Caldeira: Many people have been looking at this as a problem of getting international cooperation and international agreements. We’ve had the Kyoto Protocol and the Copenhagen Round Table coming up. But when China builds a power plant that’s going to spew carbon dioxide into the environment for at least the next 75 years, what’s important is that we build it correctly. To me the risks are so clear. Economists estimate that transforming our economy into having an energy system that does not emit carbon dioxide into the atmosphere might cost 2 percent of our wealth each year. Now, I can go to any group of people and say, “Let’s pretend we already have energy systems based on solar, wind, and other sources that don’t emit greenhouse gases.” Then I say, “You can make 2 percent more money each year, but in return for being 2 percent richer we’re going to have to melt the ice caps and acidify the oceans and shift weather patterns. Now, would you trade all that environmental risk in order to be 2 percent richer?” I’ve asked this of climate skeptics. Even they say, “Well, if we already had this carbon-neutral energy system, I would go with it.” That makes me think it’s not the cost of transforming our energy system—it’s that we don’t have the cooperation we need to start doing the job. If we wait until we have international cooperation, it will be too late. What we need is leadership that will say, “We have to stop building devices that emit carbon dioxide into the atmosphere.”
POWELL: What does “leadership” mean in this context?
Caldeira: We need to say we can’t afford to have gasoline cars that emit carbon dioxide—so can we have an electric car system with swappable batteries? We can’t afford to build a coal-fired power plant with CO2 coming out—so can we develop carbon capture and storage technologies, or should we be looking at solar-thermal? We have to start building the new energy system, and we need the political leadership to say we’re going to start doing this. We need research and development to come up with the technology because it’s not all on the shelf. I think if the United States started doing this in a serious way, Europe would follow. If the United States and Europe did this, I think it would not be long before China and India joined us.
POWELL: Snap poll: Do you consider yourselves fundamentally optimistic or pessimistic about whether we have the technological and political will to fix this problem?
Bell: I’m an optimist. Oh, we are changing the planet. We may have already changed the ice sheets to a point that some parts of them may go, but we have the ability to stop changing it more and to adapt to what we have already done.
Caldeira: I’m also optimistic about our abilities. Unfortunately I’m pessimistic about our wisdom. We have the capability to do amazing things in a short amount of time, but it takes a political decision with follow-through. I’m not confident we’ll get it.
Easterling: I temper my optimism by saying that we’re probably looking at an adaptive challenge. That is, we’re going to have to adapt to a certain amount of warming no matter what, even if we were to bring global emissions of greenhouse gases back to year-2000 levels, and that adaptation would be draconian if we were to do it all at once.
Schneider: The first time I was asked that question in a public place was sometime in the 1970s in front of a congressional committee. My answer was a little bit like Ken’s. I said, “I’m technologically optimistic and politically bleak.” That proved to be a pretty good forecast for the next 35 years. But now I’m getting more optimistic because there’s getting to be some alignment of the stars between Congress and the White House. The tough problem is going to be China, India, Indonesia, Brazil, Mexico, and the countries that are even poorer than that. Can you imagine telling this current Congress that we need half a trillion dollars’ worth of technology transfers to help developing countries go through the transition?
POWELL: That raises a good question: How much money do we need to spend on addressing global warming?
Schneider: I think we’ll need $500 billion to get going. Over time, it will be trillions.
Caldeira: But we’re talking about something that’s small compared with the money we invest in medical care. It’s smaller than what we invest in the military budget. I think we need to start looking at climate change as the kind of threat that we must spend real money on to address.
POWELL: Have you all adjusted your personal lifestyle in response to climate change? What measures are important? For instance, will driving a hybrid car or turning down your thermostat really be meaningful, or is this just a drop in the ocean?
Bell: Personally, I’ve done all the easy things. We’ve changed our lightbulbs [to compact fluorescents]. We got rid of one of our cars. But the work I do is an energy hog. I travel to events like this to talk about the changing climate. I go to Antarctica and I burn a lot of carbon to do what I do. So professionally I’m a pig when it comes to carbon. The really hard thing is airline travel. My husband won’t get on a plane for fun anymore. But he’ll go anywhere on a sailboat.
Easterling: I’m the dean of a college at Penn State, and I am notorious for being in a charcoal gray suit riding my bicycle in three inches of snow. I try to set an example, and I haven’t fallen yet.
Caldeira: I’ve done some things, like I now drive a little scooter instead of a car to work, but I really think that this emphasis on the personal carbon footprint plays into the interests of the people who would like to see our current energy system continue. We won’t solve this problem by telling people not to have toast.
Schneider: This is the hypocrisy question. Yeah, Senator Inhofe loves to ask that one of Al Gore, and I get it all the time too. In fact, I ask it of my freshmen and sophomores: “Is your professor a hypocrite?” I live in a green house with twice the legally required insulation and a heat recovery ventilator, and I drive a hybrid and I bike and I live two miles from work, but then there are those 170,000 miles up there on United Airlines, and that is 90-odd percent of my footprint, just as Robin said.
Audience member: What is the most compelling evidence you have that human behavior is actually warming the planet?
Caldeira: To me the most compelling evidence is the fact that the stratosphere—the upper atmosphere—is cooling while the lower atmosphere and the land surface are warming. That’s a sign that greenhouse gases are trapping energy and keeping that energy close to the surface of the earth. I mentioned that in ocean acidification, you actually see animals that should make shells unable to make shells anymore. You could demonstrate the same kind of effect in a bell jar in the lab. There is a level of certainty about it.
POWELL: What about you, Bill? You’re looking not at climate records but rather at agriculture. Do you see a real break from the past there, indicating a unique signature of global warming?
Easterling: One of the problems with agriculture is that it’s a highly managed ecosystem. So it’s often tricky to try to separate out the climate change signal from what might be a host of other things relating to how we manage crops and livestock. But we have seen an increase in the length of the frost-free season. We have seen changes in the incidences and the life cycles of critical agricultural pests, which can be explained only by a general warming. Of course, this is all circumstantial. What made all this come into sharp focus for me was not what we were observing but what we were able to simulate on a computer. Over the past 10 to 15 years, we have been running experiments with very complex and increasingly reliable global climate models. When we entered into the computer all the various things that forced the climate to change, we were able to faithfully reproduce the temperature record of the past 100 years globally. When you take out the component of human-generated carbon dioxide, the models don’t work at all. There are all these people who say, “Well, what about the sun? Why don’t they think about solar variability?” Of course we think about the sun. The models think about all these things, but the models work only if you put all the components in, and one of the big components is us.
POWELL: How you deal with skeptics, both in Congress and in the public, who always seem to have a contrary statistic?
Schneider: First, with regard to your due diligence as a publisher, why hasn’t DISCOVER published a compelling account of the other side? Because there isn’t any. That’s a pretty good reason. There are a lot of things in that speculative and competing explanations category, but there is no preponderance, and that is what is compelling to me. For example, take the evidence that Robin cited. If you were a cynic and you asked about the probability of the ice sheet in the north going up, it’s 50 percent. Going down? Fifty percent. And the South Pole going up? Fifty percent. Going down? Fifty percent. Probability they are both going together? Twenty-five percent. What’s the probability of the stratosphere cooling while the earth gets warmer? Again, assuming we knew nothing, 50 percent. Troposphere warming? Fifty. The probability that one will go up while the other goes down? Twenty-five percent. Same thing for other patterns, like the way high-latitude continents are warming more than low-latitude ones are. With any single line of evidence, you can say, “Oh, well, there’s still a 25 percent chance it’s random,” but what happens when you put all these events together? The probability of all these events’ lining up the same way is pretty darn low unless we are dealing with global warming.
Caldeira: Climate science has reached the point that plate tectonics reached 30 years ago. It is the basic view of the vast majority of working scientists that human-induced climate change is real. There is a real diversity of informed opinion on how important climate change is going to be to various things that affect humans, and there is a diversity of opinion on how to address this problem, but the debate over human-induced climate change is over.
Audience member: I work in a hard-rock mining industry, and the majority of my colleagues tell me I’m crazy when I talk about climate change. Where are some good sources of information that rationally discuss all of these different naysayers’ theories?
Caldeira: One useful Web site is realclimate.org.
Schneider: I have a contrarian section on my Web site, which is climatechange.net. We’re about to triple it because we had to deal with those famous climate professors, you know, professors Limbaugh and Crichton. [Laughter] They have a standard technique, doing much the same thing that the American Tobacco Institute did for a long time, which is to cite the three studies that were equivocal and ignore the 33 studies that were definitive. They use the argument that we still do not, to this day, understand the detailed biological connections between smoking and cancer, but the evidence and data are so overwhelming you’d have to be nuts not to act on it—unless you’re in the business.
Caldeira: There was a climate contrarian who testified before the Senate last week. He made the claim that climate scientists were some kind of club and they all made money by somehow supporting each other’s findings. The reality of science is that a scientific career is made by showing that all the people around you believe something that’s not true. If a scientist could provide evidence that the climate theory is incorrect and that global warming is not a product of human activities, he or she would be held up as the Darwin or the Einstein of climate science. We’re highly incentivized to show that all our colleagues are wrong. If we could come up with good evidence that they’re wrong, we would be out there publishing it. The evidence just doesn’t exist.
Easterling: Even science is not value neutral. We make decisions and we have values in our judgments, but at the end of the day we have a code of ethics that says we look at the data and, using our prior knowledge, we make our best judgment. That’s all it is.