Comments on: Lucia Liljegren on Real Climate’s Approach to Falsification of IPCC Predictions http://cstpr.colorado.edu/prometheus/?p=4415 Wed, 29 Jul 2009 22:36:51 -0600 http://wordpress.org/?v=2.9.1 hourly 1 By: Tom Fiddaman http://cstpr.colorado.edu/prometheus/?p=4415&cpage=1#comment-9961 Tom Fiddaman Mon, 19 May 2008 20:54:29 +0000 http://sciencepolicy.colorado.edu/prometheusreborn/?p=4415#comment-9961 This discussion of how one or another emissions trajectory influences results neglects one critical factor: emissions have no direct impact on radiative forcing. It is the atmospheric concentration, i.e. emissions less uptake integrated over time, that matters. Take a really simple model of the carbon cycle (from Nordhaus' original DICE model): dC/dt = a*E - (C - C0)/b where C is atmospheric carbon, a is .64 and b is 120 years and C0, preindustrial carbon, is 600 Gt. Then whether E is 10 Gt/yr or 11 Gt/yr (i.e. a big difference in emissions) makes less than a 1% difference in concentration over a decade. The impact on forcing, which is logarithmic, is correspondingly tiny. Thus, regardless of what one thinks about recent temperature, short term deviations in the CO2 emissions trajectory have little effect on the outcome. If some anthropogenic forcing matters, it would have to be one of the short term ones like aerosols. This discussion of how one or another emissions trajectory influences results neglects one critical factor: emissions have no direct impact on radiative forcing. It is the atmospheric concentration, i.e. emissions less uptake integrated over time, that matters.

Take a really simple model of the carbon cycle (from Nordhaus’ original DICE model):
dC/dt = a*E – (C – C0)/b
where C is atmospheric carbon, a is .64 and b is 120 years and C0, preindustrial carbon, is 600 Gt. Then whether E is 10 Gt/yr or 11 Gt/yr (i.e. a big difference in emissions) makes less than a 1% difference in concentration over a decade. The impact on forcing, which is logarithmic, is correspondingly tiny.

Thus, regardless of what one thinks about recent temperature, short term deviations in the CO2 emissions trajectory have little effect on the outcome. If some anthropogenic forcing matters, it would have to be one of the short term ones like aerosols.

]]> By: Lupo http://cstpr.colorado.edu/prometheus/?p=4415&cpage=1#comment-9960 Lupo Fri, 16 May 2008 20:16:43 +0000 http://sciencepolicy.colorado.edu/prometheusreborn/?p=4415#comment-9960 Yes John, I have the same conclusions that scenarios with incorrect emissions is an embarassment to notions anything other than sun and water run the weather the weather patterns and the climate. But when you guess and guess and guess a lot so you can get a wide enough range of data to prove anything you should expect to be wrong a lot individuallly and especially with your far out guesses, don't you think? Yes John, I have the same conclusions that scenarios with incorrect emissions is an embarassment to notions anything other than sun and water run the weather the weather patterns and the climate. But when you guess and guess and guess a lot so you can get a wide enough range of data to prove anything you should expect to be wrong a lot individuallly and especially with your far out guesses, don’t you think?

]]> By: jmrsudbury http://cstpr.colorado.edu/prometheus/?p=4415&cpage=1#comment-9959 jmrsudbury Fri, 16 May 2008 01:54:25 +0000 http://sciencepolicy.colorado.edu/prometheusreborn/?p=4415#comment-9959 Sly point Lupo. Including the lesser emission scenarios proves one of, or a combination of, three things: 1. CO2 forcing is not as strong as they figured 2. The feedback is not as strong as they figured 3. They missed one or more forcings that are cooling us even though there have been no major volcanic eruptions since 1992. This is just my way of saying that without calculating error bars and uncertainties, it seems likely to me that the models have been falsified. Of course, I appreciate all the work people have been doing on this and Lucia's blog to try to quantify the certainty level of the models. I just wish I had more to contribute to the discussion. John M Reynolds Sly point Lupo.

Including the lesser emission scenarios proves one of, or a combination of, three things:
1. CO2 forcing is not as strong as they figured
2. The feedback is not as strong as they figured
3. They missed one or more forcings that are cooling us even though there have been no major volcanic eruptions since 1992.
This is just my way of saying that without calculating error bars and uncertainties, it seems likely to me that the models have been falsified. Of course, I appreciate all the work people have been doing on this and Lucia’s blog to try to quantify the certainty level of the models. I just wish I had more to contribute to the discussion.

John M Reynolds

]]> By: Lupo http://cstpr.colorado.edu/prometheus/?p=4415&cpage=1#comment-9958 Lupo Thu, 15 May 2008 20:18:34 +0000 http://sciencepolicy.colorado.edu/prometheusreborn/?p=4415#comment-9958 Yes, why would we use scenarios that don't have the emissions correct? What would that prove? Yes, why would we use scenarios that don’t have the emissions correct? What would that prove?

]]> By: jmrsudbury http://cstpr.colorado.edu/prometheus/?p=4415&cpage=1#comment-9957 jmrsudbury Thu, 15 May 2008 03:05:19 +0000 http://sciencepolicy.colorado.edu/prometheusreborn/?p=4415#comment-9957 When you also take into account that the CO2 emissions have been above scenario A1, the Constant scenario should no longer be considered. The lower error bar should have a definitely positive slope. Estimating from Figure 4 graph from Lucia's post, I estimate that lower error bar should be 1 degree over 60 years or 0.167 C per decade. The mean for the models then would be well above 0.2 C per decade. John M Reynolds When you also take into account that the CO2 emissions have been above scenario A1, the Constant scenario should no longer be considered. The lower error bar should have a definitely positive slope. Estimating from Figure 4 graph from Lucia’s post, I estimate that lower error bar should be 1 degree over 60 years or 0.167 C per decade. The mean for the models then would be well above 0.2 C per decade.

John M Reynolds

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