The scientific truth about climate change

(CBS News) 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.

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