Guest post by Ira Glickstein

Some people claim that there’s a woman to blame,
But I know, it’s my own damn fault..

The original Jimmy Buffet lyrics say “woman to blame” but I changed it to “human” in the title of this post. Perhaps I should have left it as “woman” since, without their civilizing influence, we men would still be huddled in caves, wearing bearskins, and human-caused global warming would not be an issue. In 1880, WS Gilbert said women were the really civilized humans, while Darwinian Man, even when well-behaved, was nothing more than a Monkey Shaved :^)
This is the fourth of my Tale of the Global Warming Tiger series where I allocate the supposed 0.8ºC warming since 1880 to: (1) Data Bias, (2) Natural Cycles, and (3) AGW (human-caused global warming), the subject of this posting. Click Tiger’s Tale and Tail :^) to see my allocation and read the original story.

ANTHROPOGENIC GLOBAL WARMING (AGW)
This posting is about how human activities, particularly burning of fossil fuels and land use changes have contributed to the global warming experienced since 1880. According to Willis Eschenbach’s excellent WUWT posting (with the same title as mine – great minds think alike :^);

I think that the preponderance of evidence shows that humans are the main cause of the increase in atmospheric CO2. It is unlikely that the change in CO2 is from the overall temperature increase. During the ice age to interglacial transitions, on average a change of 7°C led to a doubling of CO2. We have seen about a tenth of that change (0.7°C) since 1850, so we’d expect a CO2 change from temperature alone of only about 20 ppmv.

Thus, about 80% of the CO2 rise from about 280 ppmv to 390 ppmv since 1880 is due to human activities.

I estimate that 0.1ºC of the supposed 0.8ºC warming is AGW, where we humans are to “blame” (assuming that that tiny amount of warming will make much of a difference, or, even if it does, that it will turn out to be bad).

In comments to my previous postings in this series, some WUWT readers have suggested that the entire supposed 0.8ºC warming since 1880 is data bias. In other words, there has actually been no net warming at all. I disagree. Even if the terrestrial temperature record since 1880 is questionable, particularly in light of repeated “adjustments” by the official climate Team that appear to overstate the warming, it seems to me the satellite data, available since 1979, clearly proves there has been considerable net warming since that date.

Other WUWT readers agree we are in a warming cycle but claim that natural processes are responsible for ALL the warming. Their main argument is that rising CO2 and other carbon gas levels do not cause much if any warming, and, even that amount of warming is counteracted by additional clouds that raise the Earth’s albedo. I agree the great majority of warming is natural, but I think it is clear that human activities are responsible for some of it. Yes, clouds almost certainly have a net negative feedback (despite virtually all the official climate Team models to the contrary), but, for the negative cloud feedback to work, temperatures must rise at least a little bit to generate the additional clouds.

DESCRIPTION OF MY GRAPHIC
The above graphic traces my estimate of the actual warming since 1880, and my projection several decades into the future. To liven it up I have drawn the curves atop a photo of some white-roofed houses in Greece and quoted from The Independent, 27 May 2009, under the headline Obama’s climate guru: Paint your roof white! they say:

Some people believe that nuclear power is the answer to climate change, others have proposed green technologies such as wind or solar power, but Barack Obama’s top man on global warming has suggested something far simpler – painting your roof white.

At the time, Anthony posted the news on WUWT, suggesting:

Maybe now NOAA will get rid of all remaining rooftop climate monitoring stations or stations sited over asphalt …

An alert reader, E.M. Smith, went further and wrote:

Lets start a surface stations project to paint the black roofs and asphalt under temperature stations white. We can do it to “save the planet from global warming and offset carbon”… and it would actually work to get the global temperature record down too ….

Undoubtedly, land use changes such as clearing forests and paving large areas with asphalt and erecting buildings have generally reduced the albedo of the Earth and thus increased warming. I don’t think Secretary Chu’s white roof idea will have much effect, but, any effect it does have will be in the direction of reducing warming, and I doubt it could ever be so successful that it pushes us into catastrophic global cooling!

Natural Cycles: The green line represents net warming not under human control or effect, and it shows a rise of about 0.4ºC since 1880.

The lighter green line is my projection of Natural Cycles assuming that Solar Cycle #24 will have a low Sunspot peak of 60 or less in 2013 or later, and that the following SC #25 and SC #26 will be similarly low and long. It is virtually certain SC #24 will be low, but pure speculation regarding SC #25 and SC #26. Of course, the varying strengths of ocean oscillations and volcanic eruptions and other hard to predict events may affect natural processes in either direction from my projections.

I have sketched a thin green line that indicates what may happen if we get a series of particularly strong events, similar to the El Niño that caused global temperatures to peak in 1999, and/or if subsequent Solar Cycles return to their previously high Sunspot levels.

AGW The violet line represents the sum of Natural Cycles and AGW and it shows an additional net rise of about 0.1ºC since 1880.

The lighter violet line is my projection assuming human activities will continue more or less as they have in the past, with minimal reductions in human-generated carbon gases and land use patterns, showing an additional nearly 0.1ºC rise between 2011 and 2050, for a total AGW since 1880 approaching 0.2ºC.

I have sketched a thin violet line indicating what may happen if Natural Cycles follow the thin green line projection and if, in addition, humans accelerate emissions of carbon gases and land use patterns that reduce the Earth’s albedo.

WHY AGW IS REAL
According to Roy Spencer, PhD:

Greenhouse components in the atmosphere (mostly water vapor, clouds, carbon dioxide, and methane) exert strong controls over how fast the Earth loses IR energy to outer space. Mankind’s burning of fossil fuels creates more atmospheric carbon dioxide. As we add more CO2, more infrared energy is trapped, strengthening the Earth’s greenhouse effect. This causes a warming tendency in the lower atmosphere and at the surface. As of 2008, it is believed that we have enhanced the Earth’s natural greenhouse effect by about 1%.

Absent the greenhouse effect of the atmosphere, the Earth would be cooler by about 33ºC, and 1% of that is 0.33ºC, which is more than the 0.1ºC I have allocated to AGW and that does not even include land use effects. But, again according to Spencer:

Net feedbacks in the real climate system — on both short and long time scales — are probably negative. A misinterpretation of cloud behavior has led climate modelers to build models in which cloud feedbacks are instead positive, which has led the models to predict too much global warming in response to anthropogenic greenhouse gas emissions.

He explains that IPCC climate models assume a feedback of from 0.9 to 1.9 W m-2 K-1, and that any value below 3.3 represents positive feedback, while any level above that is negative feedback. He concludes from his study of satellite data that:

the line slopes diagnosed from the satellite data … might actually be an UNDERESTIMATE of the true feedback occurring, which could be 7 W m-2 K-1 or more.

If that turns out to be true, then the actual sensitivity to CO2 doubling would be far less than the 2ºC to 5ºC or more projected by the IPCC. Indeed it could be 0.5ºC, or even less. As current CO2 levels are about 390 ppmv we are about 40% to a doubling from historic 280 ppmv levels, the actual temperature rise due to the human component of AGW could be 0.2ºC.

In addition, burning of fossil fuels has a side effect of increasing light-colored aerosols that reflect Sunlight and thus prevent some of it from reaching the surface, counteracting some of the warming due to atmospheric CO2. Efforts to clean the air are said to have reduced such aerosols and, inadvertently, caused more warming.

Please note that I have low-balled my AGW value by about half because I discount the approximately 20% of rise in CO2 levels as due to the temperature rise itself causing less CO2 to be absorbed by the polar and winter temperate oceans and more to be emitted by the equatorial and summer temperate oceans and I also believe there are other negative feedback components yet to be exposed. I expect some WUWT readers will challenge even my low estimate and I request you back your challenges up with science-based reasoning, which I would love to hear.

CONCLUSIONS AND REQUESTS
If readers have additional information or corrections to what I said about AGW, or if there are other related factors I missed, I would appreciate detailed comments to improve my summary.

It seems to me that my estimate of 0.1ºC for AGW is justified, and perhaps a bit understated. I am open to hearing the opinions of WUWT readers who may think I have over- (or under-) estimated this component of the supposed 0.8ºC rise in global temperatures since 1880.

In my first and second and third postings in this Tale of the Global Warming Tiger series, I asked for comments on my allocations: to: (1) Data Bias 0.3ºC, (2) Natural Cycles 0.4ºC, and (3) AGW 0.1ºC. Quite a few readers were kind enough to comment, either expressing general agreement or offering their own estimates.

What do you think? I have been keeping a spreadsheet record of WUWT reader’s opinions, which I appreciate and value greatly, along with their screen names, and I plan to report the results in the next posting of this series:

Is the Global Warming Tiger a Pussy Cat? – If, as many of us expect, natural processes lead to stabilization of global temperatures over the coming decades, and perhaps a bit of cooling, we will realize the whole Global Warming uproar was like the boy who saw a pussy cat and cried tiger.