I was doing a bit of research on Watts up With That (WUWT) to find a credible estimate of how much of the observed 1degree C of warming that has occurred since 1880 is attributable to man. I found this article which is quite lengthy, as many are on WUWT, but it seems to apply scientific logic and, just as I suspected, it comes up with a very small fraction of the 1 degree to be caused by man. Below are some key extracts from the article which compares the warming from around 1910 to 1940 with that from around 1976 to 2009. Both these warmings can be seen on a graph to have very similar slopes:
"The warming in the early 20th century has always been a bit of a mystery. Attempts to model this warming event have mostly failed. Generally it is considered to be natural and roughly equivalent to the warming since 1950, at least in the northern hemisphere and particularly north of 60°N. "
"We can speculate that the natural forces causing the warming trend in the early 20th century are about the same as those acting on us from 1975 to roughly 2009. If this is true, then the increase in warming rate (roughly 30% or 28%-33%) might be due to man’s influence. The extra radiative forcing estimated by the IPCC (bottom of Figure 4, 1950 to 2011) is about 1.72 Watts/m2. They have also estimated that more than half of the warming since 1951 was due to man. No warming occurred between 1945 and 1975, so we are really talking about 1975 to 2009. The increase in the rate of warming from the HadCRUT record is 35 years x 0.0048°C or 0.168°C. The NASA GISS dataset gives us a virtually identical 0.0046°C increase in slope. We assume that the natural influences from 1910 to 1945 were the same as those from 1975 to 2009. We further assume that difference in the two slopes is due to man’s influence. The actual temperature increase from 1975 to 2009, from the best fit line to the HadCRUT record, is 0.672°C. So using our estimate of man’s contribution of 0.168°C, we can estimate that man’s contribution is 25%, much less than half."
So what this article is suggesting is that man's total contribution to global warming is 0.168 degrees C. over the period from 1975 to 2009. This is probably artificially precise so let's be generous and push it up to 0.2 That is over a period of 35 years so it is approximately 0.6 degrees per century. This is supposed to be an emergency.
"The warming in the early 20th century has always been a bit of a mystery. Attempts to model this warming event have mostly failed. Generally it is considered to be natural and roughly equivalent to the warming since 1950, at least in the northern hemisphere and particularly north of 60°N. "
"We can speculate that the natural forces causing the warming trend in the early 20th century are about the same as those acting on us from 1975 to roughly 2009. If this is true, then the increase in warming rate (roughly 30% or 28%-33%) might be due to man’s influence. The extra radiative forcing estimated by the IPCC (bottom of Figure 4, 1950 to 2011) is about 1.72 Watts/m2. They have also estimated that more than half of the warming since 1951 was due to man. No warming occurred between 1945 and 1975, so we are really talking about 1975 to 2009. The increase in the rate of warming from the HadCRUT record is 35 years x 0.0048°C or 0.168°C. The NASA GISS dataset gives us a virtually identical 0.0046°C increase in slope. We assume that the natural influences from 1910 to 1945 were the same as those from 1975 to 2009. We further assume that difference in the two slopes is due to man’s influence. The actual temperature increase from 1975 to 2009, from the best fit line to the HadCRUT record, is 0.672°C. So using our estimate of man’s contribution of 0.168°C, we can estimate that man’s contribution is 25%, much less than half."
So what this article is suggesting is that man's total contribution to global warming is 0.168 degrees C. over the period from 1975 to 2009. This is probably artificially precise so let's be generous and push it up to 0.2 That is over a period of 35 years so it is approximately 0.6 degrees per century. This is supposed to be an emergency.
'We assume that the natural influences from 1910 to 1945 were the same as those from 1975 to 2009. We further assume that difference in the two slopes is due to man’s influence.'
ReplyDeleteGiven the complexity and variability of the climate system and the limited state of our knowledge about it, to what extent are these two assumptions defensible?
Dr. Richard Lindzen makes numerous excellent points in this video. Among them are that even in the absence of forcing of any kind, the climate system would vary by about as much as it has. Given that natural variation is sufficient to explain the changes we see, it doesn't seem possible to ascertain any human influence whatsoever, even if one is present. If it's there, it's buried in the noise, and as such it beyond foolish to claim it can be seen.
ReplyDeleteAs Lindzen has said, "Believing CO2 controls the climate ‘is pretty close to believing in magic’." And the last I've heard, magic ain't science.