Ian Sample
Photo: AP
VULNERABLE
REGIONS: A car is seen on a road in the dense Amazon rainforest near the northern
city of
Scientists have long agreed that climate change could have
a profound impact on the planet; from melting ice sheets and withering
rainforests, to flash floods and droughts.
Now a team of climate experts has ranked the most fragile
and vulnerable regions on the planet, and warned they are in danger of sudden
and catastrophic collapse before the end of the century.
In a comprehensive study published on Tuesday, the
scientists identify the nine areas that are in gravest danger of passing
critical thresholds or “tipping points”, beyond which they will not recover.
Though the scientists cannot be sure precisely when each
region will reach the point of no return, their assessment warns it may already
be too late to save Arctic sea ice and the Greenland ice sheet, which they
regard as the most immediately in peril. By some estimates, there will not be
any sea ice in the summer months within 25 years.
The next most vulnerable area is the Amazon rainforest,
where reduced rainfall threatens to claim large areas of trees that will not
re-establish themselves. The scientists also expressed concerns over the Boreal
forests in the north, and have predicted that El Nino, the climate system which
has a profound impact on weather from Africa to
The scientists are so concerned they have called for an
early warning system to monitor each of these fragile ecosystems.
The international team, whose study appears in the
Proceedings of the National Academy of Sciences, represents some of the world’s
most prestigious organisations, including the Potsdam Institute for Climate
Impact Research in
The scientists polled 52 environmental experts and
combined their responses with discussions among 36 leading climate researchers
at a workshop at the British embassy in
“There’s a perception that global warming is something
that will happen smoothly into the future, but some of these ecosystems go into
an abrupt decline when warming reaches a certain threshold,” said Tim Lenton,
an environmental scientist at the
“If we know when the different tipping points are, we can
use them to inform targets to limit global warming. It gives us something to
aim for,” he added.
Last year, the U.N.’s expert panel of climate scientists
warned average temperatures could increase by as much as 6.4C by the end of the
century, with a rise of 4C most likely. Such a rise would bring food and water
shortages to vulnerable parts of the world, displace millions of people and wipe
out hundreds of species. In the latest study, the scientists calculate Arctic
sea ice will go into irreversible decline once temperatures rise between 0.5C
to 2C above those at the beginning of the century, a threshold that may already
have been crossed. There is already a 50 per cent chance that the
The meltwater would raise global sea levels by seven
metres.
A temperature rise of 3C could see more intense El Ninos,
with profound effects on the weather from Africa to
Warming of 3C to 5C could reduce rainfall in the Amazon by
30 per cent, lengthening the dry season. The Boreal forests could also pass
their tipping point, with large swaths dying off over the next 50 years. In
Africa, more rainfall may regreen the
The Indian summer monsoon is predicted to become erratic
and in the worst case scenario, begin to flip chaotically, unleashing flash
floods one year and droughts the next.
Measurements of the western Antarctic ice sheet show the
balance of snowfall and melting has shifted and it is now shrinking. According
to the study, a local warming of more than 5C could trigger uncontrollable
melting, adding five metres to sea levels within 300 years. Under the same
warming, Atlantic currents that power the
“If you can get some warning that you’re nearing one of
these thresholds, you can get to work on adapting to it. You could work harder
on reducing emissions, or you might use it as impetus to try other options,”
said Mr. Lenton.
— © Guardian Newspapers Limited,
2008