Arctic News

Sunday, September 1, 2019

Blueprints of future climate trends

Blueprints of future climate trends

Extreme GHG and temperature rise rates question linear climate projections

Andrew Glikson
Earth and climate scientist
Australian National University
geospec@iinet.net.au

Abstract

The extreme greenhouse gas (GHG) and temperature rise rates since the mid-1970th raise questions over linear climate projections for the 21st century and beyond. Under a rise of CO₂-equivalent reaching +500 ppm and 3.0 W/m⁻² relative to 1750, the current rise rates of CO₂ by 2.86 ppm per and recent global temperature rise rate (0.15-0.20°C per decade) since 1975 are leading to an abrupt shift in state of the terrestrial climate and the biosphere. By mid-21st century at >750 ppm CO₂-e climate tipping points indicated by Lenton et al. 2008 and Schellnhuber 2009 are likely to be crossed. Melting of the Greenland and Antarctic ice sheets has increased by a factor of more than 5 since 1979–1990. As the ice sheets and sea ice melt, the albedo flip between reflective ice surfaces and dark infrared-absorbing water results in significant increase of radiative forcing, and complete removal of Arctic sea ice would result in a forcing of about 0.7 W/m⁻² (Hudson, 2011). The confluence of climate events, including a breach of the circum-Arctic jet stream boundary and a polar-ward migration of climate zones at a rate of 56-111 km per decade, induce world-wide extreme weather events including bushfires, methane release from Arctic permafrost and sediments. For a climate sensitivity of 3±1.5°C per doubling of atmospheric CO₂, global warming has potentially reached between +2°C to +3°C above mean pre-industrial temperatures at a rate exceeding the fastest growth rate over the last 55 million years. As ice melt water flow into the oceans temperature polarities between warming continents and cooling tracts of ocean would further intensify extreme weather events under non-linear climate trajectories. The enrichment of the atmosphere in GHG, constituting a shift in state of the terrestrial climate, is predicted to delay the onset of the next glacial state by some 50,000 years.

GHG and temperature rise

The paleoclimate record suggests that no event since 55 million years ago, the Paleocene-Eocene Thermal Maximum (PETM), when global temperatures rose by more than +5 to +8°C over a period of ~20,000 years, with a subsequent warming period of up to 200,000 years, has been as extreme as atmospheric disruption since the onset of the industrial age about 1750 AD (the Anthropocene), accelerating since 1975. During this period greenhouse gas levels have risen from ~280 ppm to above >410 ppm and to 496 ppm CO₂-equivalent (Figure 1), the increase of CO₂ reaching near-47 percent above the original atmospheric concentration. However, linear climate change projections are rare in the recent climate history (Figure 2) and linear future climate projections may not account for the effects of amplifying feedbacks from land and oceans. Given an Anthropocene warming rate faster by ~X200 times than the PETM (Figure 3), linear warming trajectories such as are projected by the IPCC may overlook punctuated tipping points, transient reversals and stadial events.

Figure 1. Growth of CO₂-equivalent level and the annual greenhouse gas Index (NOAA AGGI).
Measurements of CO₂ to the 1950s are from (Keeling et al., 2008) and from air trapped in ice and
snow between CO₂ concentrations and radiative forcing from all long-lived greenhouse gases.

According to NOAA, GHG forcing in 2018 has reached 3.101 W/m⁻² relative to 1750 (CO₂ = 2.044 W/m⁻²; CH₄ = 0.512 W/m⁻²; N₂O = 0.199 W/m⁻²; CFCs = 0.219 W/m⁻²) with a CO₂-equivalent of 492 ppm (Figure 1). The rise in GHG forcing during the Anthropocene since about 1800 AD, intensifying since 1900 AD and sharply accelerating since about 1975, has induced a mean of ~1.5°C over the continents above pre-industrial temperature, or >2.0°C when the masking role of aerosols is discounted, implying further warming is still in store.

According to Hansen et al. 2008, the rise in radiative forcing during the Last Glacial Termination (LGT - 18,000 -11,000 years BP), associated with enhancing feedbacks, has driven GHG radiative forcing by approximately ~3.0 W/m⁻² and a mean global temperature rise of ~4.5°C (Figure 2), i.e. of similar order as the Anthropocene rise since about 1900. However the latter has been reached within a time frame at least X30 times shorter than the LGT, underpinning the extreme nature of current global warming.

Figure 2. (Hansen et al. 2008). Glacial-temperature and GHG forcing for the last 420,000 years based on the Vostok
ice core, with the time scale expanded for the Anthropocoene. The ratio of temperature and forcing scales is 1.5°C
per 1 W/m⁻². The temperature scale gives the expected equilibrium response to GHG change including slow feedback
surface albedo change. Modern forcings include human-made aerosols, volcanic aerosols and solar irradiance.

The CO₂-equivalent levels and radiative forcing levels constitute a rise from Holocene levels (~280 ppm CO₂) to >410 ppm compared with Miocene-like levels (300-600 ppm CO₂), at a rate reaching 2 to 3 ppm/year, within a century or so, driving the fastest temperature rise rate recorded since 55 million years ago (Figure 3).

Figure 3. A comparison between rates of mean global temperature rise during: (1) the last Glacial Termination

(after Shakun et al. 2012); (2) the PETM (Paleocene-Eocene Thermal Maximum, after Kump 2011);

(3) the late Anthropocene (1750–2016), and (4) an asteroid impact. In the latter instance temperature

due to CO₂ rise would lag by some weeks or months behind aerosol-induced cooling

Considering the transient mitigating albedo effects of clouds, seasonal land surface albedo, ice albedo, atmospheric aerosols including sulphur dioxide and nitrate, the potential rise of land temperature could have reached -0.4 to -0.9 W/m⁻² in 2018, masking approximately 0.6 to 1.3°C potential warming once the short lived aerosol effect is abruptly reduced.

Accelerated melting of the ice sheets

The fast rate of the Anthropocoene temperature rise compared to the LGT and PETM (Figure 3) ensues in differences in terms of the adaptation of flora and fauna to new conditions. The shift in state of the Earth’s climate is most acutely manifested in the poles, where warming leads to weakening of the jet stream boundaries which are breached by outflow of cold air fronts, such as the recent “Beast from the East” event, and penetration of warm air masses.

As the poles keep warming, to date by a mean of ~2.3°C, the shrinking of the ice sheets per year has accelerated by a factor of more than six fold (Figure 4). Warming of the Arctic is driven by the ice-water albedo flip, where dark sea-water absorbing solar energy alternates with high-albedo ice and snow, and by the weakening of the polar boundary and jet stream.

Greenland. The threshold of collapse of the Greenland ice sheet, retarded by hysteresis, is estimated in the range of 400-560 ppm CO₂, already transgressed at the current 496 ppm CO₂equivalent (Figure 4). The Greenland mass loss increased from 41 ± 17 Gt/yr in 1990–2000, to 187 ± 17 Gt/yr in 2000–2010, to 286 ± 20 Gt/yr in 2010–2018, or six fold since the 1980s, or 80 ± 6 Gt/yr per decade, on average.

Antarctica. The greenhouse gas level and temperature conditions under which the East Antarctic ice sheet formed during the late Eocene 45-34 million years ago are estimated as ~800–2000 ppm and up to 4 degrees Celsius above pre-industrial values, whereas the threshold of collapse is estimated as 600 ppm CO₂ or even lower. The total mass loss from the Antarctic ice sheet increased from 40 ± 9 Gt/yr in 1979–1990 to 50 ± 14 Gt/yr in 1989–2000, 166 ± 18 Gt/yr in 1999–2009, and 252 ± 26 Gt/yr in 2009–2017. Based on satellite gravity data, the East Antarctic ice sheet is beginning to breakdown in places (Jones 2019), notably the Totten Glacier (Rignot et al., 2019), which may be irreversible. According to Mengel and Levermann (2014), the Wilkes Basin in East Antarctica alone contains enough ice to raise global sea levels by 3–4 meters.

Figure 4. (A) New elevation showing the Greenland and Antarctic current state of the ice sheets accurate to a few meters in height, with elevation changes indicating melting at record pace, losing some 500 km³ of ice per-year into the oceans; (B) Ice anomaly relative to the 2002-2016 mean for the Greenland ice sheet (magenta) and Antarctic ice sheet (cyan). Data are from GRACE; (C) the melting of sea ice 1978-2017, National Snow and Ice Data Center (NCIDC)

C. Migration of climate zones

The expansion of warm tropical zones and the polar-ward migration of subtropical and temperate climate zones are leading to a change in state in the global climate pattern. The migration of arid subtropical zones, such as the Sahara, Kalahari and central Australian deserts into temperate climate zones ensues in large scale droughts, such in inland Australia and southern Africa. In the northern hemisphere expansion of the Sahara desert northward, manifested by heat waves across the Mediterranean and Europe (Figure 5).

Figure 5. (A) Migration of the subtropical Sahara climate zone (red spots) northward into the Mediterranean climate
zone leads to warming, drying and fires over extensive parts of Spain, Portugal, southern France, Italy, Greece and
Turkey, and to melting of glaciers in the Alps. Migration, Environment and Climate Change, International
Organization for Migration Geneva – Switzerland (GMT +1); Source: https://environmentalmigration.iom.int/maps

Figure 5. (B) Southward encroachment of Kalahari Desert conditions (vertical lines and red spots) leading to
warming and drying of parts of southern Africa. Source: https://environmentalmigration.iom.int/maps

Figure 5. (C) Drying parts of southern Australia, including Western Australia, South Australia and parts of the
eastern States, accompanied with increasing bushfires. Source: https://environmentalmigration.iom.int/maps

Climate extremes

Since the bulk of terrestrial vegetation has evolved under glacial-interglacial climate conditions, where GHG range between 180 - 300 ppm CO₂, global warming is turning large parts of Earth into a tinderbox, ignited by natural and human agents. By July and August 2019, as fires rage across large territories, including the Amazon forest, dubbed the Planet’s lungs as it enriches the atmosphere in oxygen. When burnt the rainforest becomes of source of a large amount of CO₂ (Figure 6.B), with some 72,843 fires in Brazil this year and extensive bushfires through Siberia, Alaska, Greenland, southern Europe, parts of Australia and elsewhere, the planet’s biosphere is progressively transformed. As reported: ‘Climate change is making dry seasons longer and forests more flammable. Increased temperatures are also resulting in more frequent tropical forest fires in non-drought years. And climate change may also be driving the increasing frequency and intensity of climate anomalies, such as El Niño events that affect fire season intensity across Amazonia.’

Extensive cyclones, floods, droughts, heat waves and fires (Figure 6.B) increasingly ravage large tracts of Earth. However, despite its foundation in the basic laws of physics (the black body radiation laws of Planck, Kirchhoff' and Stefan Boltzmann), as well as empirical observations around the world by major climate research bodies (NOAA, NASA, NSIDC, IPCC, World Meteorological Organization, Hadley-Met, Tindale, Potsdam, BOM, CSIRO and others), the anthropogenic origin, scale and pace of climate change remain subject to extensively propagated denial and untruths.

Figure 6. (A) Extreme weather events around the world 1980-2018,
including earthquakes, storms, floods, droughts. Munich Re-insurance.

Figure 6. (B) A satellite infrared image of South America fires (red dots) during July and August, 2019, NASA.

An uncharted climate territory

Whereas strict analogies between Quaternary and Anthropocene climate developments are not possible, elements of the glacial-interglacial history are relevant for an understanding of current and future climate events. The rise of total greenhouse gas (GHG), expressed as CO₂-equivalents, to 496 ppm CO₂-e (Figure 1), within less than a century represents an extreme atmospheric event. It raised GHG concentrations from Holocene levels to the range of the Miocene (34–23 Ma) when CO₂ level was between 300 and 530 ppm. As the glacial sheets disintegrate, cold ice-melt water flowing into the ocean ensue in large cold water pools, a pattern recorded following peak interglacial phases over the last 450,000 years, currently manifested by the growth of cold regions in north Atlantic Ocean south of Greenland and in the Southern Ocean fringing Antarctica (Figure 7).

Warming of +3°C to +4°C above pre-industrial levels, leading to enhanced ice-sheet melt, would raise sea levels by at least 2 to 5 meters toward the end of the century and, delayed by hysteresis, likely by 25 meters in the longer term. Golledge et al. (2019) show meltwater from Greenland will lead to substantial slowing of the Atlantic overturning circulation, while meltwater from Antarctica will trap warm water below the sea surface, increasing Antarctic ice loss. Whereas the effect of low-density ice melt water on the surrounding oceans is generally not included in many models, depending on amplifying feedbacks, prolonged Greenland and Antarctic melting and consequent cooling of surrounding ocean sectors as well as penetration of freezing air masses through weakened polar boundaries may have profound effect on future climate change trajectories (Figure 8).

Figure 7. (A) Global warming map (NASA 2018). Note the cool ocean regions south of Greenland and
along the Antarctic. Credits: Scientific Visualization Studio/Goddard Space Flight Center;
(B) 2012 Ocean temperatures around Antarctica (NASA 2012).

Climate projections for 2100-2300 by the IPCC AR5 Synthesis Report, 2014 portray predominantly linear to curved models of greenhouse gas, global temperatures and sea level changes. These models however appear to take limited account of amplifying feedbacks from land and ocean and of the effects of cold ice-melt on the oceans. According to Steffen et al. (2018) “self-reinforcing feedbacks could push the Earth System toward a planetary threshold” and “would lead to a much higher global average temperature than any interglacial in the past 1.2 million years and to sea levels significantly higher than at any time in the Holocene”.

Amplifying feedbacks of global warming include:

The albedo-flip of melting sea ice and ice sheets and the increase of the water surface area and thereby sequestration of CO₂. Hudson (2011) estimates a rise in radiative forcing due to removal of Arctic summer sea ice as 0.7 W/m², a value close to the total of methane release since 1750.
Reduced ocean CO₂ intake due to lesser solubility of the gas with higher temperatures.
Vegetation desiccation and burning in some regions, and thereby released CO₂ and reduced evaporation and its cooling effect. This factor and the increase of precipitation in other regions lead to differential feedbacks from vegetation as the globe warms (Notaro et al. 2007).
An increase in wildfires, releasing greenhouse gases (Figure 6).
Release of methane from permafrost, bogs and sediments and other factors.

Linear temperature models appear to take limited account of the effects on the oceans of ice melt water derived from the large ice sheets, including the possibility of a significant stadial event such as already started in oceanic tracts fringing Greenland and Antarctica (Figure 7) and modeled by Hansen et al, (2016). In the shorter to medium term sea level rises would ensue from the Greenland ice sheet (6-7 meter sea level rise) and West Antarctic ice sheet melt (4.8 meter sea level rise). Referring to major past stadial events, including the 8200 years-old Laurentian melt and the 12.7-11.9 younger dryas event, a protracted breakdown of parts of the Antarctic ice sheet could result in major sea level rise and extensive cooling of southern latitudes and beyond, parallel with warming of tropical and mid-latitudes (Figure 8) (Hansen et al. 2016). The temperature contrast between polar-derived cold fronts and tropical air masses is bound to lead to extreme weather events, echoed among other in Storms of my grandchildren (Hansen, 2010).

Figure 8. (A) Model Surface-air temperature (°C) for 2096 relative to 1880–1920 (Hansen et al. 2016).
The projection betrays major cooling of the North Atlantic Ocean, cooling of the circum-Antarctic Ocean
and further warming in the tropics, subtropics and the interior of continents; (B) Modeled surface-air
temperatures (°C) to 2300 AD relative to 1880–1920 for several ice melt rate scenarios, displaying a stadial cooling event at a time dependent on the ice melt doubling time (Hansen et al., 2016). Courtesy Prof James Hansen;.

Within and beyond 2100-2300 projections (Figure 8.A, B) lies an uncharted climate territory, where continuing melting of the Antarctic ice sheet, further cooling of neighboring sectors of the oceans and climate contrasts with GHG-induced warming of land areas (Figure 8.A), ensue in chaotic climate disruptions (Figure 8.B). Given the thousands to tens of thousands years longevity of atmospheric greenhouse gases (Solomon et al., 2009; Eby et al 2009), the onset of the next ice age is likely to be delayed on the scale of tens of thousands of years (Berger and Loutre, 2002) through an exceptionally long interglacial period (Figure 9).

These authors state: ‘The present day CO₂ concentration (now >410 ppm) is already well above typical interglacial values of ~290 ppmv. This study models increases to up to 750 ppmv over the next 200 years, returning to natural levels by 1000 years. The results suggest that, under very small insolation variations, there is a threshold value of CO₂ above which the Greenland Ice Sheet disappears. The climate system may take 50,000 years to assimilate the impacts of human activities during the early third millennium. In this case, an “irreversible greenhouse effect” could become the most likely future climate. If the Greenland and west Antarctic Ice Sheets disappear completely, then today’s “Anthropocene” may only be a transition between the Quaternary and the next geological period.’

Figure 9. Simulated Northern Hemisphere ice volume (increasing downward) for the period 200,000 years BP to 130,000 years in the future, modified after a part of Berger and Loutre 2002. Time is negative in the past and positive in the future. For the future, three CO2 scenarios were used: last glacial-interglacial values (solid line), a human-induced concentration of 750 ppm (dashed line), and a constant concentration of 210 ppm inducing a return to a glacial state (dotted line).

As conveyed by leading scientists “Climate change is now reaching the end-game, where very soon humanity must choose between taking unprecedented action or accepting that it has been left too late and bear the consequences” (Prof. Hans Joachim Schellnhuber) …“We’ve reached a point where we have a crisis, an emergency, but people don’t know that ... There’s a big gap between what’s understood about global warming by the scientific community and what is known by the public and policymakers” (James Hansen).

Climate scientists find themselves in a quandary similar to medical doctors, committed to help the ill, yet need to communicate grave diagnoses. How do scientists tell people that the current spate of extreme weather events, including cyclones, devastating islands from the Caribbean to the Philippine, floods devastating coastal regions and river valleys from Mozambique to Kerala, Pakistan and Townsville, and fires burning extensive tracts of the living world, can only intensify in a rapidly warming world? How do scientists tell the people that their children are growing into a world where survival under a mean temperature higher than +2 degrees Celsius (above pre-industrial temperature) is likely to be painful and, in some parts of the world, impossible, let alone under +4 degrees Celsius projected by the IPCC?

Summary and conclusions

The current growth rate of atmospheric greenhouse gas is the fastest recorded for the last 55 million years.
By the mid-21st century, at the current CO₂ rise rates of 2 to 3 ppm/year, a CO₂-e level of >750 ppm is likely to transcend the climate tipping points indicated by Lenton et al. 2008 and Schellnhuber 2009.
The current extreme rise rates of GHG (2.86 ppm CO₂/year) and temperature (0.15-0.20°C per decade since 1975) raise doubt with regard to linear future climate projections.
Global greenhouse gases have reached a level exceeding the stability threshold of the Greenland and Antarctic ice sheets, which are melting at an accelerated rate.
Allowing for the transient albedo-enhancing effects of sulphur dioxide and other aerosols, mean global temperature has reached approximately 2.0 degrees Celsius above per-industrial temperatures.
Due to hysteresis the large ice sheets would outlast their melting temperatures.
Land areas would be markedly reduced due to a rise to Miocene-like sea levels of approximately 40±15 meters above pre-industrial levels.
Cold ice melt water flowing from the ice sheets into the oceans at an accelerated rate is reducing temperatures in large tracts in the North Atlantic and circum-Antarctic.
Strong temperature contrasts between cold polar-derived and warm tropical air and water masses are likely to result in extreme weather events, retarding habitats and agriculture over coastal regions and other parts of the world.
In the wake of partial melting of the large ice sheets, the Earth climate zones would continue to shift polar-ward, expanding tropical to super-tropical regions such as existed in the Miocene (5.3-23 million years ago) and reducing temperate climate zones and polar ice sheets.
Current greenhouse gas forcing and global mean temperature are approaching Miocene Optimum-like composition, bar the hysteresis effects of reduced ice sheets (Figure 4.A).
The effect of high atmospheric greenhouse gas levels would be for the next ice age to be delayed on a scale of tens of thousands of years, during which chaotic tropical to hyperthermal conditions would persist until solar radiation and atmospheric CO₂ subsided below ~300 ppm.
Humans will survive in relatively favorable parts of Earth, such as sub-polar regions and sheltered mountain valleys, where gathering of flora and hunting of remaining fauna may be possible.

A Postscript

The author, while suggesting the projections made in this paper are consistent with the best climate science with which he is aware, sincerely hopes the implications of these projections would not eventuate.

Saturday, August 24, 2019

Cyclone over Arctic Ocean - August 24, 2019

As illustrated by above map, Arctic heating is accelerating, with temperatures showing up in the Arctic that are up to 4.41°C hotter than the average global temperature during 1880-1920.

The image below shows two plots. On the left-hand side is the temperature plot associated with above map, had a monthly mean been selected. To smooth the data, a 4-year running mean was chosen, and the plot on the right-hand side shows the associated global mean anomalies. Note that, due to this smoothing, only data from 1882 to August 2017 are displayed in the plot of the right-hand side.

It is appropriate to adjust the data by 0.5°C, as follows:

An adjustment of 0.3°C to reflect a pre-industrial baseline (heating occurred due to people's emissions before 1880-1920);
An adjustment of 0.1°C to reflect air temperatures over oceans (as opposed to sea surface temperatures);
An adjustment of 0.1°C to better include polar temperatures (the top and bottom of the image at the top shows large polar areas that should not be excluded, the more so since the Arctic has the highest temperature anomalies).

The image below shows both adjusted and unadjusted data as dark blue lines, with a light-blue polynomial trend added over the adjusted data.

Such a trend can further smooth out seasonal differences and El Niño/La Niña variability.

Such a trend can also show the potential for further temperature rise in the near future, which can constitute an important warning.

This is particularly important as the trend shows that we could be crossing the 2°C guardrail this year, i.e. the threshold that was too dangerous to be crossed.

What is the danger? Arctic heating is accelerating, as the image at the top shows, and this could make global temperatures skyrocket in a matter of years. Where Arctic sea ice disappears, hot water emerges due to albedo changes and loss of the buffer that has until now been consuming heat as part of the melting process. This is illustrated by the image below showing the sea surface temperature difference from 1961-1990 in the Arctic at latitudes 60°N - 90°N on August 23, 2019.

Disappearance of Arctic sea ice comes with numerous feedbacks that further speed up the heating, as described in the recent post Arctic Sea Ice Gone By September 2019?. Heatwaves can strongly heat up the water that gets carried by rivers into the Arctic Ocean. As the image below shows, the water was as hot as 10.7°C or 51.3°F at green circle on August 20, 2019, i.e. 9.4°C or 16.9°F hotter than 1981-2011.

As the Arctic is heating up faster than the rest of the world, the Jet Stream gets more and more distorted. A cyclone is forecast over the Arctic Ocean for August 24, 2019, pulling hot air over the Arctic Ocean, resulting in temperatures at the green circle as high as 10.4°C or 50.6°F at 1000 hPa and 7.4°C or 45.2°F at surface level, as the image below shows.

The image below illustrates the distortion of the Jet Stream, moving over the Arctic Ocean on August 24, 2019.

Such a cyclone can pull huge amounts of hot air over the Arctic Ocean, while it can also devastate the sea ice with the destructive power of winds, rain and hail.

As above animation shows, Arctic sea ice is very thin and vulnerable at the moment. The cyclone also looks set to batter the sea ice at a time when huge amounts of ocean heat are entering the Arctic Ocean from the Atlantic and Pacific Oceans. More ocean heat looks set to be on the way. As the image below shows, sea surface temperatures around North America were as high as 33°C or 91.4°F on August 21, 2019.

The image below shows the worrying rise of Northern Hemisphere sea surface temperature anomalies from the 20th century average, with the added trend illustrating the danger that this rise will lead to Arctic sea ice collapse and large methane eruptions from the seafloor of the Arctic Ocean, further accelerating the temperature rise.

[ from an earlier post ]

The image below shows the cyclone over the Arctic Ocean on August 26, 2019.

The image below shows a close-up of the sea ice just north of the North Pole, on August 26, 2019.

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

Links

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

• Arctic Sea Ice Gone By September 2019?
https://arctic-news.blogspot.com/2019/07/arctic-sea-ice-gone-by-september-2019.html

• July 2019 Hottest Month On Record
https://arctic-news.blogspot.com/2019/08/july-2019-hottest-month-on-record.html

Tuesday, August 13, 2019

The changing face of planet Earth

The changing face of planet Earth

Andrew Glikson
Earth and Climate scientist
Australian National University

12-8-2019

Preamble

The inhabitants of planet Earth are in the process of destroying the habitability of their world through the perpetration of the largest mass extinction of species since 66 million years ago, when a large asteroid impacted Earth, and 55 million years since the Paleocene-Eocene Thermal Maximum (PETM) reaching 5–8°C. The late Holocene-Anthropocene climate change represents an unprecedented event, triggering a fast shift in climate zones and a series of extreme weather events, with consequences for much of nature and civilization. The changes are manifest where green forests are blackened by fire, droughts are turning grassy planes to brown semi-deserts, brilliant white snow and ice caps are melting into pale blue water and clear blue skies turn grey due to aerosols and jet contrails, most particularly in the northern hemisphere. Unless effective efforts are undertaken at CO₂ drawdown, the consequence would include demise of much of nature and a collapse of human civilization.

1. The scorched Earth

The transfer of hundreds of billions of tonnes of carbon from the Earth crust, the residues of ancient biospheres, to the atmosphere and oceans, condemning the bulk of life through the most extreme shift in the composition of the atmosphere and ocean Earth has experienced since 55 million years ago, with changes taking place in front of our eyes. Since the industrial revolution, about 375 billion tonnes of carbon (or 1,374 billion tonnes CO₂) have been emitted by humans into the atmosphere. The consequences are everywhere, from mega-droughts, to heat waves, fires, storms and floods. With atmospheric CO₂-equivalent rising above 500 ppm and mean temperatures by more than 1.5°C (Figure 1) look no further than the shift in climate zones, displayed for example on maps of the expanding wet tropical zones, drying sub-tropical latitudes and polar-ward migration of temperate climate zone. The ice sheets and sea ice are melting, huge fires overtake Siberia, the Sahara is shifting northward, large parts of southern Europe are suffering from droughts, heat waves and fires, the Kalahari Desert dunes are shifting and much of southern Australia is affected by warming and draughts. This is hardly compensated by a minor increase in precipitation and greening such as at the southern fringes of the Sahara Desert and parts of northern Australia.

Induced by anthropogenic carbon emissions reaching 37.1 billion tonnes CO₂ in 2018 and their amplifying feedbacks from land and oceans and, ranging from 16.5 tonnes CO₂ per capita per year from the US to 35.5 tonnes CO₂ per capita per year from Saudi Arabia and 44 tonnes CO₂ per capita per year from Australia, the inexorable link between these emissions and the unfolding disaster is hardly mentioned by mainstream political classes and the media.

Figure 1 (A) Growth of CO₂-equivalent level and the annual greenhouse gas Index (AGGI¹). Measurements of CO₂ to
the 1950s are from (Keeling et al., 1958) and air trapped in ice and snow above glaciers. Pre-1978 changes are based
on ongoing measurements of all greenhouse gases. Equivalent CO₂ amounts (in ppm) are derived from the relationship
between CO₂ concentrations and radiative forcing from all long lived gases; (B) showing how much warmer each
month of the GISTEMP data is than the annual global mean. For July (2019) temperatures rose by about +1.5°C.
¹The AGGI index uses 1990 as a baseline year with a value of 1. The index increased every year since 1979.

2. Migrating climate zones

As the globe warms, to date by a mean of near ~1.5 °C, or ~2.0°C when the masking effects of sulphur dioxide and other aerosols are considered, and by a mean of ~2.3°C in the polar regions, the expansion of warm tropical latitudes and the pole-ward migration of subtropical and temperate climate zones (Figure 2) ensue in large scale droughts such as parts of inland Australia and southern Africa. A similar trend is taking place in the northern hemisphere where the Sahara desert is expanding northward, with consequent heat waves across the Mediterranean and Europe.

In southern Africa “Widespread shifts in climate regimes are projected, of which the southern and eastern expansion of the hot desert and hot steppe zones is most prominent. From occupying 33.1 and 19.4 % of southern Africa under present-day climate, respectively, these regions are projected to occupy between 47.3 and 59.7 % (hot desert zone) and 24.9 and 29.9 % (hot steppe zone) of the region in a future world where the mean global temperature has increased by ~3°C.

Closely linked to the migration of climate zones is the southward drift of Antarctic- sourced cold moist fronts which sustain seasonal rain in south-west and southern Australia. A feedback loop has developed where deforestation and decline in vegetation in southern parts of the continent result in the rise of thermal plumes of dry air masses that deflect the western moist fronts further to the southeast.

Figure 2. Köppen-Geiger global Climate zones classification map

Since 1979 the planet’s tropics have been expanding pole-ward by 56 km to 111 km per decade in both hemispheres, leading one commentator to call this Earth’s bulging waistline. Future climate projections suggest this expansion is likely to continue, driven largely by human activities – most notably emissions of greenhouse gases and black carbon, as well as warming in the lower atmosphere and the oceans.”

An analysis of the origin of Australian droughts suggests, according to both observations and climate models, that at least part of this decline is associated with changes in large-scale atmospheric circulation, including shrinking polar ice and a pole-ward movement of polar-originated westerly wind spirals, as well as increasing atmospheric surface pressure and droughts over parts of southern Australia (Figure 3). Simulations of future climate with this model suggest amplified winter drying over most parts of southern Australia in the coming decades in response to changes in radiative forcing. The drying is most pronounced over southwest Australia, with total reductions in austral autumn and winter precipitation of approximately 40% by the late twenty-first century. Thus rainfall in southwestern Australia has declined sharply from about 1965 onward, concomitant with the sharp rise of global temperatures.

Figure 3 (A) Bureau of Meteorology (BOM) drought map, showing rainfall levels for the southern wet season from
April 1 to July 31 in 2019; (B) NASA satellite image displaying a southward deflection of Antarctic-sourced moist
cold fronts from southern Australia, a result of (1) southward migration of climate zones; (2) increasing aridity of
southern and southwestern Australia due to deforestation; (3) rising hot plumes from warming arid land.

3. Extreme weather events

The consequences of the migration of climate zones are compounded by changes in flow patterns of major river systems around the world, for example in southern an southeastern Asia, including the Indus, Ganges, Brahmaputra and Mekong river basins, the home and bread basket for more than a billion people. With warming, as snow cover declines in the mountainous source regions of rivers, river flows are enhanced, with ensuing floods, in particular during the Monsoon. For example, in 2010 approximately one-fifth of Pakistan's total land area was affected by floods (Figure 4A), directly affecting about 20 million people, with a death toll close to 2,000. And about 700 people in cyclone Isai in Mozambique (Figure 4B, C). Such changes in climate and geography are enhanced once sea level rise increases from the scale of tens of centimeters, as at present, to meters, as predicted to take place later this and next century.

An increasing frequency and intensity of cyclones constitute an inevitable consequence of rising temperatures over warm low pressure cell tracks in tropical oceans, already affecting large populations in the Caribbean and west Pacific island chains, encroaching into continental coastal zones, China, southeast USA, southeast Africa, India, northern Australia, the Pacific islands. According to Sobel et al. (2016) “We thus expect tropical cyclone intensities to increase with warming, both on average and at the high end of the scale, so that the strongest future storms will exceed the strength of any in the past”. Likewise increasing temperatures, heat waves and droughts, compounded by deforestation over continents, constitute an inevitable consequence of heat waves and droughts. A prime example is the Siberian forest fires (Figure 5B), covering an area larger than Denmark and contributing significantly to climate change. Since the beginning of the year a total of 13.1 million hectares has burned. Total losses from natural catastrophes on 2018 stated as US$160 billion.

Figure 4 (A) Pakistan flooding, shows the 2010 Indus River spanning well over 10 kilometers, completely filling
the river valley and spilling over onto nearby land. Floodwaters have created a lake almost as wide as the swollen
Indus that inundates Jhatpat; (B) Before-and-after satellite imagery of Mozambique showing massive flood
described as an "inland ocean" up to 30 miles wide following the landfall of Tropical Cyclone Idai, 2019.

Figure 5 (A) Global fire zones, NASA. The Earth data fire map accumulates the locations of fires detected by
moderate-resolution imaging radiometer (MODIS) on board the Terra and Aqua satellites over a 10-day period.
Each colored dot indicates a location where MODIS detected at least one fire during the compositing period.
Color ranges from red where the fire count is low to yellow where number of fires is large; (B) An ecological
catastrophe in Russia: wildfires have created over 4 million square km smoke lid over central northern Asia.
Big Siberian cities are covered with toxic haze that had already reached Urals.

4. Shrinking Polar ice sheets

Last but not least, major changes in the Polar Regions are driving climate events in the rest of the globe. According to NOAA Arctic surface air temperatures continued to warm at twice the rate of the rest of the globe, leading to major thaw at the fringes of the Arctic (Figure 6A) and a loss of 95 percent of its oldest ice over the past three decades. Arctic air temperatures during 2014-18 since 1900 have exceeded all previous records and are driving broad changes in the environmental system both within the Arctic as well as through the 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 an increasingly undulating jet stream barrier, as well as allowing warm air masses to move northward, further warming the Arctic and driving further ice melting (Figure 6B).

According to Rignot et al. (2011) in 2006 the Greenland and Antarctic ice sheets experienced a combined mass loss of 475 ± 158 billion tons of ice per year. IPCC models of future climate change contain a number of departures from the paleoclimate evidence, including the major role of feedbacks from land and water, estimates of future ice melt, sea level rise rates, methane release rates, the role of fires in enhancing atmospheric CO₂, and the already observed onset of transient freeze events consequent on the flow of ice melt water into the oceans. Ice mass loss would raise sea level on the scale of meters and eventually tens of meters (Hansen et al. 2016). The development of large cold water pools south and east of Greenland (Rahmstorf et al. 2015) and at the fringe of West Antarctica, signify early stages in the development of a North Atlantic freeze, consistent with the decline in the Atlantic Meridional Ocean Circulation (AMOC). As the Earth warms the increase in temperature contrasts across the globe, in particular between warming continental regions and cooling ocean regions, leads to storminess and extreme weather events, which 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 drought zones.

Figure 6 (A) Thawing at the fringes of Siberia and Canada. Scientists say 2019 could be another annus
horribilis for the Arctic with record temperatures already registered in Greenland—a giant melting ice
sheet that threatens to submerge the world's coastal areas one day; (B) Weakening and increasing undulation
of the polar vortex, allowing penetration of cold fronts southward and of warm air masses northward.

Figure 7 (A) Surface air temperature (°C) change in 2055–2060 relative to 1880–1920 according to.
A1B model + modified forcings and ice melt to 1 meter sea level rise; (B) Surface-air temperature
change in 2096 relative to 1880–1920 according to IPCC model AIB adding Ice melt with 10-year
doubling of ice melt leading to +5 meters sea level rise; (C) Surface air temperature (°C) relative to
1880–1920 for several scenarios taking added ice melt water into account (Hansen et al. 2016)

Postscript

None of the evidence and projections summarized above appears to form a priority consideration on the part of those in power—in parliaments, in corporations, among the wealthy elites and vested interests. Having to all intents and purposes given up on the habitability of large parts of the Earth and on the survival of numerous species and future generations—their actions and inactions constitute the ultimate crime against life on Earth.

Andrew Glikson

Dr Andrew Glikson

Earth and climate scientist
Australian National University
Canberra, Australian Territory, Australia

geospec@iinet.net.au

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

From Stars to Brains: Milestones in the Planetary Evolution of Life and Intelligence

The Plutocene: Blueprints for a Post-Anthropocene Greenhouse Earth

Added below is a video with an August 6, 2019, interview of Andrew Glikson by Guy McPherson and Kevin Hester, as edited by Tim Bob.

Friday, August 9, 2019

IPCC Report Climate Change and Land

The IPCC has just issued a special report Climate Change and Land, on climate change, desertification, land degradation, sustainable land management, food security, and greenhouse gas fluxes in terrestrial ecosystems. In its new report 'Climate Change and Land', the IPCC finds that vegan is the best diet to reduce emissions. Sadly, it is yet another missed opportunity to show some integrity.

[ click on image to enlarge ]

Indeed, little or nothing will change as long as the IPCC keeps downplaying the dire situation we're in.

As an example, the IPCC Report uses a very low value of 28 as Global Warming Potential (GWP) for methane, which is totally inappropriate and unacceptable given the rapidity at which the biosphere is deteriorating, given the accelerating pace at which extreme weather events are striking the land all around the world, and given the grim prospects for people worldwide in the absence of rapid and radical change.

The report finds that agriculture, forestry and other land use activities accounted for around 13% of carbon dioxide, 44% of methane, and 82% of nitrous oxide emissions from human activities globally during 2007-2016, representing 23% of total net anthropogenic emissions of greenhouse gases. If emissions associated with pre- and post-production activities in the global food system are included, the emissions could be as high as 37% of total net anthropogenic greenhouse gas emissions.

The Report adds an image showing that annual methane emissions from agriculture had reached some 4Gt CO₂eq in 2016. The IPCC notes that this 4Gt for methane's CO₂-eq is based on a GWP for methane of 28 over 100 years and without climate-carbon feedbacks, taken from its Fifth Assessment Report (AR5), published in 2014.

As said, the Report calculates that net greenhouse gas emissions from agriculture, forestry, and other land use were 23% of people's 2007-2016 emissions when using a GWP of 28 for methane. When using a GWP of 150, that share rises to 31%, as illustrated by the image on the right.

Instead of calculating methane's GWP over 100 years, a very short horizon is appropriate. Moreover, research published in 2016 and 2018 had already found methane to be more potent than IPCC's GWP for methane in AR5, as discussed in a recent post.

When using an appropriate GWP, the percentage of greenhouse gases coming from agriculture (in particular livestock products) increases dramatically, thus rightly highlighting the urgency for governments to act, e.g. by implementing local feebates, such as fees on livestock products and nitrogen fertilizers with revenues used to support soil supplements containing biochar, as recommended in a recent post.