Climate Revision Validates Sceptics
As Australians sweltered through a record-breaking summer heatwave this week, one of the world’s leading scientific bodies revised down its five-year projection for the world’s average temperature. The revision, slipped quietly into the public domain on Christmas Eve by Britain’s Met Office, has fuelled a significant and growing debate about what exactly happened to global warming.
On one analysis, the forecast confirms what many people have been saying for some time. Global warming effectively stopped 17 years ago and, if the new forecast is accurate, that “pause” will be extended to 20 years.
Using new computer models, the Met Office now believes global temperatures up to 2017 will most likely be 0.43C above the 1971-2000 average, with an error of plus or minus 0.15C.
The Met Office had previously estimated the most likely global temperature increase to be 0.54C above the 1971-2000 average during the period 2012 to 2016.
The Met Office says despite the change, “we will continue to see near-record levels of global temperatures in the next few years”.
“This means temperatures will remain well above the long-term average and we will continue to see temperatures like those which resulted in 2000-2009 being the warmest decade in the instrumental record dating back to 1850.”
But the release of the data – and the way in which it was released – has fuelled a strong reaction. David Whitehouse, of the Global Warming Policy Foundation, said the new prediction challenged the assertion that the underlying rate of change of global warming was unchanged.
“If the latest Met Office prediction is correct, and it accords far more closely with the observed data than previous predictions, then it will prove to be a lesson in humility,” Whitehouse said.
“It will show that the previous predictions that were given so confidently as advice to the UK government and so unquestioningly accepted by the media, were wrong, and that the so-called sceptics who were derided for questioning them were actually on the right track.”
In response, Britain’s science media organisation released quotes from leading climate scientists to explain the revision.
Richard Allan, reader in climate science at the University of Reading, said: “Global warming is not ‘at a standstill’ but does seem to have slowed down since 2000 in comparison to the rapid warming of the world since the 1970s.”
He said the slowdown reflected greater scientific understanding and was due in part to increased heat being trapped in the world’s oceans. “Nothing in their (Met Office) data leads me to think that global warming due to human influence has stopped, or is irrelevant. It hasn’t, and it isn’t,” he said.
Professor Myles Allen, head of the Climate Dynamics Group at the University of Oxford, effectively said the revision provided a lesson in the dangers of spin.
“A lot of people (not the Intergovernmental Panel on Climate Change) were claiming, in the run-up to the Copenhagen 2009 conference, that ‘warming was accelerating and it is all worse than we thought’. What has happened since then has demonstrated that it is foolish to extrapolate short-term climate trends.”
For the sceptical, the Met Office’s near-term predictions are coming home to roost. In 2007, it predicted that by 2014 the global average temperature was expected to have risen by 0.3C compared with 2004, and that half of the years after 2009 were predicted to be hotter than the current record hot year in 1998.
“Given that we have data for three of the five years of that period, and all show no departure from a constant temperature when analysed statistically, this is a prediction that will probably be totally wrong,” Whitehouse said.
“In any case, it is completely at odds with the new forecast.”
Responding to media reports, the Met Office said “small year-to-year fluctuations such as those we are seeing in the shorter five-year predictions are expected due to natural variability in the climate system, and have no sustained impact on the long-term warming.”
“Century-scale projections are less sensitive to natural variability and updates to the 2012 decadal forecast do not necessarily tell us anything about projections of climate change for the coming century,” the Met Office said.
In the popular British press, it has been another opportunity to beat up the Met Office for being unable to accurately forecast the weather. If nothing else, the debate highlights an inconvenient fact of life for climate scientists: that they claim to be able to predict the perils of next century with greater confidence than what is likely to happen on timescales that people can better understand.
For instance, the IPCC is “virtually certain” the world will have more hot days and warm nights through the 21st century. But there is obviously far less precision about exactly how that change may come about.
It is in part why “global warming” has been strategically rebranded as “climate change”: to overcome a conundrum that global temperatures have not followed a linear increase in a way that lobby groups find easy to explain.
Scientists say there are a host of reasons for this. Key are natural variability and genuine gaps in understanding about what makes the complex climate systems tick.
The Climate Commission will release its latest report today. Author David Karoly said: “The baseline conditions have shifted. We live in a hotter world and the risk of more frequent and severe extreme weather has already increased. Although Australia has always had heatwaves, hot days and bushfires, climate change is increasing the risk of more frequent and longer heatwaves and more extreme hot days, as well as exacerbating bushfire conditions.”
Even with the impact of climate change on extreme weather, the best advice is it will be several decades before science is able to unpack the impact of climate change from natural variability. But the new emphasis on weather sits well with the media’s insatiable demand for updates. Another storm, flood, cyclone or heatwave is always just around the corner.
A perverse result has been that – with the full blessing of government climate agencies – climate change is now reported like a cosmic soccer match, with little regard for the long-term horizons that are properly required.
Nonetheless, being held to account for predictions made over five- and 10-year periods can only be a good thing. With luck, it will help promote real science over political spin and avoid the sort of future “foolish extrapolations” highlighted by Allen.
Better models, which reflect greater scientific understanding, can only be a good thing, particularly if it means the outlook, in the near term at least, is not as bad as it once might have seemed.