Why is the content of this map important?
Changes in evapotranspiration play a central role in global change. Evapotranspiration is directly coupled to the surface energy balance and thus also to near-surface temperatures; it affects river flow as water lost by evapotranspiration no longer exists in the river systems; and it directly influences the growth of crops and natural vegetation.
Which sectors are affected by this result?
Evapotranspiration is a crucial member of the entire climate system and hence influences in some way all climate variables. Changes in evapotranspiration directly affect the availability of water and the growth of crops and natural vegetation.
What is shown on the maps?
The spatial pattern of the change in evapotranspiration mimics that of the change in precipitation, reaching maximum values in the Alps at somewhat greater than +0.10 mm/d. A more or less fixed fraction (generally 30 to 50 %) of the increase in precipitation is counteracted by enhanced evapotranspiration. Decreases in precipitation in parts of the Mediterranean region lead to less evapotranspiration. Increases in evapotranspiration reach an annual maximum in Spring, when changes in the duration of snow-cover are large and temperatures relatively high, especially in the Alps, Fennoscandia and the former Soviet Union. The largest declines in evapotranspiration occur in Summer on the Iberian Peninsula, South France and Bulgaria, due to declining amounts of soil moisture.
Details and further information:
The map of annual mean evapotranspiration during the baseline period shows that evapotranspiration increases in southerly directions from North Fennoscandia (regions with ~0.3 mm/d) to the northern part of the Mediterranean region (regions with 1.6 mm/yr). This is due to increases in temperature and solar radiation towards the South. This tendency weakens in the Mediterranean region where soil moisture is often limited. Evapotranspiration is also subdued in mountainous region like the Alps, because compared to adjacent regions temperatures are lower and the surface is more often covered by snow.
Wouter Greuell
Wageningen Universiteit (WU), Netherlands