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Despite Hurricanes Harvey and Irma, Science Has No Idea If Climate Change Is Causing More (or Fewer) Powerful Hurricanes

06 Sep 2017

Ross McKitrick

After Hurricane Harvey hit Texas, it didn’t take long for
climate alarmists to claim they knew all along it would happen.
Politico’s Eric Holthaus declared “We knew this would happen, decades ago.” Naomi
Klein stated “these
events have long been predicted by climate scientists
.” Joe
Romm at ThinkProgress wrote, “the
fact is that Harvey is exactly the kind of off-the-charts hurricane
we can expect to see more often because of climate change
.”

According to these and other authors, rising greenhouse gas
levels are at least partly to blame for the occurrence and severity
of Harvey, and probably for Hurricane Irma as well. But
after-the-fact guesswork is not science. If any would-be expert
really knew long ago that Harvey was on its way, let him or her
prove it by predicting what next year’s hurricane season will
bring.

Don’t hold your breath: Even the best meteorologists in the
world weren’t able to predict the development and track of
Hurricane Harvey until a few days before it hit.

We should not assume that
any time we have pleasant weather, we were going to have it anyway,
but a storm is unusual and proves greenhouse gases control the
climate.

This is why the idea of climate science being “settled” is so
ludicrous, at least as regards the connection between global
warming and tropical cyclones. A settled theory makes specific
predictions that can, in principle, be tested against observed
data. A theory that only yields vague, untestable predictions is,
at best, a work in progress.

The climate alarmists offer a vague prediction: Hurricanes may
or may not happen in any particular year, but when they do, they
will be more intense than they would have been if GHG levels were
lower. This is a convenient prediction to make because we can never
test it. It requires observing the behaviour of imaginary storms in
an unobservable world. Good luck collecting the data.

Climate scientists instead use computer models to simulate the
alternative world. But the models project hundreds of possible
worlds, and predict every conceivable outcome, so whatever happens
it is consistent with at least one model run. After Hurricane
Katrina hit New Orleans in 2005, some climate modelers predicted such storms
would be more frequent in a warmer world, while others predicted
the opposite, and still others said there was no connection between
warming and hurricanes.

What ensued was an historically unprecedented 12-year absence of
major (category 3 or higher) hurricanes making landfall in the
United States, until Harvey, which
ties for 14th-most intense
hurricane since 1851. The events
after 2005 were “consistent with” some projections, but any other
events would have been as well.

The long absence of landfalling hurricanes also points to
another problem when opinion writers connect GHGs to extreme
weather. Science needs to be concerned not only with conspicuous
things that happened, but with things that conspicuously didn’t
happen. Like the famous dog in the Sherlock Holmes story, the bark
that doesn’t happen can be the most important of all.

It is natural to consider a hurricane a disruptive event that
demands an explanation. It is much more difficult to imagine nice
weather as a disruption to bad weather that somehow never
happened.

Suppose a hurricane would have hit Florida in August 2009, but
GHG emissions prevented it and the weather was mild instead. The
“event,” pleasant weather, came and went unnoticed and nobody felt
the need to explain why it happened. It is a mistake to think that
only bad events call for an explanation, and only to raise the
warming conjecture when bad weather happens. If we are going to tie
weather events to GHGs, we have to be consistent about it. We
should not assume that any time we have pleasant weather, we were
going to have it anyway, but a storm is unusual and proves GHG’s
control the climate.

I am grateful to the scientists who work at understanding
hurricane and typhoon events, and whose ability to forecast them
days in advance has saved countless lives. But when opinion writers
tacitly assume all good weather is natural and GHGs only cause bad
weather, or claim to be able to predict future storms, but only
after they have already occurred, I reserve the right to call their
science unsettled.

Ross
McKitrick
is a professor of economics at the University of
Guelph and an adjunct scholar of the Cato Institute.

Click here to view the full article which appeared in CATO Journal

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