Monday, February 22, 2021

Snowstorms, the breach of the Arctic vortex and the effects of ice meltwater on the oceans

by Andrew Glikson

Warnings by leading climate scientists regarding the high sensitivity of the atmosphere in response to abrupt compositional changes, such as near-doubling of greenhouse gas concentrations, are now manifest: According to Wallace Broecker, (the “father” of climate science) “The paleoclimate record shouts out to us that, far from being self-stabilizing, the Earth's climate system is an ornery beast which overreacts to even small nudges, and humans have already given the climate a substantial nudge”. As stated by James Zachos, “The Paleocene hot spell should serve as a reminder of the unpredictable nature of climate”.

As snowstorms such as the Beast from the East (2018) and Storm Darcy (2021) sweep the northern continents, reaching Britain and as far south as Texas and Greece, those who still question the reality and consequences of global climate change, including in governments, may rejoice as if they have a new argument to question global warming.

However, as indicated by the science, these fronts result from a weakened circum-Arctic jet stream boundary due to decreased temperature polarity between the Arctic Circle and high latitude zones in Europe, Russia and North America. The reduced contrast allows migration of masses of cold Arctic air southward and of tropical air northward across the weakened jet stream boundary, indicating a fundamental shift in the global climate pattern (Figure 1).

Figure 1. (A) Extensions from the Arctic polar zone into Europe and North America; (B) Extension into North America; (C) weakening and increasing undulation of the Arctic jet stream boundary (NOAA) allowing intrusion of air masses of contrasted temperature across the boundary.

The weakening of the Arctic boundary is a part of the overall shift of climate zones toward the poles in both hemispheres, documented in detail in Europe (Figure 2). Transient cooling pauses are projected as a result of the flow of cold ice meltwater from Greenland and Antarctica into the oceans, leading to stadial cooling intervals.

Figure 2. Migration of climate zones in Europe during 1981-2010 and under +2°C. Faint pink areas represent advanced warming. (A, left) Agro‐climate zonation of Europe based on growing season length (GSL) and active temperature sum (ATS) obtained as an ensemble median from five different climate model simulations during the baseline period (1981–2010). (B, right) Ensemble median spatial patterns of agro-climate zones migration under 2°C global surface warming according to model RCP8.5. Gray areas represent regions where no change with respect to the baseline period is simulated.

A combination of ice sheet melting and the flow of melt water into the oceans on the one hand, and ongoing warming of tropical continental zones on the other hand, are likely to lead to the following:
  • Storminess due to collisions of cold and warm air masses;
  • As the ice sheets continue to melt, the cold meltwater enhances lower temperatures at shallow ocean levels, as modelled by Hansen et al. (2016) and Bonselaer et al (2018) (Figure 3A), as contrasted with warming at deeper ocean levels over large parts of the oceans. This transiently counterbalances the effects of global warming over the continents arising from the greenhouse effect; 
  • The above processes herald chaotic climate effects, in particular along continental margins and island chains.
Figure 3. A. 2080–2100 meltwater-induced sea-air temperature anomalies relative to the standard RCP8.5 ensemble (Bronselaer et al., 2018), indicating marked cooling of parts of the southern oceans. Hatching indicates where the anomalies are not significant at the 95% level; B. Negative temperature anomalies through the 21st-22nd centuries signifying stadial cooling intervals (Hansen et al., 2016); C. A model of Global warming for 2096, where cold ice melt water occupies large parts of the North Atlantic and circum-Antarctica, raises sea level by about 5 meters and decreases global temperature by -0.33°C (Hansen et al., 2016).

The extreme rate at which the global warming and the shift of climate zones are taking place virtually within a period less than one generation-long, faster than major past warming events such as at the Paleocene-Eocene boundary 56 million years ago, renders the term “climate change” hardly appropriate, since what we are looking at is a sudden and abrupt event

According to Giger (2021) “Tipping points could fundamentally disrupt the planet and produce abrupt change in the climate. A mass methane release could put us on an irreversible path to full land-ice melt, causing sea levels to rise by up to 30 meters. We must take immediate action to reduce global warming and build resilience with these tipping points in mind.”

Computer modelling does not always capture the sensitivity, complexity and feedbacks of the atmosphere-ocean-land system as observed from paleoclimate studies. Many models portray gradual or linear responses of the atmosphere to compositional variations, overlooking self-amplifying effects and transient reversals associated with melting of the ice sheets and cooling of the oceans by the flow of ice melt.

According to Bonselaer et al. (2018) “The climate metrics that we consider lead to substantially different future climate projections when accounting for the effects of meltwater from the Antarctic Ice Sheet. These differences have consequences for climate policy and should be taken into account in future IPCC reports, given recent observational evidence of increasing mass loss from Antarctica” and “However, the effect on climate is not included (by the IPCC) and will not be in the upcoming CMIP6 experimental design. Similarly, the effects of meltwater from the Greenland Ice Sheet have so far not been considered, and could lead to further changes in simulated future climate”. Depending on future warming the effect of Antarctic ice meltwater may extend further, possibly becoming global.

By contrast to ocean cooling, further to NASA’s reported mean land-ocean temperature rise of +1.18°C in March 2020 above pre-industrial temperatures, relative to the 1951-1980 baseline, large parts of the continents, including central Asia, west Africa eastern South America and Australia are warming toward mean temperatures of +2°C and higher. The contrast between cooling of extensive ocean regions and warming of the continental tropics is likely to lead to extreme storminess, in particular along continent-ocean interfaces.

The late 20th century to early 21st century global greenhouse gas levels and regional warming rates have reached a large factor to an order of magnitude faster than warming events of past geological and mass extinction events, with major implications for the nature and speed of extreme weather events.

For these reasons the term “climate change” for the current extreme warming, which is reaching +1.5°C over the continents and more than +3°C over the Arctic over a period shorter than one century, no longer applies.

The world is looking at an extremely rapid shift in the climatic conditions that have allowed civilization to emerge.

Andrew Glikson
A/Prof. Andrew Glikson
Earth and Paleo-climate scientist
The University of New South Wales,
Kensington NSW 2052 Australia

Books:
The Asteroid Impact Connection of Planetary Evolution
The Archaean: Geological and Geochemical Windows into the Early Earth
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
Asteroids Impacts, Crustal Evolution and Related Mineral Systems with Special Reference to Australia







Friday, February 12, 2021

The extreme rate of global warming: IPCC Oversights of future climate trends

by Andrew Glikson

Intergovernmental Panel on Climate Change (IPCC) reports and comprehensive summaries of the peer-reviewed literature raise questions regarding the assumptions inherent in computer modelling of future climate changes, including the supposed linearity of future global temperature trends (Figure 1).

Figure 1. Global mean surface temperature increase as a function of cumulative total global carbon dioxide (CO2) emissions from various lines of evidence. IPCC

Computer modelling does not necessarily capture the sensitivity, complexity and feedbacks of the atmosphere-ocean-land system as observed from paleoclimate studies. Underlying published IPCC computer models appears to be an assumption of mostly gradual or linear responses of the atmosphere to compositional variations. This overlooks self-amplifying effects and transient reversals associated with melting of the ice sheets. 

Leading paleoclimate scientists have issued warnings regarding the high sensitivity of the atmosphere in response to extreme forcing, such as near-doubling of greenhouse gas concentrations: According to Wallace Broecker, “The paleoclimate record shouts out to us that, far from being self-stabilizing, the Earth's climate system is an ornery beast which overreacts to even small nudges, and humans have already given the climate a substantial nudge”. As stated by James Zachos, “The Paleocene hot spell should serve as a reminder of the unpredictable nature of climate”.

Holocene examples are abrupt stadial cooling events which followed peak warming episodes which trigger a flow of large volumes of ice melt water into the oceans, inducing stadial events. Stadial events can occur within very short time, as are the Younger dryas stadial (12.9-11.7 kyr) (Steffensen et al. 2008) (Figure 2) and the 8.2 kyr Laurentian cooling episode,

Despite the high rates of warming such stadial cooling intervals do not appear to be shown in IPCC models (Figure 1).

Figure 2. The younger dryas stadial cooling (Steffensen et al., 2008). Note the abrupt freeze and thaw boundaries of ~3 years and ~1 year.

Comparisons with paleoclimate warming rates follow: The CO₂ rise interval for the K-T impact is estimated to range from instantaneous to a few 10³ years or a few 10⁴ years (Beerling et al, 2002), or near-instantaneous (Figure 3A). An approximate CO₂ growth range of ~0.114 ppm/year applies to the Paleocene-Eocene Thermal Maximum (PETM) (Figure 3B) and ~0.0116 ppm/year to the Last Glacial Termination (LGT) during 17-11 kyr ago (Figure 3C). Thus the current warming rate of 2 to 3 ppm/year is about or more than 200 times the LGT rate (LGT: 17-11 kyr; ~0.0116 ppm/yr) and 20-30 times faster than the Paleocene-Eocene Thermal Maximum (PETM) rate of ~0.114 ppm/year.

Therefore the term “climate change” for the extreme warming reaching +1.5°C over the continents and more than +3°C over the Arctic over a period of less than 100 years, requires reconsideration.

However, comparisons between the PETM and current global warming may be misleading since, by distinction from the current existence of large ice sheets on Earth, no ice was present about 55 million years ago.

Figure 3. (A) Reconstructed atmospheric CO₂ variations during the Late Cretaceous–early Tertiary, based on -
Stomata indices of fossil leaf cuticles calibrated using inverse regression and stomatal ratios (Beerling et al. 2002);
(B) Simulated atmospheric CO₂ at and after the Palaeocene-Eocene boundary (after Zeebe et al., 2009);
(C) Global CO₂ and temperature during the last glacial termination (After Shakun et al., 2012) (LGM - Last Glacial Maximum; OD – Older dryas; BA - Bølling–Alerød; YD - Younger dryas)

Observed climate complexities leading to the disturbance of linear temperature variations include:
  1. The weakening of climate zone boundaries, such as the circum-Arctic jet stream, allowing cold air and water masses to shift from polar to mid-latitude zones and tropical air masses to penetrate polar zones (Figure 4), induce collisions between air masses of contrasted temperatures and storminess, with major effects on continental margins and island chains.

  2. Amplifying feedbacks, including release of carbon from warming oceans due to reduced CO₂ solubility and therefore reduced intake from the atmosphere, release of methane from permafrost and from marine sediments, desiccated vegetation and extensive bush fires release of CO₂.

  3. The flow of cold ice melt water into the oceans from melting ice sheets—Greenland (Rahmstorf et al., 2015) and Antarctica (Bonselaer et al., 2018)—ensuing in stadial cooling effects, such as the Younger dryas and following peak interglacial phases during the last 800,000 years (Cortese et al., 2007; Glikson, 2019).
Figure 4. Weakening and undulation of the jet stream, shifts of climate zones and penetration of air masses across the weakened climate boundary. NOAA.

In the shorter term such international targets as “zero emissions by 2050” apparently do not include the export of petroleum, coal and gas, thus allowing nations to circumvent domestic emission limits. Australia, the fifth biggest miner and third biggest exporter of fossil fuels, is responsible for about 5% of global greenhouse gas emissions.

At present the total CO₂+CH₄+N₂O level (mixing ratio) is near 500 ppm CO₂-equivalent (Figure 5). From the current atmospheric CO₂ level of above ~415 ppm, at the rise rate of 2 - 3 ppm/year, by 2050 the global CO₂ level would reach about 500 ppm and the CO₂-equivalent near 600 ppm, raising mean temperatures to near-2°C above preindustrial level, enhancing further breakdown of the large ice sheets and a further rise of sea levels.

Figure 5. Evolution of the CO₂+CH₄+N₂O level (mixing ratio)


Andrew Glikson

Dr Andrew Glikson
Earth and Paleo-climate scientist
ANU Climate Science Institute
ANU Planetary Science Institute
Canberra, Australia



Books:
The Asteroid Impact Connection of Planetary Evolution
http://www.springer.com/gp/book/9789400763272
The Archaean: Geological and Geochemical Windows into the Early Earth
http://www.springer.com/gp/book/9783319079073
Climate, Fire and Human Evolution: The Deep Time Dimensions of the Anthropocene
http://www.springer.com/gp/book/9783319225111
The Plutocene: Blueprints for a Post-Anthropocene Greenhouse Earth
http://www.springer.com/gp/book/9783319572369
Evolution of the Atmosphere, Fire and the Anthropocene Climate Event Horizon
http://www.springer.com/gp/book/9789400773318
From Stars to Brains: Milestones in the Planetary Evolution of Life and Intelligence
https://www.springer.com/us/book/9783030106027
Asteroids Impacts, Crustal Evolution and Related Mineral Systems with Special Reference to Australia
http://www.springer.com/us/book/9783319745442




Wednesday, February 3, 2021

More Extreme Weather

As temperatures rise, the weather is getting more extreme. Around the globe, extreme weather events are striking with ever greater frequency and intensity. 

In 2020, in the U.S. alone, a record number of 22 climate and weather disasters took place that each caused damage of more than 1 billion dollar, while jointly causing the deaths of 262 people. 

Rising temperatures cause stronger storms, droughts, heatwaves and forest fires. Rising temperatures are also behind the cold weather that is currently hitting large parts of North America. Two mechanisms that, by distorting the Jet Stream, are contributing to more extreme weather are described below. 

Distortion of the Jet Streams - two mechanisms

The Jet Streams used to circumnavigate the globe in narrow bands. World climate zones used to be kept well apart by stable Jet Streams. 

On the Northern Hemisphere, the coldest point used to be the North Pole, so wind used to flow from the tropics to the North Pole, while the wind was moved to the side due to Earth's turning. 

Polar Jet Stream and Subtropical Jet Stream - NOAA image
This resulted in two Jet Streams forming, circum-navigating the globe in relatively narrow and straight bands, i.e. the Polar Jet Stream at 60°N and the Subtropical Jet Stream at about 30°N. 
 
Polar Jet Stream (blue) and Subtropical
Jet Stream (red) - NOAA image
First mechanism distorting the Jet Stream

The first mechanism distorting the Jet Stream is that, as the Arctic gets hit much harder by temperature rises, the difference in temperature decreases between the North Pole and the Equator.

This slows down the speed at which wind travels from the Tropics to the North Pole, in turn making the Jet Stream more wavy, just like a slow-moving river over flat land will take a winding route and meander.

For years, Jennifer Francis et al. warned that this will cause more extreme weather in mid latitudes. Arctic-News described Deformation of the Jet Stream as Opening the Doorways to Doom, i.e. one of the feedbacks (#10) of accelerated Arctic warming.

Second mechanism distorting the Jet Stream

Due to the rapid temperature rise of the Arctic Ocean, the North Pole is increasingly not the coldest place on the Northern Hemisphere.

Instead, the air over Greenland, North Canada and Siberia is increasingly more cold than before, and can be much colder than the North Pole, as illustrated by the ClimateReanalyzer image on the right.

This creates temperature and pressure conditions over the East Pacific and over North America that make the Jet Stream branch out.

On the next image on the right, the Jet Stream can be seen running over the West Pacific at speeds as high as 387 km/h or 241 mph (green circle) and
moving within a relatively narrow band.

The Jet Stream is then confronted with much different conditions over North America that make the Jet Stream branch out widely (white arrows), with one branch moving north and going circular over the Arctic Ocean, while at the other end a branch can be seen dipping below the Equator.

As a result of these two distortion mechanisms, cold air that used to stay contained over the North Pole, can descend more easily over Siberia and North America, causing more extreme weather, while also taking away opportunities for the sea ice to build up to the strength and depth than it used to have. 

The combination image below shows forecasts for February 6, 2021.


On the above combination image, the left panel shows that, not far apart from each other and at the same time, temperature anomalies over North America are forecast to approach the top end and the bottom end of the scale. The right panel shows that temperatures over North America and Siberia are forecast to be much lower than over the Arctic Ocean.

As the temperature difference between land and ocean gets stronger on the Northern Hemisphere in Winter, the transfer of water vapor and heat to the atmosphere increases (#25 on the feedbacks page, image right). Storms and clouds forming over the North Atlantic trap heat and move much heat toward the North Pole.
 
Formation of clouds can be further facilitated by aerosols (feedback #9). A recent study looks at how melting sea ice can cause more release of iodine into the atmosphere, seeding the growth of new clouds that trap longwave radiation that would otherwise go into space.

The combination image below shows in the left panel how a branch of the Jet Stream is forecast to be moving over the North Pole at speeds as high as 107 km/h or 67 mph on February 16, 2021. Hours later that day, as the globe in the right panel shows, the surface temperature on the North Pole is forecast to be -18°C, i.e. warmer than the white-blue color (about -20°C) that covers most of North America.


As the globe in the left panel of the combination image below shows, temperature anomalies in Texas were approaching the bottom end of the scale on February 15, 2021, i.e. -32°C or -57.6°F (below 1979-2000), while the globe in the right panel shows that on February 16, 2021, temperature anomalies in between Greenland and the North Pole were forecast to approach the top end of the scale, i.e. 32°C or 57.6°F (above 1979-2000). 



Above freezing at North Pole?

As the combination image below shows, the temperature at the North Pole is forecast to be 0°C or 32°F, panel right, on February 22, 2021, 18:00 UTC, while temperature anomalies at the North Pole are forecast to be at the top end of the scale, i.e. 32°C or 57.6°F above 1979-2000. 


The light-blue color over the North Atlantic on the globe on the left is a cold anomaly resulting from cold air moving from North America over the Atlantic Ocean (forecast initiated Feb.15, 2021, 18:00 UTC).

Ominously, sea ice is breaking up north of Greenland. 


And ominously, the N20 satellite recorded methane levels as high as 2835 ppb at 399.1 mb on the afternoon of February 17, 2021.


Conclusion

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


Links

• 2020: Hottest Year On Record
https://arctic-news.blogspot.com/2021/01/2020-hottest-year-on-record.html

• NOAA - U.S. Billion-Dollar Weather and Climate Disasters: Overview
https://www.ncdc.noaa.gov/billions/overview

• Climate Reanalyzer
https://climatereanalyzer.org

• Nullschool

• Feedbacks in the Arctic

• Evidence linking Arctic amplification to extreme weather in mid‐latitudes - by Jennifer Francis et al. 

• Opening the Doorways to Doom (feedback #14)