US heatwave raises climate complexity

Children playing in hydrant water Image copyright AP
Image caption US beliefs on climate change have stayed more or less constant, whatever the weather

In the last couple of Northern Hemisphere winters, with temperatures plummeting across tracts of North America and western Europe, "belief" in man-made global warming - it was widely reported - took a bit of a dip.

As to why that might be, there was no hard evidence - but plenty of the anecdotal stuff around in comments on blog posts, and from callers to phone-in programmes, suggested the weather was indeed an issue.

A recent opinion survey in the US produced an intriguing and somewhat perplexing insight into all this.

The Climate Communication programmes at Yale and George Mason Universities asked people whether their views on the issue were affected by weather extremes.

About half either "strongly agreed" or "somewhat agreed" that cold snaps had made them question their belief in global warming, while a similar proportion said heatwaves had strengthened their belief.

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Image caption Bill Maher: time to go beyond doubt on warming

So here's the conundrum.

The Yale/George Mason survey, and another from Rasmussen Reports, showed that about 60% think the world is warming, but are about evenly split on whether humanity or natural forces are the primary factor.

Those proportions have hardly changed in three years.

Perhaps people have been pushed in both directions - to strengthen their beliefs on the basis of last summer's heatwave, and to question their beliefs by the last two cold winters; who knows?

The current heatwave is unusually intense, so there must be a question over whether it will change views more than most.

The inference that any day's weather is related to the slow progress of global warming is one of the things that scientists find most frustrating - although comedian Bill Maher probably expresses that frustration more pithily than most scientists, commenting that not believing in climate change because it's snowing "is like saying the Sun might not be real because last night it got dark".

This is why columnist Thomas Friedman advocates the term "global weirding" rather than "global warming", because it includes the apparently contrary impacts that can result from an overall increase in global temperatures, such as cold snaps.

But other elements of the media have not been so keen to make clear distinction between weather and climate; and overall, the scientists who blame the media for the conflation may have a point.

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Image caption New York mayor Michael Bloomberg has added his voice - and money - to ending coal dependence

Another of their common complaints is over "false balance" - an issue that the BBC Trust has just addressed in its review of BBC science coverage.

In the US, the Yale/George Mason survey showed that 40% of Americans believe "there is a lot of disagreement among scientists about whether global warming is happening".

This is clearly not the case, as illustrated by surveys of scientists themselves; yet, somehow the perception of much doubt in the ivory towers has been promulgated, for which again the media - or parts of it, at any rate - must take part of the blame.

Climate science is a complex business and, you might argue, getting more complex all the time as we learn more about aerosols (the theme of my last post), cloud feedbacks, natural cycles, and so on.

The current US situation adds a new layer of complexity.

Because of the increased demand for air-conditioning during heatwaves, consumption of electricity rises.

As almost three-quarters of US electricity comes from burning fossil fuels, mainly coal, a spike in carbon emissions is very likely - as it is during cold snaps in winter.

From an individual weather event, the impact is small; but heatwaves are projected to become more frequent in parts of North America where they already occur as the global average temperature continues to rise - which, if those projections become reality, will mean a greater need for air-conditioning.

Despite the US history as a wind power pioneer, it lags a long way behind countries such as Spain and Germany in terms of the proportion of its electricity generated by renewables.

The future of its nuclear programme, like many others, is uncertain. And its "clean coal" research and development programmes are being shelved faster than you can say "parasitic power" - again, like those in many other countries.

Which basically leaves the US more and more dependent on coal for the electricity it is going to need in greater and greater quantities as the economy recovers and the population increases.

Throw in the potential for additional demand from more frequent heatwaves or cold snaps or both, and you have one of several human-mediated positive feedback loops for the climate.

There are other human-mediated feedbacks as well - another is the current search to open up the Arctic for oil exploration as the ice melts, because burning that will put more CO2 into the atmosphere which will melt the ice faster... and so on.

Explaining that one may not be straightforward either. But we have to if societies are to make decisions based on something more sensible than what the weather is like today.