As different as night and day

Abstract

An analysis of northern ecosystems shows that the effects on plant growth of rising night-time temperatures are opposite to those of increasing daytime temperatures — a finding that has implications for carbon-cycle models. See Letter p.88 Modelling and observational studies suggest that climate warming is likely to enhance vegetation growth in northern terrestrial ecosystems, increasing carbon storage. However, for the past 50 years the global land surface temperature has been warming faster during the night than during the day, and little is known about the potential effects of this asymmetry on the productivity of plants. Multiple lines of evidence presented in this study, including 28 years of satellite-derived data on vegetation greenness and extensive atmospheric CO2 measurements, suggest that day and night-time warming have divergent effects on vegetation productivity in the Northern Hemisphere. Daytime warming is associated with increasing productivity in wet and cool areas over boreal regions, but with decreasing productivity in dry temperate regions. In contrast, night-time warming decreases vegetation growth in boreal regions, but has mixed effects in dry temperate regions.