In view of the wide-spread negligence concerning water vapour as the most efficient greenhouse gas, its role in the recent climatic evolution is investigated.Increase of tropospheric water vapour content Bowls/Slides and rising evaporation (by about 15 %) from tropical oceans have been found in recent decades.Evidence for an accelerated hydrologic cycle is given, leading simultaneously to a remarkable intensification of the tropospheric circulation in the Northern Hemisphere.Average geostrophic wind speed at the Nevada surface and in the troposphere have increased by 6-9 % between 1967 and 1989.This (natural) internal feedback through water vapour amplifies the "dry" greenhouse effect of CO2 and other trace gases by a factor of about 5, spreading poleward from tropical oceans.