The actual value of the climate sensitivity is a multi-trillion dollar question (the cost of implementing Kyoto related penalties). If it is high, it would imply that human emissions of greenhouse gases could significantly increase the global equilibrium temperature, while if it is small, the anthropogenic effect cannot be large, and any measures we take will not have a noticeable effect. Its value is crucial.
Crucial to that value is another value. CO2 in and of itself produces an insignificant value for warming, this has been known for many years. What does matter is whether the imagined feedback effect where a tiny warming from CO2 increases the base volume of water vapour that increases the absorption of radiation that increases warmth that increases water vapour, a runaway warming effect has legitimacy and whether it is important. Does the feedback exist and can it be quantified if it does?
The answer to the first part of the question is that it would seem to be non sequitur. Could it produce runaway warming? No, water vapour is self limiting, dependent on temperature, excess vapour condenses. Were tiny WV additions to be made by CO2, they would be condensed into cloud. In support of that, previous eras saw CO2 in the thousands of ppm during cold and warm periods and runaway warming never happened. Night to day, winter to spring to summer sees increasing temperature that has never caused runaway warming. Not in 1934, 1998, 2002 or 2005.
Low cloud that additional WV produces (due to whatever process) is a negative feedback because although condensation warms and clouds absorb IR, the warming is outweighed by rain and the albedo (reflection of solar input). Rain takes CO2 and dark aerosols from the air. Aerosols are used by the condensation process so there is another warming factor that additional WV reduces. NASA, Discussion, see the math - Powerpoint or HTML
Down to business.
What is climate sensitivity?
The equilibrium climate sensitivity refers to the equilibrium change in average global surface air temperature following a unit change in the radiative forcing. This sensitivity, usually denoted as λ, has units of °K / (W/m2).
In reality it is the increase in temperature forced by increased CO2 levels that is politically important. Generally it is considered in relation to a doubling of 260, 280 or 300 ppm that are considered as preindustrial levels.
Many papers and articles have been written on the topic, either of all GHGs or CO2 alone, the most relevant are listed below;
Douglas Hoyt "The collapse of arguments for high climate sensitivity" 2007
"Combining the Lyman and Gouretski papers, the net ocean heat content between 1955 and 2005 seems to be only 0.98 x 10^23 joules with an error of (0.8 + 0.11) x 10^23 joules or 0.91 x 10^23 joules, adding the error terms of the two papers. The net heat content change is therefore essentially statistically indistinguishable from zero. The net warming of the ocean from 1948 to the present seems to be only 0.03 +/- 0.03 C.
The corresponding net radiative imbalance is about 0.1 W/m^2, well below the model predictions which equal 0.85 W/m^2 for 1993 to 2003 (Hansen et al., 2005). Instead of a climate sensitivity of 3 C for a CO2 doubling, the climate sensitivity is only about 0.4 C. There is little or no energy “in the pipeline” and thus a good reason to believe that all the observed warming of the atmosphere has already occurred.
The atmospheric warming of 0.6 C between 1900 and 2000 is presumably forced by 2.7 W/m^2 from all greenhouse gases. The forcing from a doubling of CO2 is about 3.7 W/m^2 which would correspond to a climate sensitivity of 0.8 C for a CO2 doubling if all the warming of the twentieth century was caused by greenhouse gases. Since even the IPCC concedes that half the warming may be coming from other causes (such as solar), the calculated climate sensitivity becomes 0.4 C for a CO2 doubling. This low sensitivity is consistent with the low values derived by Lindzen (0.5 C) and Idso (0.4 C) and others. It is also consistent with the analysis of the oceans discussed above.
There is no hiding of global warming in the oceans is as commonly argued. The results are consistent with the fact that 15 micron IR thermal radiation from carbon dioxide will only heat the upper 15 microns of the oceans, a topic to which we now turn./ continues
Dr. R. Pielke Snr on upper ocean heat where that is considered a metric to gauge GW (2009):
Update On A Comparison Of Upper Ocean Heat Content Changes With The GISS Model Predictions
Following on from his article;
A Litmus Test For Global Warming - A Much Overdue Requirement (2007) in which he wrote;
“A figure, such as Figure 8 in Willis, J.K., D. Roemmich, and B. Cornuelle, 2004: Interannual variability in upper ocean heat content, temperature, and thermosteric expansion on global scales. J. Geophys. Res., 109, C12036, doi: 10.1029/2003JC002260.
should be widely communicated each year (or more frequently). For example, as a requirement to NOT reject the IPCC claim for global warming, Climate Science proposes that on the scale presented in Figure 3 in Willis et al, the left axis in their Figure 8 must exceed the following values in each year
2003 8*10**22 Joules
2004 9*10**22 Joules
2005 10*10**22 Joules
2006 11*10**22 Joules
2007 12*10**22 Joules
2008 13*10**22 Joules
2009 14*10**22 Joules
2010 15*10**22 Joules
2011 16*10**22 Joules
2012 17*10**22 Joules”
This is an accumulation of heat of 1 * 10**22 Joules per year. We now have data to assess what actually occurred in terms of this metric of global warming up through the end of 2008 (i.e. see the Figure in Pielke (2008), Figure 1 in Willis et al (2008) and personal communication from Josh Willis to extend the data to the end of 2008).
The use of the ocean heat content change as the most appropriate metric to diagnose global warming was reported inLevitus, S., J.I. Antonov, J. Wang, T.L. Delworth, K.W. Dixon, and A.J. Broccoli, 2001: Anthropogenic warming of Earth’s climate system. Science, 292, 267-269 andPielke Sr., R.A., 2003: Heat storage within the Earth system. Bull. Amer. Meteor. Soc., 84, 331-335.
OBSERVED BEST ESTIMATE OF ACCUMULATION Of JOULES [assuming a baseline of zero at the end of 2002].
2003 ~0 Joules
2004 ~0 Joules
2005 ~0 Joules
2006 ~0 Joules
2007 ~0 Joules
2008 ~0 Joules
[He is very polite in his dismissal of the IPCC science and models.]
S. B. Idso "CO2-induced global warming" (1998)
"...models of the atmosphere predict that a 300 to 600 ppm doubling of the air’s CO2 content will raise mean global air temperature a few degrees Celsius, natural experiments based upon real-world observations suggest that a global warming of no more than a few tenths of a degree could result from such a CO2 increase. Which conclusion is correct?"
R. Lindzen "Lindzen on negative climate feedback" (2009)
(0.64 degC clear skies)
"The earth’s climate (in contrast to the climate in current climate GCMs) is dominated by a strong net negative feedback. Climate sensitivity is on the order of 0.3°C, and such warming as may arise from increasing greenhouse gases will be indistinguishable from the fluctuations in climate that occur naturally from processes internal to the climate system itself."
Petr Chylek et al. "Limits on climate sensitivity derived from recent satellite and surface observations" (2007)
An analysis of satellite and surface measurements of aerosol optical depth suggests that global average of aerosol optical depth has been recently decreasing at the rate of around 0.0014/a. This decrease is nonuniform with the fastest decrease observed over the United States and Europe. The observed rate of decreasing aerosol optical depth produces the top of the atmosphere radiative forcing that is comparable to forcing due to the current rate of increasing atmospheric concentration of carbon dioxide and other greenhouse gases. Consequently, both increasing atmospheric concentration of greenhouse gases and decreasing loading of atmospheric aerosols are major contributors to the top-of-atmosphere radiative forcing. We find that the climate sensitivity is reduced by at least a factor of 2 when direct and indirect effects of decreasing aerosols are included, compared to the case where the radiative forcing is ascribed only to increases in atmospheric concentrations of carbon dioxide. We find the empirical climate sensitivity to be between 0.29 and 0.48 K/Wm−2 when aerosol direct and indirect radiative forcing is included.
N. Shaviv on climate sensitivity and why it is probably small (2008?)
Earth's climate sensitivity is not expected to be that of a "black body" because of different feedbacks known to exist in the climate system.
Although Global Circulation models are excellent tools for studying some questions, they are very bad at predicting the global climate sensitivity because the cloud feedback is essentially unknown. It is the main reason why the sensitivity is (not) predicted this way with an uncertainty of a factor of 3!
Climate Sensitivity can be estimated empirically. A relatively low value (one which corresponds to net cancelation of the feedbacks) is obtained.
Empirical Climate sensitivities obtained on different time scales are significantly more consistent with each other if the Cosmic Ray flux / Climate link is included. This is yet another indication that this link is real.
That CO2 doubling produces an insignificant contribution to warming demonstrates anthropic emissions are wholly insignificant.
Further reasons to dismiss the IPCC
CO2 variation can't be used to predict temperature at any timescale, ENSO influenced by the PDO and the Sun can.
Oceans, under the influence of solar and volcanic emissions, dominate the climate via cloudiness, sea ice extent, humidity and soluble gas levels. Clouds regulate.
Increased warming produces a higher level of negative feedback, more cloud, higher precipitation. In tropical regions, evaporation causes water vapour that forms clouds. The energy from the oceans that causes evaporation rises and disperses the cloud leaving the seas free to radiate to space. The planet is self regulating.
Sulphate aerosol absence (due to regulation) was found to contribute as much as 40% of warming to Arctic warming.
Essential to the AGW dogma, the well mixed CO2 supposition is disproved by NASA.
Essential also, CO2 residence in the air of 50-200 years is disproven - Link1, Link 2, Link3 - discussed.
Falsification Link 1, Link 2, Link 3.
Arctic sea ice was mainly melted from below due to changed air and sea currents and is now recovering. (Daily update) NASA 1, NASA 2, Arctic Oscillation
"Human caused warming melts ice, human caused ozone depletion increases ice" - is absolute nonsense.
Increasing for decades:
Apr 24, 2009 Sea Ice Claims on Thin Ice
A New Record For Antarctic Ice Extent
Average winter temperature over the South Pole is about a degree F colder than in '57.
The natural warming that occurred since the emergence from the LIA is well within error margins and the expected margins of natural variation. Since 1700 it has been around 0.5decC per century. Were the IPCC measurements to be found accurate, additional warming last century amounted to ~0.1 degC.
The 20 or less climatology field related scientists in the IPCC org. are either misguided or misled. That the world has been so diverted by a blatant mistake in advising action on the basis of false suspicion is criminal. Dr. Hansen's hypothesis is long overdue withdrawal.
Remembering Dr. Lorenz who passed away on 16th April 2008.
Excerpt from the New York Times, "Dr. Lorenz’s accidental discovery of chaos came in the winter of 1961. Dr. Lorenz was running simulations of weather using a simple computer model. One day, he wanted to repeat one of the simulations for a longer time, but instead of repeating the whole simulation, he started the second run in the middle, typing in numbers from the first run for the initial conditions.
The computer program was the same, so the weather patterns of the second run should have exactly followed those of the first. Instead, the two weather trajectories quickly diverged on completely separate paths.
At first, he thought the computer was malfunctioning. Then he realized that he had not entered the initial conditions exactly. The computer stored numbers to an accuracy of six decimal places, like 0.506127, while, to save space, the printout of results shortened the numbers to three decimal places, 0.506. When typing in the new conditions, Dr. Lorenz had entered the rounded-off numbers, and even this small discrepancy, of less than 0.1 percent, completely changed the end result.
Even though his model was vastly simplified, Dr. Lorenz realized that this meant perfect weather prediction was a fantasy.
A perfect forecast would require not only a perfect model, but also perfect knowledge of wind, temperature, humidity and other conditions everywhere around the world at one moment of time. Even a small discrepancy could lead to completely different weather.
Dr. Lorenz published his findings in 1963. “The paper he wrote in 1963 is a masterpiece of clarity of exposition about why weather is unpredictable,” said J. Doyne Farmer, a professor at the Santa Fe Institute in New Mexico.
The following year, Dr. Lorenz published another paper that described how a small twiddling of parameters in a model could produce vastly different behavior, transforming regular, periodic events into a seemingly random chaotic pattern. " /Continues
So now you know why IPCC PC models can't get it right. Projection is not prediction.
Can they count? Fifty-three authors and five reviewers are all that can be said to explicitly support the claim of a significant human influence on climate. The IPCC’s total of 3750 is a myth. Not even the 2879 individuals can be shown to support the claim. The true number is about 60, or maybe if we asked each of those privately, perhaps even fewer."
Even should you doubt the evidence here, that there is and always has been substantial (supressed) contrarian science at the very least calls into question the correctness of IPCC doctrine, let alone action based on inflated IPCC assumptions. Link
Recent warming is not historically unique (link)
A Natural Limit To Anthropogenic Global Warming (link)
Sources and Sinks of Carbon Dioxide (link) - discussed
Phenomenological solar signature in 400 years of reconstructed Northern Hemisphere temperature record. (link)
Abrupt Decrease in Tropical Pacific Sea Surface Salinity at End of Little Ice Age (link)
Global Climate Change Facts: The Truth, The Consensus, and the Skeptics (link)
Why CO2 is known not to have accumulated (link)
Global warming By Marcel Leroux 2005 (link)