Air Date: Week of January 7, 2000

Host Steve Curwood talks with Kevin Trenberth, of the National Center for Atmospheric Research, about the state of the global climate at the cusp of the millennium. Dr. Trenberth says climate change caused by atmospheric pollution is clearly occurring, and that balmy winter weather in the U.S., and killer windstorms in Europe could be signs of things to come.

Transcript

CURWOOD: This is Living on Earth. I'm Steve Curwood. If there was ever a time when we could really say the future is now, this has got to be it. For many of us the year 2000 has always been that magic point when the future really begins. So now that the future is here, what's it like? Well, for one thing, it's warmer. And we're not just talking about the near-70-degree temperatures on New Year's Day in New York City. The year 2000 starts on the heels of a run of record warmth throughout the 1990s. Most climate scientists say human-induced climate change is here. Among them is Dr. Kevin Trenberth, head of the climate analysis section of the National Center for Atmospheric Research in Boulder, Colorado.

TRENBERTH: The last 10 to 20 years are clearly emerging as the warmest in the last millennium. The warmest years in order are 1998 as a clear winner, and then 1997 as second, and then 1995, 1991, and 1999 all come in next. And so, the warmest years are all in the past decade, and the reconstructions of the climate which can go back maybe a thousand years, the current indications are that what's happened in the last decade is way above anything that's happened historically.

CURWOOD: Now, is there any reasonable doubt any more that we're seeing the effects of human pollution in the atmosphere?

TRENBERTH: I don't think there's very much doubt any more. Part of the argument hinges about, well, how much has the sun done? And we believe that the sun has contributed a little bit to the warming. But it cannot account for most of what has gone on, and since the late 1970s I think there's very clear evidence that the human influence is emerging very strongly.

CURWOOD: Where I live in the Northeast, it has been unusually warm at the beginning of the year 2000. In Boston, where we do our program, we've had a string of 65-degree days. And there's all kinds of other strange weather going on. The windstorms in Europe, the horrendous rains in Venezuela. Is it fair to say that this weird weather is a sign of global climate change?

TRENBERTH: Well, of course, weather has a lot of natural variability that does occur. And what we can say is that certain of these kinds of things are consistent with what we expect to occur with global warming. But one of the things about global warming is that a lot of the extra heat that we get out of the increases in carbon dioxide in the atmosphere goes into not just raising temperature, but also evaporating moisture from the surface. This is especially so over the oceans. And so, the moisture gets into the atmosphere and that fuels all of our weather systems. It makes them more vigorous than they otherwise would, and it tends to rain harder.

CURWOOD: There are some indications from scientific studies that the climate doesn't change smoothly, but rather jumps. It has snaps. From your research, what do you think of those theories, and if you think those things do happen, are we in the middle of such a snap right now?

TRENBERTH: I think that's quite likely at some point or the other. And we have some examples of that from our climate models, that perhaps one that we can focus on a little bit is the El Nino phenomenon. In the last 20 years, since the late 1970s, we've had more El Ninos than we've had historically. It seemed as though there was a jump, a relatively abrupt jump. And so, one of the theories we have as to how this might happen, is that the climate system can sort of go along on its own way until we cross a threshold, and the global warming is large enough that it kicks it into a different way of behaving. And there are other examples where scientists are rather concerned about, if there is increased rainfall in middle latitudes, which is likely to occur with global warming, in particular over the North Atlantic Ocean, it can change therefore the ocean currents and the Gulf Stream and things like that. And this could have some big adverse effects in parts of Europe, for instance, that might be rather counter-intuitive. It could actually cool off in those regions, in spite of the fact that its close-by warming over the rest of the globe.

CURWOOD: The future is now. Climate change is here now. Is society coping with the real and threatened effects of climate change, do you think, Dr. Trenberth?

TRENBERTH: I don't really think so. For the most part, a politician's horizon is, you know, the next election, and not the decadal or 20-year or 30-year look-aheads that this kind of a problem requires. I think this a real concern that politicians do not have that long horizon, and there's very little action occurring in the United States in particular to address these kinds of problems.

CURWOOD: Kevin Trenberth is director of climate analysis for the National Center for Atmospheric Research in Boulder, Colorado. Thank you, sir, for joining us.

TRENBERTH: You're most welcome.