Flooding pt. 2: How do we know if climate change is to blame?

Today the New York Times finally broke its silence on the catastrophic flooding in Louisiana. And the piece is really good! It explicitly frames the flooding in terms of climate change and the first sentence is a fantastic articulation of one of the most under-appreciated aspects of the climate crisis: “Climate change is never going to announce itself by name.”

The natural disasters we’ve been seeing this summer — from fires in California to flooding in the South to historic heat waves in India and more — are vindicating Al Gore’s now-infamous frog-in-a-beaker analogy from An Inconvenient Truth. The effects of climate change are being felt right now, as we speak, but because there are no Joker-esque calling cards left behind in the wreckage making the climate change’s authorship of these tragedies unambiguous, we, like Gore’s frog, don’t recognize that we are rapidly approaching the boiling point.

This phenomenon is related to a climate-action obstacle that’s sort of unheralded outside of academic circles: the extremely stringent standard of scientific proof demanded by policymakers before taking responsible steps to mitigate carbon output or even acknowledging the magnitude of the problem. Every time activists hold up a natural disaster like the Louisiana floods as evidence of the importance of taking swift action on climate change, the response from some scientists and many politicians is all too predictable: there is not enough evidence to attribute it to climate change. There is even a quote to that effect from the Louisiana state climatologist in the NYT article linked above.

This discourse has two related problems. First, it’s a little unclear to me what it would even mean to “prove” that a particular weather event was “caused by climate change.” Could the Louisiana flooding have happened two hundred years ago? Obviously! No matter what your climate looks like, there will always be once-in-a-generation events.The point is that because of climate change, the once-in-a-generation storms of years past will become more common, and the once-in-a-generation storms of years to come will be more devastating. The Louisiana flooding is thus not ipso facto a portent of doom, but it becomes troubling (beyond the immediate human tragedy) in the context of other extreme weather events this summer.

The second problem, therefore, is that the climate crisis, understood properly, ought to seriously challenge many of our assumptions about the way science works and ought to work, and especially about how it should inform government policy.

Modern science is really great at answering very specific questions posed narrowly within the context of a specific discipline. Science is also great at answering questions about the way the world is now or was in the past. Examples of these kinds of questions include, “How does atmospheric carbon dioxide affect global temperatures?” and “How have global carbon dioxide levels and global temperatures varied over the past 100/1000/million years?”


Answering those kinds of questions has been crucial for achieving our current understanding of climate change. But now we need scientists to behave differently. Scientists need to ask questions that span disciplines, synthesizing atmospheric chemistry with meteorology and the knowledge of people “on the ground” in areas increasingly affected by extreme weather. They need to ask questions not about the way the world works now or has worked in the past but how it might work under different conditions in the future, questions that may not have precisely identifiable answers. Climate science as an institution has been most effective when, like in the reports of the Intergovernmental Panel on Climate Change, it has done this sort of work.

If scientists embraced this role more proactively, it would be far more difficult for politicians to invoke their work to defend the status quo. If we stop expecting scientists to have all the answers, it will become harder to cite their limitations as reason to discredit the answers they do have — and easier to frame a positive vision of a political process that does not shy away from attempting to fill in the gaps. And if we start viewing uncertainty as a feature of science rather than a bug, we can begin to stop viewing the presence of uncertainty as a justification for inaction. Because what really matters is not that scientists are unable to tell us if the storm in Louisiana was the “fault” of climate change, but that if we continue on our present course, there will be a lot more where this one came from.

Postscript: Elisabeth Lloyd and Naomi Oreskes (full disclosure: I’m currently working for Prof. Oreskes) have an article coming out soon in Climatic Change about this topic entitled “Climate Change Attribution: When is it Time to Flip the Null Hypothesis?” As the title suggests, it discusses one specific area of scientific practice where the broader mindset shift I’m calling for here could be put into action. Watch out for it!


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