That's
because water vapor increases by roughly 7 percent for every degree Celsius of warming in the lowest level of the atmosphere — or, more simply put, warmer air means warmer water, which means more of it in the form of vapor.
That exception is that the GCMs apply the Clausius - Clapeyron equation to
make water vapor increase following (lagging) increased surface temperature.
Modeled values are taken from runs with greenhouse gas (ghg) increases, but fixed water and ozone (G); Ozone, with ghg and chlorine changes, calculated ozone, and fixed water vapor (G + O); MethOx, with ghg and chlorine changes, calculated ozone, and
water vapor increases due to methane oxidation (G + O + M); and Water, with ghg and chlorine changes, calculated ozone, and increased water from methane oxidation and transport (G + O + M + W).
The Equilibrium Climate Sensitivity (ECS) The Economist refers to is how much Earth temperatures are expected to rise when one includes fast feedbacks such as
atmospheric water vapor increase and the initial greenhouse gas forcing provided by CO2.
Redently scientists that have measured the water vapor content of the atmosphere have deduce the amount
of water vapor increase has been about 1 % per year over the past ten years.
Early results show that as
water vapor increased, thicker clouds would have reflected up to half of the sunlight back into space.
Predictions related to the impact of pinatubo, post 1984 trends, the «satellite cooling» mismatch, lgm tropical sst,
water vapor increases, ocean heat content etc have all been made and verified within a short time period.
This heat - trapping, warming influence of the blanket of air over the Earth's surface is called the greenhouse effect, and it will become even stronger as greenhouse gases such as carbon dioxide, methane and
water vapor increase in concentration.
atmospheric absorption by CO2 and
water vapor increases, reducing the solar heating at the surface, and surface evaporation increases faster with temperature than the transfer of sensible heat (due to the Clausius - Clapeyron relation), both of which tend to reduce the diurnal cycle.
Because rising greenhouse gas emissions account for all or part of
the water vapor increase, it is likely to continue for many decades.
Or a little less, as
water vapor increases.
Ozone changes in 2055, when the projected equivalent chlorine loading returns to its 1980 value, show the positive impact of stratospheric cooling by GHGs and the negative impact of
water vapor increases, which outweigh the cooling.