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. The Matusevich Glacier in East Antarctica. Image from the Advanced Land Imager (ALI) on NASA’s Earth Observing-1 (EO-1)

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.”


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