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PRI's Environmental News Magazine

CO2 Spike Leaves Scientists Concerned

Air Date: Week of October 29, 2004

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A study out of Mauna Loa Laboratory reveals a dramatic jump in atmospheric levels of carbon dioxide in the last two years. Host Steve Curwood talks with David Schimel, senior scientist with the National Centers for Atmospheric Research, about the possible explanations for this spike.


CURWOOD: It’s Living on Earth. I’m Steve Curwood. Science tells us the more greenhouse gases such as carbon dioxide that are released into the atmosphere, the warmer the planet will become. And since the Industrial Revolution and the widespread use of coal, gas and oil, the average temperature of the planet has risen by a degree, and CO2 has reached levels unmatched for hundreds of thousands of years.

Now, data from the Mauna Loa Observatory in Hawaii show a sharp spike in the rate of increase of carbon dioxide over the last two years. Scientists say this jump in the rate of growth of CO2 levels could mean that we face a dramatically shortened timetable for addressing global warming. Joining me now is David Schimel, senior scientist at the National Center for Atmospheric Research in Boulder, Colorado. David, welcome to Living on Earth.

SCHIMEL: Thank you very much.

CURWOOD: We know that carbon dioxide levels have been rising for some years now. What’s different now?

SCHIMEL: Over the past decades, the increase in carbon dioxide has been roughly constant, somewhat paralleling the emissions from fossil fuel and other processes. The last two years have been very high growth rates of carbon dioxide in the atmosphere. Two consecutive years is a little bit unusual. The really unusual thing is that they’re not associated with any obvious climactic event that might trigger, say, widespread drought or unusually extensive wildfires.

CURWOOD: What are the possible explanations for this rather dramatic jump over the last two years in the amount of carbon dioxide coming into the atmosphere?

SCHIMEL: The first explanation is the scary one, which is that the steady warming that’s been occurring in the past few decades is somehow triggering a release of carbon from certain types of ecosystems: forests, or northern peatlands, or other types of ecosystems that store large amounts of carbon. And if that were to be the correct explanation, it would be of concern because that’s a feedback; the warmer it gets, potentially the more CO2 is released, contributing a fraction to the warming and then possibly releasing more carbon.

CURWOOD: So, in other words, carbon comes out of what, trees, or stuff on the (inaudible)…

SCHIMEL: Trees, soils, in the Arctic we’ve got many systems that have huge amounts of stored carbon in their soils. The soils are really just old, dead plant material, preserved there because of cold and wet conditions.

CURWOOD: Tell me about the not-so-scary explanation.

SCHIMEL: Ah, good. The not-so-scary explanation is a little bit more complicated. We believe that one of the reasons that ecosystems, forests and other types of systems, are taking up carbon now, in the 1990s and 2000s, is because there was a very large amount of forest harvesting in the U.S., in Europe, and parts of Asia between, say, 1850 and 1950. And there are large areas of re-growing forests in areas that were abandoned from agriculture and areas that were harvested, for example in the U.S. during the mining and railroad building eras in the West. And those re-growing forests take up carbon. And the young forests take it up quite rapidly; as they age they begin to take up less and less carbon. They approach a maximum size, if you will.

And it’s possible that what we’re seeing is the beginning of a turnaround in that process where all of these forests that were abandoned over the past hundred, 150 years, are beginning to mature. Now if that’s true, that’s not a good thing, we’d like to see those forests continuing to take up carbon, but it’s not a feedback cycle with warming, per se.

CURWOOD: Two years of data, looking at this increase, is obviously a very short period of time, probably too early to really tell what’s causing this jump, but at what point do you think we might be able to know if this increase in carbon dioxide is a pattern?

SCHIMEL: Well, you’ve asked the hardest question: when will we know something we don’t know now? The simple answer is if this were to continue for two to three more years, it would really be unprecedented and it would be a very conclusive result.

CURWOOD: So, at this point, it could still be a statistical fluke then?

SCHIMEL: That’s correct. And, in fact, it could be unusual conditions in the oceans and not associated with the biosphere at all, although that’s a much less likely explanation.

CURWOOD: For the sake of discussion, assuming that this increase is sustained, that we see it not for just two years, but for three, or five, or six years, how serious is this problem?

SCHIMEL: Well, it’s not going to cause the world to end any time soon. It’s certainly not leading us into a “Day After Tomorrow” scenario ten times faster than the situation that we’ve been observing over the past few decades. But it does mean that we have less time to develop new technology to implement hydrogen, solar, other alternative energies than we would otherwise.

CURWOOD: So, given these concerns, how long can we afford to wait to know for sure that this is a long-term problem? What point should we decide that it is or isn’t?

SCHIMEL: Well, if the increase in the atmosphere continues, that’s an observable fact and we’ll know it’s occurring. Federal agencies in the U.S., university groups and other nations measure this quantity with great care and precision. So, we’ll know the fact of whether it’s increasing, whether this increase is continuing, quite soon.

CURWOOD: David Schimel is a senior scientist at the National Center for Atmospheric Research in Boulder, Colorado. Thanks for taking this time.

SCHIMEL: Thanks, Steve.



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