Tuesday, 26 January 2010

Scientists must rein in misleading climate change claims

Overplaying natural variations in the weather diverts attention from the real issues
Comments (235)
Vicky Pope
guardian.co.uk, Wednesday 11 February 2009 12.30 GMT

News headlines vie for attention and it is easy for scientists to grab this attention by linking climate change to the latest extreme weather event or apocalyptic prediction. But in doing so, the public perception of climate change can be distorted. The reality is that extreme events arise when natural variations in the weather and climate combine with long-term climate change. This message is more difficult to get heard. Scientists and journalists need to find ways to help to make this clear without the wider audience switching off.

Recent headlines have proclaimed that Arctic summer sea ice has decreased so much in the past few years that it has reached a tipping point and will disappear very quickly. The truth is that there is little evidence to support this. Indeed, the record-breaking losses in the past couple of years could easily be due to natural fluctuations in the weather, with summer sea ice increasing again over the next few years. This diverts attention from the real, longer-term issues.

For example, recent results from the Met Office do show that there is a detectable human impact in the long-term decline in sea ice over the past 30 years, and all the evidence points to a complete loss of summer sea ice much later this century.

This is just one example where scientific evidence has been selectively chosen to support a cause. In the 1990s, global temperatures increased more quickly than in earlier decades, leading to claims that global warming had accelerated. In the past 10 years the temperature rise has slowed, leading to opposing claims. Again, neither claim is true, since natural variations always occur on this timescale. For example, 1998 was a record-breaking warm year as long-term man-made warming combined with a naturally occurring strong El Niño. In contrast, 2008 was slightly cooler than previous years partly because of a La Niña. Despite this, it was still the 10th warmest on record.

The most recent example of this sequence of claim and counter-claim focused on the Greenland ice sheet. The melting of ice around south-east Greenland accelerated in the early part of this decade, leading to reports that scientists had underestimated the speed of warming in this region. Recent measurements, reported in Science magazine last week, show that the speed-up has stopped across the region. This has been picked up on the climate sceptics' websites.

Again, natural variability has been ignored in order to support a particular point of view, with climate change advocates leaping on the acceleration to further their cause and the climate change sceptics now using the slowing down to their own benefit. Neither group is right and all that is achieved is greater confusion among the public.

What is true is that there will always be natural variability in the amount of ice around Greenland and that as our climate continues to warm, the long-term reduction in the ice sheet is inevitable.

For climate scientists, having to continually rein in extraordinary claims that the latest extreme is all due to climate change is, at best, hugely frustrating and, at worst, enormously distracting. Overplaying natural variations in the weather as climate change is just as much a distortion of the science as underplaying them to claim that climate change has stopped or is not happening.

Both 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.

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.

• Dr Vicky Pope is the head of climate change advice at the Met Office Hadley Centre

Climate change: give us science we can trust

It becomes difficult to resist the climate-change sceptics if the IPCC's research can't be relied on.

For those of a sceptical disposition who have been persuaded by scientists to adopt the view that global warming is either a man-made phenomenon or has been exacerbated by human economic activity, these are unsettling times. Over the past week or so, some of the supposed evidence for what we are invited to believe is no longer a contestable truth contained in the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) in 2007 has been called into question.
Last week, we learnt that an assertion that glaciers in the Himalayas were melting so fast that they would disappear by 2035 (always a far-fetched notion) was based on a single quote in a science journal news story, never repeated in peer-reviewed literature. The IPCC quickly admitted the error but dismissed it as an aberration carried on just one page of a report thousands of pages long.
However, the weekend brought further disclosures that claims in the report blaming rising temperatures for an increase in the number and severity of natural disasters such as hurricanes and floods had not been properly reviewed by other scientists. It is true that the first people to apologise for these errors and to promise to rectify them were the IPCC scientists themselves, who understand how important it is for the credibility of their case that the evidence on which it is based is copper-bottomed.
The continuing controversy over the dossiers compiled to justify the case for a war in Iraq are testament to the dangers of seeking to include conjecture as fact in order to reinforce a preferred conclusion. We have argued that a conservative case for preserving the planet's scarce resources should support much of the action demanded by concerned scientists, whether or not the case for man-made global warming can be proved. But it becomes difficult to resist the blandishments of the sceptics if a purportedly scientific document cannot be wholly relied on. The most charitable interpretation is that the drafters were sloppy.
Two things are now required. First, when the fifth IPCC report is prepared for publication, any errors must be fully acknowledged and others removed. In addition, the report should contain contrarian evidence produced by scientists to demonstrate that this is a serious document, not a holy writ. Second, the chairman of the IPCC, Rajendra Pachauri, should step down. This will please environmentalists since he was appointed after the uber-sceptic George W Bush objected to his predecessor, Dr Robert Watson; but Dr Pachauri no longer carries the credibility that is required to take this hugely important debate forward.