Swimming against the tide of scientific opinion on climate change
This post by Ros Donald first appeared on The Carbon Brief.
Environment secretary Owen Paterson gave the public an insight into his views on climate science on the BBC’s Any Questions last week. For a minister whose remit includes preparing the UK for the effects of climate change, especially the prospect of more flooding, his views on the causes of atmospheric warming seemed worryingly at odds with the weight of scientific opinion.Paterson, secretary of state for the Department of Environment, Food and Rural Affairs (Defra) as of last year, has been fairly tight lipped about his views on climate change. So we listened with interest when he answered a question about climate change from the audience (at around 33 minutes in the recording).
It didn’t begin promisingly. Paterson opened with the assertion that “the climate’s always been changing”. The evidence? Periods of earlier warming and cooling such as the Little Ice Age, and the Medieval Warming Period. But the real question, Paterson said, is whether warming “is being influenced by man-made activity in recent years”.
Natural variability alone can’t explain the temperature rise
So what does the science say in response to Paterson’s question? Human impacts aren’t the only things affecting global temperature. As history has witnessed in the periods he cites, natural fluctuations in the climate, such as volcanic eruptions and changes in the amount of solar energy reaching earth, can produce warming or cooling effects.
But natural variability alone cannot explain the observed temperature rise in the last century, as the emissions produced by industrial activity have started to mount up. In fact, if you subtract all known natural influences on global temperature over the last 30 years, you can see the long term warming trend due to greenhouse gases in the atmosphere.
The evidence is now so strong that the Intergovernmental Panel on Climate Change (IPCC) says it’s at least 90 per cent certain human activity is responsible for most of the observed temperature increase since the 1950s, mainly through burning fossil fuels. In a draft of the next IPCC report, due out in September, this conclusion looks set to be strengthened to “extremely likely”, which means at least 95 per cent certainty.
Recent warming has been uneven
Moving to present day warming, Paterson seemed unsure about whether human activity is having much effect on current temperatures. He said: “[T]he climate has not changed. The temperature hasn’t changed in 17 years.”
Paterson was referring to the fact that earth’s surface – that’s the land and top of the oceans – has warmed relatively slowly over the past fifteen years or so, compared to previous decades.
Scientists are well aware of this. In fact, periods of slow surface temperature rise aren’t particularly unusual. The likely reason for them is natural variability redistributing the sun’s heat into different parts of the climate system, notably the oceans.
In other words, the world is still warming, but less warming in one part of the climate system is balanced out by more warming in another.
It’s not just about the atmosphere and the oceans – there are many other indicators of the changing climate which show little sign of pausing. Arctic sea ice is diminishing more rapidly than scientists expected, while ice loss from the Greenland and Antarctic ice sheets is also accelerating.
Criticising government policy, but on shaky ground
Despite acknowledging “there is almost certainly bound to be some influence by man-made activity”, Paterson went on to implicitly criticise the policies the government has put in place to meet its legally binding commitments to cutting the UK’s carbon emissions. He said: “The measures that we take to counter climate change may cause more damage than they gain. They may just export the problem… There is absolutely no gain whatever in closing down industrial activity here to give everyone a warm feeling and then buying industrial products from China … China and India are building a new coal power station virtually every week.”
He was pointing out some genuine concerns. Some research has suggested that the government’s environmental policies are pushing the cost of energy for the UK’s industrial players beyond the amount that their competitors play, though mostly through exemptions to their climate policies.
Then there’s the problem of imported emissions, which the Committee on Climate Change has highlighted recently. But criticising policies is one thing; it’s another to do so on the basis of a shaky scientific argument.
More importantly in this case, climate policy isn’t just about combating emissions. In areas like flood defences, Defra is likely to have an increasingly important role in helping the country prepare for and adapt to the changing climate. It’s a mandate that depends on crafting policy to meet current and future threats based on mainstream climate science. So the fact that Paterson seemed at the very least confused about where the weight of scientific opinion about climate change lies could be cause for concern.