DISCOVER magazine has uploaded the transcript of a recent panel on climate change they hosted in San Francisco, in conjunction with the National Science Foundation. The panellists explain in simple terms how we really know that it really is us humans causing the problem, and not natural processes.

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.

One of the panellists, Stephen Schneider, addressed the question of anthropogenic causes as purely a statistical issue. Assuming we knew absolutely nothing about how the environment works…

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.

Finally, the point about the debate being settled:

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.

When asked whether they were optimistic about our ability to deal with the problem, Schneider replied

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.

Unfortunately, it appears to be a good forecast for the next 35 years too. While I’ve no doubt we have the technical ability to fix this, I think we’re too stupid to get our shit together and actually do it. The general populace doesn’t understand science at all, so they’re largely incapable of critically evaluating the scientific evidence and coming to an informed decision.

You might expect the media to inform them, but the mass media is relatively useless too. In this era of newspaper cutbacks specialist science reporters are often discarded, leaving generalist reporters to write science articles, resulting in discredited anti-warming “science” being given equal time and giving their readership the impression that there still is a scientific debate on the topic.

Unfortunately, that leaves personal experience, and by the time the general populace realises they’re directly seeing the effects of global warming, it’s almost certainly too late.