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How the BBC's More or Less confused the realities of climate change

  • 18 Jan 2012, 16:31
  • Christian Hunt

A segment on last week's More or Less programme on BBC Radio 4 revisited a bet between climate scientist Dr James Annan and Dr David Whitehouse, science editor for the climate skeptic think tank the Global Warming Policy Foundation (GWPF).

On a previous edition of More or Less in early 2008, Whitehouse had bet Annan £100 that no new global temperature record would be set within 4 years, as determined by the HadCRUT3 temperature dataset. Now that it's 2012, and with HadCRUT3 still showing 1998 to be the hottest year on record, it's seems that Annan has lost his money.

The bet was pretty pointless, given that it tells us little or nothing about global warming trends or their relation to man-made greenhouse gas emissions. And instead of taking a closer look at why yearly temperature trends have little to do with the overall global warming curve, it allowed Whitehouse to wave the short-term temperature red herring around unchallenged. It's no surprise, then, that Whitehouse, the GWPF and various  skeptic bloggers have been all over it.

It's a shame because More or Less reaches a broad audience and is usually very intelligent at unpacking the reality behind different groups' claims. Instead, the More or Less segment only served to vindicate misgivings voiced in the BBC Trust report of 'false balance' in the corporation's climate science coverage.

False balance

Tim Harford, the programme's presenter and the Financial Times's undercover economist, set the tone for the More or Less segment, saying:

"The debate still rages about whether global warming is continuing or whether the last ten years show that the temperature rises since in the 1980s and the 1990s have stopped."

This is only true if it is taken to mean that climate skeptic bloggers and lobbyists are still arguing whether global warming is continuing. There certainly isn't a debate raging in the scientific community and the peer-reviewed literature. So right from the start, the way the programme presents the debate does not accurately reflect scientific understanding of man-made climate change.

Harford goes on:

"At the time we spoke to David Whitehouse, an astrophysicist and former BBC science editor, and James Annan, a climate scientist"

It is worth noting here that Harford neglects to mention David Whitehouse's current role as the GWPF's science editor. This isn't the first time media outlets have glossed over his current affiliation when quoting him.

We might allow that when the bet was first made, the GWPF was only a twinkle in Nigel Lawson's eye. However, given that the BBC Trust's own review of the corporation's coverage of science described the GWPF as "active in casting doubt on the truth of man‐made climate change", it seems reasonable to argue that More or Less should have noted this affiliation - for the purposes of transparency.

James Annan, meanwhile, is a member of the Global Change Projection Research Programme at the Research Institute for Global Change. He has something of a penchant for making wagers with climate skeptics over temperature records. According to the Guardian, in August 2005 Annan agreed on a bet of $10,000 with Russian solar physicists Galina Mashnich and Vladimir Bashkirtsev that the earth will be warmer between 2012 and 2017 than it was between 1998 and 2003.

A pointless bet

Frankly it is hard to see what the point of the bet was. Betting on four years being hot or cold doesn't tell us anything about long-term man-made climate change. Natural variation in the climate means that temperatures do all sorts of things over short time periods - up to and including decades.

For example, natural climate cycles El Niño and La Niña cause decadal fluctuations in temperatures, atmospheric cooling from aerosols and volcanoes has an effect, and the waxing and waning of solar energy also a difference. This is all background noise to the long-term upward trend in temperatures due to man-made global warming, and any long-term temperature trend stands a good chance of being masked by natural variation over a four-year period, a point illustrated nicely by this video.

 From Climate Denial Crock of the Week

How the bet obscured the realities of climate change

Take a longer-term look, and natural variability becomes less significant. Taking the average for ten year chunks, even though temperature rise has slowed (presumably due to natural variability - it certainly isn't because greenhouse gas emissions have fallen), the noughties are still the warmest decade on record.

So it seems strange that during the programme Whitehouse says:

"I would like to see evidence of sustained warming, which means more than one year"

The warm noughties provide exactly that evidence.

And, as scientists Grant Forster and Stefan Rahmstorf (of realclimate) showed in a peer-reviewed paper published towards the end of last year, when they removed the effect of natural variations from temperature records, they can extract a remarkably clear warming trend caused by man-made greenhouse gas emissions over the last thirty years.

Foster Rahmstorf 2011

Source: Skeptical Science

Whitehouse himself concedes that the last few years have been dominated by natural variation and not man-made warming, saying in his blog post:

"My view was that the information in the [temperature] dataset was important, especially if projecting it forward just a few years when natural variations were clearly dominant."

Over a long time period the long-term effect of global warming would appear, and it is statistically likely that  a new record year might appear at some point in the future, but betting on a hot year appearing in a period as short as four years is essentially pretty meaningless.

The outcome

Fair play to Dr Whitehouse, he's a plucky gambler, and he won the bet on the terms agreed. Unfortunately his blog and his comments on the programme imply that this represents a victory for the pet theory of his GWPF buddies - that global warming has stopped. For more on why this isn't the case see our blog post on the topic.

Not only does this theory rely on cherrypicking short-term fluctuations over long term trends, it also relies on focusing on the findings of just one of the three datasets used to measure global surface temperature trends. HadCRUT3, the dataset chosen for this bet, is known to have a bias towards cooler temperatures, due the way it accounts for lack of data over the polar regions compared to the other datasets. (We have more on global temperature datasets and how they are produced here.)

Imagine the gamblers had chosen a different dataset. Unlike HadCRUT3, the other two principal datasets - NASA's GISS and the NOAA's NCDC say that 2010 was the joint warmest year on record. It's fortunate for Dr Whitehouse that the only one of the three principal datasets not putting 2010 as a record-breaking year was the one on which he was wagering!

However, Dr Whitehouse seemed unwilling to cede this point when Annan pointed it out in the show. He wrote on his blog:

"This is a moot point that also strongly reaffirms my stance."

Um.

Whitehouse did respond in a way, though, to the charge that only one of the datasets supported his win. He argues that 2010 was hotter due to a strong El Niño.

El Niño is a natural climate cycle which warms the planet slightly while it's happening. But although 2010 started off in a warming El Niño phase, by July it had shifted to its cooling La Niñacounterpart. So 2010's warmth can't be explained simply by reference to El Niño.

As it transpires, a preview of the new Hadley Centre temperature dataset HadCRUT4, which rectifies some of the cooling bias of HadCRUT3, also looks like it will put 2010 as joint warmest year with 2005. So Whitehouse's victory may well have been largely down to the cooling bias of HadCRUT3.

Quit when you're winning

Whitehouse isn't just lucky - he's also a canny gambler who knows better than to push his luck much further. When asked if he would be tempted to continue with a 'double or quits' bet, he replies that he would agree to it only if there are new temperature records over:

"more than one year,more than one standard deviation above the straight line of the past ten years."

...A sensible bit of moving the goalposts. But if he thinks temperatures are really at a standstill, why not take the same bet again?

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