Nature http://doi.org/hv9 (2012)

Credit: © ISTOCKPHOTO/THINKSTOCK

Artificial warming experiments are a key line of evidence used to estimate plant responses to climate change. Changes in phenology (the timing of recurring life-history events), such as advances in the timing of flowering and leafing, are key ecological responses to climate change that have been widely recorded and therefore offer a useful means to investigate the ability of warming experiments to reproduce observed responses.

Elizabeth Wolkovich, of the Division of Biological Sciences, University of California San Diego, USA, and co-workers compared phenology in observational studies and warming experiments spanning four continents and over 1,600 plant species using a common measure of temperature sensitivity (change in days per °C).

The results show that compared with observations, warming experiments under-represent advances in the timing of flowering and leafing by 8.5-fold and 4.0-fold respectively. The observational data also showed that species that flower earliest in the spring have the highest temperature sensitivities — a trend that was not reflected in the experimental data. The authors caution that responses to climate change that are predicted solely from experiments should be re-evaluated.