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First half 2010 hottest ever, but is it climate change?
2010-07-20 07:39:20.981 GMT
July 20 (AFP) -- The first six months of 2010 brought a
string of warmest-ever global temperatures, but connecting
these dots to long-term climate change patterns remains
frustratingly difficult, experts say.
Not only was last month the hottest June ever recorded, it
was the fourth consecutive month in which the standing high
mark was topped, according to the US National Oceanic and
Atmospheric Administration (NOAA).
Indeed, 2010 has already surpassed 1998 for the most
record-breaking months in a calendar year.
As a block, the January-to-June period registered the
warmest combined global land and ocean surface temperatures
since 1880, when reliable temperature readings began, NOAA
said.
Arctic ice cover -- another critical yardstick of global
warming -- had also retreated more than ever before by July 1,
putting it on track to shrink beyond its smallest area to date,
in 2007.
On the face of it, these numbers would seem to be alarming
confirmation of climate models that put Earth on a path towards
potentially catastrophic impacts.
Without steep cuts in greenhouse gas emissions, the global
thermometer could rise by 6.0 degrees Celsius (10.8 Fahrenheit)
compared to pre-industrial levels, making large swathes of the
planet unlivable, the UN's Intergovernmental Panel on Climate
Change (IPCC) has warned.
Voluntary national pledges made after the Copenhagen
climate summit in December would likely cap that increase at
3.5 C to 4.0 C (6.3 F to 7.2 F), still fall far short of the
2.0 C (3.6 C) limit that most scientists agree is the threshold
for dangerous warming.
But making a direct link between year-on-year variations
in the weather and changes in climate -- best measured in
centuries -- is simply not possible, scientists say.
"When we are looking at the scale of a season or a few
months, we can't talk about trends related to climate change,"
said Herve Le Treut, head of France's Laboratory of Dynamical
Meteorology.
"The problem is knowing whether these numbers fit into a
long-term evolution, and that only becomes apparent over at
least two or three decades."
For scientists, he said, it would be like trying to figure
out which way the tide is moving by watching only a few waves
lapping at the shoreline.
A hotter-than-average 2010 is due at least in part to the
influence of periodic El Ninos, which disrupt weather patterns
in the equatorial Pacific, Le Treut and other experts point
out.
"We now know that the year following an El Nino will be
globally unusually warm," said Andrew Watson, a professor at
the University of East Anglia in Britain.
"1998 was such a year. It's clear that 2010 will be very
close to 1998 and quite possibly it will beat it," he said.
At the same time the long-term trend of warming is
unmistakable, and at least one figure from last month can be
said to add to the mounting evidence that climate change is
firmly upon us.
June was the 304th consecutive month with a global surface
temperature above the 20th-century average, the NOAA reported.
The most recent month to dip below that average was
February 1985, more than a quarter century ago.
"Taken in isolation these figures say nothing about
climate change," said Barry Gromett, spokesman for Britain's
national weather and climate centre, the Met Office.
"But if taken in the context of 2000-2010 being the
warmest decade on record, and this set be another near record
or record warm year, then this is further evidence that the
climate is warming," he told AFP.
The Met Office uses different methods than the NOAA to
calculate climate trends, and has not yet calculated data for
June, he explained.
All of the ten warmest average annual global temperatures
recorded since the end of the 19th century have occurred in the
last 15 years.
mh-cls/bm/dk
-0- Jul/20/2010 07:39 GMT
