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U.N. Panel Report: Most Global Warming Is Caused By Humans

Scientists assembled by the United Nations sent out a renewed warning Friday that the planet is warming up and human beings are largely responsible. The Intergovernmental Panel on Climate Change has released a report that projects more warming air, melting ice and rising seas in this century.

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DAVID GREENE, HOST:

Scientists assembled by the United Nations sent out a renewed warning this morning that the planet is warming up and human beings are largely responsible. The Intergovernmental Panel on Climate Change released a new report in Stockholm that projects more warming air, melting ice and rising seas in this century.

The report is a consensus view on the Earth's health as it is understood by scientists from around the world. For that reason, the new IPCC report is likely to get the attention of many governments. Joining us to talk about the latest report is NPR science correspondent Richard Harris. Richard, thanks for coming in.

RICHARD HARRIS, BYLINE: My pleasure. Good morning.

GREENE: So what stands out to you in this latest report?

HARRIS: Well, the report underlines that the more scientists study this issue, the more confident they are that human activities are changing the planet. They note that the last decade was hottest on record and has set many records, or many unprecedented events they noted, unprecedented over the terms of decades to millennia.

They also acknowledge that things might not be as bad as previous projections. They acknowledged greater uncertainty about what we could be facing. But they also underline - no surprise - that it will take a huge effort to rein in carbon dioxide emissions if we're ever going to stabilize the climate.

GREENE: Well let's talk about decades, more than millennia, for the moment at least. The rest of this century - what are they predicting might happen?

HARRIS: Well, rising temperatures are still on tap. In some scenarios that would be over two degrees Centigrade, which is three and a half degrees Farenheit, about. And that's what the international community as set as a goal in the U.N. climate talks - let's not get the planet hotter than two degrees centigrade.

But interestingly, other scenarios suggest we might not reach that point, at least not in this century, either because the carbon dioxide emissions could come under control under some of these scenarios, or it is possible that, given the amount of emissions, might actually cause less warming than scientists had previously realized. Let me also touch on rising sea levels. That's, of course, another big factor, and that could be a foot or two, according to this report, by the end of the century. Or they say, in their worst case scenario, could be up to three feet - that would be parts of Antarctica start to melt rapidly. And they also note that, of course, the world doesn't stop in 2100, and sea levels would continue to rise past that point.

GREENE: You were on the air on this program, with a story recently, pointing out that over the last 15 years, global air temperatures have not really climbed. And that has some skeptics saying, you know, maybe the planet's not really warming up, maybe we've been wrong about these predictions. Did the scientists address that in this report?

HARRIS: Yes, indeed they did. And they said that a huge amount of heat that has come into the Earth's system - the energy - has soaked up in the deep ocean, something like 90 percent. And a lot of that is a temporary phenomenon, they believe, caused be a weather pattern called La Nina. So we can't count on those oceans indefinitely, to keep soaking up all that amount of heat. They also they said it's likely that particles from volcanoes and other stuff in the atmosphere might have reflected some of the energy back into space. And so we basically didn't heat up as much as we would've if those hadn't been there.

But again, that's a temporary phenomenon. So they're still extremely confident that the long-term trend in global temperatures is up.

GREENE: If we look kind of broadly at this, the IPCC, this organization has been producing reports since 1990. This is the fifth on now, the last one like six years ago. I mean, is this new report a big departure in any way or have things remained pretty consistent?

HARRIS: It's not a big departure, but it is a fresh look. Two thirds of the studies that they reviewed were actually published since 2007. And 60 percent of the authors are new, and so on the one hand, there's more confidence that in the overall role of human beings in climate change. But this report also does more, I would say, to acknowledge the uncertainties that are always present in any prediction. They've just been putting them on the paper a little bit more clearly in this report, I think. And that's reflected in acknowledging that things might not be as bad as it could be, but on the other hand, they say don't bet on that, you know - that's the low end, let's not lose track of some of the worst scenarios.

GREENE: All right, we've been talking with NPR's science correspondent Richard Harris. Richard, thanks for coming in.

HARRIS: My pleasure.

GREENE: This is NPR News.

(SOUNDBITE OF MUSIC) Transcript provided by NPR, Copyright NPR.

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