Stronger warming amplification over drier ecoregions observed since 1979

Abstract

Observations show that the global mean surface temperature has increased steadily since the 1950s and this warming trend is particularly strong and linear over land after 1979. This paper analyzes the relationship between surface temperature trends observed over land for the period 1979-2012 and enhanced vegetation index (EVI), a satellite measured vegetation greenness index, by large-scale ecoregion. The land areas between 50°S and 50°N are classified into various large-scale ecoregions based on the climatological EVI values. The regional mean temperature trends exhibit significant spatial dependence on the regional mean EVI. In general, the warming rate increases dramatically with decreasing EVI, with the strongest warming rate seen over the driest ecoregions. When anthropogenic and natural forcings are included, climate models are generally able to reproduce observed major features of the spatial dependence. When only natural forcings are used, none of the observed features are simulated. Furthermore, the simulated temperature changes in the latter are mostly far outside the range of those in the former. These results suggest stronger warming amplification over drier ecoregions in the context of global warming, pointing mainly to human influence.