[Vision2020] Searching for Clues to Calamity

[Art Deco]

  [image: The New York Times] <http://www.nytimes.com/>

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July 20, 2012
Searching for Clues to Calamity By FRED GUTERL

SO far 2012 is on pace to be the hottest year on record. But does this mean
that we’ve reached a threshold — a tipping point that signals a climate
disaster?

For those warning of global
warming<http://topics.nytimes.com/top/news/science/topics/globalwarming/index.html?inline=nyt-classifier>,
it would be tempting to say so. The problem is, no one knows if there is a
point at which a climate system shifts abruptly. But some scientists are
now bringing mathematical rigor to the tipping-point argument. Their
findings give us fresh cause to worry that sudden changes are in our
future.

One of them is Marten Scheffer <http://www.aew.wur.nl/uk/staff/MS/>, a
biologist at Wageningen University in the Netherlands, who grew up swimming
in clear lowland ponds. In the 1980s, many of these ponds turned turbid.
The plants would die, algae would cover the surface, and only
bottom-feeding fish remained. The cause — fertilizer runoff from nearby
farms — was well known, but even after you stopped the runoff, replanted
the lilies and restocked the trout, the ponds would stay dark and scummy.

Mr. Scheffer solved this problem with a key insight: the ponds behaved
according to a branch of mathematics called “dynamical systems,” which
deals with sudden changes. Once you reach a tipping point, it’s very
difficult to return things to how they used to be. It’s easy to roll a
boulder off a cliff, for instance, but much harder to roll it back. Once
the ponds turned turbid, it wasn’t enough to just replant and restock. You
had get them back to their original, clear state.

Science is a graveyard of grand principles that fail in the end to explain
the real world. So it is all the more surprising that Mr. Scheffer’s idea
worked.

By applying the principles of dynamical systems, Mr. Scheffer was able to
figure out that to fix the ponds, he had to remove the fish that thrive in
the turbid water. They stir up sediment, which blocks sunlight from plants,
and eat the zooplankton that keep the water clear. His program of fixing
the Netherlands’ ponds and lakes is legendary in ecology.

Mr. Scheffer and other scientists are now trying to identify the
early-warning signals for climate that precede abrupt transitions. Tim
Lenton, a climate scientist at the University of Exeter in England, has
identified a handful of climate systems that could reach tipping points in
the not-too-distant future. These are not so much related to global average
temperatures — the main metric for climate-change arguments — as they are
to patterns of climate that repeat themselves each year.

El Niño <http://www.elnino.noaa.gov/> is one such pattern — a gigantic blob
of warm water that sloshes around in the Pacific Ocean, causing weather
changes across wide swaths of the globe. Another is the West African
monsoon, which brings rain to the west coast of the continent. Each is
subject to behaving like dynamical systems — which means they are prone to
“flip” from one state to another, like one of Mr. Scheffer’s ponds, over
time periods that vary from a year to a few hundred.

The most frightening prospect that Mr. Lenton has found is the
vulnerability of the Indian monsoon. More than a billion people depend on
this weather pattern each year for the rain it brings to crops. The
monsoon, though, is being affected by two conflicting forces: the buildup
of carbon dioxide in the atmosphere is adding energy to the monsoons,
making them more powerful. On the other hand, soot from fires and coal
plants acts to blocks the sun’s energy, weakening the monsoons.

This opposition creates potential instability and the possibility that the
atmospheric dynamics that bring the monsoons could change suddenly. Mr.
Lenton’s analysis shows this could occur in a remarkably short time. The
monsoons could be here one year, then gone the next year.

Other possible tipping points are the melting of the North Pole’s sea ice,
Greenland’s glaciers and the Antarctic ice sheets, and the destruction of
the Amazon rain
forest<http://topics.nytimes.com/top/news/science/topics/forests_and_forestry/rain_forests/index.html?inline=nyt-classifier>and
Canada’s boreal forests.

We know that the dynamical-systems idea worked for Mr. Scheffer’s ponds
because he achieved real-world results. But why should we believe that the
principle explains things like El Niño and the Indian monsoon? The acid
test will be whether the real world behaves the way Mr. Lenton says it
will. If the Indian monsoon disappears, we’ll know he is right.

What then? The real worst-case scenario would have one such event
triggering others, until you have a cascade of weather flips from one end
of the planet to another. It wouldn’t be quite as dramatic as Hollywood
might want to depict, perhaps, but it would be dramatic enough to rewrite
the predictions for sea level and temperature rises that are part of the
current consensus. This worst case is highly speculative, but sudden shifts
in climate patterns may already be happening.

The policy makers aren’t likely to be discussing dynamical-systems theory
anytime soon. Fortunately, scientists like Mr. Scheffer and Mr. Lenton are
trying to work out the details of how closely nature hews to these
mathematics, what a true tipping point would look like and what we might do
if and when we face one.

We need a tipping point in climate politics, where all of a sudden we start
paying attention.

Fred Guterl<http://blogs.scientificamerican.com/observations/about.php?author=15>is
the executive editor of Scientific American and the author of “The
Fate
of Species: Why the Human Race May Cause Its Own Extinction and How We Can
Stop It.”
  ________________________________

Also thanks to Ted Moffett for his letter to yesterday's *Daily News*

-- 
Art Deco (Wayne A. Fox)
art.deco.studios at gmail.com
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