BEST: The science behind Richard Muller's 'conversion'
- 30 Jul 2012, 16:40
- Verity Payne
The Earth's average land temperature has warmed by around 0.9
degrees Celsius, probably down to manmade greenhouse gas emissions,
according to new
research from the Berkeley Earth Surface Temperature (BEST)
project. Given that much of the
media interest focuses on
Muller's suggestion that he is a converted skeptic, the
findings of the work have been somewhat obscured. Here's our guide
to the research behind Muller's self-described conversion.
What is BEST?
The BEST project was
launched and chaired by Professor Richard
Muller, a physicist at the University of California at
Berkeley. It aims to address criticisms
raised by climate skeptics about how existing records of the
Earth's average surface temperature have been compiled. Team
members include physicist Robert Rohde,
climatologist Judith
Curry, and other physicists and statisticians.
Previous research
from the BEST group, released in October 2011, addressed concerns
raised by skeptics about records of surface temperatures, including
the urban heat island effect and poor weather station siting. These
issues were not found to have a significant effect on the global
land surface temperature record.
What does the latest BEST research show?
This latest research from the BEST team confirms that the
Earth's average land temperature has risen by roughly 0.9 degrees
Celsius since the 1950s, and by 1.5 degrees Celsius over the last
250 years. This is in line with existing records, which put average
global land temperature rise over the last 50 years at 0.81 - 0.93
degrees Celsius:
The study also uses a simple model to work out whether the
change in global land temperature fits best with changes in
atmospheric carbon dioxide levels, volcanic activity or solar
activity - and find the best fit with a combination of change in
atmospheric carbon dioxide and volcanic activity:
The contribution of solar activity, it concludes, must be
negligible.
Muller
notes this doesn't prove that carbon dioxide is responsible for
warming, but adds:
"To be considered seriously, any
alternative explanation must match the data at least as well as
does carbon dioxide."
How do the latest BEST results differ from previous
studies?
The BEST temperature reconstruction of global land temperature
records differs from other records - produced by the NOAA National
Climatic Data Center (NCDC),
the NASA Goddard Institute for Space Studies (GISS), and a
collaboration between the UK Met Office Hadley Centre and the
Climatic Research Unit at the University of East Anglia (HadCRUT)
- because it uses many more station records.
The BEST team also use a different
statistical method to calculate the average land temperature
record from the methods used by NOAA, GISS and HadCRUT. The team
boasts that its approach is simple,
pointing out that it doesn't rely on complicated climate
models.
The attribution of much of the last 50 years' warming to human
activity is in line with
several
recent studies
using
a variety of sophisticated approaches to calculate the
contributions of natural
and human causes of global warming. The studies agree that
human activity is the dominant cause of warming over the last
century, and particularly over the last 50 years.
Is the BEST research peer reviewed?
This new research is not yet peer reviewed. The BEST team
explains why:
"Some people think that peer review
consists of submitting a paper to a journal and waiting for the
anonymous comments of referees. Traditional peer review is much
broader than that and much more open. In science, when you have a
new result, your first step is to present it to your colleagues
[...] Such traditional and open peer review has many advantages. It
usually results in better papers in the archival journals, because
the papers are widely examined prior to publication. It does have a
disadvantage, however, that journalists can also pick up preprints
and report on them before the traditional peer-review process is
finished."
When the BEST team last released papers they were also
non-peer-reviewed preprints. Those papers have since been submitted
to peer-reviewed journals. Only one out of those four, however,
appears to have been accepted for publication so far, according to
the BEST
website.
The peer review process allows independent qualified experts to
scrutinise scientific methods, results and interpretations before
they are made public. It provides a kind of stamp of approval for
new research, in that it shows that the research is considered
valid, significant and original by experts in the field. So the
fact that any BEST research has attracted so much media attention
before even being peer reviewed is a little worrying - the research
could turn out to be good, but could also turn out to be flawed or
incomplete.
How much does the BEST study matter?
Beyond the media the new results have had a
mixed reception. Climate scientist William Connolley is
not impressed:
"[The BEST team has] done none of the
attribution work you'd expect, in order to talk about attribution.
And what they say [...] appears absurdly naive."
Climate scientist Ken Caldeira
points out:
"The basic scientific results have been
established for a long time now, so I do not see the results of
Muller et al as being scientifically important. However,
their result may be politically important. It shows that even
people who suspect climate scientists of being charlatans, when
they take a hard look at the data, see that the climate scientists
have been right all along."
BEST member Curry
describes its temperature record as "the best land surface
temperature data set that we currently have", but
declined to be a co-author on the latest paper, since she
disagrees with its interpretation attributing the temperature rise
to atmospheric carbon dioxide.
The climate skeptic community meanwhile, is largely
dismissive of the new findings, and has been keen to point out
that Muller was
never truly a skeptic.
What about the Watts et al. paper?
Coinciding with the release of the latest BEST team results
comes news
from climate skeptic weatherman and blogger Anthony Watts. Watts
and colleagues have released new, yet-to-be-peer-reviewed research
into where US weather stations are sited, and whether this affects
the average US temperature trend.
Watts has long blogged about the siting of weather stations, and
in 2011 co-authored a
paper on the topic which concluded that poorly sited US weather
stations gave biased temperature readings - either artificially hot
and artificially cold - but that these balanced each other out, not
affecting the overall temperature trend.
Watts and colleagues'
hastily produced new paper - he apparently released it at the
same time as the BEST study deliberately - seems to revoke his
previous conclusions. He now suggests that:
"U.S. Temperature trends show a spurious
doubling due to NOAA station siting problems and post measurement
adjustments."
Roger Pielke Sr. - acknowledged in the paper from Watts and
colleagues for his help in its production - decribes the new
research as "seminal". But the research has come under criticism
from climate scientist
Victor Venema, University of Bonn, and is at odds with recent
research.
Despite all the publicity, neither of these papers have received
the important stamp of approval from the rest of the scientific
community that constitutes peer-review. Will they make it through
the peer review process? We'll have to wait and see, but until
they've been reviewed by specialists, it's difficult to assess how
scientifically significant they are.
Updated 10:48 01/08/12 to reflect
Roger Pielke Sr.'s involvement with the paper by Watts and
colleagues.