dbindoff
Thanks for the reference to the 2013 paper by Hansen, Karecho and Sato.
On their Figure 1., "Global Fossil Fuel CO2 Annual Emissions" the black curve (Total) is the same curve as on my graph, but I have converted it to Log10 values. This is proper: the basic model relating global temperature to emissions is that temperature increases with the log of the emissions. ("fast-feedback climate sensitivity is ~3 °C for doubled CO2").
Because of this scale conversion, the sharp rise in CO2 emission rates after 2000 is not so pronounced on my graph, and is almost obscured by my "2005" label. My graph makes abundantly clear what is hard to detect on the other graph: the near-constant proportional rate of increase in emissions from 1945 (or 1950) to 1973 was more than twice as high as that from 1973 onwards. This is precisely the opposite of what the basic model predicts.
A lot of the discussion in the paper you reference is about variability from year to year. You will remember that I posted graphs about this many pages earlier in this thread e.g:
http://www.ata.org.au/forums/topic/2190/page/14#post-24127
Hansen, Karecho and Sato write mainly about the last 30 years, because many things simply were not observed earlier.
I believe you are right to mention in particular the factor: negative forcing due to human-generated aerosols. I think that may well be the key to understanding the rather strange relation between increasing CO2 emissions and global temperature rise shown on my graph. (To be fair, johnmath mentioned this, which I will answer below.)
The concept is "global dimming".
Hansen and a co-worker had earlier described the opposing effects of (a) blocking of sunshine by aerosols produced by burning fuels (especially coal) and (b) trapping of sunshine by emission of carbon dioxide as a "Faustian Bargain" - a deal with Satan.
http://pubs.giss.nasa.gov/docs/1990/1990_Hansen_Lacis.pdf
Burning dirty fuels, such as coal, and polluting the sky with aerosols, reduces the rate of warming for the time being only. It does not affect the rate of accumulation of CO2, so it merely postpones an inevitable warming.
I infer that the reason scientists such as Dr Hansen have not put forward a model based on aerosols that accounts for the 33-year period without global warming is simply a lack of data on aerosols. There is very little data now, let alone in 1950.
"The difficulty is human-made aerosols. Aerosols are readily detected in satellite observations, but determination of their climate forcing requires accurate knowledge of changes in aerosol amount, size distribution, absorption and vertical distribution on a global basis—as well as simultaneous data on changes in cloud properties to allow inference of the indirect aerosol forcing via induced cloud changes. Unfortunately, the first satellite mission capable of measuring the needed aerosol characteristics (Aerosol Polarimetry Sensor on the Glory satellite, (Mishchenko et al 2007)) suffered a launch failure and as yet there are no concrete plans for a replacement mission."
(Note: This is the paper that contains the famous statement: "What is clear is that most of the remaining fossil fuels must be left in the ground if we are to avoid dangerous human-made interference with climate.")
johnmath
On 27th July you said:
"The mid-century cooling was primarily caused by a rapid increase in atmospheric pollution from the burning of fossil fuels, causing global dimming.
The main reason for the sudden movement in global temperature from the '70s was the passage of Clean Air Acts around the world in response to air pollution and acid rain, thus removing the dimming effect of pollution."
When I asked:
"Where is this explanation documented? Is it well supported?"
You replied in generalities.
I have since found that same explanation here:
http://www.skepticalscience.com/The-main-culprit-in-mid-century-cooling.html
That is not a website that I trust, so I remain unconvinced.
Clearly James Hansen does not endorse this explanation, or he would have mentioned it.
Posted Monday 29 Jul 2013 @ 12:46:12 pm from IP
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