by Joseph Romm.
The devastation of Joplin, Mo., has led to a super-storm of media
stories on the link between climate change and extreme weather,
including tornadoes. After April saw records set for most tornadoes in a
month and in 24 hours, I examined the link in great detail here, looking at the data, the literature, and expert analysis. That piece concluded:
When discussing extreme weather and climate, tornadoes should not be
conflated with the other extreme weather events for which the
connection is considerably more straightforward and better documented, including deluges, droughts, and heat waves.
Just because the tornado-warming link is more tenuous doesn’t mean
that the subject of global warming should be avoided entirely when
talking about tornadoes.
The flattening of a city, and the death of 117 people—“the single
deadliest tornado since officials began keeping records in 1950,” as The Washington Post reported—is naturally going to spin up media interest. Since it is a complicated subject, one would expect the coverage to be mixed.
ABC News had a very good story, with the help of climatologist Heidi Cullen:
Multiple scientific studies find that indeed the weather has become
more extreme, as expected, and that it is extremely likely that humans
are a contributing cause.
The Washington Post piece was pretty good, examining the
multiple factors that contribute to tornadoes. It noted that research
on the tornado-warming link is “is at an early stage, making it
difficult to draw conclusions,” and ran this quote:
“Climate change could be boosting one of those
ingredients [for tornadoes], but it depends on how these ingredients
come together,” said Robert Henson, a meteorologist at the University
Corporation for Atmospheric Research.
The AFP ran a piece titled, “No link between tornadoes and climate change: U.S.” That flawed piece led Kevin Trenberth, senior scientist with the
Climate Analysis Section of the National Center for Atmospheric
Research, to send an email explaining that yes, warming can boost the
conditions for tornadoes, especially warming of sea surface temperatures
(SSTs):
The SSTs in the Gulf have been running perhaps 2 deg F
above pre 1970 values. Warm waters also extend across the tropical
Atlantic north of the equator in the region favored for hurricanes, and
hence the recent NOAA forecast for an above average hurricane season
(although the La Nina is fading and will likely be over by August, so
there may be more competition from the Pacific).
Of those 2 def F, 1 can be assigned to human influence.
With 1F increase in SST there is 4% increase in water holding capacity
over the oceans and hence in this case the plentiful supply of moisture
means there is likely to have been 8% increase in moisture flowing in
the southerlies into the warm sector, thereby acting as fuel for the
thunderstorms, and thus increasing the likelihood they would become
super cells, with the attendant risk of tornadoes. And of course heavy
rains. In spring the westerly jet stream aloft and southerlies at the surface create a wind
shear environment that is favorable for tornadoes as the wind shear can
be turned into rotation. This part of the situation is largely in the
realm of weather. The climate part is the warmth and moistness of the
air flowing out of the Gulf and the resulting very unstable atmosphere.
So while a big part of that is natural variability, a substantial part
was anthropogenic global warming.
You can listen to a local CBS radio interview with Trenberth here.
Trenberth’s perspective is similar to that of Stu Ostro, Weather
Channel senior meteorologist, in his post from earlier this month “The Katrina of tornado outbreaks”:
The atmosphere was explosively unstable with summerlike
heat and humidity, interacting with a classic wind shear setup as a
strong jet stream and upper-level trough crashed overhead …
The atmosphere is extraordinarily complex, and ultimately
what’s happened the past month is probably a combination of influences,
including La Nina, other natural variability, and anthropogenic
global warming.
Today weatherman Al Roker appears to have gone beyond the data with his suggestion that “climate change” is bringing tornadoes to urban areas, although, admittedly, it is a brief clip and it’s not exactly clear what he is saying.
Here is how meteorologist and former hurricane hunter Jeff Masters put it today:
In summary, this year’s
incredibly violent tornado season is not part of a trend. It is either a
fluke, the start of a new trend, or an early warning symptom that the
climate is growing unstable and is transitioning to a new, higher
energy state with the potential to create unprecedented weather and
climate events. All are reasonable explanations, but we don’t have a
long enough history of good tornado data to judge which is most likely
to be correct.
Masters made a broader point to me in a December email:
In my thirty years as a meteorologist, I’ve never seen
global weather patterns as strange as those we had in 2010. The stunning
extremes we witnessed gives me concern that our climate is showing the
early signs of instability. Natural variability probably did play a
significant role in the wild weather of 2010, and 2011 will likely not
be nearly as extreme. However, I suspect that crazy weather years like
2010 will become the norm a decade from now, as the climate continues to
adjust to the steady build-up of heat-trapping gases we are pumping
into the air. Forty years from now, the crazy weather of 2010
will seem pretty tame. We’ve bequeathed to our children a future with a
radically changed climate that will regularly bring unprecedented
weather events—many of them extremely destructive—to every corner of the
globe. This year’s wild ride was just the beginning.
And on this broader issue, Reuters had a very good story last week, “Floods, Droughts Are ‘New Normal’ Of Extreme U.S. Weather Fueled By Climate Change, Scientists Say”:
Heavy rains, deep snowfalls, monster floods and killing
droughts are signs of a “new normal” of extreme U.S. weather events
fueled by climate change, scientists and government planners said on
Wednesday.“It’s a new normal and I really do think that global weirding
is the best way to describe what we’re seeing,” climate scientist
Katharine Hayhoe of Texas Tech University told reporters.
While none would blame climate change for any specific weather event,
Hayhoe said a background of climate change had an impact on every
rainstorm, heat wave or cold snap.
“What we’re seeing is the new normal is constantly evolving,” said
Nikhil da Victoria Lobo of Swiss Re’s Global Partnerships team.
“Globally what we’re seeing is more volatility … there’s certainly a
lot more integrated risk exposure.”
There’s no question that if one wants to minimize deaths from extreme
weather, a top priority is to maintain and expand our satellite-based
weather forecasting capability, which Republicans are working overtime to gut. And we obviously need to improve housing for those in tornado alley.
But if we don’t want the weather of 2010 and 2011 to be an every
other year event—then just as obviously we need an aggressive strategy
for reducing GHGs that also supports real adaptation. The Boston Globe editorializes today on the need to pursue multiple strategies, “In a season of violent weather, prepare, protect—and prevent”:
Early preparation and planning has helped save lives. Technology and
engineering have made weather predictions more reliable. A mature
alert system notified residents of Joplin of an impending danger.
It is also inspiring to hear residents express a determination to
rebuild. But that can-do spirit rarely translates into political action.
In policy debates about environmental issues, evidence of extreme
weather is often dismissed as fleeting anecdotes. But it is hard
to ignore the cumulative impact of science, technology, and
experience. Last week, an expert panel assigned by Congress in 2008 to
recommend ways to deal with climate change provided a sobering analysis
of what is at stake: Every ton of greenhouse gases entering the
atmosphere not only drives up the earth’s temperature, causing
potentially disruptive weather events, but raises the cost of taking
action later on.
Call it global warming, global weirding, or just a really freaky
weather year. If we don’t begin to address the underlying causes of all
this killer weather, 2011 may just be the beginning of a very
dangerous new normal.
And finally, we have a must-read op-ed by Bill McKibben in The Washington Post today:
Caution: It is vitally important not to make connections …
It is far better to think of these as isolated, unpredictable,
discrete events. It is not advisable to try to connect them in your
mind with, say, the fires burning across Texas—fires that have burned
more of America at this point this year than any wildfires have in
previous years. Texas, and adjoining parts of Oklahoma and New Mexico,
are drier than they’ve ever been—the drought is worse than that of
the Dust Bowl. But do not wonder if they’re somehow connected.
If you did wonder, you see, you would also have to wonder about
whether this year’s record snowfalls and rainfalls across the Midwest— resulting in record flooding along the Mississippi—could somehow be
related. And then you might find your thoughts wandering to, oh, global
warming, and to the fact that climatologists have been predicting for
years that as we flood the atmosphere with carbon we will also start
both drying and flooding the planet, since warm air holds more water
vapor than cold air.
It’s far smarter to repeat to yourself the comforting mantra that no
single weather event can ever be directly tied to climate change. There
have been tornadoes before, and floods—that’s the important thing.
Just be careful to make sure you don’t let yourself wonder why all these
record-breaking events are happening in such proximity—that is, why
there have been unprecedented megafloods in Australia, New Zealand and
Pakistan in the past year. Why it’s just now that the Arctic has melted
for the first time in thousands of years …
Because if you asked yourself what it meant that the Amazon has just
come through its second hundred-year drought in the past five years,
or that the pine forests across the western part of this continent have
been obliterated by a beetle in the past decade—well, you might have
to ask other questions. Such as: Should President Obama really just
have opened a huge swath of Wyoming to new coal mining? Should
Secretary of State Hillary Clinton sign a permit this summer allowing a
huge new pipeline to carry oil from the tar sands of Alberta?
… Better to join with the U.S. House of Representatives, which voted
240 to 184 this spring to defeat a resolution saying simply that
“climate change is occurring, is caused largely by human activities,
and poses significant risks for public health and welfare.” Propose
your own physics; ignore physics altogether. Just don’t start asking
yourself whether there might be some relation among last year’s failed
grain harvest from the Russian heat wave, and Queensland’s failed grain
harvest from its record flood, and France’s and Germany’s current
drought-related crop failures, and the death of the winter wheat crop
in Texas, and the inability of Midwestern farmers to get corn planted
in their sodden fields. Surely the record food prices are just freak
outliers, not signs of anything systemic.
It’s very important to stay calm. If you got upset about any of
this, you might forget how important it is not to disrupt the record
profits of our fossil fuel companies. If worst ever did come to worst,
it’s reassuring to remember what the U.S. Chamber of Commerce told the
Environmental Protection Agency in a recent filing: that there’s no
need to worry because “populations can acclimatize to warmer climates
via a range of behavioral, physiological, and technological
adaptations.”
Hear! Hear! Or, rather, climate change is here, here!
In fact, the population hasn’t even acclimatized to the climate
change we’ve had already—in part because the GOP and the
fossil-fuel-funded disinformation campaign have obfuscated efforts to
inform the public. Hypocritically, the chamber itself led the effort to
stop this country from creating a serious adaptation fund.
We’ve only warmed about a degree Fahrenheit in the past
half-century. We are on track to warm nearly 10 times that this
century. Indeed, if we listen to the chamber and the politicians it backs,
emissions and temperatures will just keep rising, and by the second half
of the century, sea levels will be rising six to 12 inches a decade for
centuries. How precisely to you acclimatize yourself to a climate that
is always changing?
A commenter offers this bumper sticker: “Mother nature is only warming up.”
Related Links:
Chicago’s government prepares for climate change to turn the city into Baton Rouge
The Rapture didn’t come, but don’t worry, the world is still boiling
A violent climate is the new normal, say scientists
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