Tuesday, July 16, 2019

Most Important Message Ever

This is the most important message ever posted.
Please share it widely and add your comments!
(click on share in the box underneath this post)

A catastrophe of unimaginable proportions is unfolding. Life is disappearing from Earth and runaway heating could destroy all life. At 5°C heating, most life on Earth will have disappeared. When looking only at near-term human extinction, 3°C will likely suffice. Study after study is showing the severity of the threat that too many keep ignoring or denying it, at the peril of the world at large. Have a look at the following:

Crossing the 2°C guardrail

The image below shows two trends, a long-term trend (blue) and a short-term trend (red) that better reflects El Niño peaks.


The image confirms an earlier analysis that it could be 1.85°C (or 3.33°F) hotter in 2019 than in 1750.

June 2019 was the hottest June on record, it was 2.08°C (or 3.74°F) hotter than the annual global mean 1980-2015, which was partly due to seasonal variations, as the image below shows.


This gives an idea of how hot the year 2019 will be. July 2019 is on course to be hottest month on record, further highlighting the danger that a strengthening El Niño could cause a steep temperature rise soon.

Remember the 2015 Paris Agreement, when politicians pledged to act on the threat of climate change, including by “Holding the increase in the global average temperature to well below 2°C above pre-industrial levels . . . ”

The image at the top highlights the danger of a rapid temperature rise occurring soon and of the 2°C (or 3.6°F) guardrail getting crossed soon, i.e. in 2020 (the blue long-term trend, based on 1880-June2019 data), or in 2019 (red trend, based on 2011-June 2019 data). Moreover, the danger is that temperatures will not come down after crossing 2°C, but instead will continue in a steep rise toward 3°C.


We are already at about 2°C above pre-industrial

In the image at the top, NASA data are adjusted by 0.57°C. Such adjustment is appropriate for a number of reasons.  First of all, NASA uses the period 1951-1980 as their default baseline. Most of the adjustment is due to the use of a 1750 baseline, which better reflects pre-industrial.

Furthermore, air temperatures over oceans and higher polar anomalies are more appropriate, as confirmed by a recent study that concludes that missing data have been responsible for an underestimation of global warming by 0.1°C.

The image on the right, from a recent study, shows how much difference it makes when using surface air temperatures globally (black line), versus when sea surface temperatures are used for oceans (dark blue line) and in case of incomplete coverage (light blue line).

At a 3°C rise, humans will likely go extinct

The image at the top shows two trends, a long-term trend in blue and a short-term trend in red which follows variations such as El Niño more closely. The blue trend points at a 3°C (or 5.4°F) rise by 2026, while the red trends shows that a 3°C rise could eventuate as early as in 2020 in case of a persistently strengthening El Niño.

At a 3°C rise, humans will likely go extinct, as habitat for humans (and many other species) will disappear. Such a rise will cause a rapid decline of the snow and ice cover around the globe, in turn making that less sunlight gets reflected back into space. Associated changes are discussed in more detail at this page and this page, and include that the jet stream will further get out of shape, resulting in more extreme weather events such as droughts, heatwaves and firestorms. Changes to the jet stream will also contribute to a further strengthening of storms, which threatens to push large amounts of hot, salty water into the Arctic Ocean, triggering eruptions of more and more seafloor methane.

From a 4°C rise, Earth will have a moist-greenhouse scenario

As the temperature rise gains further momentum, runaway heating may well turn Earth into a lifeless planet. This danger was discussed in a 2013 post, warning that, at 4°C rise, Earth will enter a moist-greenhouse scenario and without anything stopping the rise, it will continue to eventually destroy the ozone layer and the ice caps, while the oceans would be evaporating into the atmosphere's upper stratosphere and eventually disappear into space.

[ from an earlier post ]
At 5°C rise, most life on Earth will be extinct

At 5°C rise, most life on Earth will be extinct. A 2018 study by Strona & Bradshaw indicates that most life on Earth will disappear with a 5°C rise (see box on the right).

As the temperature keeps rising, chances are that all life on Earth will go extinct, as Earth would be left with no ozone layer to protect life from deadly UV-radiation. Furthermore, Earth would no longer have water, an essential building block of life. Soil moisture, ground water and water in oceans would evaporate and eventually disappear into space, as discussed in an earlier post.

There are several reasons why the temperature will keep rising well beyond a 5°C rise, as discussed below.

Could Earth go the same way as Venus?

At first glace, such a lifeless planet scenario may seem unlikely, as Earth did experience high temperatures before, but each time it did cool down again. While many species went extinct as a result of steep temperature rises, each time some species did survive the mass extinction events in the past.

This time, however, the situation is much more dire than during previous mass extinctions, and temperatures could keep rising, due to:
  • Brighter Sun - The sun is now much brighter than it was in the past;
  • No sequestration - The rapidity of the rise in greenhouse gases and of the associated temperature rise leaves species little or no time to adapt or move, and leaving no time for sequestration of carbon dioxide by plants and by deposits from other species, nor for formation of methane hydrates at the seafloor of oceans; 
  • No weathering - The rapidity of the rise also means that weathering doesn't have a chance to make a difference. Rapid heating is also dwarfing what weathering (and vegetation) can do to reduce carbon dioxide levels; and
  • Methane - Due to the rapid temperature rise, there is also little or no time for methane to get decomposed. Methane levels will skyrocket, due to fires, due to decomposition of dying vegetation and due to releases from melting terrestrial permafrost and from the seafloor (see more on methane further below). 

The methane threat

Our predicament

The predicament of this geological time is that methane in hydrates has been accumulating for a long time, especially in the Arctic, where there is little or no hydroxyl present in the atmosphere in the first place, while some 75% of the East Siberian Arctic Shelf (ESAS) is shallower than 50 m, as also discussed in this earlier post and this earlier post.

As more methane rises abruptly from the seafloor in plumes, the chance reduces that it will get decomposed in the water, and especially so in the Arctic where long uni-directional sea currents prevent microbes to return to the location of such plumes.

Shallow seas (light blue areas on the image on the right) make waters prone to warm up quickly during summer peaks, allowing heat to penetrate the seabed.

Methane rising through shallow waters will also enter the atmosphere more quickly. Elsewhere in the world, releases from hydrates underneath the seafloor will largely be oxidized by methanotroph bacteria in the water. In shallow waters, however, methane released from the seabed will quickly pass through the water column.

Large abrupt releases will also quickly deplete the oxygen in the water, making it harder for bacteria to break down the methane.

[ from an earlier post ]
The image on the right highlights methane's accelerating rise, showing levels of methane (CH₄), carbon dioxide (CO₂) and nitrous oxide (N₂O) in the atmosphere that are, respectively, 257%, 146% and 122% their 1750 levels.

Hydroxyl depletion extending methane's lifetime

The graph on the right also shows that methane levels in the atmosphere remained almost unchanged during the period 2000-2007. One explanation for this is that, as the world heated up due to the rising levels of greenhouse gases in the atmosphere, the amount of water vapor in the atmosphere rose accordingly (at a rate of 7% for each degree Celsius rise), which translated into more hydroxyl getting produced that resulted in more methane getting decomposed. So, while methane emissions kept rising, the amount of methane in the atmosphere remained relatively stable, as more methane got decomposed. Eventually, in 2007, the continued rise in methane emissions started to overwhelm the capacity of hydroxyl to decompose methane.  

The danger is that, as huge amounts of methane get released rapidly, hydroxyl depletion will extend its lifetime, in turn further accelerating heating and resulting in further releases of seafloor methane.

Methane's GWP

Measured over a few years, methane's global warming potential (GWP) is very high. The image on the right, from IPCC AR5, shows that over a 10-year timescale, the current global release of methane from all anthropogenic sources exceeds all anthropogenic carbon dioxide emissions as agents of global warming; that is, methane emissions are more important than carbon dioxide emissions for driving the current rate of global warming.

The values for methane's GWP that are used in the image on the right are also used in the image below, which shows that over the first few years, methane's GWP is more than 150 times higher than carbon dioxide.


Above image is actually conservative, as the IPCC also gives higher values for methane's GWP in AR5, i.e. for fossil methane and when including climate change feedbacks, while there also is additional warming due to the carbon dioxide that results from methane's oxidation. Furthermore, new research has calculated that methane's radiative forcing is about 25% higher than reported in IPCC AR5, so methane's GWP will be over 150 for longer than for a few years.

Self-reinforcing feedback loops further accelerate heating in the Arctic and just one of them, seafloor methane, could suffice to cause runaway heating.

from an earlier post (2014)  
As the image below shows, in which a GWP of 150 for methane is used, just the existing carbon dioxide and methane, plus seafloor methane releases, would suffice to trigger the clouds feedback tipping point to be crossed that by itself could push up global temperatures by 8°C, within a matter of years.


As described on above image and in an earlier post, a rapid temperature rise could result from a combination of elements, including albedo changes, loss of sulfate cooling, and methane released from destabilizing hydrates contained in sediments at the seafloor of oceans.

[ from an earlier post ]
In the video below, Professor Peter Wadhams and Stuart Scott discuss the threat of large methane releases (recorded March 2019, published July 2019).


Seafloor methane releases could be triggered soon by strong winds causing an influx of warm, salty water into the Arctic ocean, as described in an earlier post and discussed in the 2017 video below. In the above images, methane is responsible for a temperature rise of as much as 1.1°C in a matter of years, but the rise won't stop there. A study published in 2012 calculates that 1000-fold methane increase could occur resulting in a rise of as much as 6°C within 80 years, with more to follow after that.




In the May 2019 video below, Professor Guy McPherson and Thom Hartmann discuss our predicament.



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


Links

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

• Geographical Distribution of Thermometers Gives the Appearance of Lower Historical Global Warming - by Rasmus Benestad et al.
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2019GL083474

• July on course to be hottest month ever, say climate scientists - The Guardian
https://www.theguardian.com/environment/2019/jul/16/july-on-course-to-be-hottest-month-ever-say-climate-scientists

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

• Estimating and tracking the remaining carbon budget for stringent climate targets - by Joeri Rogelj et al.
https://www.nature.com/articles/s41586-019-1368-z

• 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

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

• Damage of Land Biosphere due to Intense Warming by 1000-Fold Rapid Increase in Atmospheric Methane: Estimation with a Climate–Carbon Cycle Model, by Atsushi Abata et al. (2012)
https://journals.ametsoc.org/doi/full/10.1175/JCLI-D-11-00533.1

• Extreme weather
https://arctic-news.blogspot.com/p/extreme-weather.html

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

• Albedo and Latent Heat
https://arctic-news.blogspot.com/p/albedo.html

• Earth is on the edge of runaway warming
https://arctic-news.blogspot.com/2013/04/earth-is-on-the-edge-of-runaway-warming.html

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

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

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



Monday, July 8, 2019

Alaska On Fire

Fires are raging over Alaska. The satellite image below shows the situation on July 8, 2019.


The satellite image below shows the situation on July 9, 2019.


The image below shows carbon monoxide levels as high as 43,443 ppb over Alaska on July 8, 2019.


Carbon dioxide levels were as high as 561 ppm over that same spot in Alaska on July 8, 2019. Carbon dioxide levels were as high as 888 ppm on July 10, 2019, as the image below shows.


The image below shows a forecast for July 10, 2019, with temperatures forecast to be as high as 35.5°C or 95.8°F.


What causes such extreme weather events to occur?

The Arctic has been heating up faster than the rest of the world, due to self-reinforcing feedback loops such as the decline of the snow and ice cover in the Arctic, which results in less sunlight getting reflected back into space and more sunlight instead getting absorbed in the Arctic.

As the image on the right shows, sea surface temperatures in the Bering Sea were as high as 19.8°C or 67.64°F on June 21, 2019.

As the image underneath shows, sea surface temperatures in the Bering Sea were as high as 21.6°C or 70.88°F on July 15, 2019.

Warm water from rivers flowing into the Bering Strait have contributed to some of the high temperatures of the water near the coast of Alaska.

Furthermore, as the June 21, 2019, image below shows, sea surface temperature anomalies have also been high around Alaska further away from the coast.

Indeed, more than 90% of the extra energy caused by humans goes into oceans, and sea currents carry a lot of this extra heat toward the Arctic Ocean.

As a result, ocean temperatures have been high for some time around Alaska.

The image below shows sea surface temperature anomalies around Alaska on June 21, 2019.


Another feedback is that, as the Arctic heats up faster than the rest of the world, the jet stream becomes more wavy, making it easier for cold air to flow out of the Arctic to the south and for warm air from the south to enter the Arctic. These changes to the jet stream also cause stronger storms to occur in the Arctic and more water vapor to enter the atmosphere. All this further contributes to more heating to occur in the Arctic and more extreme weather events.

Heatwaves also cause more forest fires to occur in Alaska, and these forest fires are causing large amounts of soot to get deposited on mountains and on sea ice, thus further blackening the surface. More generally, the Arctic is getting more deposits of soot and dust, as well as stronger growth of algae, moss and microbes, all further speeding up the demise of the snow and ice cover in the Arctic.

The image below shows sea surface temperature anomalies around Alaska on July 11, 2019, with an anomaly of 7.7°C or 13.8°F compared to 1981-2011 showing up north of Alaska in the Arctic Ocean. The light blue areas indicate sea surface that is colder, due to heavy melting of the sea ice in those areas.


The image below shows a deformed jet stream (forecast for July 9, 2019) that enables hot air from the south to move over Alaska.


from an earlier post (2014)  
Heatwaves and forest fires are symptoms of the rapid heating that is taking place in the Arctic. Self-reinforcing feedback loops further accelerate heating in the Arctic and just one of them, seafloor methane, threatens to cause runaway heating.

Just the existing carbon dioxide and methane, plus seafloor methane releases, would suffice to trigger the clouds feedback tipping point to be crossed that by itself could push up global temperatures by 8°C, within a matter of years, as the image below shows.


As described on above image and in an earlier post, huge amounts of methane could be released from destabilizing hydrates contained in sediments at the seafloor of the Arctic Ocean. Such releases could be triggered by strong winds causing an influx of warm, salty water into the Arctic ocean, as described in an earlier post and discussed in the 2017 video below.



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


Links

• Extreme weather
https://arctic-news.blogspot.com/p/extreme-weather.html

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

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

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

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



Tuesday, June 25, 2019

It’s time to pursue hospice, by Guy McPherson

It’s time to pursue hospice



A Hearing was held by the New York City Council Committee on Environmental Protection on June 24, 2019, on the Resolution Declaring a climate emergency and calling for an immediate emergency mobilization to restore a safe climate. Below is Guy McPherson's testimony.

Thank you for the opportunity to address the Council’s Committee on the topic of Resolution 864. The topic under discussion is the most important in the history of our species. We face a stunningly severe existential risk that is routinely ignored or downplayed by governments, the corporate media, and paid climate scientists.

I am Guy McPherson, professor emeritus of conservation biology at the University of Arizona. I began my tenure at that University in 1989. I was granted tenure and promoted to associate professor, and then full professor, earlier than is customary. I am one of the relatively few people in history to achieve the status of full professor before turning 40 years of age. My lengthy resume is replete with scholarly publications, including dozens of peer-reviewed journal articles, the “gold standard” by which the process of science creates reliable knowledge. I received the highest awards given by each of the two transdisciplinary colleges at the University of Arizona, and I was granted the honor of emeritus status upon declining further paychecks from the university at the young age of 49 years. To stave off boredom during these two decades, I also served as a faculty member at the University of California-Berkeley, Southern Utah University, and the tiny liberal-arts school, Grinnell College.

But this isn’t about me. We are meeting here today to discuss the most important topic in human history.

I left active service in the academy more than a decade ago to set an example. I stepped away from the monetary system, which I knew was driving anthropogenic climate change and also the worst of the Mass Extinction Events on Earth. I hoped that many people would follow my lead as I lived off-grid in a straw-bale house, secured my water supply with two solar pumps and a hand pump, grew a vast majority of my food, defecated in a bucket, and contributed to the creation of a decent human community. These actions seemed like great sacrifices at the individual level. They did not produce the desired outcome, in part because the sacrifices did not “scale up” to the level of society.

We are in the midst of abrupt, irreversible climate change. We are in the midst of the Sixth Mass Extinction on Earth. As a result of these two, ongoing phenomena, we are faced with near-term human extinction.

Earth is currently at the highest global-average temperature experienced by Homo sapiens. There is no known technology to reduce the global-average temperature. We seem intent upon raising the global-average temperature until all habitat is gone, for humans and many other species.

There are several paths by which we could abruptly lose habitat for humans throughout the world. Habitat loss is already driving refugee crises in the Middle East, northern Africa, the South Pacific, Central America, and within the United States. The refugees attempting to cross the southern border of this country are not seeking a vacation to Disney Land. Rather, they are seeking a means of survival for themselves and their families.

How shall we act in the face of the greatest existential threat our species has ever encountered? The approach offered by Extinction Rebellion is to declare a climate emergency. This approach has been adopted by several government entities around the world. It is a fine starting point.

If declaring a planetary-scale emergency is the starting point, what follows? Where do we go from here?

If we are all going to die – and we are – then how shall we proceed, as a society? If our species is going extinct in the near future – and it is – then how shall we proceed, as a community? These are the two critical questions I pose to you today. These are the important questions I would like the Council, and all of us, to ponder during the coming days and weeks.

How we respond to these two questions defines our humanity. Is there a better measure of our character than how we face our individual death and the demise of our species?

I’m here to ask these questions. Unlike Socrates, I’m here to do more than ask difficult questions: I will also propose a response. Before I reveal my response, I would like to read a short passage from Viktor Frankl’s 1946 book, Man’s Search for Meaning. Written shortly after Frankl was a prisoner-of-war in Nazi Germany, Man’s Search for Meaning was published. It has inspired millions of people, including me.

“Between a stimulus and a response there is a space. In that space is the power to choose our response. In our response lies our growth and our freedom. The last of human freedoms is to choose one’s attitude in any set of circumstances.”

I would add that we can choose not only our attitude, but also our actions. Again, what better measure of our character than how we respond in the face of impossible odds?

I support Extinction Rebellion in its call for a climate emergency. However, abundant evidence indicates it is too late for a declaration of emergency to prevent our imminent extinction. The strategy I propose goes beyond sounding the alarm. I propose planetary hospice.

Lest you believe otherwise, I am not proposing we “give up” the fight against climate change. However, as the best-informed doctor in the room, and probably on the planet, I believe it is time to accept that we are in Stage 4 as a species. I’ll repeat that, because it’s important to understand: The living planet is almost certainly in the fourth and final stage of a terminal condition. Neither hope nor action will stave off the Sixth Mass Extinction. Neither hope nor any known combination of actions will slow or stop human extinction. It is long past time we admitted hospice is the appropriate way forward.

How do people act when they accept their imminent demise? How do people respond to palliative care within hospice? A quick look into these issues suggests a path forward for this community.

Physicians, especially oncologists, used to lie regularly to their patients. Through the 1960s, lying was considered perfectly appropriate. After all, hope was viewed as unimpeachably good, and removing hope by presenting the facts was therefore undesirable.

More recently, and with much discussion among medical doctors and ethicists, it has become acceptable to tell the full truth to patients. Based upon research conducted during the last few decades, hope is no longer viewed as a motivator for many patients. In response, physicians tend to reveal the full truth to patients. It seems the medical community is ‘catching up’ with common sense in concluding that hope is a poor motivator for action.

It’s time to tell the full truth. It’s time to pursue hospice, with as much honesty, integrity, and compassion as we can muster. It’s time to admit that ignoring the decades-long warnings about climate change have led directly to the expected outcome. It’s time to comfort the afflicted, which includes each of us.

I am often asked for advice about how to live during these tenuous times. In response, I recommend living fully. I recommend living with intention. I recommend living urgently, with death in mind. I recommend the pursuit of excellence. I recommend the pursuit of love. In light of the short time remaining in your life, and my own, I recommend all of the above, louder than before. More fully than you can imagine. To the limits of this restrictive culture, and beyond. Live like you are dying. The day draws near.

Each of us was born into a set of living arrangements over which we have no control. The scorched-Earth policies we have adopted and implemented during the last two centuries have led to the expected outcome: a scorched Earth.

The time for blame has long passed. The time for shaming others has long passed. No blame, no shame: At the edge of extinction, only love remains. Let’s pursue hospice as one expression of our love.


References:

Yesterday’s Testimony, by Guy McPherson
https://guymcpherson.com/2019/06/yesterdays-testimony/

Video of Guy McPherson's Testimony



Guy McPherson talks with Professor Yonder Gillihan, Boston College, March 27, 2019 (Short Version)


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) CO-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 CO, methane (CH) and nitrous oxide (NO) expressed as CO-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 CO 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 
rise/year
CH4 forcing ≥25 CO2e
CH4 ppb
rise/year
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 CO2
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 CO-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 CO-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
  1. Global greenhouse gases have reached a level exceeding the stability threshold of the Greenland and Antarctic ice sheets, melting at an accelerated rate
  2. The current growth rate of atmospheric greenhouse gas of 3.42 ppm CO₂/year is the fastest recorded for the last 55 million years
  3. 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. 
  4. Due to hysteresis the large ice sheets outlast their melting temperatures. 
  5. 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. 
  6. 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.
  7. 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
The Asteroid Impact Connection of Planetary Evolution
Asteroids Impacts, Crustal Evolution and Related Mineral Systems with Special Reference to Australia
Climate, Fire and Human Evolution: The Deep Time Dimensions of the Anthropocene
The Plutocene: Blueprints for a Post-Anthropocene Greenhouse Earth
Evolution of the Atmosphere, Fire and the Anthropocene Climate Event Horizon
From Stars to Brains: Milestones in the Planetary Evolution of Life and Intelligence