2008 will be slightly cooler than recent
years globally but will still be among the top 10 warmest years
on record since 1850 and should not be seen as a sign global
warming was on the wane, British forecasters said.
The Met Office and experts at the University of East Anglia
on Thursday said global average temperatures this year would be
0.37 of a degree Celsius above the long-term 1961-1990 average
of 14 degrees and be the coolest since 2000.
They said the forecast took into account the annual Pacific
Ocean La Nina weather phenomenon which was expected to be
particularly strong this year and which would limit the warming
trend.
It also took account of rising atmospheric concentrations
of so-called greenhouse gases, solar variations and natural
changes in the ocean currents.
"The fact that 2008 is forecast to be cooler than any of
the last seven years does not mean that global warming has gone
away," said Phil Jones, director of climate research at UEA.
"What matters is the underlying rate of warming - the
period 2001-2007 with an average of 0.44 degree C above the
1961-90 average was 0.21 degree C warmer than corresponding
values for the period 1991-2000."
La Nina and its opposite El Nino ocean-atmosphere
phenomenon have strong influences on global temperatures. La
Nina reduces the sea surface temperature by around 0.5 degrees
Celsius while El Nino has the opposite effect.
"Phenomena such as El Nino and La Nina have a significant
influence on global surface temperature and the current strong
La Nina will act to limit temperatures in 2008," said Chris
Folland from the Met Office Hadley Centre.
"However mean temperature is still expected to be
significantly warmer than in 2000, when a similar strength La
Nina pegged temperatures to 0.24 degree C above the 1961-90
average. Sharply renewed warming is likely once La Nina
declines," he added.
The current La Nina is now the strongest since 1999-2000.
The lag between La Nina and the full global surface temperature
response means that the cooling effect is expected to be a
little greater in 2008 than it was during 2007.
The World Meteorological Organisation said last month there
were indications that the 10 years from 1998 to 2007 were the
hottest decade on record.
The Met Office Hadley Centre said the top 11 warmest years
have all occurred in the last 13.
By Jeremy Lovell
Source : Reuters
