I have been wanting to write a diary on this topic for some time, but did not want to jeopardize my publication by providing 'prior publication'. My paper is in press now at the Journal of Atmospheric Chemistry and Physics. I wanted to discuss it here with the people who get things going and make a difference... you.
The problem is that temperatures might go up 7 deg F instead of 3 deg F in the next 20 years due to a curious pairing of water molecules called water dimer. Water dimer or some related continuum absorption was predicted by Albert Arking to absorb red and infrared wavelengths in significant amounts based on his climate models in 1996 in Science. In 1999 he published in Geophysical Research Letters his measurements between aircraft and found that there was some significant absorption. He couldn't tell which wavelengths it was with his instruments.
He calculated that there would be an additional 2 deg C rise in the average temperature in 20 years over the 1.7 deg C that was currently accepted. Reports are starting to come in of temperatures exceeding the models. For the sake of all us Americans understanding that is almost 7 deg F of warming, and that is just the average temperature. The highs could be worse.
His measurements were questioned and then ignored because it would be impossible to tell if his measurements came from water dimer or coincidental scattering by particles, and then measurements in the laboratory showed that red light is not absorbed by water dimer.
Water dimer is what it is called when two water molecules stick together. It happens with about 2 in 1000 water molecules in the air depending on the conditions. It is actually more common than the pollutants in smog, but wouldn't matter except that it seems to have a remarkably strong absorption, not where Arking thought it would be but further over in the green to violet regions of light. As the temperatures go up, water evaporates, and water dimer goes up by nearly the square of the water vapor. Direct absorption of sunlight by water causes the air temperature to go up in what is called positive water vapor feedback.
I have measured this absorption many times in the last few years using a sensitive technique called cavity ring-down spectroscopy, and I have found that the water molecules fall apart more as the temperature rises in agreement with calculations. This temperature effect goes counter to the problem but not significantly enough.
The consequence is that we have to act quickly to minimize the disaster. I realize this is preaching to the Choir and we already are trying our best to avoid reaching a tipping point in climate change, but knowledge is power, so here is some knowledge to use.
My work needs to be confirmed by other groups and extended. Arking has made calculations already but it is not clear that they are perfect.
You might think with more water vapor there would be more clouds and cooler temperatures but the higher temperatures couteract the formation of clouds. Clouds may be the biggest uncertainty remaining.
My paper will be coming out shortly and will probably draw a lot of fire. Hopefully we can still do something to minimize the damage of the results. As for so many things, you heard about it here first. Spread the word.