National

Nov 11, 2012 4:17 PM by CBS News

The scientific truth about climate change

Climate Change . . . fact, or fiction? It's one of the most vigorously debated questions of our time, given more urgency in the eyes of many by the destruction wrought by superstorm Sandy. Our Cover Story is reported by David Pogue of The New York Times:

I'll admit it. I have global warming anxiety. No, it's worse than that - I have global warming anxiety anxiety. I don't know how much I should be worried. I mean, we're bombarded by conflicting opinions.

You've got the scientists going "Burning fossil fuels heats the atmosphere. Record temperatures. Extreme weather!"

And then you've got the skeptics going, "Don't be silly! The Earth has always had warming cycles. Human activity has nothing to do with it."

And I feel sorry for the poor guy caught in the middle!

So I decided it's time to go on a quest to visit the top experts to answer three essential questions:

Is there climate change?

Are WE causing it?

And if so, is there anything we can do about it?

Here's what we know for sure: The decade beginning in the year 2000 was the hottest decade ever recorded. Arctic ice has melted to its lowest levels in recorded history, and sea levels have risen eight inches since 1870.

If anyone knows the details, it's the IPCC - the Intergovernmental Panel on Climate Change - which was created by the United Nations in 1988. Its job is to collect climate-change studies from around the world, and draw conclusions. Its chairman is Rajendra Pachauri, who says the impacts of climate change are becoming progressively more serious.

"Most of the warming that has taken place is the result of human reactions," Pachauri said. "Greenhouse gases, carbon dioxide being the most dominant."

So what makes scientists so sure that those gases are building up in the atmosphere? Easy: Every week, they go out and rustle up some air! - at a measuring station high up in Boulder, Colo., run by NOAA (the National Oceanic and Atmospheric Administration).

At about 2.2 miles above sea level - and with no cars allowed nearby - they get air unchecked by any sort of local pollution.

Duane Kitzis showed me how it's done: "This is one of 70 sample sites in our network, around the world, so that these are different points on a grid, if you will, of the surface of the Earth."

They collect 20,000 flasks of air a year, from all over the world.

At other locations, the air is sampled from the top of thousand-foot towers, to make sure that the sample isn't contaminated by nearby civilization.

All of those bottles from around the world get shipped to labs which analyze the gases inside. One after the other, they get injected into measurement machines.

"The data show that CO2 is going up - there's absolutely zero doubt about that," said Pieter Tans, chief scientist at NOAA's global monitoring division. The air-sample collecting program is his baby.

"Is anybody still arguing that the changes in temperature are just part of natural Earth cycles?" Pogue asked.

"Oh, they have been, yes," said Tans. "There are these natural fluctuations of climate. However, there is something different. You look at the rate of increase, when the Earth was in one of its natural cycles. The rate of increase of CO2 then was on average .02 parts per million per year. And now it's 2 PPM a year. So what we're now having is a 100 times as fast as what was happening during these natural cycles."

So, how can there be such a thing as a skeptic community?

"There's only a small fraction of skeptics who want to deny that the increase of greenhouse gases is due to mankind. Most of them actually accept that."

That's true; there aren't many climate-change deniers anymore. But there's still plenty of discussion (and that's the polite word for it) about how much the planet is changing.

Berkeley physics professor Richard Muller and his daughter Elizabeth were global-warming skeptics - until they spent two years conducting their own study.

Elizabeth Muller showed me a graph, showing temperatures recorded at 39,000 stations around the world averaged together. This is the temperature record.

"The thick, black line is carbon dioxide plus volcanoes," she said, "and everything else is the actual temperature record. And the amazing thing is how well the two fit right on top of each other."

In a New York Times editorial, the Mullers described themselves as converted global-warming skeptics - but they sure don't sound very converted.

"The number of hurricanes has not been going up. The number of tornadoes has not been going up," said Richard Muller.

And what about the droughts and the fires in the West? "Well, that's because we're building closer to the fire areas," he said. "The number of fires in the United States has actually been decreasing with time."

And what about polar bears? They're dying because of global warming, no?

"No," said Muller. "There's no good scientific evidence for that. There's a problem in that some people, whenever they see something they don't like, they attribute it to global warming - whether it's the death of the frogs, or the demise of the corals in the Pacific Ocean. But that's kind of cherry-picking, where they're simply saying, 'If it's bad, it must be global warming.'"

And that brings us to the elephant in the room: Hurricane Sandy. The largest Atlantic hurricane ever recorded, it could cost $50 billion in damage, second only to Hurricane Katrina.

Are these superstorms related to global warming? John Mutter, who teaches environmental science at Columbia University, says there are two questions to address: "One is, 'Will there be more storms?' And the second is, 'Will more of those storms be intense?'

"What's happening is that, if the world is warmer overall, the area that's occupied by the tropics will get larger. So if the tropics expand, they'll bring with them their tropical weather, which includes hurricanes.

"So imagine that now we have ten hurricanes per year, and two of them are really monsters," said Mutter. "In the future, the expectation is there will still be ten, but four of them will be monsters."

There may be legitimate scientific disagreement - and plenty of nasty bickering online - about how much climate change we're seeing now. But the really frightening part is what's coming.

Beth Russell runs a NOAA exhibit called "Science on a Sphere," which can presents massive amounts of temperature data visually. She shows us temperatures over a century, beginning in the 1880s. "We really start to notice a trend past the year 2000 especially. Continuing to step through time, the globe's starting to turn more yellows and reds."

"It's baking in here!" said Pogue.

"Yeah, it's pretty dramatic what we show in this model," said Russell. "It gets us up to 717 parts per million of carbon dioxide, which is almost double what we have today."

Tans said there is one thing climate models agree upon: "There will be more extreme weather. That means crop failures, for example. Extreme storms also will drive people from their homes. International conflicts would easily result from it. The problem now is us, if we don't unite and try to do something about it. We all bicker until it happens."

Even the Mullers are worried about the future.

"We don't care about what we have already seen in terms of the warming, which has been quite small," said Elizabeth Muller. "What we care about is the warming that we're going to have over the next 50 years."

"Why? What will happen?"

"There's lots of people who say, 'Oh, we're gonna have more hurricanes, we're gonna have more droughts. We're gonna have more problems.'" But the fact is we don't know."

Here's something else nobody can agree on: What to do about global warming.

"I believe that by approaching this with these interim solutions of energy efficiency and clean natural gas, that that can get us to the era, 30, 40, 50 years from now when solar and wind and nuclear can all be competitive and take over at that point," said Richard Muller.

China will have to be a big part of the solution: It surpassed the U.S. in greenhouse gas production in 2006, and Muller says by the end of this year it will be producing twice the greenhouse gases of the United States.

Even there, the IPCC's Rajendra Pachauri sees glimmers of hope: "I spend a lot of time in China. I see a distinct acceptance of the fact that they need to move to a low-carbon future now."

So the debate will continue over how fast the Earth is warming and what the effects will be. But on the three key questions, all my experts are unanimous.

Is climate change real? Yes.

Is human activity contributing to it? Yes.

And is there anything we can do about it? Yes.

"We can do a lot. If we decide this is serious, we can avoid most of it," said Tans.

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