Kirsten L. Findell, Alexis Berg, Pierre Gentine, John P. Krasting, Benjamin R. Lintner, Sergey Malyshev, Joseph A. Santanello Jr., Elena Shevliakova. Nature Communications.

Land surface processes modulate the severity of heat waves, droughts, and other weather extreme events. Vegetation and surface moisture conditions have been shown to impact both the severity and duration of heat wave events, as well as future aridity over land. An earth system model, GFDL’s ESM2G, was used to investigate the regional impacts of historical anthropogenic land use/land cover change (LULCC) on combined extremes of temperature and humidity. The authors show that conversion of forests to cropland has contributed to much of the upper central U.S. and central Europe experiencing extreme hot, dry summers every 2-3 years instead of every 10 years.

Assessing temperature and humidity offers a more complete measure of global change in extremes, as both are central to human experience of near-surface climate conditions. This work highlights the importance of vegetation cover and land use practices for regional climate extremes.

Figure 1: Red colors indicate regions where anthropogenic conversion of native land cover to crops and pastures has increased the occurrence of hot/dry June months from once-in-a-decade to once every 2-3 years.
Figure 2: Mean differences resulting from anthropogenic LULCC for June-August (JJA) in the northern hemisphere and for December-February (DJF) for the southern hemisphere in (λq, cpT) phase space, with differences of 2m values of λq and cpT plotted according to the 2-dimensional colorgrid shown at the right. q is specific humidity, λ is the latent heat of condensation, T is temperature, and cp is the specific heat of dry air at constant pressure.