Arctic Amplification and Climate Crisis, with Prof. Peter Wadhams
Parvati Magazine interviewed sea ice researcher Peter Wadhams, who recently published the book “A Farewell to Ice” about the alarming prospect of an ice-free Arctic.
Parvati Magazine: Can you briefly describe why the Arctic, or Arctic amplification, is a pivotal element in the global climate crisis?
Peter Wadhams: The Arctic is warming about three times as rapidly as lower latitudes or the Antarctic.The reasons for this Arctic amplification are complex. Today the amplification is increased by the retreat of snow on land and sea ice in the ocean, which reduce the average albedo over the Arctic, causing more solar radiation to be absorbed by the earth and sea surfaces, warming the lower atmosphere (troposphere). However, amplification appears to have been occurring in the past as well, before snow-ice retreat became a large effect. The underlying mechanism appeared to be connected to the Arctic troposphere, which is shallower than at lower latitudes, so that a given amount of heat absorption is distributed over a smaller height of the lower atmospheric column and so warms the temperature more.
PMAG: You would project increasingly sea ice-free summers by as early as 2020. How does this translate with respect to sea level, sea temperature, or global temperature rise?
PW: Ice-free summers lead to warmer air masses in summer drifting over the Greenland ice sheet, increasing the melt rate. It is no accident that 2012, the summer of greatest ice retreat, also featured a period when the entire Greenland ice sheet surface was in a state of melt. There are widely varying predictions of what this increased melt rate (now the greatest single contributor to global sea level rise) will achieve by the end of the century. The Intergovernmental Panel on Climate Change (IPCC) still speaks of 60-90 cm; most glaciologists predict well beyond 1 metre and some outliers speak of 4 metres. Regarding sea temperatures, the ice-free Arctic shelves are already showing 5-7°C rise at the surface and this is increasing. Regarding air temperatures, it has been estimated that the albedo feedback from snow and sea ice retreat is adding 50% to the direct heating effect of greenhouse gases.
PMAG: You also discuss implications for shipping route access with ice-free waters during the summer months. Have such activities (commercial shipping, tourism) been studied in terms of effects on the local environment?
PW: Yes, the US National Academy of Sciences had a panel in 2013, which I was on, producing a report on oil spills in ice in Alaskan coastal waters, pointing out the enormous difficulty of cleaning up a spill or blowout in ice covered seas
PMAG: Can you briefly discuss the role of feedback loops in accelerating the loss of ice and warming?
PW: There are many feedbacks. Snow-ice albedo feedback is an important one enhancing warming. Feedback on Greenland melting increases global sea level. The offshore shelf warming in summer leads to thawing of offshore permafrost which allows the escape of methane plumes, enhancing global warming and possibly leading to a catastrophic event if the methane all comes out at once. [Editor’s note: methane is 23 times more powerful than CO2 as a greenhouse gas in enhancing warming.]
PMAG: Since greenhouse gases stick around, reducing emissions would be more effective sooner rather than later and thus, this is an urgent imperative. At the same time, you argue that even significant reductions are insufficient.
PW: Yes. A warming of 2°C will have very significant effects on crop production and on the stability of the atmosphere and of remaining ice, which is why the Paris agreement seeks 1.5°C. Yet even the pledges made by nations in Paris, if kept in full, will still lead to 3.9°C warming, while longer-term warming (because of the persistence of CO2 in the atmosphere) will go higher still. And there is no evidence that the major emitting nations will really be prepared to disrupt their societies to the extent needed to stick to these pledges. Everyone is living in a fantasy world, in other words. That is why I believe we have to start now, seriously, in implementing geoengineering methods to put a sticking plaster on global warming, and we need urgently to develop methods of taking CO2 out of the atmosphere.
Peter Wadhams is professor of Ocean Physics, and Head of the Polar Ocean Physics Group in the Department of Applied Mathematics and Theoretical Physics, University of Cambridge. He is also current president of the International Association for the Physical Sciences of the Ocean) Commission on Sea Ice. Professor Wadhams has served on the editorial board of multiple academic journals and most recently, the author of “A Farewell to Ice: A Report from the Arctic.”