Figure 7) (Hansen et al., 2016). These authors used paleoclimate data and modern observations to estimate the effects of ice melt water from Greenland and Antarctica, showing cold low-density meltwater tends to cap increasingly warm subsurface ocean water, affecting an increase ice shelf melting. This affects acceleration of ice sheet mass loss (Figure 4) and slowing of deep water formation (Figure 5).

Figure 4. Greenland and Antarctic ice mass change. GRACE data are extension of Velicogna et al. (2014)
gravity data. MBM (mass budget method) data are from Rignot et al. (2011). Red curves are gravity data for
Greenland and Antarctica only; small Arctic ice caps and ice shelf melt add to freshwater input. (Hansen et al. 2016)

Figure 5. (a) AMOC (in Sverdrup) at 28°N in simulations (i.e., including freshwater injection of 720 Gt year⁻¹ in 2011
                around Antarctica, increasing with a 10-year doubling time, and half that amount around Greenland).
(b) SST (°C) in the North Atlantic region (44–60°N, 10–50°W).

Future trends and Tipping points

Whereas the precise nature tipping point/s ensuing from the confluence of numerous processes (Figure 2) remains little defined, the weakened boundaries between the Arctic and sub-Arctic zones (Figure 7) and the build-up of cold ice melt pools in the oceans fringing Greenland and Antarctica represent an initial stage in the development of a stadial freeze. The warming of the Arctic, formed approximately 3.6-2.2 million years ago when CO₂ levels were about 400 ppm and polar temperatures near 2°C higher than in the late Holocene, heralds conditions somewhat similar to those of the Pliocene. Whereas reports of the International Panel of Climate Change (IPCC, 2018) (Figure 9), based on thousands of peer reviewed science papers and reports, offer a confident documentation of past and present processes in the atmosphere (Climate Council 2018), the portrayal of mostly linear temperature rise trends need to be questioned. Already early stages of a stadial event are manifest by the build-up of a large pools of cold water in the North Atlantic Ocean south of Greenland (Figure 6A) (Rahmstorf et al., 2015) and at the fringe of West Antarctica (Figure 6A) signify early stages in the development of a stadial freeze in large parts of the oceans, consistent with the decline in the Atlantic Meridional Ocean Circulation (AMOC) (Figure 6A).

Figure 6. (A) 2018 global temperature (NASA);
(B) projected 2055-2100 surface-air temperature to +1.19°C above 1880-1920
(AIB model modified forcing, ice melt to 1 meter) (Hansen et al., 2016).

These projections differ markedly from linear model trends (Figure 9) of IPCC models, which mainly assume long term ice melt (Ahmed, 2018). Rignot et al. (2011) report that in 2006 the Greenland and Antarctic ice sheets experienced a combined mass loss of 475 ± 158 Gt/yr, equivalent to 1.3 ± 0.4 mm/yr sea level rise”. For the Antarctic ice sheet the IEMB team (2017) states the sheet lost 2,720 ± 1,390 billion tonnes of ice between 1992 and 2017, which corresponds to an increase in mean sea level of 7.6 ± 3.9 millimeter (IMBIE team 2017). Hansen et al. (2008) consider global temperature higher than 1.0°Celsius due to CO₂ level of ~450 ppm would lead to irreversible ice sheet loss, given most climate models did not include amplifying feedbacks effects such as ice sheet disintegration, vegetation migration, and greenhouse gas release from soils, tundra, or ocean sediments. Such feedbacks can lead to climate tipping points leading to irreversible runaway climate change (Ahmed, 2018).

Figure 7. Global surface-air temperature to the year 2300 in the North Atlantic and Southern Oceans,
including stadial freeze events as a function of Greenland and Antarctic ice melt doubling time (Hansen et al., 2018)

According to NOAA (2018) Arctic surface air temperatures continue to warm at twice the rate relative to the rest of the globe (Figure 8B), leading to a loss of 95 percent of its oldest ice over the past three decades. Arctic air temperatures for 2014-18 have exceeded all previous records since 1900 and are driving broad changes within the Arctic as well he sub-Arctic through weakening of the jet stream which separates the Arctic from warmer climate zones. The recent freezing storms in North America represent penetration of cold air masses through a weakening and increasingly undulating jet stream barrier (Figure 8A). This weakening also allows warm air masses to move northward, further warming the Arctic and driving further ice melting. The freezing storms in North America (Figure 8C) are cheering those who refuse to discriminate between the climate and the weather.

Figure 8. – A. The weakened undulating Jet stream bounding the polar vortex.
Red represents the fastest air flow (Berwyn 2016). The "big freeze" in North America
results from a slow-moving depression of a Rossby wave⁵. The troughs and ridges of
these waves carry wind around the world and generally have a speed rating
of six or seven, with higher numbers representing faster moving winds;
B. The North American and Siberian freeze event 30 January 2019 (NOAA Global
Forecast system model) (Francis 2019). Predicted near-surface air temperature
differences from normal, relative to 1981-2010. Pivotal Weather, CC BY-ND (Francis 2019);
C. North America is experiencing the weather pattern on the left, while Europe enjoys the other one⁶.

IPCC models of future climate change (Figure 9) contain a number of departures from patterns deduced from the paleoclimate evidence. The role of feedbacks from land and water, estimates of future ice melt rates, sea level rise rates, rates of methane release from permafrost and the extent of fires in enhancing atmospheric CO₂, and the already observed onset of ocean cooling south of Greenland and fringes of Antarctica freeze events need to be quantified. According to Hansen et al. (2016) ice mass loss would raise sea level by several meters in an exponential rather than linear response even within the 21st century. According to Rignot et al. (2011) the Greenland and Antarctic ice sheets experienced in 2006 a combined mass loss of 475 ± 158 billion tons per year.

According to a Met Office briefing evaluating the implications of the UN report, once we go past 1.5°C, we dramatically increase the risks of floods, droughts, and extreme weather that would impact hundreds of millions of people. According to the IPCC this would just be the beginning: as we are currently on track to hit 3-4°C by end of century (Figure 9), which would lead to a largely unlivable planet (Ahmed, 2018). The progressive melting of Greenland and the Arctic Sea ice, formed in the Pliocene approximately 3.6-2.2 million years ago when CO₂ levels were about 560-400 ppm (Stone et al. 2010). Future climate model projections by the IPCC (Figure 9) contain a number of significant departures from observations based on the paleoclimate evidence. This includes factors related to amplifying feedbacks from land and water, ice melt rates, temperature trajectories, sea level rise rates, methane release rates, the role of fires, and observed onset of transient stadial (freeze) events. As the Earth continues to heat, cold air masses breach the Arctic boundary and move southward and warm air penetrates into the Arctic, temperature contrasts between polar and subpolar climate zones decrease, further weakening the polar divide. Temperature contrasts between Arctic-derived cold air masses and subtropical air masses result in an increase in the intensity and frequency of extreme weather events.

Figure 9. IPCC AR5: Time series of global annual mean surface air temperature anomalies relative to 1986–2005
from CMIP5 (Coupled Model Inter-comparison Project) concentration-driven experiments.
Projections are shown for each RCP for the multi model mean (solid lines) and the 5–95% range
(±1.64 standard deviation) across the distribution of individual models (shading) (Easterbrook 2014).⁽⁴⁾

As the Earth warms, the increase in temperature contrasts across the globe, and thereby an increase in storminess and extreme weather events, occurring at present, need to be taken into account when planning adaptation measures, including preparation of coastal defenses, construction of channel and pipelines from heavy precipitation zones to draught zones. A non-linear climate warming trend, including stadial freeze events, bears significant implications for planning future adaptation efforts, including preparations for transient deep freeze events in parts of Western Europe and eastern North America for periods lasting several decades (Figure 7) and coastal defenses against enhanced sea levels and storms. In Australia this should include construction of water pipelines and channels from the flooded north to parched regions such as the Murray-Darling basin.

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² Hysteresis: The phenomenon in which the value of a physical property lags behind changes in the effect causing it, as for instance when magnetic induction lags behind the magnetizing force.
³ The Anthropocene is a proposed epoch dating from the commencement of significant human impact on the Earth's geology and ecosystems. https://en.wikipedia.org/wiki/Anthropocene
⁴ Steve Easterbrook, New IPCC Report (Part 6). Azimuth. https://johncarlosbaez.wordpress.com/2014/04/16/what-does-the-new-ipcc-report-say-about-climate-change-part-6/
⁵ https://oceanservice.noaa.gov/facts/rossby-wave.html
⁶ https://www.dw.com/en/understanding-the-polar-vortex/a-17347788

Andrew Glikson

Dr Andrew Glikson
Earth and Paleo-climate science, Australia National University (ANU) School of Anthropology and Archaeology,
ANU Planetary Science Institute,
ANU Climate Change Institute,
Honorary Associate Professor, Geothermal Energy Centre of Excellence, University of Queensland.

Books:

The Archaean: Geological and Geochemical Windows into the Early Earth

http://www.springer.com/gp/book/9783319079073

The Asteroid Impact Connection of Planetary Evolution

http://www.springer.com/gp/book/9789400763272

Asteroids Impacts, Crustal Evolution and Related Mineral Systems with Special Reference to Australia

http://www.springer.com/us/book/9783319745442 

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

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Stronger Extinction Alert

The February 2019 temperature is in line with an earlier analysis that 2019 could be 1.85°C above preindustrial and that a rapid temperature rise may take place over the next few years, as illustrated by the image on the right.

Let's walk through the steps once more.

Baseline adjustment

The combination image below shows that the February 2019 temperature was 0.93°C above a 1951-1980 baseline (left) and 1.21°C above a 1885-1915 baseline (right), a difference of 0.28°C.

In other words, when using a baseline that is centered around 1900, the data should be adjusted by 0.28°C. In the image below, the gold graph uses 1951-1980 as baseline and two linear trend are added, one using data starting in 1880 (gold) and one using data starting in 1900 (blue).

Both linear trends are out of line with the recent temperature rise, the gold trend even more so than the blue trend, illustrating that starting a linear trend from an earlier year can make an analysis worse.

As said, if we want to use a baseline that is centered around 1900, the data should be adjusted by 0.28°C, and this is what the green graph does. A 4th-order polynomial trend is added that lines up perfectly with zero at the year 1900.

Further adjustment is needed for a 1750 baseline, which better reflects preindustrial as in the Paris Agreement. As discussed in an earlier post, this could result in an additional adjustment of 0.3°C.

Higher Arctic temperature

Furthermore, have another look at above maps. Much of the extreme anomalies are in line with changes to the Jet Stream, as also illustrated by the insert. More cold air escaping the Arctic and more warm air entering the Arctic are both speeding up Arctic warming. In the map on the right, much of the Arctic is left grey, since no data are available for the Arctic around 1900, but the Arctic should not be left out of the picture and adding a further 0.1°C adjustment seems appropriate to better include the Arctic.

Air temperature over oceans

Finally, the NASA temperatures for oceans are the surface temperatures of the water, but it makes more sense to use air temperatures close to the water, which likely adds a further 0.1°C. This adds up a total adjustment of 0.78°C as applied in the red graph, which also has an 8th-order polynomial trend added.

Which trendline works best?

How appropriate is it to apply an 8th-order polynomial trend to climate data? Have another look at above graphs and consider that in the gold graph, R²=0.687 for the gold linear trend (1880-Feb 2019 data) and R²=0.752 for blue linear trend (1900-Feb 2019 data), while in the green graph, R²=0.812 for the dark green 4th-order polynomial trend, and in the red graph, R²=0.828 for the pink 8th-order polynomial trend. In other words, the pink trend better follows the ups and downs of the data than the lower-order polynomial trend, and it does so much better than the linear trends that both are clearly unrealistic in an analysis of warming acceleration.

Selecting the axes

Is warming accelerating? Trend analysis that uses data going back many years can only be part of the picture; it's also important to anticipate changes that loom in the near future. When taking the many feedbacks, tipping points and further warming elements more fully into account, warming could accelerate even more strongly than depicted in the red trend in the graph at the top.

In the 'Extinction Alert' graph at the top,  the vertical axis is cut off at 5°C, since life on Earth will already have disappeared by then (see box on the right), but when looking at near-term human extinction, 3°C will likely suffice.

How soon could 3°C warming be reached? The 'Extreme Alert' image below looks at data over the past decade, and a fifth-order polynomial trend (red) shows how warming could cross 3°C as early as next year.

How could such a scenario eventuate?

In such a rapid warming scenario:

1. a stronger-than-expected El Niño would contribute to
2. early demise of the Arctic sea ice, i.e. latent heat tipping point + 
3. associated loss of sea ice albedo, 
4. destabilization of seafloor methane hydrates, causing eruption of vast amounts of methane that further speed up Arctic warming and cause 
5. terrestrial permafrost to melt as well, resulting in even more emissions, 
6. while the Jet Stream gets even more deformed, resulting in more extreme weather events
7. causing forest fires, at first in Siberia and Canada and
8. eventually also in the peat fields and tropical rain forests of the Amazon, in Africa and South-east Asia, resulting in 
9. rapid melting on the Himalayas, temporarily causing huge flooding, 
10. followed by drought, famine, heat waves and mass starvation, and
11. collapse of the Greenland Ice Sheet.

Even when adding a rather inappropriate linear trend (as done in the 'Extreme Alert' image, in blue),  warming still looks set to cross 2°C by 2026 in the Extreme Alert image, but as the chart below shows, there could be a rise of as much as 18°C by 2026.

[ from an earlier post ]

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


links

• Co-extinctions annihilate planetary life during extreme environmental change, by Giovanni Strona and Corey Bradshaw (2018)
https://www.nature.com/articles/s41598-018-35068-1

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

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

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

Accelerating Rise In Greenhouse Gas Levels

Carbon dioxide

The rise in the levels of carbon dioxide (CO₂) in the atmosphere continues to accelerate. Over the past 31 days, CO₂ levels at Mauna Loa, Hawaii, have been above 410 ppm, while on March 3, 2019, some average hourly readings exceeded 415 ppm. The levels recorded in the year up until now weren't expected to occur until April/May 2019, as illustrated by the image below.

How much could carbon dioxide levels grow over the next decade?

An earlier Met Office forecast expects annual average CO₂ levels at Mauna Loa to be 2.75 ppm higher in 2019 than in 2018. Looking at above levels, growth could be even stronger than that.

The image below shows NOAA 1959-2018 CO₂ growth data (black) with above Met Office forecast added for 2019 (brown). The growth figures for 2018 and 2019 are spot on a trend that is added in line with an earlier analysis.

[ from an earlier post ]

Strong CO₂ growth could occur over the next few years, due to releases from increased burning of fossil fuel and biomass, more forest fires and melting permafrost, and the added impact of stronger El Niño events and less uptake of carbon dioxide by oceans and ecosystems. An earlier analysis concludes that CO₂ growth could raise temperatures by 0.5°C or 0.9°F by 2026.

Methane

Levels of methane (CH₄) are also rising at accelerating pace, as illustrated by the image below.

[ from an earlier post ]

Above graph shows July 1983 through October 2018 monthly global methane means at sea level, with added trend. Higher methane means can occur at higher altitudes than at sea level, as illustrated by the image below that shows the highest mean methane levels recorded by the MetOp satellites on March 10 for the years 2013 to 2019 at selected altitudes.

[ click on images to enlarge ]

Global methane levels in March are at a seasonal low. The highest global means occur in September. On September 3, 2018, global methane means as high as 1905 ppb were recorded at 307 mb, an altitude at which some of the strongest growth in methane has occurred, as discussed in earlier posts such as this one.

The MetOp satellites have some difficulty measuring methane at lower altitudes. Above NPP satellite image shows high methane levels across the Arctic Ocean close to sea level, with mean levels of 1842 ppb recorded at 1000 mb, i.e. surface level. This indicates that high methane levels do occur as a result of releases from the Arctic Ocean. The above-mentioned analysis concludes that seafloor methane releases alone could raise the global temperature by 1.1°C or 1.98°F by 2026. Growth in methane releases elsewhere, e.g. due to permafrost melt and forest fires, could further raise methane levels and thus temperatures.

Above image shows that peak methane levels were as high as 2947 ppb on March 7, 2019. The image also shows worryingly high methane levels over Antarctica, as also discussed earlier, in a 2013 post.

Nitrous Oxide

Growth in nitrous oxide (N₂O) is not often discussed, yet it's very important both because of the high global warming potential and long lifetime of N₂O, and because of the ozone depletion it causes in the stratosphere. The image below shows mean levels of N₂O of 320 ppb, with peaks reaching levels as high as 345.2 ppb at 1000 mb (sea level) on March 10, 2019.

Above image also shows high levels of nitrous oxide over the Arctic Ocean. Levels of greenhouse gases in the atmosphere are generally higher in the Arctic than in the rest of the world, which contributes to the accelerating warming of the Arctic.

[ from an earlier post ]

Accelerating Rise In Greenhouse Gas Levels

The image on the right shows that CH₄, CO₂ and N₂O levels in the atmosphere are, respectively, 257%, 146% and 122% their 1750 levels, according to IPCC and WMO data.

In summary, greenhouse gases in the atmosphere are rising at accelerating pace, and this spells bad news, the more so since, next to CH₄, CO₂ and N₂O, there are additional warming elements that can further speed up the temperature rise, such as black carbon, or soot, water vapor, loss of Arctic sea ice, etc.

How much could the global temperature rise? The above-mentioned analysis concludes that a temperature rise of 18°C or 32.4°F could eventuate by 2026, while life on Earth will already have disappeared with a 5°C or 9°F temperature rise.

The situation is dire and calls for comprehensive and effective action as described in the Climate Plan and as also discussed in this recent post.


Links

• CO₂ levels reach another record high
https://arctic-news.blogspot.com/2019/02/co2-levels-reach-another-record-high.html

• As El Niño sets in, will global biodiversity collapse in 2019?
https://arctic-news.blogspot.com/2018/11/as-el-nino-sets-in-will-global-biodiversity-collapse-in-2019.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

• Care for the Ozone Layer
https://arctic-news.blogspot.com/2019/01/care-for-the-ozone-layer.html

• Methane hydrates (2013)
https://methane-hydrates.blogspot.com/2013/04/methane-hydrates.html

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

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

A rise of 18°C or 32.4°F by 2026?

A catastrophe of unimaginable proportions is unfolding. Life is disappearing from Earth and all life could be gone within one decade. Study after study is showing the size of the threat, yet many people seem out to hide what we're facing.

In the Arctic alone, four tipping points look set to be crossed within a few years:

1. Loss of the Arctic sea ice's ability to act as a buffer to absorb incoming ocean heat
2. Loss of Arctic sea ice's ability to reflect sunlight back into space (albedo)
3. Destabilization of sediments at the seafloor of the Arctic Ocean
4. Permafrost melt (melting of snow and ice to such an extent that soils thaw and don't stay permanently frozen anymore)

Crossing these tipping points triggers a number of feedbacks that kick in at accelerating speed, including even more absorption of heat by the Arctic Ocean, further changes to the Jet Stream resulting in even more extreme weather, seafloor methane release, water vapor feedback and emissions from land such as CH₄ (methane), N₂O (nitrous oxide) and NOₓ (nitrogen oxide), due to permafrost melt, storms and forest fires. Temperatures also threaten to rise strongly over the next few years as sulfate cooling falls away while more black carbon and brown carbon gets emitted as more wood gets burned and more forest fires occur.

A recent study points at yet another tipping point, i.e. the disappearance of marine stratus clouds, which could result in a global temperature rise of eight degrees Celsius (8°C or 14.4°F). In the model used in the study, the tipping point starts to occur at 1,200 ppm CO₂e, i.e. a stack of greenhouse gases including CH₄, N₂O, CO₂ and H₂O, and changes in clouds resulted in global surface warming of 8°C at 1,300 ppm CO₂e, as stratocumulus decks did break up into cumulus clouds and evaporation strengthened, and average longwave cooling at the level of the cloud tops dropped to less than 10% of what it was in the presence of stratocumulus decks.

This 8°C rise would come on top of the warming that would already have occurred due to other warming elements, resulting in a total rise of as 18°C or 32.4°F from preindustrial, as pictured on the right and below.

What would it take to reach 1200 ppm CO₂e? The IPCC's AR4 contains a scenario of 1,200 ppm CO₂e getting reached with a corresponding temperature rise of between ~5°C and ~10°C above preindustrial. NOAA's figures for greenhouse gases add up to a current level of 500 ppm CO₂e. NOAA's figure for methane's GWP is too low, especially when considering a rise within a decade. When using this 500 ppm CO₂e, it would take 700 ppm to reach 1,200 ppm, and if 1 ppm equals 7.81 Gt of CO₂, then 700 ppm equals 5467 Gt of CO₂, which may seem a lot, but at a GWP for methane of 130 (10-year horizon) it could be reached instantly with a burst of methane of some 42 Gt, i.e. less than Natalia Shakhova's warning that 50 Gt of methane is ready for release at any time. In above image, further warming elements are included, in addition to methane and CO₂ and it takes until the year 2026.

As an earlier study points out, life on Earth will already have disappeared with a 5°C rise (see box on the right).

How precious life is

It took a long time for life to evolve on Earth. At first, hardly any species could live on land, as there was no ozone layer to protect them from UV radiation. Also, there was no oxygen in the air to breathe. Life formed some 3 billion years ago and bacteria first developed the ability to decompose carbon dioxide (and produce oxygen) some 2.3  billion years ago.

Then, worm-like creatures started to multiply strongly, using more and more oxygen and producing more and more carbon dioxide. Eventually, this resulted in a sharp fall in oxygen levels, leading to extinction of these species. This first mass extinction was followed by a spike in oxygen as both the species in the oceans and plants on land continued to produce oxygen, while these first animals went extinct.

Temperature changes dominate in subsequent mass extinctions, and each time it took life a long time to recover. We've now entered the Sixth Mass Extinction, as oxygen levels are falling, oceans are acidifying and species are going extinct at accelerating rates. A 2013 study calculated that species are facing warming that occurs 10,000 x faster than their natural ability to adapt.

A rise of 18°C or 32.4°F by 2026?

The speed at which temperatures and greenhouse gas levels are now jointly rising is so large and so unprecedented in Earth's history that many doubt that there will be any life left on Earth by 2026.

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

Can humanity change its course? 

Given that humanity appears to be on a course to omnicidal destruction, what position can we best take in response? In the light of the dire situation, dramatic reduction in pollution is needed, as well as further action. Indeed, the Paris Agreement constitutes a global commitment to comprehensive and effective action. The Climate Plan calls for multiple parallel lines of action (the green lines on the image below).

The green lines of action each need to be implemented in parallel, i.e. no line of action should wait for another, nor should action on one line be used as an excuse to delay action on another line. Where lines of action are grouped together in three parts, numbers merely show relationships with the kinds of warming pictured at the top of the image.

While implementation of some of these lines of action requires U.N. supervision, the Climate Plan prefers local implementation, with communities deciding what works best locally, provided a community does take sufficient action to achieve the necessary dramatic reductions in each type of pollution. Examples of implementation of some of these lines of action are depicted in the image below, showing examples of how progress can be achieved through local feebates.

Where progress is lacking, swift escalation is recommended as follows:

1. Where a local community fails to make progress, state (or provincial) fees are imposed in that locality.
2. Where a state fails to make progress, national fees are imposed in the state.
3. Where a nation fails to make progress, other nations impose fees on imports from and export to that nation with revenues used to fund clean development in the other nations.

Warm air and water moving toward the Arctic Ocean

The need for action such as marine cloud brightening is illustrated by the following two images. The image below shows that, despite the presence of large amounts of meltwater off the North American coast, sea surface temperatures on March 2, 2019, were as much as 13.8°C or 24.8°F warmer than during 1981-2011, indicating how much more ocean heat is now carried to the Arctic Ocean along the Gulf Stream.

How is it possible for anomalies to get this high? As the Arctic is warming up faster than the rest of the world, the Jet Stream is becoming more wavy. A more wavy Jet Stream enables more cold air to move out of the Arctic. As a result, cold Arctic air can descend deep into the North American continent. At the same time, a more wavy Jet Stream enables more warm air and water to move into the Arctic. This is illustrated by the February 24, 2019, combination image that shows temperature on the left and the Jet Stream on the right.

As oceans get warmer, the temperature difference between land and oceans also increases in Winter. This larger temperature difference results in stronger winds that can carry more warm, moist air north in the North Atlantic. These winds can also speed up the amount of heat carried by the Gulf Stream toward the Arctic Ocean, with the threat that a large influx of warm, salty water will destabilize sediments at the seafloor of the Arctic Ocean and trigger eruption of huge amounts of methane.

In conclusion, the situation is dire and calls for comprehensive and effective action, as described at the action, policies and feebates pages at the Climate Plan.


Links

• Possible climate transitions from breakup of stratocumulus decks under greenhouse warming, by Tapio Schneider et al.
https://www.nature.com/articles/s41561-019-0310-1

• High CO2 Levels Can Destabilize Marine Layer Clouds (News release associated with above study)
https://www.caltech.edu/about/news/high-cosub2sub-levels-can-destabilize-marine-layer-clouds

• Early Palaeozoic ocean anoxia and global warming driven by the evolution of shallow burrowing, by Sebastiaan van de Velde et al.
https://www.nature.com/articles/s41467-018-04973-4

• Brock University-led team discovers way of tapping into and testing Earth’s prehistoric air
https://brocku.ca/brock-news/2016/07/brock-university-led-team-discovers-way-of-tapping-into-and-testing-earths-prehistoric-air

• Rates of projected climate change dramatically exceed past rates of climatic niche evolution among vertebrate species, by Ignacio Quintero et al.
https://onlinelibrary.wiley.com/doi/abs/10.1111/ele.12144
https://www.researchgate.net/publication/242016225_Rates_of_projected_climate_change_dramatically_exceed_past_rates_of_climatic_niche_evolution_among_vertebrate_species

• Extinction Alert
https://arctic-news.blogspot.com/2019/02/extinction-alert.html

• Co-extinctions annihilate planetary life during extreme environmental change, by Giovanni Strona and Corey Bradshaw (2018)
https://www.nature.com/articles/s41598-018-35068-1

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

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