Arctic News: feedbacks

Showing posts with label feedbacks. Show all posts

Friday, June 21, 2019

Beyond climate tipping points

Beyond climate tipping points
Greenhouse gas levels exceed the stability limit of the
Greenland and Antarctic ice sheets

by Andrew Glikson

Abstract

The pace of global warming has been grossly underestimated. As the world keeps increasing its carbon dioxide (CO₂) emissions, rising in 2018 to a record 33.1 billion ton of CO₂ per year, the atmospheric greenhouse gas level has now exceeded 560 ppm (parts per million) CO₂-equivalent, namely when methane and nitrous oxide are included. This level surpasses the stability threshold of the Greenland and Antarctic ice sheets. The term “climate change” is thus no longer appropriate, since what is happening in the atmosphere-ocean system, accelerating over the last 70 years or so, is an abrupt calamity on a geological dimension, threatening nature and human civilization. Ignoring what the science says, the powers-that-be are presiding over the sixth mass extinction of species, including humanity.

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” (Prof. James Hansen).

Rising greenhouse gases and temperatures

By May 2019 CO₂ levels (measured at Mauna Loa, Hawaii) reached 414.66 ppm, growing at a rate of 3.42 ppm/year, well above the highest rate recorded for the last 65 million years. The total CO₂, methane (CH₄) and nitrous oxide (N₂O) expressed as CO₂-equivalents has reached at least 560.3 ppm (Table 1) (at a very low forcing value for methane ¹), the highest concentration since 34 - 23 Million years ago, when atmospheric CO₂ ranged between 350 and 500 ppm.

Table 1. Total atmospheric CO2e from CO2, CH4 and N2O

CO2	CO2 rate	CH4	CH4 rate	N2O
414.66 ppm	3.42 ppm/year	1865.4 ppb	9.2 ppm/year	332ppb
CO2 ppm	CO2 ppm rise/year	CH4 ppm CH4 forcing ≥25 CO2e	CH4 ppb rise/year	N2O ppm N2O forcing = 298 CO2e
CO2 ppm 414.7		CH4 ppm forcing 1.865 x ≥25 = ≥46.6 ppm CO2e (equivalent)		N2O ppm forcing 0.332 x 298 = 99 ppm CO2e (equivalent)

Total CO2e: 414.7+46.6+99 = >560.3 ppm CO2e

¹A methane forcing value of 25 x CO2 is very low. Higher forcing values are more appropriate.
Plus: SF₆, CHF3, CH2F2, CF4, C2F6, C3F8, C4F10, C4F8, C5F12, C6F1

Figure 1. Projected CO₂ levels for IPCC emission scenarios

The current rise of the total greenhouse gas levels to at least 560 ppm CO₂-equivalent, twice the pre-industrial CO2 level of 280 ppm, implies that global warming has potentially reached +2°C to +3°C above pre-industral temperature. Considering the mitigating albedo/reflection effects of atmospheric aerosols, including sulphur dioxide, dust, nitrate and organic carbon, the mean rise of land temperature exceeds +1.5°C (Berkeley Earth institute).

The threshold for collapse of the Greenland ice sheet is estimated in the range of 400-560 ppm CO₂ at approximately 2.0 - 2.5 degrees Celsius above pre-industrial temperatures, and is retarded by hysteresis (where a physical property lags behind changes in the effect causing it). The threshold for the breakdown of the West Antarctic ice sheet is similar. The greenhouse gas level and temperature conditions under which the East Antarctic ice sheet formed about 34 million years ago are estimated as ~800–2000 ppm at 4 to 6 degrees Celsius above pre-industrial values. Based mainly on satellite gravity data there is evidence the East Antarctic ice sheet is beginning to melt in places (Jones, 2019), with ice loss rates of approximately 40 Gt/y (Gigaton of ice per year) in 1979–1990 and up to to 252 Gt/y in 2009–2017 (Rignot et al., 2019).

The cumulative contribution to sea-level rise from Antarctic ice melt was 14.0 ± 2.0 mm since 1979. This includes 6.9 ± 0.6 mm from West Antarctica, 4.4 ± 0.9 mm from East Antarctica, and 2.5 ± 0.4 mm from the Antarctic Peninsula (Rignot et al., 2019). Based on the above the current CO₂-equivalent level of at least 560 ppm closely correlates with the temperature peak at ~16 million tears ago (Figures 2 and 5), when the Greenland ice sheet did not exist and large variations affected the Antarctic ice sheet (Gasson et al., 2016).

Figure 2. Updated Cenozoic pCO₂ and stacked deep-sea benthic foraminifer oxygen isotope curve for 0 to
65 Ma (Zachos et al., 2008) converted to the Gradstein timescale (Gradstein et al., 2004).
ETM2 = Eocene Thermal Maximum 2, PETM = Paleocene/Eocene Thermal Maximum.

Transient melt events

As the glacial sheets disintegrate, cold ice-melt water flowing into the ocean ensue in large cold water pools, a pattern recorded through the glacial-interglacial cycles of the last 450,000 years, manifested by the growth of cold regions in the north Atlantic Ocean south of Greenland and in the Southern Ocean fringing Antarctica (Figures 3 and 4). The warming of the Arctic is driven by the ice-water albedo flip (where dark sea-water absorbing solar energy alternate with high-albedo ice and snow) and by the weakening of the polar boundary and jet stream. Penetration of Arctic-derived cold air masses through the weakened boundary results in extreme weather events in North America, Europe and northern Asia, such as the “Beast from the East event”.

Warming of +3°C to +4°C above pre-industrial levels, leading to enhanced ice-sheet melt, would raise sea levels by 2 to 5 meters toward the end of the century, and 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. The effects of ice sheet-melt waters on the oceans were hardly included in IPCC models. Depending on the amplifying feedbacks, prolonged Greenland and Antarctic melting (Figures 3 and 4) and a consequent freeze event may ensue, lasting perhaps as long as two to three centuries.

Figure 3. (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).

21st–23rd centuries uncharted climate territory

Modelling of climate trends for the 2100-2300 by the IPCC AR5 Synthesis Report, 2014 portrays predominantly linear models of greenhouse gas rise, global temperatures and sea levels. These models however appear to take little account of amplifying feedbacks from land and ocean and of the effects of cold ice-melt water 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 in melting sea ice and ice sheets and the increase of the water surface area and thereby the sequestration of CO₂. Hudson (2011) estimates a rise in radiative forcing due to removal of Arctic summer sea ice of 0.7 Watt/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 loss in some regions, and thereby reduced evaporation with its cooling effect. This factor and the increase of precipitation in other regions lead to a differential feedbacks from vegetation as the globe warms (Notaro et al. 2007).
An increase in wildfires, releasing greenhouse gases.
Release of methane from permafrost, bogs and sediments and other factors.

Linear temperature models do not appear to take into account the effects on the oceans of ice melt water derived from the large ice sheets, including the possibility of a major stadial event such as already started in oceanic tracts fringing Greenland and Antarctica (Figure 3). In the shorter term sea level rises include 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 event and the 12.7-11.9 younger dryas event, a prolonged breakdown of parts of the Antarctic ice sheet could result in major sea level rise and extensive cooling of northern and southern latitudes, parallel with warming of tropical and mid-latitudes (Figure 4) (Hansen et al., 2016). The clashes between polar-derived cold weather fronts and tropical air masses are bound to lead to extreme weather events, echoed in Storms of my grandchildren (Hansen, 2010).

Figure 4. Model Surface-air temperature (°C) for 2096 relative to 1880–1920 (Hansen et al. 2016).
The projection portrays 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, including Siberia and Canada.

Summary and conclusions

Global greenhouse gases have reached a level exceeding the stability threshold of the Greenland and Antarctic ice sheets, melting at an accelerated rate.
The current growth rate of atmospheric greenhouse gas of 3.42 ppm CO₂/year is the fastest recorded for the last 55 million years.
Allowing for the transient albedo enhancing effects of sulphur dioxide and other aerosols, mean global temperature has reached about 2 degrees Celsius above pre-industrial temperatures.
Due to hysteresis the large ice sheets outlast their melting temperatures.
Cold ice melt water flowing from the ice sheets at an accelerated rate will reduce the temperature of large ocean tracts in the North Atlantic and circum-Antarctic. Strong temperature contrasts between cold polar-derived air and water masses and tropical air and water masses would result in extreme weather events, retarding agriculture in large parts of the world.
Humans will survive in relatively favorable parts of Earth, such as sub-polar regions and sheltered mountain valleys, where hunting of surviving fauna may be possible.
In the wake of partial melting of the large ice sheets, the Earth climate would shift to polarized conditions including reduced polar ice sheets and tropical to super-tropical regions such as existed in the Miocene (5.3 - 23 million years ago) (Figure 5).

Figure 5. Late Oligocene–Miocene inferred atmospheric CO2 fluctuations and effects on global temperature
based on Stromata index (SI) of 25 and 12 Ma (late Oligocene to late middle Miocene) fossil leaf remains;
(A) Reconstructed late Oligocene–middle Miocene CO2 levels based on individual independently
calibrated tree species; (B) Modeled temperature departure of global mean surface temperature from
present day, calculated from mean CO2 estimates by using a CO2–temperature sensitivity study. Red
discontinuous lines: 2019 CO2-e levels and 2019 temperatures (discounting the aerosol masking effects).

Current greenhouse gas forcing and global mean temperature are approaching Miocene Optimum-like composition, bar the hysteresis effects of reduced ice sheets (Figure 5). Strong temperature polarities are suggested by the contrasts between reduced Antarctic ice sheet and super-tropical conditions in low to mid-latitudes. Land areas would be markedly reduced due to a sea level rise of approximately 40 ± 15 meters.

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.

Monday, April 8, 2019

Blue Ocean Event Consequences

A Blue Ocean Event looks set to occur in the Arctic when there will be virtually no sea ice left. At first, the duration of this event will be a few weeks in September, but as more heat accumulates in the Arctic, the event will last longer each year thereafter.

Indeed, a Blue Ocean Event will come with accumulation of more heat, due to loss of latent heat, as a dark (blue) ocean absorbs more sunlight than the reflective ice, etc. Consequences will extend far beyond the Arctic, as shown on the image below that features Dave Borlace's Blue Ocean Top Ten Consequences.

Dave Borlace goes into more detail regarding these consequences in the video Blue Ocean Event : Game Over?

A Blue Ocean Event could happen as early as September 2019. The image below shows that Arctic sea ice extent on April 7, 2019, was 12.97 million km², a record low for measurements at ads.nipr.ac.jp for the time of year. By comparison, on May 28, 1985, extent was larger (13.05 million km²) while it was 51 days later in the year.

In the video below, Paul Beckwith also discusses the rapid decline of the sea ice and the consequences.

Clearly, the rapid decline of the sea ice has grave consequences. When also looking beyond what's happening in the Arctic, there are further events, tipping points and feedbacks that make things worse. An earlier post contains the following rapid warming scenario:

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

Importantly, depicted above is only one scenario out of many. Things may eventuate in different order and occur simultaneously, i.e. instead of one domino tipping over the next one sequentially, many events reinforcing each other. Further points should be added to the list, such as falling away of sulfate cooling due to economic changes, ocean stratification and stronger storms that can push large amounts of warm salty water into the Arctic Ocean.

Global sea ice extent is also at a record low for the time of year. Global sea ice extent on April 8, 2019, was 17.9 million km². On April 8, 1982, global sea ice extent was 22.32 million km², i.e. a difference of 4.42 million km². That constitutes a huge albedo loss.

As discussed in an earlier post, this all adds up to further global warming that may eventuate very rapidly. The image below shows how a total rise of 18°C or 32.4°F from preindustrial could eventuate by 2026.

Friday, August 24, 2018

The once-thickest Arctic sea ice has gone

The image below shows Arctic sea ice north of Greenland and around Ellesmere Island. This is the area where for thousands of years the sea ice has been the thickest, in many places remaining thicker than 5 meters (16.4 ft) throughout the year.

[ The once-thickest sea ice has gone - click on images to enlarge ]

The image is a compilation of NASA Worldview images over seven days, from August 14 through to August 21, 2018. The least cloudy areas have been selected from each image to get the best insight in the magnitude of this catastrophe.

The loss of this sea ice indicates that the buffer is gone. Sea ice acts as a buffer that absorbs heat, while keeping the temperature at the freezing point of water, about zero degrees Celsius. As long as there is sea ice in the water, this sea ice will keep absorbing heat, so the temperature doesn't rise at the sea surface.

Once the buffer is gone, further energy that enters the Arctic Ocean will go into heating up the water. The amount of energy absorbed by melting ice is as much as it takes to heat an equivalent mass of water from zero to 80°C.

[ The Latent Heat Buffer has gone, feedback #14 on the Feedbacks page ]

At the same time, decline of the snow and ice cover in the Arctic causes more sunlight to get reflected back into space, resulting in more energy getting absorbed in the Arctic Ocean.

[ Albedo Change, feedback #1 on the Feedbacks page ]

Numerous feedbacks are associated with sea ice loss. As the temperature difference between the Arctic and the Equator decreases, changes are taking pace to the Jet Stream that in turn trigger a multitude of further feedbacks, such as more extreme weather and a more scope for heat to enter the Arctic Ocean (see feedbacks page).

A further huge danger is that, as warming of the Arctic Ocean continues, heat will reach methane hydrates at the seafloor of the Arctic Ocean, causing them to get destabilized and release methane.

[ Seafloor methane, feedback #2 on the Feedbacks page ]

Adding up all warming elements associated with disappearance of the sea ice could result in additional global warming many times as much as the current global warming, all in a few years time.

Meanwhile, for the first time in human history, mean global methane levels as high as 1900 ppb have been recorded. The measurements were recorded by the MetOp-1 satellite on the morning of August 22, 2018, at 280 mb, 266 mb, 307 mb and 321 mb, as shown by the images below.

At 293 mb, MetOp-1 recorded an even higher level, i.e. mean global methane level was 1901 ppb on the morning of August 22, 2018.

Sunday, July 1, 2018

Can we weather the Danger Zone?

[ click on image to enlarge ]

As an earlier Arctic-news analysis shows, Earth may have long crossed the 1.5°C guardrail set at the Paris Agreement.

Earth may have already been in the Danger Zone since early 2014. This is shown by the image on the right associated with the analysis, which is based on NASA data that are adjusted to reflect a preindustrial baseline, air temperatures and Arctic temperatures.

As the added 3rd-order polynomial trend shows, the world may also be crossing the higher 2°C guardrail later this year, while temperatures threaten to keep rising dramatically beyond that point.

What is the threat?

As described at the Threat, much carbon is stored in large and vulnerable pools that have until now been kept stable by low temperatures. The threat is that rapid temperature rise will hit vulnerable carbon pools hard, making them release huge amounts of greenhouse gases, further contributing to the acceleration of the temperature rise.

Further release of greenhouse gases will obviously further speed up warming. In addition, there are further warming elements that could result in very rapid acceleration of the temperature rise, as discussed at the Extinction page.

The Danger Zone

Below are some images illustrating just how dire the situation is, illustrating how vulnerable carbon pools are getting hit exactly as feared they would be with a further rise in temperature.

On July 5, 2018, it was as hot as 33.5°C or 92.3°F on the coast of the Arctic Ocean in Siberia (at top green circle, at 72.50°N). Further inland, it was as hot as 34.2°C or 93.5°F (at bottom green circle, at 68.6°N).

The satellite image below shows smoke from fires over parts of Siberia hit strongly by heat waves.

The fires caused carbon monoxide levels as high as 20,309 ppb over Siberia on July 3, 2018.

Methane levels that day were as high as 2,809 ppb.

On July 4, 2018, forest fires near the Lena River cause smoke over the Laptev Sea and East Siberian Sea. CO (see inset) and CO₂ levels that day were as high as 45080 ppb and 724 ppm (at the green circle), as illustrated by the image below.

The Copernicus image below shows aerosol forecasts for July 4, 2018, 21:00 UTC, due to biomass burning.

Another Copernicus forecast shows high ozone levels over Siberia and the East Siberian Sea.

EPA 8-hour ozone standard is 70 ppb and here's a report on recent U.S. ozone levels. See Wikipedia for more on the strong local and immediate warming impact of ozone and how it also makes vegetation more vulnerable to fires.

The global 10-day forecast (GFS) below, run on July 3, 2018, with maximum 2 meter temperature, shows that things may get even worse over the coming week or more.

Could we move out of the Danger Zone?

What can be done to improve this dire situation?

One obvious line of action is to make more effort to reduce emissions that are causing warming. There's no doubt that this can be achieved and has numerous benefits, as described in an earlier post. Emission cuts can be achieved by implementing effective policies to facilitate changes in energy use, in diet and in land use and construction practices, etc.

One complication is that the necessary transition away from fossil fuel is unlikely to result in immediate falls in temperatures. This is the case because there will be less sulfur in the atmosphere to reflect sunlight back into space. Furthermore, there could also be an increase in biomass burning, as discussed at the Aerosols page, while the full wrath of recent carbon dioxide emissions is yet to come. As said, the resulting rise in temperature threatens to trigger numerous feedbacks that could accelerate the temperature rise even further. For more on how much temperatures could rise, see the Extinction page.

While it's clear that - besides emission cuts - further action is necessary, such as removing greenhouse gases from the atmosphere and oceans, the prospect is that such removal will have to continue for decades and decades to come before it can bring greenhouse gases down to safer levels. To further combat warming, there are additional lines of action to be looked at, but as long as politicians remain reluctant to even consider pursuing efforts to reduce emissions, we can expect that the world will be in the Danger Zone for a long time to come.

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