May 19, 2014 | Energy & Climate, IIASA Network
John Schellnhuber
Scientists who have worked for many years in the field of climate change sometimes grow cynical about the possibility that the world will address the problem. After over 40 years of research on the subject, there is still no global agreement on climate change, and greenhouse gas emissions continue to increase. This despite growing evidence of the severity of the problem.
But John Schellnhuber, director of the Potsdam Institute for Climate Impact Research (PIK) since its founding in 1992, remains hopeful.
“The odds are against us, but they are not zero,” he told an audience of IIASA researchers on 13 May. In a wide-ranging lecture for IIASA staff, Schellnhuber highlighted some of the most recent findings on climate change from PIK researchers, but also shared his thoughts on the potential for the world to take action to mitigate the emissions that are leading to climate warming.
The human race has blossomed on this planet only in the last 11,000 years, a period of very stable climate known as the Holocene. Without this stability, Schellnhuber pointed out, humans would not have been able to develop agriculture, let alone the technological advances of the industrial revolution or the population explosions that followed from these developments. Destabilizing this climate that has led to such success could be dangerous—and evidence suggests that it will be most dangerous to people in developing countries, who did the least to cause the problem.
Some of the more worrisome research to come out of PIK and other climate research centers in recent years focuses on possible tipping points or “non-linearity” in the climate system. For example, changes in the jet stream, related to declining Arctic sea ice cover and warming in the Arctic, are already proving to have major effects on weather, possibly contributing to recent heat waves like the 2010 heat wave in Russia, as well as floods in more southern regions—such extreme weather events are likely to become more frequent, said Schellnhuber, in a world with greater warming.
A new study from PIK researchers shows that the East Antarctic Ice Sheet may also be in danger of melt that would raise sea levels. (Image courtesy NASA Goddard)
At the same time, a new study from PIK scientists suggests that the glaciers which serve as the outlet for the massive East Antarctic Ice Sheet might melt, effectively unplugging the passages that hold the ice sheet in place. Schellnhuber said, “If global warming removes that plug, there could be an unstoppable flow of ice into the ocean.”
New research from NASA announced this week suggests that the West Antarctic Ice Sheet may already have been so destabilized. Schellnhuber points out that the countries that will experience the greatest impacts of sea level rise—primarily in the tropics—contributed the least to the problem.
A moral issue
Many researchers at both IIASA and PIK work closely with policymakers to help define the costs and benefits of climate action. But Schellnhuber argued that only a social movement will provide the push that policymakers need in order to support strong action. When he talks to heads of government, he said, they listen to what he has to say. But without broad support, they cannot or will not act.
“I think it is a moral issue in the end. People have to decide whether they want to do something,” he said. “The older I get and the more I learn about the challenges, the more I think this is the only way.”
References
Tang, Q, Zhang X, Francis JA. (2014). Extreme summer weather in northern mid-latitudes linked to a vanishing cryosphere. Nature Climate Change 4, 45–50 (2014) doi:10.1038/nclimate2065
Levermann, A., Bamber, J., Drijfhout, S., Ganopolski, A., Haeberli, W., Harris, N.R.P., Huss, M., Krüger, K., Lenton, T., Lindsay, R.W., Notz, D., Wadhams, P., Weber, S. (2012): Potential climatic transitions with profound impact on Europe – Review of the current state of six ‘tipping elements of the climate system’. Climatic Change 110 (2012), 845-878, [DOI 10.1007/s10584-011-0126-5]
Joughin, I, Smith BE, Medley B. (2014) Marine Ice Sheet Collapse Potentially Underway for the Thwaites Glacier Basin, West Antarctica. Science. 10.1126/science.1249055
Rignot E, Mouginot J, Morlighem M, Seroussi H, and Scheuchl B. (2014) Widespread, rapid grounding line retreat of Pine Island, Thwaites, Smith and Kohler glaciers, West Antarctica from 1992 to 2011. Geophysical Research Letters. DOI: 10.1002/2014GL060140
Nov 7, 2013 | Energy & Climate, Science and Policy
Peter Lemke, head of the Climate Sciences Research Division at the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research in Bremerhaven, Germany, is an expert on sea ice, a polar explorer, and the Chair of the IIASA Council. In this interview Lemke explains how climate change is affecting the Earth’s polar regions, and talks about a recent winter expedition to Antarctica.
On Monday, 11 November Lemke will give a public lecture on the topic at IIASA in Laxenburg.
Peter Lemke – Credit: Stephanie von Neuhoff (AWI)
How did you get interested in the cryosphere? What drew you to the poles?
When I was a young scientist, I was involved in climate modeling and especially the role of polar regions. For my PhD thesis I worked on sea ice extent data, trying to understand why we see changes.
That was in the late seventies, so it was not really climate change which was driving us, we just wanted to understand the climate system. Polar regions are an important part of the climate system. We tried to understand how they impact the other regions on the globe such as mid-latitudes and even the tropics.
When did you realize that climate change was affecting the polar regions?
Well the globe was already warming when I was starting my research in the mid-1970s. Sea ice was decreasing in extent, and ice was melting on the continents. Year by year, this trend became more significant. By the 1990s it was quite clear that there was a trend which was not just natural variation. The third IPCC report in 2001 just made it clear that man had an impact on the warming; at least a substantial part of it was due to increased greenhouse gases in our atmosphere.
A helicopter that was used to measure sea ice during Lemke’s 2013 Antarctic expedition. Credit: Peter Lemke (AWI)
What is happening now?
The changes we see now are even more dramatic than before, especially considering the Arctic sea ice. It hit a record low minimum in 2007 and we thought that this was the ultimate—as low as it would go. But then ice extent went even lower in 2012. While the ice extent this last summer was not quite so low, there is a strong trend in summer extent of sea ice. Our data indicate that it’s not just the extent but the thickness that’s changing. Measurements of sea ice thickness which our institute has performed over the last decade or so show a sharp thinning of the sea ice in the interior of the Arctic: The sea ice has thinned from an average of 2.5 to about 1 meter in only 10 years.
The other thing that is interesting is that the sea ice extent in the Antarctic is not decreasing at the same rate. On the contrary, it’s increasing in extent slightly. The question is of course is the ice mass also increasing, or is it just spreading out and thinning—like a dough that you roll out, getting wider but thinner?
How do you explain the growth in Antarctic sea ice, while Arctic sea ice is declining?
One explanation is that in the Southern Hemisphere the westerly winds are increasing, and through friction this drives the ice towards lower latitudes and the extent is getting a bit bigger. When the ice expands there is open water between ice floes, and it’s still cold enough in winter that ice freezes in the open patches.
There are other physical processes that may be involved, such as the heavy snow cover that blankets the Antarctic sea ice. Sometimes the heavy snow load submerges the ice floe underwater so that the interface of ice and snow is actually below sea level, and seawater drains into the snow and freezes. That may be one process, but there are others that are not really resolved yet.
We don’t yet have the answers to these questions, because there are very few measurements and you cannot deduce snow from satellite remote sensing data, yet. To find out, you have to go there and make measurements yourself. But winter expeditions are very rare. There are very few icebreakers that can actually go into the Antarctic winter into the sea ice. I have participated in four expeditions over the last 25 years: in 1989, 1992, 2006, and now 2013.
Working site during the 2013 Antarctic expedition. The wind chill was often between -50 and -60°C. Credit: Peter Lemke (AWI)
What did you find on your latest expedition?
Most of the data have yet to be analyzed. But from our early results, it looks like that the sea ice mass around Antarctica has increased slightly. Our measurements showed that the sea ice was more extensive, thicker and more densely packed as compared to our 1992 expedition, which was on the same track during the same season.
We have also observed a continuous warming in the deep ocean, which indicates that the warming trend that we see over the last couple decades is continuing. This indicates that the ocean has taken up a large fraction of the heat due to the increased greenhouse effect.
Why should people care what happens in the Arctic or in Antarctica?
Both polar regions are pristine regions not affected by humans as much as lower latitudes. Still you see the effects of mankind there. Once the sea ice is gone in the Arctic, we have lost an entire ecosystem which is adapted to the sea ice. Sea ice is a porous medium, and in the small cavities, there is rich life—tiny algae, crabs, krill—and this ecosystem supports an entire food chain up to the polar bear, whales, penguins that you find depending on which pole you are looking at.
Do you think that IIASA has a role to play in polar research?
IIASA is currently considering a new Arctic initiative, which could involve not just the climate system and the ecosystem but also the human system. Changes in the Arctic are already affecting people living at the coastlines. This coastline is made up of sand and ice, which is thawing. And as the sea ice is retreating, the coastline is now exposed to the increasing waves in the open ocean. Already now villages are already eaten up by the sea. At the same time, hunting grounds are changing for Inuit and other indigenous people who rely on sea ice for hunting. I think that’s something that IIASA can actually look at from a holistic view: human system, ecosystem, climate system.
What is one thing you want people to know?
Well often the poles, especially the Arctic, seem so far away that people don’t think that it is important for their lives. But if you have a polar storm coming from Svalbard, within two days it reaches the German coast, and within 10 days the entire Northern Hemisphere may be affected. The Arctic is only a few days away from us, and conditions that are changing in the Arctic will affect the climate conditions also in our region.
Emperor penguins spotted during Lemke’s 2013 Antarctic expedition. Credit: Peter Lemke (AWI)
-82.862752-135
You must be logged in to post a comment.