Skeptics say "global warming is happening"

  • 24 Oct 2011, 15:00
  • Verity Payne

Last week the Berkeley Earth Surface Temperature (BEST) study released four reports that gained a huge amount of media coverage (for a scientific study) - particularly for work that has not yet been peer reviewed. Media reports focused on the project's finding that the average global temperature on land has increased by around 1°C since the middle of the 20th century.

Michael Hanlon, science editor for the Daily Mail, and self confessed ex-climate skeptic, suggests that the BEST study is likely to do a lot to answer some of the criticisms of climate skeptics, saying:

"In the end, the sceptics - the genuine sceptics (ie not those with say a financial stake in climate change denial) - will come round. But it will take time and more extraordinary evidence like that produced by this latest analysis."

This was certainly the intention of the BEST study team, whose executive director Elizabeth Muller hoped their work would "cool the debate over global warming".

So has the BEST study persuaded any climate skeptics to change their minds and cool the debate? We take a look at the response from climate skeptic commentators:

We've never disputed warming

Some skeptic commentators seem to be swiftly backtracking from previously held opinions over global warming and the 'corruption' amongst climate scientists. Take for example James Delingpole, who wrote in response to the BEST study:

"Global warming is real...Professor Muller [of the BEST team] sets up his straw ascribing to "skeptics" views that they don't actually hold. Their case, he pretends for the sake of his wafer-thin argument, rests on the idea that the last century's land-based temperature data sets are so hopelessly corrupt that they have created the illusion of global warming where none actually exists.

"It has been a truth long acknowledged by climate sceptics, deniers and realists of every conceivable hue that since the mid-19th century, the planet has been on a warming trend..."

This is in contrast to a post Delingpole wrote on his website entitled " Global warming: is it even happening?" in January 2010, where he argued that:

"the surface temperature records are such a mess that they simply can't be trusted"

Or a 2009 blogpost from the Telegraph immediately after the leaking of the UEA emails:

"As Andrew Bolt puts it, this scandal could well be "the greatest in modern science". These alleged emails - supposedly exchanged by some of the most prominent scientists pushing AGW theory - suggest: 'Conspiracy, collusion in exaggerating warming data'...

"The world is currently cooling."

We don't know what's caused the warming

The Global Warming Policy Foundation (GWPF)'s David Whitehouse says:

"the Berkeley researchers themselves say they cannot determine why the world has warmed."

Whilst the Daily Mail, whose recent coverage of climate science has been decidedly questionable, ran with the headline:

"New analysis of 1.6 billion weather records concludes the world IS warming (but still can't say what's causing it)"

In fact the BEST study's objectives have never included determining the cause of global warming. Their aim has been to answer some of the doubts that skeptics have about global temperature records, including meteorological station quality and the urban heat island effect.

Other studies (see here, here, and here for example) have investigated how human activity influences global surface temperature and have concluded that natural climate variations alone (including volcanic activity, solar activity, changes to ocean and atmospheric currents) cannot account for the warming over the last 40 years. Only when manmade greenhouse gases are included can the observed trends be simulated by climate models.

This has also been found to be the case for warming in specific regions, such as at the poles and over North America.

Other climate features such as rainfall, ocean temperature, surface humidity and air temperature have also been attributed to human activity, whilst recent research found that man-made climate change is "having a significant impact on physical and biological systems globally and in some continents".

Human component of warming overstated

Whitehouse feels that the headline "missed by all" media outlets was:

"Scientists say human component of global warming may be overstated."

One of the four BEST study papers investigated the correlation between cycles in the North Atlantic and the land surface temperature. The researchers suggest the 'Atlantic Multidecadal Oscillation' (AMO) as an area for further study, as it might contribute to global land temperature variation.

The AMO refers to changes in North Atlantic cycles. The BEST researchers themselves point out however that these changes could be a result of man-made global warming:

"If the long-term AMO changes have been driven by greenhouse gases then the AMO region may serve as a positive feedback that amplifies the effect of greenhouse gas forcing over land. On the other hand, some of the long-term change in the AMO could be driven by natural variability, e.g. fluctuations in thermohaline flow. In that case the human component of global warming may be somewhat overestimated."

Currently climate scientists believe that warming resulting from man-made greenhouse gases outweights the temperature influence from AMO.

The BEST report has errors

The methods of the BEST study have come in for criticism, notably from Anthony Watts of the skeptic blog WUWT. When the BEST work was in development, Watts was strongly supportive of it and wrote that he was "prepared to accept whatever result they produce, even if it proves my premise wrong." Since the release of the reports, however, he has criticised the BEST methodology.

Specifically Watts complains that in the BEST paper investigating weather station quality, researchers used 60-year records not 30-year records to determine station quality. Watts implies this might impair the BEST temperature analysis, although it is hard to see how limiting their analysis to Watts' 30-year suggestion would significantly alter the BEST study's key findings.

Watts has also criticised the BEST team's decision to publicly announce their findings before peer-review. Yet, as the BBC's Richard Black points out, WUWT frequently features non-peer-reviewed science, yet is now heavily criticising the BEST study for making the papers public before peer-review.

Overall, the BEST study has made a good media story but it unclear how successful it will be in its stated aim of 'cooling the global warming debate'. Sir Brian Hoskins, Director of the Grantham Institute said:

"If and when such a study is peer-reviewed and published, hopefully we can then focus on the implications for the future of this warming rather than wrangling over whether the warming is really there."

This is to be hoped for. It wil be interesting to see whether it happens.


Modified 15.15 24/10/11 to correct typo: 19th changed to 20th century

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