Summer-time Mediterranean amplification to different climate drivers

The Mediterranean region is particularly sensitive to climate change as it is located at the crossroads of atmospheric processes. In the Mediterranean, and particularly in it’s eastern parts, the rate of warming is more pronounced than the global mean rate of warming, with projected increase up to  2.5-3.0 °C and simultaneous decrease in precipitation of 15 % by the end of the century.

Here, we investigate the contribution of different climate drivers to regional warming trends, focusing in the summer season. We are analyzing surface and atmospheric temperature trends in simulations from nine climate models participating in the Precipitation Driver and Response Model intercomparison project (PDRMIP). The model simulations have assumed idealized and abrupt forcing applied in global scale, specifically: doubling the CO₂ concentrations, 10 times the present-day black carbon concentrations, 5 times the SO₄ concentration, 3 times the CH₄ concentration and 2% increase in total solar irradiance (TSI). Model results are compared with trends in reanalysis datasets and long-term radiosonde soundings in selected locations in the eastern Mediterranean. 

Increases in CO₂, CH₄ and TSI cause a very similar seasonal variation of the temperature amplification, with a stronger magnitude simulated at the upper troposphere. Consistent to the surface amplification, the strongest warming in the upper troposphere is found in the June-July-August (JJA) season. SO₄ causes a stronger upper tropospheric temperature amplification, particularly in July and August. BC aerosols, on the other hand cause a considerably stronger amplification in the JJA season which spreads to the upper troposphere the following months.

Our analysis highlights the important role of aerosols in the observed summer-time temperature trends in the Mediterranean and mechanisms are discussed.