Now we are not so sure

The more scientists know about global warming, the less able they are to predict the outcomes
November 17, 2010
Mexican standoff: climate talks in Cancun have been undermined by the global recession and a loss of confidence in scientists’ forecasts

Cancun in Mexico is one of the least environmentally friendly places on Earth—built out of sandy nothing to attract tourists. Yet it is here, from 29th November to 10th December, that governments will attempt to repair the damage from last year’s failed climate talks in Copenhagen.

In truth, hopes are not high for reaching agreement on a replacement for the Kyoto protocol. After the scale of Copenhagen, Cancun will be a downbeat affair. Heads of state will be largely absent. Even optimists only hope Cancun might be a stepping stone to a deal at the end of 2011.

Three things have gone wrong. First, the global recession has given politicians other priorities. Second, in international diplomacy, failure breeds failure. Having not delivered last year, few leaders want to invest political capital in another try. And finally, there is the cataclysm that has overtaken climate science in the meantime. “Climategate”—the release of damaging emails from the University of East Anglia’s (UEA) Climatic Research Unit—raised questions about the way climate scientists work; as did revelations about flaws in the 2007 assessment of the UN’s Intergovernmental Panel on Climate Change (IPCC). The most notorious was “glaciergate”: a claim that the Himalayan glaciers would melt away by 2035 was probably wrong by about three centuries.

All this has badly drained public confidence in climate forecasts. It may never fully recover and it may not deserve to. Although the basic science behind the argument that we are warming the world is sound, scientists have sometimes skated over the uncertainties about how it will play out. And some have resorted to dubious tricks to simplify their message.

Nobody seriously denies that greenhouse gases like carbon dioxide trap heat, and that this will warm the globe. Nor does anyone doubt that these gases are accumulating in the atmosphere as a result of our activities. But the detail is much less clear. And the climategate emails show how, when challenged, mainstream climate researchers have on occasion preferred infighting to making a scientific case.

This happened when sceptics questioned whether the world today is warmer than 1,000 years ago. The ensuing row about the “hockey stick” graph gave the issue an importance it did not deserve, since natural variability in climate is normal and the precise history of past temperatures sheds little light on future man-made climate change. It happened, too, when sceptics questioned how much urban warming may have distorted records of overall global temperature trends. Again, there was a standoff rather than sensible debate. And the row obscured the fact that “urban heat islands” cannot explain the warming across the two thirds of the world’s surface that is ocean.

More important for the future are unanswered questions about the feedbacks that some scientists believe could roughly triple the initial greenhouse gas effect—such as the white of melting ice giving way to darker ocean; the colour change means that more solar heat will be absorbed. The biggest joker in the pack is the possible change in the amount and type of clouds as the world warms. These could cool us off. But other feedbacks, like methane bubbling out of melting permafrost, could set in motion runaway warming.

Under pressure to deliver simple messages, scientists have often pretended to know more than they do. Their critics have responded by accusing the IPCC of scaremongering. A more rational response might be to fear that, if we know so little, the real outcome could be far worse.

Some leading climate scientists have claimed their critics are motivated by money and politics. One of the most-criticised of the climategate emailers, Michael Mann of Pennsylvania State University, wrote in New Scientist in October that “front groups for the fossil fuel industry have been waging an orchestrated, well-funded campaign against climate science and climate scientists for more than two decades.” This may be true but it is no defence, still less a way to rebuild trust. And certainly some people on the mainstream side of the climate debate are driven by politics and money too.

The good news is that other scientists have responded to criticism by being more honest and humble about the uncertainties. UEA’s Mike Hulme told me the scandals were “a game-changer. The community has been brought up short by the row over their science. There is a new tone. Researchers are more open and explicit about their uncertainties.”

I hear that too, in public meetings with scientists, including a recent debate organised by Southampton’s Tyndall Centre for Climate Change Research. Many scientists realise that less packaging of their message and more candidness is the only way forward. Interestingly, they have been led by the man most vilified by climategate, Phil Jones of the UEA’s Climatic Research Unit, who has responded with what former critic Judy Curry, of the Georgia Institute of Technology, calls “genuine repentance… speaking with humility about the uncertainties in the data sets.”

Meanwhile Bob Watson, former IPCC chairman and now the government’s chief environment scientist, says scientists need to do a better job of sharing not just their uncertainties, but their data. There are already moves to archive large amounts of raw climate data for public access.

This won’t solve science’s problems, however. As Kevin Trenberth, of the US National Centre for Atmospheric Research, has warned: even as the science of climate change accumulates, the uncertainties grow. The existing forecasts of the possible range of warming expected from a doubling of atmospheric CO2 is between 1.8 and 4.0 degrees Celsius. The IPCC’s next assessment is likely to see the range widen—at the top as well as the bottom.

“While our knowledge of certain factors [responsible for climate change] does increase, so does our understanding of factors we previously did not account for or even recognise,” wrote Trenberth in Nature earlier this year. This sounds alarmingly like Donald Rumsfeld’s warning about “unknown unknowns.” Humility may be their best hope. Too often the relationship between scientists and the public is built on a convenient lie. The public wants certainty; scientists pretend to deliver. The debates of the past year have cruelly exposed that lie.

If scientists are to be honest, they will have to hope that wider society—from saloon-bar sceptics to high-level diplomats—will accept that uncertainty has to be the basis for action on climate change. If diplomats in Cancun can reach a deal, that approach has a chance. But if they make scientific uncertainty an excuse for delay, then we may only discover the truth of the predictions when reality hits.