James Hansen Talks Climate Risks, Without the Mute Button

03/28/2016 01:26 pm ET Updated Dec 06, 2017







When I was doing research on the influenza virus that killed some 40 million people in 1918 and 1919, I felt a huge weight of responsibility. What if I made a mistake?  What if a pandemic started to spread because I missed a vital clue? In other words, I really, really cared about what I was working on. That doesn't make me unusual - all the scientists I know care deeply about getting it right.

If I had felt that evidence of an imminent pandemic was being ignored or dismissed, I'm not sure how I would've reacted. There are many ideological reasons for ignoring the truth, but the idea that people might die as a result would have made me want to warn the world.

Scientists disagree about how to talk to the public about scary risks. Some believe that emphasizing the risks stimulates public support for investment in prevention, preparedness and research, others fear that playing up the risks too much results in public fatigue and disillusionment, especially if the scary thing fails to materialize.

When it comes to climate change, though, I wonder if scientists may be erring too much on the side of caution. "Maybe," they seem to be thinking, "if I am super reasonable, and calm, and play down the scariest implications of my work, I'll be able to avoid the alarmist label and get people to listen to me."

I thought about that when I read a recent paper by James Hansen and his colleagues claiming that even a two degree Celsius rise in world temperature could have more dire consequences than models currently predict. (World leaders have agreed to this two-degree target, but we have collectively not figured out how to meet it.) If you want to know more about the study, you can listen to James Hansen himself explain it here.

This paper has been extensively peer-reviewed (you can read about its unusual history here), which means that the science is credible and the arguments justified. Does that mean the paper is "the truth" and everything it predicts will come to pass? No, of course not. That's not how science works. But it does mean that as future scientists evaluate the interactions between oceans, currents, and melting ice, they'll have to take Hansen's work into account and show how their evidence substantiates or conflicts with his conclusions.

Hansen could be entirely right. He could be partially right. New evidence may show that the risks are lower than this paper suggests. Or - and this is the part where I'm afraid self-censorship might be a problem - the risks may eventually be shown to be even greater than his paper suggests.

Ever since his landmark 1988 Congressional testimony on climate change, Hansen has repeatedly refused to follow the strategy of "I'm going to downplay the risks so no one can accuse me of being an extremist." He calls the science as he sees it. This directness makes people uncomfortable. So does Hansen's unabashed political activism calling for immediate and dramatic policy interventions to reduce carbon emissions.

I'll be the first to say that it's vitally important for scientists to be careful and clear in distinguishing their scientific conclusions from their arguments for particular policies. And it's completely legitimate for the scientific community to apply an extra layer of scrutiny when a researcher's scientific results appear conveniently consistent with that researcher's (or funder's) other interests. (That's why it's so important that all researchers divulge any potential conflicts of interest, such as funding from tobacco, fossil fuel, or pharmaceutical companies.) We can't eliminate conflicts of interest. But we can be transparent about them and manage them responsibly. Scientists' political opinions or funding sources don't automatically make their scientific conclusions right or wrong. Fortunately, science has a process by which results are reviewed, made publically available, subjected to ongoing testing, and potential verification or refutation. If it makes it through peer review, it's met a certain standard of scrutiny. Rejection or acceptance of the results then has to be based on evidence, not accusations of bias. That's how science works.  

Climate scientists have been repeatedly accused of exaggerating, lying, being alarmist, even of conspiring to skew results. Many people reflexively reject all climate science out of hand, regardless of evidence. So it's not surprising that many climate scientists present new results in a way calculated to avoid an automatic backlash.

It's fine for some climate scientists to choose to bend over backwards not to scare people, and emphasize the middle, or even low, end of the possible risks. But it should be OK for other scientists to say out loud that the risks at the high end cannot be dismissed. Without those voices, like Hansen's, the public is only getting half the picture.

Photo credit: Cookies and Milk by Dayland Shannon