The verdict is in on climate change

Recently I had jury duty, and during jury selection something remarkable occurred. Early in the proceedings, the judge posed a hypothetical question to the 60 or so potential jurors in the room: “If I were to send you out now and ask you to render a verdict, what would it be? How many of you would vote not guilty?� A few raised their hands. “How many would vote guilty?� A few more raised their hands. “And how many would say you didn’t know enough to decide?� Every remaining hand — about 50 people — went up immediately.

That, of course, was the wrong answer, and the judge proceeded to explain why. In the American system of justice, there is a presumption of innocence. Because no evidence had been presented, the state had not proved its case beyond a reasonable doubt, and we would have to render a verdict of not guilty. After her explanation, she posed the question again, and (except for a few who clung to guilty and were sent home) we all raised our hands for not guilty.

Jury duty was in some ways difficult, but in one respect, it was easy: We were given clear instructions by a recognized authority and we followed them. No one argued about who had the burden of proof. No one suggested that the judge was not an appropriate authority, or that we should reject her instructions. On the contrary, when the time came to deliberate, we referred on more than one occasion to her instructions, and when the time came to vote, we had little trouble reaching a unanimous verdict. Driving home, I found myself contrasting this with the issue on which I work in my professional life: climate change.

I study the history of climate science, and my research has shown that the think tanks and institutes that deny the reality or severity of climate change, or promote distrust of climate science, do so out of self-interest, ideological conviction or both. Some groups, like the fossil fuel industry, have an obvious self-interest in the continued use of fossil fuels. Others fear that if we accept the reality of climate change, we will be forced to acknowledge the failures of free-market capitalism. Still others worry that if we allow the government to intervene in the marketplace to stop climate change, it will lead to further expansion of government power that will threaten our broader freedoms.

But most Americans do not work for the fossil fuel industry, and most Americans accept that there is an appropriate role for government to protect human and environmental health. So why has the denial of climate change achieved so much traction?

In my travels, I have met many, many people who have told me that they are not in denial about climate change; they simply don’t know enough to decide. It strikes me that these people aren’t unlike my fellow jurors at the start of jury selection. They are trying to keep an open mind, something that we are routinely enjoined to do in many other aspects of daily life.

But just as open-mindedness can be the wrong answer in jurisprudence, it can also be the wrong answer in science and public policy. Since the mid-1990s, there has been clear-cut evidence that the climate is changing because of human activities: burning fossil fuels and cutting down forests. For the last decade or so it has been increasingly clear that these changes are accelerating, and worrisome.

Yet many Americans cling to the idea that it is reasonable to maintain an open mind. It isn’t, at least not to scientists who study the matter. They have been saying for some time that the case for the reality and gravity of climate change has been proved beyond a reasonable doubt. But there’s the rub. The public seems to view scientists as the equivalent of the prosecuting attorney trying to prove a case. The think tanks, institutes and fossil fuel corporations take on the mantle of the defense.

We have to get over that flawed notion. Scientists don’t play the role of prosecutor trying to prove a case. Rather, they are the jury trying to evaluate the evidence. And they have rendered their verdict. The problem is not that scientists have become advocates, as some have claimed. The problem is that there is no judge, no recognized authority giving us instructions we accept, and no recognized authority to accept the scientists’ verdict and declare it final.

Consider for a moment the case against tobacco. There too scientists were nearly unanimous in their conclusion, based on research, that tobacco use had serious health consequences. Meanwhile, the tobacco industry tried to play the role of defense attorney, offering up denials and dodges and pseudo-scientific studies denying a link between smoking and lung cancer. So how did Americans decide whom to believe?

In that case, there was a judge whose instructions had a large effect on public consciousness: the U.S. surgeon general. Without a scientist general to instruct us on climate change, we as a nation have been adrift, looking for leadership and not finding it.

But there is one notable exception: California. In the absence of federal leadership, in the absence of a scientist general, our state has acted on the scientific verdict. Both our current Democratic and our previous Republican governor understood the need for brisk action on climate change to prevent costly damage, and they have also seen economic opportunities available to those offering solutions. This bipartisan effort has made a difference.

As we enter 2012, California is the only state in the nation to be implementing controls on greenhouse gas emissions. As of Jan. 1, California has adopted a legal framework to reduce such emissions to 1990 levels by 2020, and ultimately achieve an 80% reduction by 2050.

It is possible to move forward, even without a judge in black robes telling us what to do.

Naomi Oreskes is a professor of history at UC San Diego and the coauthor of “Merchants of Doubt: How a Handful of Scientists Obscured the Truth on Issues from Tobacco Smoke to Global Warming.�