Biden's position is well-known: Like his running mate, Sen. Barack Obama, and like all of the world's major climatological institutions, the Delaware senator believes that human industrial activity is the primary culprit. Senator Obama's opponent, Sen. John McCain, also frequently states unambiguously that climate change is human-caused. In 2003 he and Sen. Joe Lieberman of Connecticut introduced the firs- ever climate bill, the Climate Stewardship Act, which would have established a carbon cap-and-trade system.
But as I wrote on Wednesday, Gov. Sarah Palin's beliefs are harder to pin down. Shortly, before joining the McCain ticket, she told the conservative magazine Newsmax the she is "not one though who would attribute [global warming] to being man-made." But she subsequently softened her position somewhat, telling ABC News's Charlie Gibson and CBS New's Katie Couric that human activity could be – but was not definitely – a contributing factor, but that natural, cyclical changes also play a role.
Here's how she said it last night (CNN has a transcript of the whole debate):
IFILL: Governor, I'm happy to talk to you in this next section about energy issues. Let's talk about climate change. What is true and what is false about what we have heard, read, discussed, debated about the causes of climate change?
PALIN: Yes. Well, as the nation's only Arctic state and being the governor of that state, Alaska feels and sees impacts of climate change more so than any other state. And we know that it's real.
I'm not one to attribute every man – activity of man to the changes in the climate. There is something to be said also for man's activities, but also for the cyclical temperature changes on our planet.
But there are real changes going on in our climate. And I don't want to argue about the causes. What I want to argue about is, how are we going to get there to positively affect the impacts?
We have got to clean up this planet. We have got to encourage other nations also to come along with us with the impacts of climate change, what we can do about that.
Palin then goes on to discuss how, as Alaska governor, she established a subcabinet in September 2007 to address how to adapt to climate change, and how she and McCain favor an "all of the above" approach – which includes expanded drilling for oil and natural gas as well as alternative energy projects – to deal with climate change and to achieve energy independence for the United States.
So it looks as though we can safely say that Palin believes that global warming is real. Indeed, it's pretty hard to miss in Alaska: The state has warmed about 5 degrees F. in the past century, shrinking glaciers, thawing permafrost, flooding coastal villages, sparking forest fires, and inviting insect infestations.
As for the causes, Palin seems to agree that humanity has had a hand in heating the globe, but she has yet to come out and say it without hedging. Last night she said that "there is something to be said" for humanity's role in climate change. In her interview with Ms. Couric this week she said that "there are man’s activities that can be contributed to the issues that we’re dealing with now." (She may have meant to say "attributed" or "contributing.") And she told Mr. Gibson in September that "man’s activities certainly can be contributing to the issue of global warming" and that she is "attributing some of man’s activities to potentially causing some of the changes in the climate right now." Not exactly straight talk, but it would be unfair to call her a global warming denier.
But whenever she mentions humanity's role, she always makes it a point to mention natural temperature cycles as well. Last night it was "cyclical temperature changes." With Couric it was "because the world’s weather patterns are cyclical," and with Gibson it was "part of the cyclical nature of our planet, the warming and the cooling trends."
So what, exactly are the cyclical temperature variations? And could they be enough to account for the warming that we've experienced so far?
Palin is light on specifics here. She could be talking about the periodic wobbles in the earth's orbit that have caused the earth's 100,000-year ice ages (but that would conflict with her reported belief that the world is only a few thousand years old). Or she could be alluding to changes in the sun and the amount of energy that it emits. Or she could be thinking of El Niño events, or of the temperature oscillations ocurring in our oceans. Or maybe she's talking about volcanic activity, which isn't really cyclical but nonetheless changes the composition of the atmosphere and therefore affects the climate.
The problem with each of these explanations is that there is not yet any theory to explain how they account for the rapid warming that we have seen beginning in the second half of the 20th century. Nobody has managed come up with a model that is satisfactory to the scientific community that explains how any of these natural processes account for the roughly one-degree-Fahrenheit rise in global surface temperatures over the past 30 years. In fact, the Fourth Assessment Report of the Intergovernmental Panel on Climate Change says that such natural variabilities "would likely have produced cooling" during this time.
But we do have a model that explains how human activity – namely, the burning of fossil fuels and changes in land use – accounts for this rise in temperature. This model has been endorsed by the overwhelming majority of climate scientists, and most of the presidential and vice presidential candidates endorse it, too. Except, it seems, Sarah Palin.