Science, scepticism and climate change

Dr Vicky Pope, head of the climate change office at the Hadley Centre (one of the world’s most reputable sources of climate change modelling) recently wrote a thoughtful piece for The Guardian which everyone concerned with climate change should read.

The Hadley Centre has been one of the research organisations consistently alerting the world community to the reality and potential dangers of climate change.  Much of the development of climate change modelling has been carried out at the Hadley Centre.  This modelling has informed the IPCC’s reports over the past decade.

So on the face of it, it may seem surprising to read Dr. Pope’s plea for ‘reining in’ claims about climate change.  It may be taken as support for climate change scepticism.  Not at all.  But it is a plea for scientific care and probity that is well worth reading.

Dr. Pope’s point is that inferring trends from climatic data of all kinds is extraordinarily difficult.  There are no simple leaps of logic to be made.  In particular, it is dangerous to make simplistic inferences from isolated observations.  For example, climate sceptics often argue that the world has cooled over the past ten years.  Dr Pope points out that 1998 had the highest temperature on record because of the superimposition of an El Nino event on the long-term warming trend.  2008 was slightly cooler because of the superimposition of an El Nina event on that trend; but it was still the 15th warmest year on record.

The combination of natural variability and the time-scales needed to observe trends make it very difficult to make valid inferences.  Sophisticated statistical treatment and computer modelling is the only valid way of scientifically extracting such underlying trend information from the statistical noise.  It is now well established that the scientific models cannot account for observed global warming by using only natural factors: anthropogenic factors are required to account for it fully.

It’s important to bear in mind this kind of careful investigation and interpretation when evaluating new data.  For example, it is at present being widely reported that researchers have found increasing ice in Antarctica, not decreasing; this, some sceptics have immediately argued, shows that climate change is not occurring.  Not so.  When you look at the research in details, you find that what is being reported is increasing ice in East Antarctica and increased melting in West Antarctica.  Moreover, the increase in ice in the east is coming about from increased snowfall, one of the long-held predictions of climate change models for that region.  Hence the findings are supporting the predictions of current climate change models.

Similar claims are being made with respect to Greenland’s ice-cap, from both sides of the equation.  Dr Pope points out that both positions are unsupported:  the natural variability of Greenland ice makes them scientifically untenable.  She argues that overplaying natural variations as demonstrating climate change is as damaging as underplaying it: both are distortions, and entirely unhelpful to the complex task of seeing the underlying facts.

Dr Pope’s main plea is for careful, conservative science, to ensure that the scientific facts on climate change are able to speak for themselves, without being diverted by this kind of frivolous attack.  These kinds of diversions “undermine the basic facts that the implications of climate change are profound and will be severe if greenhouse gas emissions are not cut drastically and swiftly over the coming decades.”

The facts, Dr Pope notes, don’t need to be exaggerated in order to have their effect: they are already beyond serious in their implications.  Her sober conclusion is worth hearing by people of all climate change persuasions:

“When climate scientists like me explain to people what we do for a living we are increasingly asked whether we “believe in climate change”.  Quite simply it is not a matter of belief.  Our concerns about climate change arise from the scientific evidence that humanity’s activities are leading to changes in our climate.  The scientific evidence is overwhelming.”