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.


 BEST_temp Rise

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.



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