Showing posts with label global. Show all posts
Showing posts with label global. Show all posts

Sunday, September 8, 2019

Arctic Ocean overheating


The Arctic Ocean is overheating, as illustrated by above image.
[ from earlier post ]

Heating of the water in the Arctic Ocean is accelerating, as illustrated by above map that uses 4-year smoothing and that shows temperatures in the Arctic that are up to 4.41°C hotter than the average global temperature during 1880-1920.

The NOAA image on the right shows the sea surface temperature difference from 1961-1990 in the Arctic at latitudes 60°N - 90°N on September 7, 2019.

Where Arctic sea ice disappears, hot water emerges on the image, indicating that the temperature of the ocean underneath the sea ice is several degrees above freezing point.

The nullschool.net image on the right shows sea surface temperature differences from 1981-2011 on the Northern Hemisphere on September 8, 2019, with anomalies reaching as high as 15.2°C or 27.4°F (near Svalbard, at the green circle).

Accelerating heating of the Arctic Ocean could make global temperatures skyrocket in a matter of years.

Decline of the sea ice comes with albedo changes and further feedbacks, such as the narrowing temperature difference between the North Pole and the Equator, which slows down the speed at which the jet stream circumnavigates Earth and makes the jet stream more wavy.


Disappearance of the sea ice also comes with loss of the buffer that has until now been consuming ocean heat as part of the melting process. As long as there is sea ice in the water, this sea ice will keep absorbing heat as it melts, so the temperature will not rise at the sea surface. 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. Once the sea ice is gone, further heat must go elsewhere.

[ click on images to enlarge ]
The Naval Research Laboratory image on the right shows a forecast for Sep. 8, 2019, run on Sep. 7, 2019, of the thickness of the sea ice. Sea ice has become terribly thin, indicating that the heat buffer constituted by the sea ice has effectively gone. Only a very thin layer of sea ice remains in place throughout much of the Arctic Ocean.

This remaining sea ice is stopping a lot of ocean heat from getting transferred to the air, so the temperature of the water of the Arctic Ocean is now rising rapidly, with the danger that some of the accumulating ocean heat will reach sediments at the seafloor and cause eruptions of huge amounts of methane.


This situation comes at a time that methane levels are very high globally. Mean global methane levels were as high as 1911 parts per billion on the morning of September 3, 2019, a level recorded by the MetOp-1 satellite at 293 mb (image below).


[ from an earlier post ]
As the image on the right shows, mean global levels of methane (CH₄) have risen much faster than carbon dioxide (CO₂) and nitrous oxide (N₂O), in 2017 reaching, respectively, 257%, 146% and 122% their 1750 levels.

Compared to carbon dioxide, methane is some 150 times as potent as a greenhouse gas during the first few years after release.

Huge releases of seafloor methane alone could make marine stratus clouds disappear, as described in an earlier post, and this clouds feedback could cause a further 8°C global temperature rise.

In total, global heating by as much as 18°C could occur by the year 2026 due to a combination of elements, including albedo changes, loss of sulfate cooling, and methane released from the ocean seafloor.

from an earlier post (2014)  

In the image below, from an earlier post, a global warming potential (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 few years time, adding up to a total rise of 18°C by 2026.


Progression of heating could unfold as pictured below.

[ from an earlier post ]

In the video below, John Doyle describes out predicament.



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

• Cyclone over Arctic Ocean - August 24, 2019
https://arctic-news.blogspot.com/2019/08/cyclone-over-arctic-ocean-august-24-2019.html

• Most Important Message Ever
https://arctic-news.blogspot.com/2019/07/most-important-message-ever.html


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
  1. The current growth rate of atmospheric greenhouse gas is the fastest recorded for the last 55 million years.
  2. 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.
  3. 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.
  4. 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.
  5. 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.
  6. Due to hysteresis the large ice sheets would outlast their melting temperatures.
  7. Land areas would be markedly reduced due to a rise to Miocene-like sea levels of approximately 40±15 meters above pre-industrial levels.
  8. 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.
  9. 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.
  10. 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.
  11. 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).
  12. 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.
  13. 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.


Sunday, March 31, 2019

Arctic Warming Up Fast

On March 30, 2019, Arctic sea ice extent was 13.42 million km², a record low for the measurements at ads.nipr.ac.jp for the time of year.


[ click on images to enlarge ]
As the Arctic warms up faster than the rest of the world, the temperature difference between the North Pole and the Equator narrows, making the jet stream wavier, thus enabling warm air over the Pacific Arctic to move more easily into the Arctic.

The image on the right shows that, on March 31, 2019, the Arctic was 7.5°C or 13.5°F warmer than 1979-2000.

The earlier forecast below shows a temperature anomaly for the Arctic of 7.6°C or 13.68°F for March 31, 2019, 12:00 UTC and in places 30°C or 54°F warmer. The inset shows the Jet Stream moving higher over the Bering Strait, enabling air that has been strongly warmed up over the Pacific Ocean to move into the Arctic.


A wavier Jet Stream also enables cold air to more easily move out of the Arctic. The inset shows the Jet Stream dipping down over North America where temperatures lower than were usual were recorded.

The later forecast below shows a temperature anomaly for the Arctic of 7.7°C or 13.86°F for March 31, 2019, 12:00 UTC.


The image below shows that El Niño can be expected to push temperatures up higher in 2019 during the Arctic sea ice retreat.

A warmer sea surface can cause winds to grow dramatically stronger, and they can push warm, moist air into the Arctic, while they can also speed up sea currents that carry warm, salty water into the Arctic Ocean.

Rivers can also carry huge amounts of warm water from North America and Siberia into the Arctic Ocean, as these areas are getting hit by ever stronger heatwaves that are hitting the Arctic earlier in the year.

With Arctic sea ice at a low, it won't be able to act as a buffer to absorb heat for long, with the danger that an influx of warm, salty water will reach the seafloor and trigger methane eruptions.

As warmer water keeps flowing into the Arctic Ocean and as air temperatures in the Arctic are now starting to rise on the back of a strengthening El Niño, fears for a Blue Ocean Event in 2019 are rising, which would further accelerate the temperature rise as less sunlight gets reflected back into space.

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

Links

• Arctic sea ice extent
https://ads.nipr.ac.jp/vishop/#/extent

• Climate Reanalyzer
https://climatereanalyzer.org

• ENSO Update by Climate Prediction Center / NCEP 25 March 2019
https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/lanina/enso_evolution-status-fcsts-web.pdf

• Blue Ocean Event
https://arctic-news.blogspot.com/2018/09/blue-ocean-event.html

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


Saturday, March 23, 2019

Climate Tipping Points

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

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

Abstract

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

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

Paleoclimate records

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

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

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

Anthropocene tipping points

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

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

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

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

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

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

Figure 4. Greenland and Antarctic ice mass change. GRACE data are extension of Velicogna et al. (2014)
gravity data. MBM (mass budget method) data are from Rignot et al. (2011). Red curves are gravity data for
Greenland and Antarctica only; small Arctic ice caps and ice shelf melt add to freshwater input. (Hansen et al. 2016)
Figure 5. (a) AMOC (in Sverdrup) at 28°N in simulations (i.e., including freshwater injection of 720 Gt year⁻¹ in 2011
                around Antarctica, increasing with a 10-year doubling time, and half that amount around Greenland).
(b) SST (°C) in the North Atlantic region (44–60°N, 10–50°W).

Future trends and Tipping points

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

Figure 6. (A) 2018 global temperature (NASA);
(B) projected 2055-2100 surface-air temperature to +1.19°C above 1880-1920
(AIB model modified forcing, ice melt to 1 meter) (Hansen et al., 2016).
These projections differ markedly from linear model trends (Figure 9) of IPCC models, which mainly assume long term ice melt (Ahmed, 2018). Rignot et al. (2011) report that in 2006 the Greenland and Antarctic ice sheets experienced a combined mass loss of 475 ± 158 Gt/yr, equivalent to 1.3 ± 0.4 mm/yr sea level rise”. For the Antarctic ice sheet the IEMB team (2017) states the sheet lost 2,720 ± 1,390 billion tonnes of ice between 1992 and 2017, which corresponds to an increase in mean sea level of 7.6 ± 3.9 millimeter (IMBIE team 2017). Hansen et al. (2008) consider global temperature higher than 1.0°Celsius due to CO₂ level of ~450 ppm would lead to irreversible ice sheet loss, given most climate models did not include amplifying feedbacks effects such as ice sheet disintegration, vegetation migration, and greenhouse gas release from soils, tundra, or ocean sediments. Such feedbacks can lead to climate tipping points leading to irreversible runaway climate change (Ahmed, 2018).

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

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

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

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

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

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

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

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


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

Books:
The Archaean: Geological and Geochemical Windows into the Early Earth
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


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