Water Vapor Wildcard in Global Warming Game

by Val Germann

Left out of almost all discussions concerning “global warming” is the fact that water vapor contributes about two-thirds of the warming effect caused by our atmosphere. This lacuna exists because water vapor is not considered a “greenhouse gas” by the people who regulate such things, in part because water vapor can’t be regulated. But water vapor is important — very important — and must not be ignored.

And it won’t be ignored much longer because it appears to be on the increase, world wide, driven by the temperature effects of the designated “greenhouse gases” like carbon-dioxide, methane, and the various CFCs and HFCs. Here’s a quote from a late-2005 National Geographic News article concerning the rapid warming Europe has seen, which is melting glaciers in the Alps :

By plotting recent climate data and geographical data, the researchers found that the increase in greenhouse gases in Europe has caused a major disruption in the natural cycle of water evaporating from the surface of the Earth.

The water cycle—in which water evaporates, rises into the atmosphere, and eventually returns to Earth in the form of precipitation—has been disrupted to the point where the water vapor itself is helping to fuel the temperature increase, Philipona said.

Though I can’t locate the reference at this time, recent data from the Boulder, Colorado, atmospheric observing station indicates that water vapor there has been increasing about one percent per-year for the last two decades. The implications are clear: a water vapor positive feedback loop has likely been activated, kicked into gear by the temperature increases caused by CO2 and its fellow travelers.

Here is the REAL wildcard in the global warming game, one that could send the planet rapidly reeling upward in temperature, to a new equilbrium many degrees higher than currently thought possible. This is so even though increased water vapor may lead to increasing cloud cover.

That is, the planet Venus, with a surface temperature so high that lead would run like water, is totally covered by dense clouds everywhere and all the time.

Read the entire article here.

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One Response to “Water Vapor Wildcard in Global Warming Game”

  1. David L. Brown says:

    Hello, Val — Water vapor is a two-edged sword. Atmospheric H2O is actually a more powerful greenhouse gas than CO2, and plays an critical role in the planet’s temperature balance. As you mention, greater cloud cover is also a factor, one which can mediate warming by reflecting more sunlight back into space. However, that same cloud cover can retain captured heat by preventing it from radiating back into space.

    Because it can both cool and warm the earth, increased moisture in the air has the potential to affect the Earth in different ways. Thus, we are dealing with a dangerous effect here, a hand grenade of global proportions, because as water vapor increases the threat of reaching a tipping point becomes greater. But which way will it go? The alternatives could include a hotter and dryer planet, or a hotter and wetter planet. Neither option would be a good one.

    My personal theory is that the present effects of air traffic are balancing off the two effects. The jet contrails cause water vapor to form into high, thin clouds during the day when most air traffic takes place. This shields the surface of the planet from some insolation (incoming solar rays) by reflecting them. At night, when jet traffic is lowest, the contrail-induced cloud cover fades and heat is allowed to radiate away from the Earth. Thus, human effects may be staving off the true global warming effect. The U.S.. experienced unusually high temperatures in the week after 9/11 when air traffic was suspended. What will happen when the Oil Peak makes massive air travel and transport a thing of the past? — David L. Brown