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There is a lot of fuss about two new papers arguing, from
mathematical models, that extreme downpours have become and will
become more common in the
northern hemisphere and specifically
Britain as a result of man-made climate
Let's ignore the fact that this looks awfully similar to
the habit of blaming specific weather events on climate trends,
something we `lukewarmers' (who think climate change is real but
slow enough to adapt to through the foreseeable future) are
reprimanded for doing when we point out that an especially cold
winter or cool summer weakens the case for the alarming version of
the theory. So now we can do that too, can we?
Let's ignore the fact that neither paper comes up with any
actual evidence that greenhouse gases have caused more extreme
downpours - other than circumstantial correlation. Their sole
argument is that they cannot think of any other explanation for the
increase in downpours. Or as the
BBC puts it:
The researchers suggest there is
nothing that can explain this trend except the slow
steady increase in temperatures caused by greenhouse gas
I'm sorry but when I was a scientist correlation was not
considered a proof of causation.
Let's ignore the fact that these are only two studies and
that another recent study concluded the opposite. According the
summary of this study
by Anne Jolis in the Wall Street
In other words, researchers have yet to
find evidence of more-extreme weather patterns over the period,
contrary to what the models predict.
Let's ignore the fact that 2010-one of the hottest years
in recent memory-saw the fewest tropical cyclones (including
hurricanes) since 1970, and that the global cumulative energy in
these cyclones was among the lowest ,
which is inconvenient, to say the least.
Let's instead assume these two papers are right, that
there is an increase in extreme downpours and that it is caused by
rising greenhouse gas emissions.
How lethal are downpours compared with, say, cold winters?
We all agree that global warming will create fewer cold winters,
right? And since more people die in cold weather than in hot
weather, global warming will reduce deaths. Is that effect bigger
or smaller than the extra deaths from downpours? Answer: much, much
Here are some
numbers. The annual excess mortality in
winter is over 100,000 in the US, 50,000 in Japan, 25,000 in
Britain and even 23,000 in Spain. Just a 10% drop in those numbers
and you are saving tens of thousands of lives, far more than die in
By contrast, ask yourself how many people died as a result
of excess precipitation in Britain in the wet autumn of the year
2000, the episode on which one of the above papers focuses.
According to the BBC,
That autumn saw the highest rains in
England and Wales since records began in 1766.
The Hampshire village of Hambledon was
underwater for six weeks, and insurers put the final cost to the
country at more than £1bn.
as far as we can make out, nobody
As it happens, the number of people dying from extreme
weather events has gone down by 93% since the
Was this because we controlled the weather? No. It was
because we adapted to it. So even if extreme downpours do increase,
death rates as a result of them will continue to decline so long as
we continue to get more people access to roads, telephones, houses
and information. It's like malaria: it retreated rapidly in the
twentieth century despite rising temperatures, and it will retreat
rapidly in the twenty-first century despite rising
As the above figure shows, globally the average annual
death toll from all extreme weather events is about 35,000. Compare
this to the hundreds of thousands of excess winter deaths that
occur annually. Perhaps we should try to control winter before we
tackle climate change! Oddly enough, while we may not be able to
control the weather, in the U.S., millions have done the next best
thing-they have migrated from colder northeastern climes to the
warmer southwestern states. This, according to a paper in MIT
Press's Review of Economics and Statistics by
econometricians Deschênes and Moretti, is responsible for 8%-15% of
the total gains in life expectancy in the U.S. population from 1970
So even if it is true, the downpour argument does not even
begin to help make the case for carbon mitigation