The H2O also rises

Roy W. Spencer:


Contrary to popular accounts, very few scientists in the world - possibly none - have a sufficiently thorough, "big picture" understanding of the climate system to be relied upon for a prediction of the magnitude of global warming. To the public, we all might seem like experts, but the vast majority of us work on only a small portion of the problem.

Here, for example, is an insight that even many climate scientists are unaware of: The one atmospheric process that has the greatest control on the Earth's climate is the one we understand the least - precipitation.

Over most of the planet, water is continuously evaporating, humidifying the air to form the Earth's dominant greenhouse gas: water vapor. Climate scientists will tell you that the extra CO2 we are putting in the atmosphere causes a "warming tendency" at the surface, which will evaporate even more water, which will amplify the warming. This positive water vapor feedback, so the theory goes, ends up turning the relative benign direct warming effect of CO2 - only 1 degree of warming late in this century - into a much more serious problem.

But surface evaporation is not what determines how much water vapor, on average, resides in the atmosphere - precipitation systems do. These not only control the water-vapor portion of the greenhouse effect, they directly or indirectly control most of the next most important greenhouse ingredient: clouds.

These systems continuously recycle the Earth's air, and so exert strong controls over the entire climate system. For instance, the rising air in precipitation systems is what causes the sinking, cloudless air over desert areas. Vast oceanic areas of stratus clouds form below a temperature inversion that is also caused by air being forced to sink by precipitation systems, usually thousands of miles away.

So, what does all this have to do with global warming? Unless we know how the greenhouse-limiting properties of precipitation systems change with warming, we don't know how much of our current warmth is due to mankind, and we can't estimate how much future warming there will be, either. To solve the global-warming puzzle, we first need to learn much more about the precipitation-system puzzle.


Those concerned about rising sea levels do not take into account the effects of evaporation in reducing water levels. I see it all the time in my pond. They also do not explain the precipitation cycle that results from the evaporation. For example the summer weather pattern along the Texas Gulf coasts involves an almost daily 20 percent chance of rain which is caused by clods forming up over the warm Gulf waters in the evening that move to the warmer land areas during the day time and when the land is at its hottest in the mid to late afternoon, they dump a shower somewhere.

Some times it is dumped on the land than drains into my pond and refills water that has evaporated. In the hottest time of the year, hurricanes are sometimes formed that dump more rain over the land. In especially dry areas of Mexico, these storms are considered a blessing. The fact is that it is part of the whether cycle and the clouds and the rain also cool the land.


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