For those whose curiosity has been piqued by the Himalayan glacier error in the IPCC’s report, Nature magazine has a great article on the real holes in climate science. Far from undermining climate science, though, it underlines the importance of continuing research.
The story notes that the IPCC highlights 54 ‘key uncertainties’ in its 2007 report, but it picks out four key areas of concern:
Regional climate prediction: “To plan for the future, people need to know how their local conditions will change, not how the average global temperature will climb. Yet researchers are still struggling to develop tools to accurately forecast climate changes for the twenty-first century at the local and regional level.” This makes it difficult for countries to make specific adaptation plans – and simply extrapolating from global forecasts risks enhancing weaknesses in the broader model.
Precipitation: Knowing how rising temperatures will affect the hydrological cycle – more simply, evaporation and rain – is another challenge. Different models agree that subtropical areas will be dryer, increasing precipitation at higher altitudes. But beyond that, they tend to diverge. Robust predictions were particularly problematic for winter precipitation, which is most important for water supplies. And, worryingly, the models appear to underestimate the changes that have already occurred.
Aerosols, or airborne liquid or solid particles, are also a big source of uncertainty. Exactly how aerosols interact with sunlight and clouds to affect the temperature, and how extensive their effects are, is not clear. Actual data on the presence of aerosols is lacking too. (Bad news, we suspect, for those putting hope in geo-engineering based on aerosols.)
Tree rings: The subject of much of the controversy over the climategate emails, and the Michael Mann/Stephen McIntyre debate. In short, tree rings are one of several ‘proxy’ records used to estimate temperatures pre-1850, or before more reliable records were kept. While they mostly reflect known changes in temperature, tree rings from a few sites began to diverge from the recorded temperatures in recent decades. Why this happens isn’t known – “It may be that when temperatures exceed a certain threshold, tree growth responds differently,” writes Nature. In any case, the ‘trick’ referred to by Phil Jones in the most famous climategate email involved substituting actual temperature data for those trees when they did begin to diverge.
However as the story concludes, the IPCC’s recommendations were based on the totality of research, and not on any one particular observation.
Nature also takes a look at the six most enduring climate myths, featuring all the classics such as ‘global warming stopped 10 years ago’ and ‘temperatures were higher in pre-industrial times’.
Himalayan glaciers – another climategate? Not quite (FT Energy Source, 19/01/10)
Top 10 questions for 2010: Climate change and clean tech edition (FT Energy Source, 23/12/09)