Arctic warming will accelerate climate change and impact global economy

Iceberg in Greenland.

Carbon released into the atmosphere by the increasing loss of Arctic permafrost, combined with higher solar absorption by Earth's surface due to the melting of sea ice and land snow, will accelerate climate change -- and have a multi-trillion dollar impact on the world economy.

A new paper in Nature Communications reveals a combination of these factors has the potential to increase the long-term economic impact of climate change by just under $70 trillion, under mitigation levels consistent with current national pledges to cut carbon emissions (5% of the estimated total cost of climate change for this scenario).

Under the Intergovernmental Panel on Climate Change (IPCC) Paris Agreement target of global temperature rises being limited to 1.5C from pre-industrial levels, the extra impact drops to $25 trillion (4% of the total cost for this scenario). In both cases, the primary driver behind the additional costs is the emitted permafrost carbon.

The interdisciplinary research team hope their assessments will provide a better understanding of the socio-economic risks from climate change under different scenarios and help guide policy-makers towards prudent decisions on emissions reduction targets.

Researchers explored simulations of complex, state-of-the-art, physical models to quantify the strength of the permafrost carbon feedback (PCF), driven by the additional carbon released from thawing permafrost, and of the surface albedo feedback (SAF), driven by the extra solar energy absorbed by Earth's surface as the white sea ice and land snow cover declines, exposing darker ocean and land.

Nearly all climate policy studies to date have implied a constant SAF and zero PCF. However, recent observations and computer models show the permafrost feedback is the stronger of the two and that both are nonlinear, their strength changing in complex ways as the climate warms. This affects their impact on both the global climate and economy.

"Arctic sea ice and land snow currently contribute around a third each to the global albedo feedback," said lead author Dmitry Yumashev, of the Pentland Centre for Sustainability in Business at Lancaster University.

"These two components are set to peak for global temperatures within the range covered by the Paris Agreement, but if the climate warms further, the summer and spring sea ice and land snow covers will retreat further north and the albedo feedback will actually weaken.

"The permafrost feedback, however, grows progressively stronger in warmer climates. Both feedbacks are characterised by nonlinear responses to warming, including a varying lag between rising global temperature and permafrost carbon emissions.

"Compared with zero PCF and constant SAF from present-day climate -- legacy values used in climate policy modelling to this point -- the combined nonlinear PCF and SAF cause significant extra warming globally under low and medium emissions scenarios.

Low emissions scenarios in the study include meeting the 1.5°C and 2°C Paris Agreement targets relative to pre-industrial conditions by 2100, while medium emissions scenarios include mitigation levels consistent with current national pledges (NDCs). Under the NDCs, the world is set to warm by around 3°C relative to pre-industrial by 2100.

High emissions scenarios, such as the current business as usual trajectory (BaU) -- expected to lead to around 4°C of warming by 2100 and cause by far the highest impacts on ecosystems and societies -- are also included. Under these, the strength of the PCF reaches its peak and does not increase further, while the continued weakening of the SAF gradually cancels the warming effect of the PCF.

For the purposes of the research, other major planetary feedbacks, such as those driven by changes in clouds and water vapour in response to warming, are assumed to remain constant, supported by the last two generations of climate models.

Under all scenarios, using the nonlinear Arctic feedbacks compared to previous constant values leads to an increase to the total cost of climate change, consisting of the mitigation costs of cutting emissions, climate adaptation costs and residual climate-related impacts. The increases occur primarily through additional temperature-driven impacts on economy, ecosystems and human health, and additional impacts from sea level rise.

All costs were estimated using simulations in specially developed integrated assessment model PAGE-ICE, which includes simple statistical representations of the Arctic feedbacks derived from complex models. It has multiple updates to climate science and economics, including up-to-date uncertainty estimates.

Under the NDCs scenario, the additional estimated impact based on thousands of simulations of the nonlinear PCF and SAF is just under $70 trillion compared to their previously used values -- exceeding by around 10 times current estimates for long-terms economic gains from transit shipping routes and mineral resource extraction in the Arctic region.

With previous estimates for Arctic feedbacks, the total cost of climate change associated with the 1.5C and 2C scenarios is virtually the same and is around $600 trillion -- in comparison, the estimated cost of business as usual is around $2000 trillion. Nonlinear PCF and SAF add further $25 trillion to the $600 trillion figure for the 1.5C scenario and $34 trillion for the 2C scenario. Thus, the nonlinear Arctic feedbacks make the more ambitious 1.5C target marginally more economically attractive.

Dr Yumashev added: "Our findings support the need for more proactive mitigation measures to keep global temperature rise well below 2C.

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Arctic warming contributes to drought

Icebergs float on Jokulsarlon glacier lagoon at sunrise, in Iceland.

When the Arctic warmed after the ice age 10,000 years ago, it created perfect conditions for drought.

According to new research led by a University of Wyoming scientist, similar changes could be in store today because a warming Arctic weakens the temperature difference between the tropics and the poles. This, in turn, results in less precipitation, weaker cyclones and weaker mid-latitude westerly wind flow -- a recipe for prolonged drought.

The temperature difference between the tropics and the poles drives a lot of weather. When those opposite temperatures are wider, the result is more precipitation, stronger cyclones and more robust wind flow. However, due to the Arctic ice melting and warming up the poles, those disparate temperatures are becoming closer.

"Our analysis shows that, when the Arctic is warmer, the jet stream and other wind patterns tend to be weaker," says Bryan Shuman, a UW professor in the Department of Geology and Geophysics. "The temperature difference in the Arctic and the tropics is less steep. The change brings less precipitation to the mid-latitudes."

Shuman is a co-author of a new study that is highlighted in a paper, titled "Mid-Latitude Net Precipitation Decreased With Arctic Warming During the Holocene," published today (March 27) online in Nature, an international weekly science journal. The print version of the article will be published April 4.

Researchers from Northern Arizona University; Universite Catholique de Louvain in Louvain-In-Neuve, Belgium; the Florence Bascom Geoscience Center in Reston, Va.; and Cornell University also contributed to the paper.

"The Nature paper takes a global approach and relates the history of severe dry periods of temperature changes. Importantly, when temperatures have changed in similar ways to today (warming of the Arctic), the mid-latitudes -- particularly places like Wyoming and other parts of central North America -- dried out," Shuman explains. "Climate models anticipate similar changes in the future."

Currently, the northern high latitudes are warming at rates that are double the global average. This will decrease the equator-to-pole temperature gradient to values comparable with the early to middle Holocene Period, according to the paper.

Shuman says his research contribution, using geological evidence, was helping to estimate how dry conditions have been in the past 10,000 years. His research included three water bodies in Wyoming: Lake of the Woods, located above Dubois; Little Windy Hill Pond in the Snowy Range; and Rainbow Lake in the Beartooth Mountains.

"Lakes are these natural recorders of wet and dry conditions," Shuman says. "When lakes rise or lower, it leaves geological evidence behind."

The researchers' Holocene temperature analysis included 236 records from 219 sites. During the past 10,000 years, many of the lakes studied were lower earlier in history than today, Shuman says.

"Wyoming had several thousand years where a number of lakes dried up, and sand dunes were active where they now have vegetation," Shuman says. "Expanding to the East Coast, it is a wet landscape today. But 10,000 years ago, the East Coast was nearly as dry as the Great Plains."

The research group looked at the evolution of the tropic-to-pole temperature difference from three time periods: 100 years ago, 2,000 years ago and 10,000 years ago. For the last 100 years, many atmospheric records facilitated the analysis but, for the past 2,000 years or 10,000 years, there were fewer records available. Tree rings can help to expand studies to measure temperatures over the past 2,000 years, but lake deposits, cave deposits and glacier ice were studied to record prior temperatures and precipitation.

"This information creates a test for climate models," Shuman says. "If you want to use a computer to make a forecast of the future, then it's useful to test that computer's ability to make a forecast for some other time period. The geological evidence provides an excellent test."

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More persistent weather patterns in US linked to Arctic warming

These are land surface temperatures from December 26, 2017 to January 2, 2018, compared with the 2001 to 2010 average for the same eight-day period. The persistent warm West and cold East pattern that was so prevalent last winter caused a western drought that led to summer fires, a prolonged cold spell in much of the East and a parade of nor'easters along the East Coast.

Persistent weather conditions, including dry and wet spells, generally have increased in the United States, perhaps due to rapid Arctic warming, according to a Rutgers-led study.

Persistent weather conditions can lead to weather extremes such as drought, heat waves, prolonged cold and storms that can cost millions of dollars in damage and disrupt societies and ecosystems, the study says.

Scientists at Rutgers University-New Brunswick and the University of Wisconsin-Madison examined daily precipitation data at 17 stations across the U.S., along with large upper-level circulation patterns over the eastern Pacific Ocean and North America.

Overall, dry and wet spells lasting four or more days occurred more frequently in recent decades, according to the study published online today in Geophysical Research Letters. The frequency of persistent large-scale circulation patterns over North America also increased when the Arctic was abnormally warm.

In recent decades, the Arctic has been warming at least twice as fast as the global average temperature, the study notes. The persistence of warm Arctic patterns has also increased, suggesting that long-duration weather conditions will occur more often as rapid Arctic warming continues, said lead author Jennifer Francis, a research professor in Rutgers' Department of Marine and Coastal Sciences.

"While we cannot say for sure that Arctic warming is the cause, we found that large-scale patterns with Arctic warming are becoming more frequent, and the frequency of long-duration weather conditions increases most for those patterns," said Francis, who works in the School of Environmental and Biological Sciences.

The results suggest that as the Arctic continues to warm and melt, it's likely that long-duration events will continue to occur more often, meaning that weather patterns -- heat waves, droughts, cold spells and stormy conditions -- will likely become more persistent, she said.

"When these conditions last a long time, they can become extreme events, as we've seen so often in recent years," she said. "Knowing which types of events will occur more often in which regions and under what background conditions -- such as certain ocean temperature patterns -- will help decision-makers plan for the future in terms of infrastructure improvements, agricultural practices, emergency preparedness and managed retreat from hazardous areas."

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