Nature Climate Change | Climate Feedback

Climate Prediction: keeping it in perspective

Olive Heffernan

<img alt=“oct2009_1_3_orig2.jpg” src=“http://blogs.nature.com/climatefeedback/oct2009_1_3_orig%5B2%5D.jpg” width=“254” height=“170” align=“right” hspace=“10px”//>“Imagine farmers being able to determine what to plant and where based on drought forecasts three to five years out”, said Jane Lubchenco, head of NOAA, in Geneva last month.

Speaking to delegates at the World Climate Conference, Lubchenco was lending her voice to the vision of climate services, which would deliver climate predictions as reliable and useable as weather forecasts, and tailored to meet the needs of specific end-users. Underlying the vision of climate services is the assumption that further research will result in reliable climate predictions indispensable to adaptation planners.

In July, Germany opened a centre in Hamburg to provide the nation with such services. The Waxman-Markey Bill, passed by the US House of Representatives in June, would launch a similar service within the US, and headed by NOAA, to develop and distribute climate information and predictions to decision-makers.

But in a new Commentary on Nature Reports Climate Change, Mike Hulme and co-authors urge caution in relying on climate predictions to aid adaptation. They write:

Scientists and decision-makers should treat climate models not as truth machines, but instead as one of a range of tools to explore future possibilities.

They highlight that unlike weather forecasts – whose value in informing decision-making can routinely be tested over time by comparison with observed weather patterns – the skill of climate predictions is unknown, especially at the decade-to-century timescale.

Hulme and co-authors illustrate the perils of relying on the predict-then-adapt mode of planning with an example from the Australian state of Victoria. In this case, predictions from a 2005 study of the water supply to Melbourne assured decision-makers that existing plans provided a sufficient buffer against projected climate change up to 2020. But by 2006, water supply levels had dropped far below that predicted even for the most severe climate change scenario (see figure below).

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Their point is not to abandon hope of developing skillful climate predictions or to pooh-pooh the nation of climate services, but to highlight that there are a range of approaches that can be used selectively, or in combination, based on the problem at hand. Building a climate-resilient future is about much more than straining to know the unknowable, they say.

Read the Commentary in full here (free access).

Image: Jane Lubchenco addresses delegates at the World Climate Conference in Geneva, September 2009. NOAA

Figure legend: Victoria state commissioned a 2005 modelling study that projected a decline in average annual flow by 2020 of between 3 and 11 per cent, and concluded that measures in place “were an adequate buffer”. Yet the average flow for the three years since 2005 was nearly 50 per cent below the 1913–2005 average, prompting an entirely new investment strategy. Our Water Our Future The Next Stage of the Government’s Water Plan. State of Victoria Department of Sustainability and Environment June 2007.

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