News•October 12, 2012

Panel: Extreme Weather Adds Urgency on Climate Policy

The recent rash of extreme weather and climate events — droughts, heat waves, extreme precipitation — has provided a greater impetus for taking action to reduce planet warming greenhouse gas emissions. But a lack of political will and the complexities of the climate system pose enormous obstacles, according to international development and climate scientists who spoke at a Columbia University forum on Thursday.

The U.S. has had its warmest January-to-September period on record.
Credit: NOAA/NCDC.

The gathering of United Nations advisers, climate experts, and international students was billed as a snapshot of the “State of the Planet.” And it did not paint a rosy picture.

Jan Eliasson, a veteran diplomat who serves as the deputy secretary general of the U.N., ran through a litany of the sustainable development and environmental goals that have eluded policy makers in recent years, and he and other speakers emphasized the urgency of tackling global warming.

“We’re already past the point of dangerous [manmade] interference with the climate system — not approaching it — past it,” said Jeffrey Sachs, an economist who directs Columbia’s Earth Institute.

NASA climatologist James Hansen said that to date, we’ve only seen about half the warming that is likely to occur due to the greenhouse gases that have already been emitted, yet we’re already feeling major impacts. The climate system responds slowly to the added heat from greenhouse gases, with the oceans taking much longer to warm compared to land surfaces. This means that even if all emissions were to be stopped today, warming would continue for several decades.

“That inertia is not our friend, because it can cause the climate system to pass tipping points,” Hansen said.

At one point in July, 88 percent of the corn-growing region of the U.S. was affected by heat and drought conditions.
Credit: USDA.

Hansen’s recent research has shown that the warming that has occurred to date has already caused a dramatic increase in the odds of certain weather extremes, which is raising awareness of the climate challenge. However, Hansen said natural climate variability and the vagaries of day-to-day weather fluctuations ensure that climate change impacts are often difficult for people to discern at the local level.

“It’s hard for most of the public to recognize that we have an emergency because the climate system is a complex, stochastic system, but the changes are already becoming apparent,” he said.

Lisa Goddard, the new director of the International Research Institute for Climate and Society (IRI), said that the large role played by natural climate variability creates a communication challenge for climate scientists and the media.

“Climate change . . . is happening now, but it is only part of what we’re experiencing, especially at a local setting,” she said. According to Goddard, at regional scales there are many areas that have not warmed appreciably in recent decades, which influences people’s perceptions of climate change. “We need to have some sympathy with local experience,” she said of scientists who are trying to communicate climate science findings.

Goddard and Hansen reacted to the newly released poll conducted by George Mason and Yale Universities that showed a majority of Americans link recent extreme weather events to manmade global warming. The poll, Hansen said, reflects the warm winter and the very hot and dry summer in the U.S., and the numbers are likely to shift with future weather patterns, even though long-term climate change does mean that extreme events are more likely to occur.

“Those numbers can go down again when we get the next cool season, and we have to make that clear,” he said.

“It’s a crapshoot, there are going to be some seasons that are going to be cooler than average. The perceptive person should be able to notice that the dice are becoming loaded.”

Hansen uses the concept of loaded dice to illustrate how the odds are shifting in favor of heat and precipitation extremes as a result of manmade global warming.