On the consistency of trends in radiation and temperature records and implications for the global hydrological cycle

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Abstract

[1] Several studies indicate that incident shortwave radiation at land surfaces has significantly decreased between 1960 and 1990. Despite this, land temperature has increased by 0.4°C over the same period. From a surface energy balance perspective, this counterintuitive behaviour can be resolved either 1) through an increase in the downward longwave radiation which outweighs the decreased insolation or 2) through a decrease of surface evaporation and associated reduced evaporative surface cooling. It is suggested that 1) may not be large enough, so that the available energy for evaporation may rather have decreased than increased over the period considered. This is in line with an analysis of observed surface net radiation records. The inferred decrease of evaporation would further imply that the observed intensification of the hydrological cycle over extratropical land has been more likely due to increased moisture advection from the oceans than due to increased local moisture release through evaporation.

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