The Earth's surface really is getting warmer, a new analysis by a US scientific
group set up in the wake of the "Climategate" affair has concluded.
The Berkeley Earth Project has used new methods and some new data, but finds
the same warming trend seen by groups such as the UK Met Office and Nasa.
The project received funds from sources that back organisations lobbying
against action on climate change.
"Climategate", in 2009, involved claims global warming had been exaggerated.
Emails of University of East Anglia (UEA) climate scientists were hacked,
posted online and used by critics to allege manipulation of climate change
data.
Fresh start
The Berkeley group says it has also found evidence that changing sea
temperatures in the north Atlantic may be a major reason why the Earth's
average temperature varies globally from year to year.
Saul Perlmutter The group includes physicist Saul Perlmutter, a Nobel Prize
winner this year
The project was established by University of California physics professor
Richard Muller, who was concerned by claims that established teams of climate
researchers had not been entirely open with their data.
He gathered a team of 10 scientists, mostly physicists, including such
luminaries as Saul Perlmutter, winner of this year's Nobel Physics Prize for
research showing the Universe's expansion is accelerating.
Funding came from a number of sources, including charitable foundations
maintained by the Koch brothers, the billionaire US industrialists, who have
also donated large sums to organisations lobbying against acceptance of
man-made global warming.
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Start Quote
Our biggest surprise was that the new results agreed so closely with the
warming values published previously
Richard Muller Berkeley group founder
"I was deeply concerned that the group [at UEA] had concealed discordant data,"
Professor Muller told BBC News.
"Science is best done when the problems with the analysis are candidly shared."
The group's work also examined claims from "sceptical" bloggers that
temperature data from weather stations did not show a true global warming
trend.
The claim was that many stations have registered warming because they are
located in or near cities, and those cities have been growing - the urban heat
island effect.
The Berkeley group found about 40,000 weather stations around the world whose
output has been recorded and stored in digital form.
It developed a new way of analysing the data to plot the global temperature
trend over land since 1800.
What came out was a graph remarkably similar to those produced by the world's
three most important and established groups, whose work had been decried as
unreliable and shoddy in climate sceptic circles.
Graph The Berkeley group's record of global land temperature mirrors existing
ones closely
Two of those three records are maintained in the US, by the National Oceanic
and Atmospheric Administration (Noaa) and National Aeronautics and Space
Administration (Nasa).
The third is a collaboration between the UK Met Office and UEA's Climatic
Research Unit (CRU), from which the e-mails that formed the basis of the
"Climategate" furore were hacked two years ago.
"Our biggest surprise was that the new results agreed so closely with the
warming values published previously by other teams in the US and the UK," said
Professor Muller.
"This confirms that these studies were done carefully and that potential biases
identified by climate change sceptics did not seriously affect their
conclusions."
Since the 1950s, the average temperature over land has increased by 1C, the
group found.
They also report that although the urban heat island effect is real - which is
well-established - it is not behind the warming registered by the majority of
weather stations around the world.
They also showed that in the US, weather stations rated as "high quality" by
Noaa showed the same warming trend as those rated as "low quality".
'Time for apology'
Professor Phil Jones, the CRU scientist who came in for the most personal
criticism during "Climategate", was cautious about interpreting the Berkeley
results because they have not been published in a peer-reviewed journal.
"I look forward to reading the finalised paper once it has been reviewed and
published," he said.
Professor Phil Jones The findings so far provide validation for Phil Jones,
targeted during the "Climategate" affair
"These initial findings are very encouraging, and echo our own results and our
conclusion that the impact of urban heat islands on the overall global
temperature is minimal."
The Berkeley team has chosen to release the findings initially on its own
website.
They are asking for comments and feedback before preparing the manuscripts for
formal scientific publication.
In part, this counters the accusation made during "Climategate" that climate
scientists formed a tight clique who peer-reviewed each other's papers and made
sure their own global warming narrative was the only one making it into print.
But for Richard Muller, this free circulation also marks a return to how
science should be done.
"That is the way I practised science for decades; it was the way everyone
practised it until some magazines - particularly Science and Nature - forbade
it," he said.
"That was not a good change, and still many fields such as string theory
practice the traditional method wholeheartedly."
This open "wiki" method of review is regularly employed in physics, the home
field for seven of the 10 Berkeley team.
Bob Ward, policy and communications director for the Grantham Research
Institute for Climate Change and the Environment in London, said the warming of
the Earth's surface was unequivocal.
"So-called 'sceptics' should now drop their thoroughly discredited claims that
the increase in global average temperature could be attributed to the impact of
growing cities," he said.
"More broadly, this study also proves once again how false it was for
'sceptics' to allege that the e-mails hacked from UEA proved that the CRU land
temperature record had been doctored.
"It is now time for an apology from all those, including US presidential
hopeful Rick Perry, who have made false claims that the evidence for global
warming has been faked by climate scientists."
Ocean currents
The Berkeley group does depart from the "orthodox" picture of climate science
in its depiction of short-term variability in the global temperature.
The El Nino Southern Oscillation (ENSO) is generally thought to be the main
reason for inter-annual warming or cooling.
But by the Berkeley team's analysis, the global temperature correlates more
closely with the state of the Atlantic Multidecadal Oscillation (AMO) index - a
measure of sea surface temperature in the north Atlantic.
There are theories suggesting that the AMO index is in turn driven by
fluctuations in the north Atlantic current commonly called the Gulf Stream.
The team suggests it is worth investigating whether the long-term AMO cycles,
which are thought to last 65-70 years, may play a part in the temperature rise,
fall and rise again seen during the 20th Century.
But they emphasise that anthropogenic global warming (AGW) driven by greenhouse
gas emissions is very much in their picture.
"Had we found no global warming, then that would have ruled out AGW," said
Professor Muller.
"Had we found half as much, it would have suggested that prior estimates [of
AGW] were too large; if we had found more warming, it would have raised the
question of whether prior estimates were too low.
"But we didn't; we found that the prior rise was confirmed. That means that we
do not directly affect prior estimates."
The team next plans to look at ocean temperatures, in order to construct a
truly global dataset.