Simple Chemistry and the Real Greenhouse Effect.

Blogging Tories ^ | March 2010 | Bill MacLean

[steelyourfaith]

 

Beam me to Planet Gore !

[palmer]

The mechanism is that the earth warms from solar changes, then after many 100's to 1000 years or so, CO2 comes out of the deep ocean and that causes more warming and there is a slow feedback loop. The ice age atmosphere is generally very dry and CO2 has a greater proportional effect and it is going from 200 to 280 and is logarithmic.

Finally with the CO2 at around 260-280, and the atmosphere warmed and wetter, the feedback loop stops. That's why the interglacial periods stop around the current temperature or a little higher. The current addition of 100 more ppm has little effect for two reasons: the log scale means less warming for each additional amount of CO2. More importantly, weather starts to limit warming (see Eschenbach and Lindzen on thermostat-like mechanisms). The water cycle is a powerful global cooling mechanism and should operate a bit faster with a bit of CO2 warming. But mostly the water cycle responds to solar effects including geomagnetic effects that manifest in weather changes (e.g. more low clouds from more galactic cosmic rays or less from less).

I try to stay away from CO2 did this or that in ancient history (e.g. when it was much higher) because the earth was very different then. Many more volcanoes (the source of the CO2) affecting the climate, the sun was cooler, the continents were laid out differently. There are no clear relationships when you look very far back.

It is definitely a fact that we are in an extended ice age with scarce CO2. Now our extra CO2 may or may not help to keep us from falling out of the current interglacial back into the ice age. In the other direction, the chance of "catastrophic" warming from the extra CO2 is zero. Not even a tiny chance, it simply will not happen in our current geological configuration.

[allen_carl]

“This new data set shows that as surface temperature increases, so does atmospheric humidity,” Dessler said. “Dumping greenhouse gases into the atmosphere makes the atmosphere more humid. And since water vapor is itself a greenhouse gas, the increase in humidity amplifies the warming from carbon dioxide.”

I couldn’t find the original paper on which this statement is based. It only referenced a secondary article published in a journal by a writer who added his own unsubstantiated assertions to the original article. Be that as it may, it glosses over a very important reality. Increasing surface temperatures may or may not increase atmospheric humidity depending upon the presence or absence of water in that surface. It is axiomatic that heat can only evaporate water into water vapor if there is water present in the first place. For example, Death Valley, California is very arid even though it is very hot because very little rain falls there; therefore there is very little water in the soil in Death Valley to evaporate (create humidity) when the surface is heated.

Conversely, Huntsville, Alabama gets lots of rain and the surface if very wet. It, therefore, unlike Death Valley gets very humid when the ground is heated. Both of these locations lie roughly along the same parallel so they both receive roughly the same amount of sunlight every day throughout the year, yet the relative humidity in Death Valley is only about 24% on average and the relative humidity in Huntsville is over 70%.

I obtained the above numbers from the National Weather Service. Empirically measured Huntsville has nearly three times the amount of water vapor in the air than does Death Valley. So, if water vapor traps heat in the air and creates a positive heating feedback loop one would expect Huntsville to be much warmer on average than Death Valley, but its not; its cooler.

Huntsville, the city with nearly three times the amount of the “greenhouse gas” water vapor in the air, is about 7 °C cooler than Death Valley! It is only 17 °C on average while Death Valley, the city with about one third the amount of the “greenhouse gas” water vapor in the air, is about 24 °C on average. Again, they both lie along the same parallel so they both receive roughly the same amount of sunlight every day all year long.

Therefore, we observe that the city with nearly three times the amount of water vapor in the air is not only cooler than the city with one third the amount of water vapor in the air, it is significantly cooler. The water vapor in Huntsville, contrary to the “greenhouse effect” hypothesis in reality has a marked cooling effect, not a warming effect, on the climate in and around Huntsville. This is an “anti-greenhouse” effect.

The more water vapor there is in the air the cooler the air is (according to the figures that I obtained from the National Weather Service.) This is a negative feedback and explains why the earth, which is covered with 70% oceans, has not already experienced runaway “water vapor feedback.” As the surface temperature increases by whatever means, if there is water in the ground to evaporate, that extra heat will create more humidity; this, in turn, cools the surface, which inhibits further evaportion. This reality is reflected in the temperature record which shows Huntsville to be about 7 °C cooler on average than Death Valley even though they both receive the same amount of sunlight.

Should one assert that this cooling is due to the greater cloud cover in Huntsville that would simply affirm the powerful negative feedback that clouds provide as they mitigate surface warming through shade and rain.