According to google reader, RP Sr posted the below today to his “blog” (only its not really a blog cos it doesn’t allow comments), in a post entitled Question The Weblog Real Climate. And indeed he did; the comment is here. This is something RP has been harping on about for a while. Gavin gave him the obvious answer: I fail to see how you are parsing this to find an inconsistency. The footnote is clear that the term ‘radiative forcing’ in the IPCC report refers to the change in forcing from a 1750 baseline. More precisely, it is defined as the change in radiation at the tropopause after stratospheric temperature adjustment but with all other factors kept fixed when going from 1750 conditions to a new value. The caption to the figure discusses the radiative forcing (which remember is defined relative to 1750) in 2005. i.e. the forcing calculated in going from 1750 conditions to 2005. What is the problem? Oddly, though, RP *hasn’t* posted Gavins response but seems to have deleted the entire misconceived post. Anyway, here is RP’s question:
Climate Science has asked the questions below in a comment on the weblog Real Climate. Their answer will be posted here also.
Climate Science has a question for Real Climate (the answer of which will also be posted on that website). The 2007 IPCC Statement for Policymakers [Figure SPM.2] has the following caption
“Global average radiative forcing (RF) estimates and ranges in 2005 for anthropogenic carbon dioxide (CO2 ), methane (CH4 ), nitrous oxide (N2O) and other important agents and mechanisms, together with the typical geographical extent (spatial scale) of the forcing and the assessed level of scientific understanding (LOSU).”
but also the footnote on page 2 that
“Radiative forcing is a measure of the influence that a factor has in altering the balance of incoming and outgoing energy in the Earth-atmosphere system and is an index of the importance of the factor as a potential climate change mechanism. Positive forcing tends to warm the surface while negative forcing tends to cool it. In this report, radiative forcing values are for 2005 relative to pre-industrial conditions defined at 1750 and are expressed in watts per square metre (W m-2)…..”
Which of the two are correct?
Assuming that you agree that the footnote is correct, and the figure caption is in error, what is the Real Climate estimate in Watts per meter squared in 2005 (or in 2007) of the radiative forcing components and range for a figure analogous to Figure SPM.2 in the Statement for Policymakers?
[Update: the post is back, with no explanation. RP repeats his question. The answer is that the figure and the footnote are both correct, but "what is the current radiative forcing (i.e radiative imbalance)" is wrong]