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Oct312012

"Climate change caused ...": linguistics, empirics, & reasoned discourse

Here are some reflections occasioned by (1) Andy Revkin's excellent dotearth blog post on the relationship between climate change and Sandy; (2) the anger that Revkin's post aroused among at least some climate-change-policy advocates, who proposed the laughable but still disturbing idea that Revkin be publicly censured in some way (others, it should be noted, responded in a critical but reasoned way to issues about advocacy and science information that are admittedly complex); and (3) a columin in the Huffington Post by George Lakoff, who has figured out that the problem here is confusion over language, which if used properly resolves important practical, empirical issues without the need to consult evidence (including evidence of how the public engages with climate science)...

There are 3 issues here: (1) one relating to whether "climate changed caused x" in general; (2) another to whether it caused Sandy in particular; and (3) a final one to the polemics of "caused by climate change..."

1. General.  Hansen et al. are much more helpful than Lakoff on this issue. When we ask the question, "did climate change cause x," the issue is not "semantic" but practical & empirical: we want to understand what the physical relationship is between climate change & particular events &  what effect to assign to particular events in trying to asses the impact of climate change.  The issue isn't what word or phrase to use; it's what to do. Hansen et al. tell us *exactly* what we need to know: climate change shifts the normal distribution of weather events, making certain outcomes more likely & hence more frequent than they otherwise would have been. Accordingly, we can say that climate change made a particular event "y times more likely" than it would have been, if that's useful (Hansen et al. identify events for which y is very very very high!); but more importantly we can speak instructively to the question of what the impact of climate change is in practical terms-- "more events like this per yr/decade, which will cost $z billion, kill q x 10^3 people  etc".  

It's ironic that Lakoff refers to black-lung & cigarettes. The law got over being confused on causation for mass torts when it stopped trying to wring practical guidance from vague, impressionistic, & ultimately question-begging/-obscuring concepts like "direct vs. indirect," & w/ the help of toxicologists, epidemiologists, economists & others started to think in practical, empirical terms akin to those being proposed by Hansen et al. At that point, the law adopted doctrines that made companies that manufacture products that increase the incidence of some harm pay the price of that extra harm w/o getting tied in conceptual knots about whether this particular actor "caused" that particular injury.

 2. Sandy. I myself am still not sure whether climate change increased the likelihood of a weather event like Sandy. I would have thought the answer was clearly yes. But Revkin's excellent dotearth post showed me that there is at least a division of opinion on this among experts; whether Sandy belongs to the class of events the likelihood of which was increased to a very high degree by climate change is not as cut & dried, apparently, as whether climate change increased the likelihood of, say, persistence of summer heat waves, or wild fires in western US.

But I might be misunderstanding & I'm sure there is more to day. I'd like to hear it. But I won't if people agree to talk the way Lakoff does: whatever one thinks of his "systemic causation" linguistically, the way he uses it ("Global warming systemically caused the huge and ferocious Hurricane Sandy...") begs the practical/empirical question.

3. Polemics of "causation." The furor over Revkin's column & over the use of the word "cause" in general is bound up with strategic political & moral issues. Many of those who want to create public engagement with climate change believe that it is essential to be able to say "climate change caused x" extreme event. I can see why; "causation" implies responsibility, and we are  motivated (very appropriately) to regulate and otherwise hold accountable those responsible for harm. But is it really clear that one can't get the responsibility/accountability point across by saying "climate change makes x event times more likely"-- particularly where y is astronomically high? Or by saying (if we have evidence for saying it) that "climate change means we can expect to see an x event -- one that kills q x 10^3 people & costs $billion -- every 2/5/10 yrs" etc? I'm not sure; be interesting to try to test these things. Lakoff criticizes Hansen's communication skills, but doesn't himself present any evidence to support his assertion that his own proposed way of using terms would promote public comprehension or engagement. I, at least, can think of some pretty plausible counter-hypotheses.

One thing I am sure about, though: those who are insisting that science journalists or others use the term "causation" in a way that avoids even asking the practical, empirical question & getting an answer to it (not to mention those advocates who have proposed attacking Revkin as a way to create a "teaching moment" for journalists & other reflective participants in public discussion) believe in a form of democratic deliberation that involves a smaller role for appeals to citizens' reason than I am comfortable with. 


 

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Reader Comments (3)

Mayor Bloomberg's comments about Sandy seem wise in the light of what leading climate scientists are saying about global warming, climate change, and violent weather. Bloomberg says that we must make decisions based on the probabilities of the case, rather than waiting for certitude that we will have too late, if ever.

James Hansen cautions against attributing particular instances of extreme weather to global warming, saying that global warming merely "loads the dice" in favor of such instances. Thus, just as a single toss of the dice cannot tell us whether the dice have been tampered with, a single storm cannot tell us whether the climate has been biased in favor of storms that would previously have been anomalously powerful.
As for Sandy, Kerry Emanuel of MIT has noted that it was a hybrid storm, a type of storm about which little research has yet been done, making it difficult to attribute Sandy directly to global warming.

Still, evidence is growing that the dice have in fact been loaded. Emanuel's research on tropical storms shows that the total amount of energy released by tropical storms each year has increased dramatically since the 1970s, the increase owing mainly to increases in the duration and intensity of storms.

All this amounts to saying that climate change can be perceived only in trends, and that we can never know exactly when we crossed the line separating the normal from what was previously abnormal. When we have traveled sufficiently far beyond that line, there won't be any doubt. Unfortunately, by the time doubt is removed by events, we will have suffered great harm.

That is why Mayor Bloomberg is right to insist that we cannot wait for complete certainty about global warming, climate change, and violent weather before taking action to protect ourselves. We need to start making preparations in the expectation that global warming will bring more Sandys than we would have had to contend with otherwise. With the well being of so many human beings at stake, the risk of having overreacted is preferable, by far, to the risk that we will not have done enough.

November 2, 2012 | Unregistered CommenterJohn Breithaupt

@John -- agree! Mayor Bloomberg shows that you *can* reason like a Bayesian & make your point clear as day for a thoughtful citizen. I'd vote for him for something except he shouldn't get so worked about about how much pop people want to drink and whether they think it's a pain in the ass to breastfeed their kids! Actually, even those positions make him a pretty interesting fellow & an interesting addition to the mix for our political culture

--dmk38

November 2, 2012 | Unregistered Commenterdmk38

"Emanuel's research on tropical storms shows that the total amount of energy released by tropical storms each year has increased dramatically since the 1970s, the increase owing mainly to increases in the duration and intensity of storms."

Are you sure he didn't just mean the Atlantic?

Here's the global accumulated cyclone energy (ACE) since 1970.
http://policlimate.com/tropical/frequency_12months.png

(Source: http://policlimate.com/tropical/ )

Here's the same number for the Atlantic basin:
http://en.wikipedia.org/wiki/File:Atlantic_ace_timeseries_1850-2007.jpg

If you look for 1970 in that graph, you can see that the level rises after that.

The question, though is why would global climate change only affect the Atlantic. Cherrypicking?

While events like Sandy give opportunities for persuasive polemics, using them that way is polarising. People who believe global warming causes hurricanes see it as confirmation, people who don't believe global warming causes any detectable rise in hurricanes see it as deceptive propaganda, and it confirms their impressions of dishonesty. Thus polemicists on both sides cheer, both sides seeing their views confirmed, both getting plenty of new ammunition to use. And the divide gets wider.

Whereas Revkin, by speaking up against the hype, both boosts his credibility with undecideds/believers on the later occasions when he does make connections, and earns the respect of sceptics for his honesty. In the long run, it's probably worth the lost opportunities for short-term gain, and it narrows the divide. The big problem with it is that the gain in credibility is at the expense of that of the polemicists on his own side, not the other, which obviously is not popular.

November 3, 2012 | Unregistered CommenterNiV

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