The BEST study is finally peer reviewed (and basically confirms what scientists already knew)
- 21 Jan 2013, 17:50
- Roz Pidcock
This week saw the results of the Berkeley Earth Surface
Temperature (BEST) study published
in a peer-reviewed journal. Originally set up to test scientific
consensus on human induced climate change, the study sparked
considerable interest among climate skeptics. But after much
commotion and with BEST study now coming to a close, do we know
anything now that we didn't already?
What's BEST?
In 2011, self-proclaimed climate "agnostic" Richard Muller and
colleagues at the Berkeley Earth Surface Temperature (BEST) launched an
investigation into whether or not earth's temperature is rising -
and if so, what the most likely reason could be.
As we wrote
at the time, the motivation for doing this was that Muller
remained unconvinced
by existing scientific analysis which concluded that carbon dioxide
emissions resulting from human activity had warmed the planet in
the last century and a half.
To tackle what he saw as methodological flaws in other analyses
of global temperature, Muller and colleagues independently analysed
land temperatures from more than 35,000 stations worldwide between
1753 and 2011. They then compared changes in temperature with other
factors that could influence the climate, including carbon dioxide
concentrations, volcanic eruptions and changes in solar
activity.
Media frenzy
Since the premise of the BEST study was to rigorously test the
scientific consensus around anthropogenic climate change, its
launch attracted the attention of climate skeptics the world over.
One notable example was skeptic blogger Anthony Watts, who said
at the time:
"I'm prepared to accept whatever result
they produce, even if it proves my premise wrong...[The method
used] gives me greater confidence in the result being closer to a
bona fide ground truth than anything we've seen yet."
Yet, when the results - published online last year - were
found to support the scientific consensus on human-induced climate
change,
criticism still flowed that the study hadn't yet been subject
to peer-review.
Well, this weekend the results of the BEST study were finally
published in a peer-reviewed journal - albeit a brand new one -
called Geoinformatics and Geostatistics: An Overview, published by
SciTechnol. So what
does the paper say?
Hotting up
The data show global temperature on land has risen by 0.9
degrees Celsius since the 1950s. As Muller says in the paper,
"there is no statistically significant disagreement" between this
and the three main global temperature datasets from NOAA, NASA and the Met
Office.
Global land temperature 1753 to 2011. The BEST dataset
is in black, NOAA in green, NASA in blue and the Met
Office HadCRU in red. Source: Rohde et al.
(2012)
The rate of warming has been faster in the northern hemisphere
than the southern hemisphere, according to the BEST analysis. As
Muller notes in the paper, this also "agrees with prior
assessments" and is mainly due to the amplifying effect that
melting snow has on warming and the average distance of land from
large bodies of water.
Solar influence not important
According to the paper, the observed rate of global warming of
the past 250 years can be explained by the increase in atmospheric
carbon dioxide caused by human activity together with known
volcanic eruptions.
When a volcano erupts it spits out a large amount of sulphate
particles, which scatter sunlight and have a temporary
cooling effect on global temperature.
On the subject of the sun's influence on global temperatures,
Muller says categorically:
"Solar forcing does not appear to
contribute to the observed global warming of the past 250
years".
He continues that while the BEST study doesn't rule out long
term natural causes of global temperature rise, his analysis would
suggest such forces are insignificant. He says:
"[S]ince all of the long-term (century
scale) trend in temperature can be explained by a simple response
to greenhouse gas changes, there is no need to assume other sources
of long-term variation are present".
In line with the IPCC
The results from the BEST study back up a number of other
conclusions made by the Intergovernmental Panel on Climate Change
(IPCC) in the
4th Assessment Report.
The BEST estimates that the amount by which a doubling of carbon
dioxide increases global temperature is "broadly consistent" with
the IPCC's estimate of
between two and 4.5 degrees of warming.
What's more, Muller and colleagues conclude that large swings in
global temperature prior to 1850 - which includes the period
commonly referred to as the
Little Ice Age - are likely to be "closely linked to regional
changes in Europe and North America, rather than to global
processes".
Brand new journal
The journal in which the BEST results are published does appear
to be a
brand new one - the current edition being volume one, issue
one. This had led some to speculate over the quality of the
journal.
But Muller has justified his choice of journal, telling Guardian
environmental analyst Leo
Hickman:
"SciTechnol has a good reputation and we
liked GIGS's focus on statistics, their quick turn around time, and
their providing free access to articles".
According to the press release from Saturday, the BEST group has
also released a number of other materials to coincide with the
publication of the paper, including more recent data (up to 2012,
the paper only goes up to 2011) and some new animations of global
warming.
As you were....
After all the furore and column inches about the BEST study, the
results come as no great shock, essentially appearing to back up
what scientists already knew about climate change. But let's look
on the bright side - while the BEST study may have essentially
spent two years getting to where climate science was at some time
ago, it does suggest that on the big questions of climate change,
science stands up to the some fairly rigorous scrutiny.