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'Lethal ice age' prevented by climate change?

  • 09 Jan 2012, 18:28
  • Verity Payne

A Nature Geoscience paper (published online) has found that man-made climate change might delay the onset of the next ice age, expected to begin some 1,500 years from now. This has caused quite a stir among climate skeptics, who have rushed to proclaim that man-made climate change " may save us from the next ice age".

This enthusiastic reporting neatly exposes some inconsistencies in a few of their favourite arguments.

The Nature Geoscience paper: Man-made emissions may delay ice age

It's thought that ice ages are triggered by small changes in the Earth's orbit around the sun. The pattern of these changes indicate that another ice age might begin in around 1,500 years.

However, scientists have now found that man-made greenhouse gas emissions are warming the Earth enough to prevent it from responding in the way that it has over the last million years.

Professor Jim Channell, University of Florida, one of the report's co-authors, explains:

"We know from past records that Earth's orbital characteristics during our present interglacial period are a dead ringer for orbital characteristics in an interglacial period 780,000 years ago."

Scientists would expect the Earth to behave in a similar way to that period, but human greenhouse gas emissions may have disrupted the normal glaciation cycle. As Channell puts it:

"The problem is that now we have added to the total amount of CO2 cycling through the system by burning fossil fuels, the cooling forces can't keep up."

Skeptics struggle to get their story straight

This finding has prompted an excited response from climate skeptic lobbyists and certain newspapers, who are claiming that man-made global warming will ' thwart' the next ice age and is therefore a good thing.

There are three reasons why this is an odd argument. First, it is a tacit admission that man-made climate change is happening, will alter temperatures significantly, and has far-reaching consequences for human society. This might seem like a surprising thing for climate skeptics to admit. It's hardly news however that climate skeptic arguments are often selective and incoherent - as we discussed following the publication of the BEST study results.

Secondly, on at least two occasions last year (see here and here for examples), skeptics were claiming that the Earth was poised to enter a new 'mini ice age'. To subsequently trade on the idea that climate change is good because it will prevent ice ages does look suspiciously like having it both ways at once.

But the biggest problem for the skeptics is that being pleased about a (potential) lack of climate disruption occurring 1,500 years into the future does rather beg the question of why they aren't worried about climate disruption occurring much sooner - over the next century, say.

It's a basic error to sensationalise a possible event that's more than a thousand years away while ignoring the disruption to the climate expected in the interim - but this is exactly what the media coverage does. The Daily Mail opt for the headline ' Human carbon emissions could put OFF a lethal new ice age, say scientists' - parroting the skeptic blogs in claiming that "we would be better off in a warmer world." This statement doesn't fit with the most comprehensive assessment of the scientific literature to date - that conducted by the IPCC in 2007 ( AR4).

Meanwhile the Telegraph turn to climate skeptic lobbyists the Global Warming Policy Foundation (GWPF) for their information:

"The Global Warming Policy Foundation said the study demonstrated that man-made carbon dioxide emissions were preventing a 'global disaster'".

...in 1500 years time, surely?

"The think tank, set up by Lord Lawson, cited a controversial theory proposed by Sir Fred Hoyle and Professor Chandra Wickramasinghe in 1999 which said we 'must look to a sustained greenhouse effect to maintain the present advantageous world climate.'"

One might wonder why the GWPF are focusing on a potential benefit which is 1,500 years away, on the basis of a single scientific paper, when they are so vociferous in their rejection of the consensus scientific position, which is supported by the work of thousands of researchers.

Missing the point

Indeed, the reaction of skeptics to this study misses the point, according to co-author Dr Luke Skinner, department of Earth Sciences at the University of Cambridge. He points out that the skeptic notion that we are somehow 'preserving' our climate by releasing greenhouse gases is flawed:

"Where we're going is not maintaining our currently warm climate but heating it much further, and adding CO2 to a warm climate is very different from adding it to a cold climate.
"The rate of change with CO2 is basically unprecedented, and there are huge consequences if we can't cope with that."

Skinner also comments on BBC Radio 4's Today programme:

"If anything, the study... suggests that the climate system is quite sensitive to quite small changes in CO2, let alone the huge change that we've been responsible for over the last 200 years."

In other words, what Dr Skinner is saying is that you can't have it both ways. If human greenhouse gas emissions are capable of preventing disruptive climate shifts in 1,500 years time, they're capable of causing disruptive climate shifts well before then.

After all, the average global temperature difference during an ice age can be as little as 4°C - and we might see that by the end of the century, never mind in 1,500 years' time.

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