WARMING UP
June 7, 2001

The National Academy of Sciences report concludes the Earth is getting warmer and humans are helping cause it.

 

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	Humans are making it hotter
	RAY SUAREZ: Mr. Cicerone, what was the assignment that was given you by the White House? RALPH CICERONE: Well, the request went from the White House to a national research council -- and that's the Academy of Sciences in Washington four or five weeks ago -- in the form of a number of specific questions. There were about a dozen of them, so, in fact, what we tried to do was to answer the questions. RAY SUAREZ: Using already available signs, rather than new research? RALPH CICERONE: Right. There was no way that we could do any meaningful new research in a three or four week period; it just doesn't happen that way, so we had to stick with what's known, what we're aware - what we were already aware of, and what is recorded in fact in this new inter-governmental panel on climate change report, which is about 800 pages. RAY SUAREZ: And what would you call the main conclusions? RALPH CICERONE: Well, we tried very hard to address the questions that the White House had given us, and I hope we were responsive. We added our voice to the view that the observed warming, i.e., the fact that the planet is warming up and that it has been warming up for the past few decades, but with particularly rapid warming in the last 20 years, we agreed with the previous findings that the weight of the evidence, the weight of the scientific opinion is that most of that warming of the past 20 years is caused by human activities.
	Understanding the skeptics
	RAY SUAREZ: And how were you able to come to that conclusion? Some of the skeptics in the past have noted that Earth is a very complex system and it's hard to tell what humans bring to the world ecosystem. What did you say about the variable? RALPH CICERONE: Well, climate is wondrously complex and very tricky to research. I think the key here is that as the climate record, the real data, get longer, long periods of time, and the fact that this temperature increase of the past 20 years or so has persisted at such a high rate is convincing people that natural variability, which has always occurred, climate is always changing on the Earth, and it has done so over geologic history and even the past couple of centuries, but the rate of this increase and the size of it seems to be larger than natural variability can explain, at least everything we know so far about natural ability - natural variability. So we do have some caveats and some qualifications here, but the weight of the evidence is that this increase has broken beyond the size of natural variability. RAY SUAREZ: Are there people who assisted in the preparation of this report, who once were skeptics and this recent evidence that we talked about has sort of brought them over to the other side? RALPH CICERONE: Well, there are 11 of us on this committee, and I think probably all 11 of us were skeptical at some point in the past. It's just a question of how long ago. It's only been a couple of decades that all of us as humans and as scientists, as scientists have come to the view that human activities are really capable of affecting the physical environment of the entire planet, so all of us started out skeptical about all of these issues, and we don't have a uniform opinion right now amongst the 11 of us of the degree of certainty because there are uncertainties. We have a couple of ideas about natural variability that could be causing some of this, even most recent year temperature increase but I think the weight of evidence has really shifted, and that's what our committee said. RAY SUAREZ: Well, for those people in your field who still are skeptical, who still are wondering about modeling, about whether the known temperature of the Earth is broad enough for you take conclusions over centuries, what are some of the sticking points that are keeping skeptics from supporting data like that, that you observed? RALPH CICERONE: Well, a couple of ideas. For example, just focusing on the last two, three or four decades is that there are thoughts that the Sun, itself, may be putting out more energy that comes to the Earth, and there is some good physical reasoning that says that that's possible and that it could have explained some of the warming over the past century. But, once again, if we point to the last 20-year period, there's something else distinctive here. Not only are the temperatures going up fast around the entire planet at the surface, but this is the only 20-year period where we've had instruments in space measuring the Sun's output carefully. The measurements are just beautiful, and they show hardly any change in the Sun's output, except for the 11-year cyclic behavior which people were already aware of, so we say that that seems to show that at least recently the Sun hasn't had the kind of impact that some people were hoping or thought that it might. The other idea is that maybe there's some kind of natural variability out there that we simply don't understand yet, and we certainly admit the possibility of that, but we don't know what it is.
	Climate expectations
	RAY SUAREZ: What are some of the effects that we may be able to see here on the Earth in the coming years? RALPH CICERONE: Well, of course, temperature is what we watch for -- the daily maximum temperatures going up - they're actually going up slower than the nighttime minimum temperatures are, which, again, is compatible with this greenhouse effect due to the greenhouse gases, but climate is much broader than just temperatures. We have to be watching for the kinds of severe storms and whether they change, whether our precipitation patterns, rain and snow alike, and snow accumulation change in a way that's not compatible with previous data, whether the frequency of droughts increases, the frequency of floods, because climate change is going to play out differently in different regions of the world, and that's really the rub of it in knowing what to anticipate in the future and how we might adapt to it. RAY SUAREZ: So even with the most voluminous data in the history of record keeping, it's hard for you to make a model that looks ten, twenty years down the road? RALPH CICERONE: It is, and when you think of ten, twenty, one hundred years down the road, and the ITCC expert scientific establishment was trying to look down the road a hundred years, you see that even human activities themselves are part of the uncertainties in the future. What kind of energy usage patterns are we going to have, how many people will there be on the planet, what is the trajectory and the numbers of human population, what kind of standard of living are we going to have, so we have to try to make estimates and predictions. When you do that and you assume a kind of business as usual approach, continued growth in our usage of fossil fuels, continued growth in population, continued ascent up to a higher standard of living, which often takes more energy, that's where the projections have come from that there are going to be significant climate changes in the next one or two human generations. RAY SUAREZ: Well, what if we manage to stop the growth of greenhouse gases entering into the atmosphere now, if we capped it at 2001 levels, would the climate continue to warm anyway? RALPH CICERONE: Yes, the climate would continue to warm because there's already some extra heating built into the system in the exchange of energy between atmosphere and oceans. In other words, temperatures will continue to rise perhaps for the next 50 years or so even if the amount of greenhouse gases in the atmosphere stay constant and don't increase any further. And, by the way, for carbon dioxide, the main greenhouse gas, if we hold emissions constant right now, that is our rate of fossil fuel release of CO2 constant around the world, concentrations will continue to rise, so that we have a double problem there. If we hold the amount in the air constant, temperatures will rise, but if we hold the emissions constant, which heat the atmosphere and will increase the concentrations, then temperatures and climate change will continue in an accelerated way, let alone if we accelerate the emissions of carbon dioxide and the other greenhouse gases, which would add on top of the first two plateaus that I just described. RAY SUAREZ: Ralph Cicerone, thank you very much for being with us. RALPH CICERONE: Thank you. Good night.