Ik citeer even uit Fontiers of Climate Modeling (edited by JT Kiehl en V Ramanathan), 2006, hoofdstuk 9: water-vapour feedback, geschreven door David H Rind (medewerker aan nasa goddard institute of space studies):
'Trends in stratospheric water vapour have recently become of great interest, as it appears as if water vapour in this region has been increasing by about 1% per year (Oltmans e al.,2000; Rosenlof et al., 2001). It is larger than would be implied by methane increases, and may be due to added water vapor in the upper troposphere, or more water-vapor advection through the sub-tropics, hence avoiding the tropical "cold trap" associated with minimum tropical tropopause temperatures (Rosenlof et al., 2001). It is apparantly not due to increased tropical tropopause temperatures, for they appear to be decreasing (e.g., Zhou et al., 2001). Whatever the reason, Shindell (2001) has calculated that it may have contributed ~24% to global warming over the past two decades.'
Die toename aan stratosferische waterdamp werd al vastgesteld in het vorige IPCC rapport, maar echte gevolgen (in de orde van het door Shindel gegeven effect)voor de temperatuur werden daar toen niet aan gekoppeld.
mvg,
Dieter
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