My Comments On The Andy Lacis Post On CO2 As A Climate Thermostat

At the moment, I would rather drive over Tollgate later today under the protective cover of a greenhouse gas grown out of control than what is my current reality. Think of the cost reduction of warmer weather! Don’t need two sets of tires. Won’t need to replace my rock chipped window. Won’t have to warm up my car before driving off. Won’t need to umph up the thermostat in the morning just to get dressed. Won’t need shoes AND snow boots. AND! Won’t need to replant my #$%-ing grass every year due to snow mold kill.

Could the gulf be any wider?
“Water vapor and clouds are fast-acting feedback effects, and as such, they are controlled by the radiative forcing supplied by the non-condensing GHGs.”

According to this site (http://motls.blogspot.com/2006/07/carbon-dioxide-and-temperatures-ice.html), it is clear that higher concentrations of CO2 and CH4 did NOT lead to any tipping point. After CO2 and CH4 reached high concentrations, the temperatures went down again. Apparently this is due to Milankovitch cycles meaning the distances and inclinations of Earth relative to the sun are much more important “control knobs” than CO2.
This does not, of course, prove that concentrations of at least 100 ppm of CO2 are not necessary to get things started. However that is only of academic interest anyway. It may or may not be the control knob some people think it is. What IS of importance in the present debate on AGW is whether increasing the CO2 from 400 ppm to 600 ppm is of huge significance. I interpret the CO2, CH4, temperature graph from the above site in Figure 1 to indicate that EVEN IF low concentrations of CO2 act as control knobs, concentrations above 180 ppm have virtually no additional controlling powers. Some may argue that this graph only goes from 180 to 280 ppm. However even the IPCC agrees that the effect is logarithmic, so if increases from 180 to 280 cause no tipping point, there is no reason to suspect 400 to 600 would cause any catastrophe all of a sudden. Certainly the last 12 years have not shown any reason to be alarmed.

Ulric Lyons – November 12, 2010 at 6:54 pm: “Looks to me like the Sun must have been varying the amount of water vapour every 150 million years then;”
That’s a really nice geologic time chart you show. You are quite right about the approximately 150 million years between cool periods. They are the ice ages, and we are in one of them right now even though we live in an an interglacial period. The reason for the occurrence of ice ages is not clear. Drifting continents have been suggested but the fit is not good. I personally favor Nir Shaviv’s theory of spiral arm passage. The spiral arms are actually density waves and stars can and do pass through them. They are also the birthplace of many supernovas so the environment is charged with lots of high energy cosmic rays. According to Svensmark’s theory these cosmic rays then seed more clouds, more cloudiness increases the total albedo of the earth, and the climate cools. Sounds interesting and believable but needs lots of loose ends to be fixed. But take another look at your own geologic chart. In between the ice ages the temperature is pretty uniformly the same for tens of millions of years at a stretch. This is what I am talking about.

Bill Illis says:
November 12, 2010 at 8:21 pm

So why is CO2 such a big control knob and Albedo is not considered at all?

Bill, I think Lacis et al made a mistake in the title of their paper. It should have been Atmospheric CO2: Principle Control Knob Governing GISS ModelE’s “temperature”.

Something didn’t look right on Lacis’ plot showing changes in cloud cover, snow cover, albedo, water vapor, etc. but I couldn’t put my finger on it. I thought cloud cover was probably excessive and albedo too low. Water vapor a bit high. It showed the stock temperature drop of 30C everyone always mentioned. I attributed the unlikely looking terminal condition to the ocean not yet having time to reach equilibrium.
Here’s the deal. It’s one thing to model this and some of the model inputs and assumptions are more reliable than others but actual observations must always trump models once we’re assured that the method of observation isn’t flawed. There’s a certain observation that I often consider when applicable. That is the average temperature and albedo of the moon.
We know from experiments performed on and below the surface of the moon that it’s average temperature is -23C and we also know from direct observation that its average albedo is 15%. Insolation is of course the same as the earth.
Lacis’ chart reaches a terminal surface temperature of -20C which is close enough to the -23C of the moon. So at first blush things look about right – virtually no greenhouse gases and we get a result close to the average temperature of the moon. The 3C discrepancy might be attributed to the tiny amount of water vapor remaining in the frigid atmosphere.
But there’s a BIG problem. In Lacis’ chart the earth is shown to have an albedo over 40% which is far higher than the moon’s albedo. The terminal surface temperature in equilibrium must therefore be far lower than -23C because of the much greater albedo.
In all fairness Lacis’ projection only goes out 50 years which likely isn’t enough time for the global ocean to equilibrate. It will eventually become solid ice almost everywhere except where volcanic activity might melt it but that won’t be a significant amount. There would also be volcanic ash and micrometeorite debris accumulating on the surface which would lower albedo substantially over the course of millions of years to approxmitely that of the moon but I serously doubt either volcanic activity or extra-terrestrial dust are included in the model.
The temperature on Lacis’ graph appears like it might still be slowly declining after 50 years but it’s hard to tell. It would be interesting to see the model results after say 10,000 years which is probably enough time for the global ocean to reach equilibrium which at those temperatures is going to be solid ice from top to bottom with an average temperature far lower than -23C due to very high surface albedo compared to the moon.
The long and the short of my view is that CO2 does far more warming than it’s given credit for when low temperatures shut down the hydrologic cycle and far less than it’s give credit for when the hydrologic cycle is running full steam (pun intended).
CO2 is “kindling” that ignites the water cycle. Without it the earth wouldn’t be a water world it would be an ice world with an average temperature below -100C at least until volcanic ash covered enough of it to give it the same albedo as the moon. Once we have a water world CO2’s role as a GHG is over and done with except for being in the background keeping the temperature high enough for a liquid ocean when the water cycle is otherwise effectively shut down by low temperatures.
So there is some truth in my view to CO2 being something of a thermostat but it only serves to set the minimum low temperature. Water (liquid and vapor) limits the maximum high temperature.
Of course the bottom line remains that the earth is and has been a deep ice age for the past 3 million years with historically minimal (even today with anthropogenic CO2 contribution) which is not the usual state of things. The usual state of things is about 8C warmer than today, CO2 at 2000+ ppm, very little ice anywhere, and green pole to pole. As far as the biosphere is concerned the warm times described in the previous sentence are the conditions where most of evolution of extant multicellular life and all terrestrial evolution took place i.e. from the pre-Cambrian period 600 mya forward. That is the “optimum” climate if the concern is really for the biosphere as a whole. The problem is that human civilization “evolved” in an eyeblink of history which all happened in a few thousand years during a comparatively stable interglacial period. Civilization was optimized for that environment and that environment is NOT normal or long lived. So this is really about what’s best for our fragile civilization not what’s best for all living things. What’s best for all living things is an end to the ice age. Clearly pre-industrial CO2 of 280ppm is not sufficient to end an ice age and I seriously doubt 390ppm is enough to do it either given the exponentially diminishing GHG effect of additional CO2 beyond the first 100ppm or so. We need doublings (plural) from pre-industrial level to have a shot at ending the ice age. The problem is we probably don’t have enough recoverable fossil fuel for two doublings and we certainly don’t have enough to sustain that level for very long. The end of the Holocene interglacial appears to be inevitable and it won’t be pretty for human civilization when everything north of 40 degrees latitude is buried under a mile of ice.

By the way, one curious thing to me in Roger Pielke Sr.’s post is the statement:

With respect to the early Earth atmosphere, CO2 was emitted from volcanic eruptions but so was water vapor. The two acted together to warm the climate.

To me it seems rather surprising to suggest that the input of water vapor from volcanic eruptions would be so large as to significantly alter the distribution as water vapor in the troposphere given the fast rate of exchange of water vapor with liquid water at the earth’s surface via evaporation and condensation / precipitation. Is there any support for the idea that this was happening…Or, is the idea that it altered the water vapor in the stratosphere where the exchange rate might be slower?
Perhaps he could clarify this?

Joel Shore says:
November 13, 2010 at 7:08 am
re; early earth
How early?
The sun was much dimmer billions of years ago but the earth was born molten due to gravitational contraction and radioactive isotopes were a lot more abundant then (all but the longest lived have gone through numerous reductions in half during each half-life cycle) which also kept it heated. The late heavy bombardment (widely accepted but not undisputed) impeded the solidification of the crust which today insulates the surface (mostly) from the remaining heat of formation and remaining radioisotope decay.
Mars was evidently a water world for a period of time but due to its smaller mass and greater distance from the sun it cooled off a lot faster than the earth.
The early earth is thought to have had an exceedingly dense atmosphere composed primarily of CO2 and water vapor. Although the surface temperature was far above 100C liquid water could still exist because the early atmosphere was far denser than today and the higher surface pressure raised the boiling point of water.
Details of one likely scenario (no early earth scenarios are writ in stone) can be found here:
Initiation of clement surface conditions on the earliest Earth
While there’s controversy about all this it’s mostly in the details. The earth was born hot with a very heavy atmosphere which was initially rock-vapor at thousands of degrees C and as the heat of formation bled off became a heavy atmosphere of CO2 and water vapor which remained far above 100C until inorganic chemistry reduced the gaseous CO2 into carbonate minerals which reduced the temperature and pressure to the point where thermophilic forms of life could survive.

On the subject of CO2 and albedo control knobs.
It is noticeable that CO2 levels were dropping during the last 100 million years, finally dropping below 300 ppm 20 million years ago, at which time the Antarctic ice sheet started expanding, and later the northern hemisphere ice ages began. All this was permitted by the low CO2 values, so we can argue CO2 supersedes ice albedo on the longer time scales, and at higher concentrations. Ice ages only have a role in a low-CO2 world.
Interestingly, now we approach 400 ppm again, we seem to be in a regime where ice sheets are not viable on a long time scale. The book “The Long Thaw” by David Archer, argues that we may have averted the next ice age that was due 25-50 thousand years from now with projected CO2 levels from fossil fuel burning.

Joel Shore says:
November 13, 2010 at 6:50 am
And, what causes the albedo to spontaneously vary? …and your notion that its change is the largest contributor to the ice age cycles is the current scientific understanding … the albedo change is understood to be the result of the variations in earth’s orbit and distribution of solar insolation; it doesn’t just spontaneously happen.
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Move North America and Europe just 100 kms farther south (as in simple continental drift) and the Milankovitch Cycles have no impact – there is no ice age cycle. They are no longer succeptible to the Milankovitch Cycles.
Move them 100 kms farther north and there is a permanent ice age.
Glacial ice and sea ice has an Albedo of 70%. Normal land and ocean cover (at higher latitudes) has an Albedo of 40%. That is just enough change to have a large impact on the global Albedo.
The ice ages in the far distant past have always occurred when the continents where at, over or very near the poles allowing high Albedo glacial ice to build up. Global Albedo has followed suit. This explains the climate history far better than CO2.
So, yes Albedo can spontaneously change (although it will most often change more slowly and it is only when continents are in the Milankovitch succeptible latitudes, that we have more rapid ice age/interglacial Albedo-controlled cycles). Put them closer to the poles, as in Antarctica, and the ice is permanent. CO2 is not as big of a control knob as Albedo is.
Clouds, as well, are a little more than half of the global Albedo and this also varies, at least with the ENSO cycle and Albedo-dominated temperatures levels (although this runs counter to the glacial ice levels) and who knows what else influences cloud levels.