The Daily Express cherrypicks new research on projections of warming
The Daily Express published an article yesterday claiming new research “adds to a growing body of evidence against extreme global warming.” But the authors tell us the newspaper obscured their main message, which is that it’s now “very likely” we’ll exceed the international target of two degrees of global warming.
The Express’s story stems from a piece of research by Australian climate scientists published in Nature Climate Change last week. The research looked at how uncertainty around temperature projections from climate models could be reduced.
The newspaper claims the “dramatic” new research shows “the effects of climate change may be less severe than had been feared”. But Professor David Karoly from the University of Melbourne, one of the authors of the research, tells us this interpretation “misrepresented our study.”
Narrowing uncertainty
When it comes to climate modelling, a certain degree of uncertainty is inevitable because of the complexity of the earth’s climate system.
That’s why the Intergovernmental Panel on Climate Change (IPCC) provides a range of possible temperatures for each emissions scenario rather than a single prediction.
In the new research, Karoly and his colleagues looked at one way to narrow the uncertainty – by better representing how carbon cycles through the atmosphere, oceans and vegetation.
The thinking behind narrowing the range of uncertainty is that it produces more accurate indication of the amount of warming we’re likely to experience in a given time period.
Carbon cycling
The researchers built a detailed simulation of the carbon cycle into a climate model and used it to project temperature rise up to 2100, assuming emission trajectories continue as they are now.
Unlike in previous studies, the researchers used observations of atmospheric carbon dioxide concentrations in the last 50 years to constrain their model representation, making it as realistic as possible.
The results showed that refining the carbon cycle in the model successfully narrowed the range of projected global warming, as the image below shows. One consequence of this, as the Express reports, is that the researchers deemed it “unlikely” we’ll exceed six degrees Celsius of warming this century – which is pretty much the IPCC’s highest-end projection.
Image - Karoly _Temp Proj (note)Global mean temperature rise expected by 2100 for a business-as-usual emissions scenario, relative to preindustrial levels. the black line is the median estimate, the sidebars represent the IPCC’s likely range and the corresponding range from the new study. The black lines within the side bars are the respective best estimates – which don’t differ much. Source: Bodman et al., (2013).
But narrowing the range of uncertainty eliminates the lower extremes too. The research also deemed it “very likely” we will now exceed two degrees warming above pre-industrial levels – a politically significant limit most countries have associated with dangerous climate change, and committed to avoiding.
Although the Express briefly mentions this conclusion, the emphasis is clearly on what’s happening at the top of the temperature scale – as illustrated by the headline ‘Forecasts for global warming ‘too high”.
Contrary to the newspaper’s suggestion that temperature projections are too high, the research actually suggests little change in the best estimate of how much warming we can expect by the end of the century. As the scientists say in the paper:
“[Our projections] show how the uncertainty ranges are reduced, although the central estimates reveal little change.”
No excuse for delay
Climate models contain sources of uncertainty other than the carbon cycle, most notably climate sensitivity – the amount of warming we can expect per doubling of atmospheric carbon dioxide. There’s also uncertainty about aerosols – tiny particles in the atmosphere that can have a warming or cooling effect.
The researchers explain that uncertainty in models should be no excuse to delay action on mitigation and adaptation plans. On the contrary, Karoly says in the press release the group’s findings reinforce the importance of strong action on climate change:
“[The results] reconfirm the need for urgent and substantial reductions in greenhouse gas emissions if the world is to avoid exceeding the global warming target of two degrees Celsius [above pre-industrial levels] needed to minimise dangerous climate change.”
Needless to say this isn’t the angle the Express takes, choosing instead to end the article with a quote from ex-BBC presenter and well-known climate skeptic David Bellamy insisting that “man-made global warming is a myth”.
The Express has particularly bad form when it comes to inaccurate reporting on climate change, and has opted out of the Press Complaints Commission – the process which, in theory, holds newspapers accountable for inaccurate or misleading coverage. That might be particularly worrying when you consider that the newspaper reached an average of more than half a million readers each day last month – the sixth highest of the national dailies.
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Updated 4th June to make it clearer that the major difference between the new study and previous ones is the use of carbon dioxide concentrations in the last 50 years to constrain their model representation of the carbon cycle.