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Contact Jim: jdipeso@rep.org (253) 740-2066 / 2009 Archive / 2008 Archive / 2007 Archive / 2006 Archive / 2005 Archive
It's the Long-Term Record That Counts
March 26, 2008
The latest wheeze trotted out by the climate change denial crowd is an argument that global warming has “stopped.”
That’s progress of sorts. Before, they were arguing that global warming
is a hoax. So at least they’re implicitly acknowledging that something
has been going on in the atmosphere.
But not anymore, they’re asserting triumphantly. Since 2001, the
skeptics say, average temperatures haven’t risen. If greenhouse gas
emissions are rising, shouldn’t temperatures rise with them? If not,
then the scientists must have screwed up, and it’s time to order up
another heapin’ helping of fossil fuels.
Well, they’re wrong about the temperature trend. Eleven of the last 12 years have been the warmest on record.
Even if the deniers were correct about the temps, however, the flaw in
their argument is confusion between short-term variability and
long-term trends. The onset of global warming does not mean that
weather fluctuations will go away. Short-term variability, including
cold snaps and spring snowstorms, will still occur. You’ll still be
better off booking your beach vacation for the Riviera rather than
Greenland.
Climate is a chaotic system, meaning there are many pressure points
that can cause short-term variations in the atmosphere’s behavior. An
El Nino can heat things up for a bit. A volcanic eruption can cool
things down for a time.
Over a longer period, however, variations smooth out and long-term
trends can be discerned. But that takes a long data record. Basing
conclusions about long-term trends on cherry-picked data from a short
time frame is a dangerous game.
The
global mean temperature was lower in 1993 than it was in 1990. Does
that mean that global warming “stopped” in 1990? No, it means that the
Pinatubo volcanic eruption temporarily cooled the climate for a few
years. After the volcano's detritus cleared out of the atmosphere, the
long-term upward trend became clear again.
If
climate is too abstract, let’s try a more prosaic example that
illustrates the short-term versus long-term distinction. Like climate,
baseball players are chaotic systems whose performance is affected by
numerous pressure points from ankle injuries to boo birds. You can’t
predict how they will perform on any given day because there are too
many variables.
But you can make a reasonable projection how players are likely to do
over the course of a season if you look at their lifetime records. If a
star slugger’s lifetime batting average is .300, you wouldn’t
precipitously trade him just because he’s in a batting slump. That
would be confusing short-term variability with long-term trends. Even
Babe Ruth had bad days when he couldn’t find the ball.
Likewise, if a journeyman player with a lifetime average of .220
unexpectedly goes on a weeklong home run tear, it wouldn’t be smart to
ply him with a 10-year, $100 million contract.
The upshot is that one heat wave is not definitive evidence of global
warming, nor is one cold snap proof that it’s a fraud. The long-term
record, however, makes for a compelling case that the earth is warming.
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