Scientists are starting to link natural disasters to rising greenhouse gases.
In the past year, every continent except Antarctica has
seen record-breaking floods. Rains submerged one-fifth of Pakistan, a
thousand-year deluge swamped Nashville and storms just north of Rio caused the
deadliest landslides Brazil has ever seen.
Southern France and northern Australia had floods, too.
Sri Lanka, South Africa, the list goes on.
And while no single weather event can be linked
definitively to global climate change, a growing number of scientists say these
extreme events represent the face of a warming world.
“Any one of these events is remarkable,” said Jay
Gulledge, senior scientist for the Pew Center on Global Climate Change. “But
all of this taken together could not happen without the extra heat that’s in
the ocean. It defies common sense to overlook that link.”
That link works more or less like this. Concentrations of
greenhouse gases are the highest the earth has seen in 15 million years [2].
These gases trap heat, warming both the air and the oceans. Warmer oceans give
off more moisture, and a warmer atmosphere can hold more of it in suspension.
The more moisture in the air, the more powerful storms tend to grow. When these
supercharged weather systems hit land, they don’t just turn into rain or snow,
they become cyclones, blizzards and floods.
“There is a lot of tropical moisture in the atmosphere
that is getting transported over very long distances and is dropping out in
various places around the world in dramatic fashion,” Gulledge said.
Last year tied with 2005 as the warmest on record,
according to the U.S. National Oceanic and Atmospheric Administration [3]. And
floods in 2010 weren’t the only extremes.
In Russia, 15,000 people died during a record heat wave.
Australia suffered its warmest summer on record. Pakistan witnessed its hottest
day in history, as did Los Angeles. The U.S. East Coast has struggled under
unusually heavy snows for two winters running. The Brazilian Amazon suffered
one of the worst droughts in its history [4]. And even as the Brazilian
government recovered the bodies of those killed by record storms in the state
of Rio de Janeiro, it trucked drinking water to cities in the north blighted by
drought [5].
Weather like this matches the predictions of numerous
recent climate studies. In 2007, the Intergovernmental Panel on Climate Change
noted that severe droughts and heavy rains were already on the rise in many
parts of the world [6], and linked them to the surge in greenhouse gases. A
study [7] published last year by the National Academy of Sciences predicted an
increase in heavy rainfall of somewhere between 3 and 10 percent for every
Celsius degree of warming. Each additional degree would also cause the amount
of area burned by wildfires in North America to double or quadruple, according
to the same report.
“If you think it’s bad now — when we’ve had about 0.7
degrees Celsius of warming — wait until we’ve had 3 or 4,” Gulledge said.
“There’s absolutely no reason to think it will not continue getting worse and
worse and worse.”
Some scientists are starting to worry that natural weather
patterns, which played a role in some of the biggest recent flooding, are also
showing effects of human-driven climate change. This year’s rainy season in
Australia is linked to a phenomenon called a La Nina, which occurs when water
in the equatorial region of the Pacific is cooler than normal.
La Nina and its warm-water counterpart, El Nino, are part
of a natural pattern of ocean currents and atmospheric winds that redistribute
heat by moving it from one part of the world to another. Even as La Nina and El
Nino influence the overall climate, much like organs in a body, they may remain
vulnerable to system-wide shocks, said Paul Mayewski, director of the Climate
Change Institute at The University of Maine.
So far scientists have found no definitive link between
rising greenhouse gases and changes to El Nino and La Nina events. But Mayewski
thinks that might be changing.
“This is a naturally occurring phenomenon,” Mayewski
said. “That doesn’t mean it can’t be impacted by humans.”
He is investigating whether greenhouse gases may have so
disturbed the balance of heat that natural patterns, like El Nino and La Nina,
may begin to speed up and intensify.
“We may very well be changing this El Nino-La Nina system
much faster and more radically,” Mayewski said. “It’s a naturally occurring
system that we may be giving a lot more push to.”
And, if he’s right, that could mean even less stable,
more extreme weather in the foreseeable future.
For some agencies working to help countries prevent and
recover from natural disasters, there’s no question that they’re getting worse.
“There was never any doubt in our mind that, in reality,
the frequency and severity and number of people that were affected kept
increasing,” said Margareta Wahlstrom, the United Nations' assistant secretary
general for disaster risk reduction.
In an increasingly urbanized world, people, goods and
infrastructure are concentrated, meaning that each natural disaster has the
potential to cause an unprecedented amount of damage.
“The losses are increasing very rapidly,” Wahlstrom said.
“Today is decision time. We know what the risks are. We can see the trends.”
With the effects of global warming already manifest,
Wahlstrom said, countries need to improve disaster preparation even as they
negotiate to cut emissions that cause the problem in the first place.
For a country such as Brazil, that means developing early
warning systems for heavy rains and better evacuation plans, as well as moving
people out of the most vulnerable neighborhoods. The government has pledged to
do just that in response to the recent tragedies.
Tackling the problem after the fact is devastatingly
expensive. Officials in cities destroyed by the floods here say it will take a
decade and hundreds of millions of dollars to rebuild. And a recent study [8]
predicts that a warming climate could cost Latin American countries about 1
percent of their GDP every year from now until 2100.
While natural disasters tend to be more deadly in
developing countries, this last year has shown extreme weather can strike
planet-wide.
“The attitude that many of us probably have lived with
for decades, because we’ve lived in fairly safe countries, is that disasters
are something that happens to others,” Wahlstrom said. “That is no longer
viable.”
**Source URL (retrieved on January 22, 2011 17:35 ):
http://www.globalpost.com/dispatch/brazil/110120/climate-change-floods-natural-disasters
Links:
[1]
http://www.globalpost.com/dispatch/brazil/110120/climate-change-floods-natural-disasters
[2]
http://newsroom.ucla.edu/portal/ucla/last-time-carbon-dioxide-levels-111074.aspx
[3] http://www.ncdc.noaa.gov/sotc/global/
[4]
http://www.globalpost.com/dispatch/brazil/101102/amazon-drought-climate-change
[5]
http://g1.globo.com/brasil/noticia/2011/01/exercito-distribui-agua-aos-afetados-por-seca-no-nordeste.html
[6] http://www.ipcc.ch/publications_and_data/ar4/wg2/en/
ch1s1-3-2-2.html
[7] http://www.nap.edu/catalog.php?record_id=12877
[8]
http://www.eclac.org/cgi-bin/getProd.asp?xml=/publicaciones/xml/9/41909/P41909.xml&xsl=/
dmaah/tpl-i/p9f.xsl&base=/tpl-i/top-bottom.xsl