Los
científicos que analizan los modelos climáticos advierten que debemos esperar
altas subidas de temperatura - es decir, un clima más extremo, más pronto
A satellite image of superstorm Sandy. Photograph:
Nasa/Getty Images
Climate change is likely to be more severe than some models have implied, according to
a new study which ratchets up the possible temperature rises and subsequent
climatic impacts.
The
analysis by the US National Centre for Atmospheric Research (NCAR) found that
climate model projections showing a greater rise in global temperature were
likely to be more accurate than those showing a smaller rise. This means not
only a higher level of warming, but also that the resulting problems –
including floods, droughts, sea level rise and fiercer storms and other
extreme weather – would be correspondingly more severe and would come sooner
than expected.
Scientists
at the NCAR published their study on Thursday in the leading peer-reviewed journal Science. It is based on
an analysis of how well computer models estimating the future climate reproduce
the humidity in the tropics and subtropics that has been observed in recent
years. They found that the most accurate models were most likely to best
reproduce cloud cover, which is a major influence on warming. These models were
also those that showed the highest global temperature rises, in future if
emissions of greenhouse gases continue to increase.
John Fasullo, one of the researchers, said: "There is a striking
relationship between how well climate models simulate relative humidity in key
areas and how much warming they show in response to increasing carbon dioxide. Given
how fundamental these processes are to clouds and the overall global climate,
our findings indicate that warming is likely to be on the high side of current
projections."
Extreme
weather has been much in evidence around the globe this year, with superstorm Sandy's devastating
impact on New York the most recent example. There has
also been drought across much of the US's
grain-growing area, and problems with the Indian monsoon. In the UK, one of the
worst droughts on record gave way to the wettest spring recorded, damaging crop
yields and pushing up food prices.
The new NCAR findings come just weeks ahead of a crucial UN conference
in Doha, where ministers will discuss the future of international action on
greenhouse gas emissions. The ministers will have to take the first steps to a
new global climate treaty, to kick in from 2020, but so far have shown little
sign of urgency.
The
next comprehensive study of our knowledge of climate change and its effects
will come in 2014, when the Intergovernmental Panel on Climate Change publishes
its fifth assessment report. Before that, next September, the first part of the report will deal
with the science of climate change and predictions of warming.
There
has already been increasing evidence of a warming effect this year – the Arctic's summer
ice sank to its lowest extent and volume yet recorded, and satellite pictures showed that surface ice melting was more
widespread across Greenland than ever seen in years of observations. Experts
have predicted that the Arctic seas could be ice-free in winter in the next
decade.
The
International Energy Agency warned earlier this year that on current emissions
trends the world would be in for
6C of warming – a level scientists warn would
lead to chaos. Scientists have put the safety limit at 2C, beyond which warming
is likely to become irreversible.
Given this year's extreme weather, the results of the NCAR may not
surprise some. But for scientists, narrowing down the uncertainties in climate
models is a key activity. "The dry subtropics are a critical element in
our future climate," Fasullo says. "If we can better represent these
regions in models, we can improve our predictions and provide society with a
better sense of the impacts to expect in a warming world."
· A satellite image of superstorm Sandy. Photograph:
Nasa/Getty Images
