Climate change – more uncertainty or better presentation?


What do the following have in common?  Driving our cars, flying in a plane or using electricity made by burning coal or gas.  They all consume fossil fuels and they all put extra carbon dioxide in to the atmosphere.  The carbon dioxide is a “greenhouse gas” and there is broad agreement among scientists that increases in atmospheric carbon dioxide levels have driven an increase of just under one degree in global temperature during the last century.  There is also broad agreement that if we continue with our cars, planes and electricity the way we are, this will lead to further increases in global temperature coupled with climate instability.  These will lead in time to major effects on human lifestyle.

File:GISS temperature 2000-09 lrg.png
How the planet has warmed over the past 50 years

We rely on climate models to predict the extent of future change in global temperature.  These models are complex computer simulations that try to take account of as many of the variables affecting the climate as possible.  They are, however, only models and their predictions are affected by the uncertainty of some of the information used.  For example, a key variable is the amount of carbon dioxide that will be produced in the future and this is difficult to predict with accuracy, especially with the current economic upheavals. 

A problem is now emerging with the climate models which may provide new ammunition for the climate change-deniers.  The models are becoming ever more sophisticated, which sounds good, but according to Mark Maslin and Patrick Austin, writing in last week’s Nature (“Climate models at their limit”) the new more sophisticated models may contain greater uncertainty in their predictions.   This seems to be because the models now include a wider range of influences on the climate.  If there is uncertainty in each of these influences then there will be even more uncertainty in the outcome.   This does not mean the models are worthless.  The models are still able to predict future climate change; it’s just that there is a bit more wobble on the predictions.

Maslin and Austin are concerned that “To the public and to policy makers, this will look as though the scientific understanding of climate change is become less, rather than more, clear.”   

They continue: “Scientists need to decide how to explain this effect.  Above all, the public and policy makers need to be made to understand that climate models may have reached their limit.  They must stop waiting for further certainty or persuasion and simply act.”

Maslin and Austin propose a subtle change in presentation of modelling data and call this the “when” not “if” approach.  They suggest placing the uncertainty of predictions on the date by which things will happen rather than onto whether they will happen at all.   

Let’s restate this to emphasise this important conclusion:  we know that climate change is occurring and will get worse but we cannot be sure about the precise time scale.

Somehow also we need to unblock the political process whereby so little is being done about the problem of global warming.  As Maslin and Austin put it “Politicians use public opinion and scientific uncertainty as excuses for inaction.  They used to say “we need to wait until scientists prove that mankind is causing climate change”.  That hurdle has, arguably, passed, so now they have moved on to “we need to wait until scientists can tell us exactly what will happen and what the costs are” or “we need to wait for public opinion to be behind action””. 

The reality is that scientists have already provided enough information showing that something needs to be done to halt climate change.  All countries now need to set carbon reduction targets.  These do not need to be the same for all countries and may reflect different local circumstances but unless we move to carbon reduction there will at some point be severe consequences for the planet.

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