Will a warming world bring more or less rain?
Christopher Potter says there are going to be winners and losers.
Some people are beginning to refer to climate change as “climate chaos.” The fact is, there are many uncertainties about Earth’s climate in the coming decades. What will it be like? No one knows. In this interview, we asked if a warmer world will lead to more or less rainfall across the globe. Will the world be wetter or drier? We asked Christopher Potter, a scientist who is using satellite data to learn how climate change and human activities are changing our world. Earth & Sky’s Eleanor Imster talked with him in May 2005.
Imster: Our climate is warming. Will than mean more or less rainfall?
Potter: There is some consensus that a warming climate often brings higher rainfall amounts to many areas of the land surface. So surprisingly, we may see that we accelerate the water cycle, but we don’t turn it off. That’s what we can hope for. And there is, I think, some consensus that it’s a strong possibility. But there are going to be winners and losers. It depends on where you live.
Imster: And can we predict who will get more rainfall, and who will get less?
Potter: There’s a lot of uncertainly. The smaller the scale, the bigger the uncertainly. The smaller the place you’re trying to look at, the more difficult it is to take the climate model information and scale it down to say, “you’re going to be OK, and you’re not.”
The new satellite observing systems can see areas across the entire globe that resolve down to the size of about a football stadium. That’s a lot of information. It’s like drinking from a fire hose when you try to digest and understand that information. But it’s an extremely valuable archive and baseline against which to test future change. We can see a lot that we’ve never been able to see before and now it’s time to take advantage of it and act on it.
We’re using the satellite record, that now extends back 20 to 30 years, to try to characterize which areas have changed, which have become more desert–like or maybe become more green. We do see in the record some places in Europe and Asia that seem to be greening up pretty rapidly. We see it green up for a while, and then we see it turn back down. And we try to understand the interacting factors of climate, human land use change and put it all together to inform decision–makers and policy–makers about what’s changing most rapidly, who’s being affected, what we might be able to do about it.
Imster: During Earth’s history, there have been times when the climate was even warmer and there was even more CO2 in the atmosphere than today. During those warm periods, was it rainier? Or were there more deserts?
Potter: That’s a good question. We have some sparse records around to tell us maybe what rainfall was by looking at the plant composition. There’s not a lot of consensus on whether the rainfall patterns were more abundant during high CO2 times. It’s possible that it was more humid. More CO2, more heating, more humidity, and more clouds, therefore more rain. I don’t think we even know that answer to that for the contemporary period, much less going backwards in time, about the rainfall patterns.
Imster: It seems that humans are changing our planet. How significant an effect will that be in the next, say, 25 years?
Potter: I think there’s pretty broad consensus among scientists that humans leave their mark, unmistakably, on our climate, on our landscape, on our oceans and the cycling of the greenhouse gases that affect climate. Is it as much as half of the effects we see now? Possibly. But it depends on the strength of certain large climate events. Like an El Nino can come along and just change everything, and we don’t know if humans are impacting that or not. During some years, our effects are amplified, and other years, nature takes over again.
I like to think we have options to decrease our footprint. But we are locked into a certain amount of effect, because the greenhouse gases we’ve emitted have a long lifetime in the atmosphere – decades and centuries – and it’s very expensive to remove them.
I think we’d like to find ways of repackaging our effects in a way that provides the developing world, or other parts of the world, with other models for decreasing their footprint effect on the planet. We can lead by example in the US. There’s no doubt about it.
It’s not too late yet. We’ve got time to act. But time’s a–wasting. We should do what we can to maximize the way we help people to live more prosperous lives, but in a way that minimizes our footprint on the atmosphere and the biosphere. After all, that?s where we live, in that interface.
Imster: Thank you, Dr. Potter.
Christopher Potter is a research scientist at the Ecosystem Science and Technology Branch of “NASA Ames Research Center”:http://www.nasa.gov/centers/ames/home/index.html.
