Proceed with planning despite multiple models.

In his News Focus story “Time to adapt to a warming world, but where's the science?” (25 November 2011, p. [1052][1]), R. A. Kerr reports on the frustration expressed at a recent meeting in Denver about the lack of “actionable science” that can be used as a basis for planning adaptation to climate change. Understandably, people planning new storm drain systems with a 75-year lifetime, for example, would like to know the maximum flow of water they will need to accommodate over that period. The general expectation seems to be that if we can just get more accurate and more granular climate models, then we can provide definitive answers to this type of question. Unfortunately, even if we can deal with the tremendous complexity of the physical and biological mechanisms involved, as Lempert et al. have pointed out, predicting the future is fundamentally impossible, as it will be influenced by people's future actions, which are currently unknown ([ 1 ][2]). It is productive to consider multiple scenarios of plausible futures (as the Intergovernmental Panel on Climate Change has done) and formulate plans and strategies that provide acceptable outcomes across a broad range of possibilities, rather than to try to find an optimum solution based on a single forecast of future climate. Better climate models will certainly play a key role in making the scenarios more realistic, but we will not enjoy the luxury of having definitive forecasts on which to base our adaptation planning. 1. [↵][3] 1. R. Lempert 2. et al ., Shaping the Next One Hundred Years (RAND Corporation, MR-1626, 2003). [1]: /lookup/doi/10.1126/science.334.6059.1052 [2]: #ref-1 [3]: #xref-ref-1-1 "View reference 1 in text"