The cause of Global Warming and Climate Change.
The prime factor governing the “Global Warming”, resulting in “Climate Change”, is the radiation from the Sun which gives a varying energy flux of about 340 W/m2 (Watts per square meter) entering the Earth´s atmosphere. Of this amount 30% or about 100 W/m2 is reflected back into space while the rest, or about 240 W/m2, is absorbed by land, water and the atmosphere (including clouds). The increasing amounts of greenhouse gases 'emitted by human activities do, however, change this equilibrium of energy flux – although only slightly – by increasing absorption of part of the Sun radiation. The increase of absorption during the last 250 years has been estimated to be about 2.4 W/m2 which corresponds to about only 1% increase of the absorption. Although comparatively small this amount is significant in terms of global warming and of climate change. Small changes – large effects!
The transfer of the energy to the greenhouse gases starts by the back radiation from the Earth´s surface. The greenhouse gases have the property of absorbing the infrared and its nearby parts of the spectrum of the back radiation. This absorption of the back radiation results in a rise of the air temperature. Besides that H2O is more abundant in the atmosphere than the other major greenhouse gases (about 80 times more abundant than CO2 ) it has very strong absorption properties. It also has a feedback effect due to cloud formation reflection. NASA has by measurements with the Atmospheric Infrared Sounder onboard its Aqua Spacecraft found that water vapor amplifies the warming caused by increased levels of CO2 in the atmosphere. By extensive spectroscopic investigations it has been found that there is considerable excess absorption that cannot be solely attributed to monomeric H2O. This excess absorption is referred to as the water vapor continuum.
Among the increasing amounts of the major greenhouse gases CO2, H2O, CH4 and N2O in the atmosphere it is the increasing amounts of H2O (= water vapor) that are most responsible for the temperature increase and the climate change. H2O can be loaded with large amounts of latent heat that can be transported and released under specific conditions. To evaporate 1 kilogram of water at the temperature of 20 degrees centigrade about 2450 Joules is required and about 2250 Joules at 100 degrees centigrade. The rise of the temperature from human activities means that the atmosphere can carry more water vapor and more latent heat and therefore more and heavier rain falls, floods and severe weather phenomena can appear. It is a great energy transport system.
Increasing amounts of H2O in the atmosphere – both as water vapor and in liquid form (in clouds) – is the major cause of the temperature increase and the climate change by its strong infrared radiation absorption capacity. The solution of the problem of increased global warming and climate change has to take H2O into account in the first place.
(The description above refers to the particular solution of the “global warming-climate change problems” which has been developed and does not totally exclude the influence of other causes of the “global warming” and the “climate change” problems like those due to variations of the solar radiation intensity or due to soot and other particles in the air and deposited on the ice and snow covered or other areas of the Earth or due to the warming effects of other minor greenhouse gases.)
Remark: IPCC (The Intergovernmental Panel on Climate Change) has been using the term “radiative forcing” for greenhouse gases as a measure of the “greenhouse effect”. It has been given an exact definition and expressed in watts per square meter. Although water vapor is a major greenhouse gas radiative forcing has not been used for this gas.