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Global temperatures 'to decrease'
Global temperatures for 2008 will be slightly cooler than last year as a
result of the cold La Nina current in the Pacific, UN meteorologists have
said.
The World Meteorological Organization's secretary-general, Michel Jarraud,
told the BBC it was likely that La Nina would continue into the summer.
But this year's temperatures would still be way above the average - and we
would soon exceed the record year of 1998 because of global warming induced
by greenhouse gases.
The WMO points out that the decade from 1998 to 2007 was the warmest on
record. Since the beginning of the 20th Century, the global average surface
temperature has risen by 0.74C.
While Nasa, the US space agency, cites 2005 as the warmest year, the UK's
Hadley Centre lists it as second to 1998.
Researchers say the uncertainty in the observed value for any particular
year is larger than these small temperature differences. What matters, they
say, is the long-term upward trend.
Rises 'stalled'
La Nina and El Nino are two great natural Pacific currents whose effects are
so huge they resonate round the world.
El Nino warms the planet when it happens; La Nina cools it. This year, the
Pacific is in the grip of a powerful La Nina.
It has contributed to torrential rains in Australia and to some of the
coldest temperatures in memory in snow-bound parts of China.
Mr Jarraud told the BBC that the effect was likely to continue into the
summer, depressing temperatures globally by a fraction of a degree.
This would mean that temperatures have not risen globally since 1998 when El
Nino warmed the world.
Watching trends
A minority of scientists question whether this means global warming has
peaked and argue the Earth has proved more resilient to greenhouse gases
than predicted.
Animation of El Nino and La Nina effects
But Mr Jarraud insisted this was not the case and noted that 2008
temperatures would still be well above average for the century.
"When you look at climate change you should not look at any particular
year," he said. "You should look at trends over a pretty long period and the
trend of temperature globally is still very much indicative of warming.
"La Nina is part of what we call 'variability'. There has always been and
there will always be cooler and warmer years, but what is important for
climate change is that the trend is up; the climate on average is warming
even if there is a temporary cooling because of La Nina."
China suffered from heavy snow in January
Adam Scaife, lead scientist for Modelling Climate Variability at the Hadley
Centre in Exeter, UK, said their best estimate for 2008 was about 0.4C above
the 1961-1990 average, and higher than this if you compared it with further
back in the 20th Century.
Mr Scaife told the BBC: "What's happened now is that La Nina has come along
and depressed temperatures slightly but these changes are very small
compared to the long-term climate change signal, and in a few years time we
are confident that the current record temperature of 1998 will be beaten
when the La Nina has ended."
Global temperatures for 2008 will be slightly cooler than last year as a
result of the cold La Nina current in the Pacific, UN meteorologists have
said.
The World Meteorological Organization's secretary-general, Michel Jarraud,
told the BBC it was likely that La Nina would continue into the summer.
But this year's temperatures would still be way above the average - and we
would soon exceed the record year of 1998 because of global warming induced
by greenhouse gases.
The WMO points out that the decade from 1998 to 2007 was the warmest on
record. Since the beginning of the 20th Century, the global average surface
temperature has risen by 0.74C.
While Nasa, the US space agency, cites 2005 as the warmest year, the UK's
Hadley Centre lists it as second to 1998.
Researchers say the uncertainty in the observed value for any particular
year is larger than these small temperature differences. What matters, they
say, is the long-term upward trend.
Rises 'stalled'
La Nina and El Nino are two great natural Pacific currents whose effects are
so huge they resonate round the world.
El Nino warms the planet when it happens; La Nina cools it. This year, the
Pacific is in the grip of a powerful La Nina.
It has contributed to torrential rains in Australia and to some of the
coldest temperatures in memory in snow-bound parts of China.
Mr Jarraud told the BBC that the effect was likely to continue into the
summer, depressing temperatures globally by a fraction of a degree.
This would mean that temperatures have not risen globally since 1998 when El
Nino warmed the world.
Watching trends
A minority of scientists question whether this means global warming has
peaked and argue the Earth has proved more resilient to greenhouse gases
than predicted.
Animation of El Nino and La Nina effects
But Mr Jarraud insisted this was not the case and noted that 2008
temperatures would still be well above average for the century.
"When you look at climate change you should not look at any particular
year," he said. "You should look at trends over a pretty long period and the
trend of temperature globally is still very much indicative of warming.
"La Nina is part of what we call 'variability'. There has always been and
there will always be cooler and warmer years, but what is important for
climate change is that the trend is up; the climate on average is warming
even if there is a temporary cooling because of La Nina."
China suffered from heavy snow in January
Adam Scaife, lead scientist for Modelling Climate Variability at the Hadley
Centre in Exeter, UK, said their best estimate for 2008 was about 0.4C above
the 1961-1990 average, and higher than this if you compared it with further
back in the 20th Century.
Mr Scaife told the BBC: "What's happened now is that La Nina has come along
and depressed temperatures slightly but these changes are very small
compared to the long-term climate change signal, and in a few years time we
are confident that the current record temperature of 1998 will be beaten
when the La Nina has ended."
