The Earth’s Thermostat
|July 11, 2008||Posted by Dave S. under Global Warming, Off Topic|
I wrote a longish reply to someone on an obscure forum about global warming and thought as long as I put the work into it I should reproduce it to a wider audience so here it is:
You didn’t figure out the shoe size/salary correlation. It’s a classic example in why correlation doesn’t equal causation.
On the face of it’s a strong correlation. The reason it’s strong is so many people with small shoes are children who don’t earn any salary at all.
Correlations are all well and good as indicators that there may be a connection but, listen up because this how experimental science is conducted, variables under investigation must be isolated. Just because there’s a rough correlation between CO2 and temperature increase (which by the way has ZERO correlation in the past 10 years) doesn’t mean that’s the cause of temperature increase. There are far more variables involved than just CO2. Blithely parroting the Mauna Loa CO2 record does not indict it as the cause for temperature increase. In fact the findings from the Vostok Ice cores unambiguously show that over the past million years temperature rise preceded CO2 rise by about 400 years. Yet no runaway greenhouse occured and the earth has been a LOT warmer than present in the past with a LOT higher concentration of CO2 in the air. To any reasonable person this is rather strong evidence that there’s a negative feedback which caps temperature rise regardless of atmospheric CO2 concentration.
One of the most famous living climatologists alive today, often called “the father of climatology”, believes that rising temperature causes the water cycle to speed up and that falling rain acts like a swamp cooler to bring the air temperature down. That’s sound science as any dummy should know that water absorbs a lot of heat in changing phase from liquid to vapor. Pull out that crufty old chemistry book you must have there an look up how many kilocalories that would be per gram of water. I know you must have it as you love to bandy about the kilocalories involved in the phase change from ice to water.
Moreover cloud cover has a much higher albedo than ground or water. Clouds in the sky reflect a very large amount of sunlight directly back into space.
The climate models employed by the IPCC hysterics don’t know how to treat clouds and rain. That’s a variable they don’t know how to isolate. So they ignore it.
Now follow along because this is almost certainly how the earth’s thermostat works to limit rising temperatures:
As temperature rises, ice melts and cools the oceans (phase transition from solid to liquid). This increases the surface area of the oceans so that the sun beating down on a greater surface area increases the total amount of evaporation. This causes more clouds to form which reflect more sunlight back into space. More clouds produce more rain and the evaporating raindrops cool the air through another phase transition from liquid to gas.
That’s three distinct negative feedback mechanisms in atmospheric temperature rise. None of these are accounted for in climate models because no one understands what weighting factor to give them. So they don’t weight them at all and without those negative feedbacks you get runaway greenhouse. And a runaway greenhouse is simply something that has never before happened in the earth’s entire history even when global average temperature was far higher, all glaciers gone and sea level hundreds of feet higher, and CO2 an order of magnitude higher than mankind could get it even if every last gram of fossil fuels were burned today.
Unfortunately the converse is not true. There is much evidence that the earth has become a giant snowball in the past (in fact it’s called “snowball earth”) and no one has figured out what reverses runaway cooling. With the earth covered in snow an awful lot of sunlight is reflected back into space which is a positive feedback. Possibly only something like an asteroid strike of biblical proportion can bring the earth back from a snowball state.