Beyond climate tipping points

[Vice-Regent]

Greenhouse gas levels exceed the stability threshold of the ice sheets

 

by Andrew Glikson

 

Abstract

As the world keeps increasing its carbon emissions and exports, rising in 2018 to a record 33.1 billion ton per year, the atmospheric greenhouse gas level has now exceeded 560 ppm CO₂-equivalent when methane and nitrous oxide are included, intersecting the stability threshold of the Greenland and Antarctic ice sheets. The term “climate change“ is 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 to be are presiding over the sixth mass extinction of species, including humans.

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.


1. Rising greenhouse gases and temperatures

By May 2019 CO₂ levels measured at Mouna Loa, Hawaii, reached 414.66 ppm, growing at a rate of 3.42 ppm/year, the highest rate recorded for the last 65 million years when the dinosaurs went extinct. The total CO₂, methane (CH₄) and nitrous oxide (N₂O) expressed as CO₂-equivalents has reached 560.3 ppm (Table 1), the highest concentration since the Oligocene (33.9 to 23 Million years ago) when atmospheric CO₂ ranged between 400-500 ppm.

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

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

Total CO₂e: 414.7 + 46.6 + 99 = 560.3 ppm CO₂e
Plus: SF₆, CHF3, CH2F2, CF4, C2F6, C3F8, C4F10, C4F8, C5F12, C6F1

 

Figure 1. Projected CO₂ levels for IPCC emission scenarios

The current rise of total GHG to about 560 ppm CO₂-equivalent implies that, for a climate sensitivity of 3 degrees Celsius per doubling of atmospheric CO₂, global warming has potentially reached 3°C. This level is almost 3 times the 2018 global land-ocean temperature of 0.8°C above pre-industrial levels as reported by NASA. A rise of about 1.5°C in land temperatures is reported by the Berkeley Earth institute. Considering the albedo effects of aerosols, including sulphur dioxide, dust, nitrate and organic carbon, the mean rise of land temperature exceeds 1.5°C.

The threshold for collapse of the Greenland ice sheet is estimated in the range of 400-560 ppm CO₂ and approximately 2.0 - 2.5 degrees Celsius above pre-industrial temperatures. The threshold for the breakdown of the West Antarctic ice sheet is similar. The temperature conditions under which the East Antarctic ice sheet formed in the late Eocene - early Oligocene abrupt cooling period (34.1 to 33.6 Ma) are in the range of ~800–2000 ppm and 4 to 6 degrees Celsius above pre-industrial temperatures. Based mainly on satellite gravity data there are signs the East Antarctic ice sheet is beginning to melt in places (Jones, 2019), with ice loss rates of 40 ± 9 Gt/y (Gigaton ice/year) in 1979–1990 and up to to 252 ± 26 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, including 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 560 ppm is higher than the mid-Miocene (~23 to 5.3 million years ago) atmospheric range of about 400-500 ppm and 3 - 4°C (Figure 2) 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.

2. Transient Stadial freeze events

As the glacial sheets disintegrate cold ice melt water flowing into the ocean lead to the formation of large cold water pools, as indicated by interglacial records of the last 450 kyr, including a growth of cold pools in the northern Atlantic Ocean south of Greenland and in the southern Ocean fringing Antarctica (Figures 3, 4). Warming of the Arctic driven by the ice-water albedo flip and the weakening of the North Atlantic Thermohaline Circulation lead to weakening of the jet stream and the Arctic boundary. Penetration of Arctic-derived cold air masses southward through the weakened boundary ensues in extreme weather events in North America, Europe and northern Asia.
 

Warming of 3 to 4 degrees Celsius above pre-industrial levels leading to enhanced ice-sheet melt would raise sea level by 2 to 5 meters toward the end of the century, and likely by 25 meters in the longer term, a level consistent with Pliocene global temperatures of +2 to 3°C. 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, creating a positive feedback that increases Antarctic ice loss. However the effects of ice-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 long term stadial freeze event may ensue, lasting perhaps as long as two to three centuries as in the 8200 years-old Laurentian melt event, and even as long as the Younger dryas 12.9-11.7 Kyr.

 

 

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).

 

3. 21st–23rd centuries uncharted climate territory

Modelling of climate trends for the 21st to 23rd centuries by the IPCC AR5 Synthesis Report, 2014 portrays predominantly linear models for 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, increasing 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 as 0.7Watt/m², which is a value close to the total of methane release since 1750 (~0.5Watt/m²).
• Reduced ocean’s CO₂ intake due to lesser solubility of the gas at higher temperatures.
• Vegetation desiccation and loss in some regions, and thereby reduced evaporation with its cooling effect. This factor and the increase of precipitations 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 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.

 

Andrew Glikson

[blizzard1024]

Based on the latest map from University of Maine's "climate change institute" todays global anonmaly is + 0.2C.  This dataset uses a 1979-2000 climo.  It is has been running negative at times lately. The  UAH was at  0.32C for May. If the equivalent CO2 is now at 560 ppm because of other GHGs then we have doubled since pre-industrial era. It is a little warmer now than before. Not much to see here. This is why action is very slow to go to renewables.  So climate scientists are trying to relate weather events to climate change which is ridiculous. Hurricane Harvey stalled over Texas because it was unusually cold aloft and hence an upper level low captured a tropical cyclone, then it stalled. That will give you 60" of rain. 

[Vice-Regent]

The Northern Hemisphere anomaly is rather warm and continues to run warm for the foreseeable future. Antarctica will warm up as it does every year in the warm season. There is a AGW positive snowcover feedback in the winter for the regions poleward enough to enjoy it.

Even if you subscribe to the bullshit narrative. Cloud heights are dropping worldwide because the stratosphere is cooling. Exactly as you would expect.

[Buckeyes_Suck]

My take is that all of the subsidy money spent on going "green" would be better spent on infrastructure projects to better protect/and or relocate people. If the entire world were to go green and try to reduce emissions there would at least be a chance, but the actions of the US are just a drop in the pond compared to what china and india are doing to the planet. Over the next 50 years the population in asia and africa will continue to explode and further industrialization of these areas is inevitable. 

We're well past the tipping point.

[chubbs]

On 6/24/2019 at 6:32 AM, blizzard1024 said:

Based on the latest map from University of Maine's "climate change institute" todays global anonmaly is + 0.2C.  This dataset uses a 1979-2000 climo.  It is has been running negative at times lately. The  UAH was at  0.32C for May. If the equivalent CO2 is now at 560 ppm because of other GHGs then we have doubled since pre-industrial era. It is a little warmer now than before. Not much to see here. This is why action is very slow to go to renewables.  So climate scientists are trying to relate weather events to climate change which is ridiculous. Hurricane Harvey stalled over Texas because it was unusually cold aloft and hence an upper level low captured a tropical cyclone, then it stalled. That will give you 60" of rain.

The switch to fv3 has messed up Maine's anomaly calc, June is going to be warm, top 3 most likely.

[SENC]

Just read THIS thread.. All is Well..

https://threadreaderapp.com/thread/1109923374568890368.html

 

[Vice-Regent]

6 minutes ago, SENC said:

Just read THIS thread.. All is Well..

https://threadreaderapp.com/thread/1109923374568890368.html

 

I agree we shouldn't antagonize people with false hope that this problem can be solved in a meaningful way. When we talk about solving climate change we usually imply public policy actions designed to minimize damage to civilization and by association the lives and property of humanity. The main problem to date is getting people to actually care about the environment in a way that is not exploitative. With this alone you can solve up to 95% of land base exploitation as people will willingly set aside space for nature without the requirement of regulations and cooperation of corporations with the government. (if there are any left by that point)

My posting style would hopefully be more supportive of giving people emotional support in these extreme times if not for the continuous resurgence of trolls and what not.

[CAD_Wedge_NC]

On 6/28/2019 at 4:20 PM, SENC said:

Just read THIS thread.. All is Well..

https://threadreaderapp.com/thread/1109923374568890368.html

 

That just about sums it up .... Kudos to the ones that took the time to create this. I am old enough to remember that "global cooling" scare.

[bdgwx]

On 7/3/2019 at 4:05 PM, CAD_Wedge_NC said:

That just about sums it up .... Kudos to the ones that took the time to create this. I am old enough to remember that "global cooling" scare.

THE MYTH OF THE 1970s GLOBAL COOLING SCIENTIFIC CONSENSUS