Climate models have invariably predicted that the upper atmosphere would become moister as a result of global warming, the question remained whether these disturbances are natural or anthropogenic.  A new research that used satellite readings found that indeed rising vapor content in the upper troposphere comes as a result of man-made global warming. The findings further strengthen climate models and add to a body of evidence that supports anthropogenic climate change.

A wetter atmosphere

The authors write in the paper abstract, published in PNAS :

“Our analysis demonstrates that the upper-tropospheric moistening observed over the period 1979–2005 cannot be explained by natural causes and results principally from an anthropogenic warming of the climate. By attributing the observed increase directly to human activities, this study verifies the presence of the largest known feedback mechanism for amplifying anthropogenic climate change.”

The amount of water vapor in the atmosphere exists in direct relation to the temperature. If you increase the temperature, more water evaporates and becomes vapor, and vice versa. So when something else causes a temperature increase (such as extra CO2 from fossil fuels), more water evaporates. Then, since water vapor is a greenhouse gas, this additional water vapor causes the temperature to go up even further. Effectively, water vapor causes a positive feedback loop and it can get quite dangerous. According to skepticalscience.com, for every 1°C change caused by CO2, the water vapor will cause the temperature to go up another 1°C.

Climate change models predict a moistening of the atmosphere. Researchers at the University of Miami sought to make the first measurements and thus verify whether or not the model projections of anthropogenic climate change are genuine. Radiant heat was measured using satellite imaging and they found that it has changed over the past 30 years. This change could be attributed to increased temperature or water vapor, so to separate potential effects the researchers complemented their initial readings with others made at different wavelengths.

They then tested their findings using the best and most accurate to date climate models to see if the observed changes in moisture were due to natural changes in the Earth’s climate or man-made activity. Only human-emitted greenhouse gases matched the observations, causing the team to conclude:

“Concerning the satellite-derived moistening trend in recent decades, the relations of trend and associated range among three experiments lead to the conclusion that an increase in anthropogenic greenhouse gases is the main cause of increased moistening in the upper troposphere”

The findings are of great importance since it yet again proves that climate change models are accurate and adds to a pilling body of evidence supporting the man-made climate change.