Annex I is a good proxy for developed countries and hansen has the sign wrong.

Note non-Annex I has a typo, should be 0.45%, also off by a large factor. See my subsequent post on this subject for an update.

Thanks!

and
2) the mean annual CO2 increases — particularly AFTER 2000 when scenario C assumed the annula increases would CEASE and the trend is CLEARLY still in the postive direction! ( The trend is much more important than averages but for the years 2000-2005, CO2 increased on average by 2.0ppm per year. The slight acceleration in increase might just be “scatter about the mean” of the longer period, but the CO2 level would still seem to be increasing linearly, at a minimum)

http://www.cmdl.noaa.gov/ccgg/trends/

Given 1 and 2 above, it is a bit much (to say the least) to conclude that the
“Most Accurate CO2 Assumption = Scenario C”

not only that, The CRITICAL thing about scenario C (as hansen points out) is that it assumes the CO2 level LEVELS off in 2000,

(“specifically greenhouse gases were assumed to stop increasing after 2000″ — JH)
http://www.columbia.edu/~jeh1/hansen_re-crichton.pdf

which is CLEARLY NOT what has happened:

annual mean groth rate
2000 1.78
2001 1.60
2002 2.55
2003 2.31
2004 1.54
2005 2.53

(which average to 2.05 ppm yearly increase over the years 2000-2005, by the way)

http://www.cmdl.noaa.gov/ccgg/trends/

That certainly coems as no surprsie to Hansen. He said that this scenario (based on the assumption of a “drastic curtailment of emissions”) was probably unrealistic to begin with. Hansen is not about the business of emissions predictions, at any rate, which is why he provided different senarios in the first place (a point that seems to elude some critics of the IPCC to this day).

Furthermore, whether any given emission scenario actually matched reality is important ONLY from the standpoint of evaluating the predicted temperatures vs actual.

And for that purpsoe, what is really important is not the overall average (of yearly increase in CO2 concentration) over a time span of several years (which actually comes out about 1.71ppm for the span between 1988-2005) but the TREND, which matches scenario B more closely than scenario C (because of the leveling off assumption for scenario B referred to above)

The upshot is that the claim that the CO2 emissions matched scenario C most closely is simply NOT correct.

That much CAN be said EVEN without seeing Hansen’s actual CO2 forcing numbers for the years between 1998 and the present for scenarios A and B.

But without seeing ALL of Hansen’s CO2 forcing numbers for years past 1998 to present I would not conclude anything further — specifically in regard to how closely scenario has B matched reality since 1998.

As far as emissions pathway, saying that it lies between Scenarios B and C seems incorrect. hansen writes,

“Fig. 5A reveals that the “actual” greenhouse gas forcing falls near or just below scenario C.”

Thanks!

Thanks, that link helps. From figure 5 and the text, it looks like the actual emissions pathway has been in between B and C of the original projections. So, the fact that observed temperatures have tracked within the range of model runs B and C suggests that Hansen’s original 1988 forecasts were very good, no? Of course, an updated version of the combined forcings through 2005 would be useful.

My earlier point (b) was just that your original method of skill-scoring the projected emissions pathways — by CH4, N2O and CO2 separately — may not be as “meaningful” as if the GHG emissions pathways (A, B, & C vs. observed) were presented in CO2 equivalents (CO2E), or in terms of total W/m^2 forcing (as done in Figure 5 of Hansen et al., 1998). I didn’t use the word “irrelevant.” Misunderstanding…

Best, james

Our comments may have crossed in the ether, but my response to Tom addresses your points. See Figure 5C in this paper:

Hansen, J., Mki. Sato, J. Glascoe, and R. Ruedy 1998. A common sense climate index: Is climate changing noticeably?. Proc. Natl. Acad. Sci. 95, 4113-4120.

http://pubs.giss.nasa.gov/docs/1998/1998_Hansen_etal_1.pdf

This goes through 1996 (apparently?). I am unaware of any update to this figure.

As far as your point b), I can’t imagine how one can conclude that estimates of future emissions are “irrelevant” since such estimates are the basis for predictions of the type Hansen has offered since 1988.

Thanks.

Regarding your first point. I think the figure basically speaks for itself… especially when results from all of the model runs are left on the figure so that the viewer can make a judgment. Michaels, on the other hand, had to *erase* two of the runs to make his point seem valid.

I will grant you that one of Krugman’s points is misleading: “The original paper showed a range of possibilities, and the actual rise in temperature has fallen squarely in the middle of that range.” But Hansen never said this.

Also, regarding you conclusions:
“a) Temperature has followed the curves of B and C”

OK, fair enough.

“b) However, neither scenario provides a good representation of actual emissions paths underlying the scenarios.”

In the context of this discussion of model skill with respect to GHG forcing, I think that this point is meaningless without calculating the CO2 equivalents.

“c) But perhaps they (by accident) B and C got GHG forcing about right”

Again, I think you need to calculate the CO2 equivalents to say this with any accuracy.

Thanks, James

In response to you BTW2:

The emissions rates I cite are from table 3 of this paper:

Hansen, J., Mki. Sato, J. Glascoe, and R. Ruedy 1998. A common sense climate index: Is climate changing noticeably?. Proc. Natl. Acad. Sci. 95, 4113-4120.

http://pubs.giss.nasa.gov/docs/1998/1998_Hansen_etal_1.pdf

Take a close look at Figure 5C which is a more sophistocated analysis than that presented here. Through 1998 it actually suggests that scenario C was the more accurate of the three.

In that paper, Hansen wrote:

“The large interannual variability of even global mean temperature makes it difficult to draw inferences about model validity based on only a decade of observations. But, at least so far, the real world is behaving more like the model driven by scenarios B and C, rather than the model driven by scenario A.”

Thanks for your response.

“So I am less concerned with Inhofe’s and Gore’s “portrayal of reality” than with the practical implications of such portrayals for actual policy action.”

That seems reasonable to me.

Although, as you may recall, I tend to get more upset by Inhofe because 1) of my own policy preferences and 2) the Senator from OK is in a very powerful position when it comes to actually making public policy, not just proposing it (while Al Gore is not). Also, Inhofe took an oath to serve the public, but he chooses to use his influential committee to host talk-show-style panels with fiction writers posing as scientists. This puts off a strong scent of contempt for an honest debate and so I think it does more than distort reality… it undermines public trust in the democratic process and good governance.

Sorry if this strays too far off topic. Thanks again for your response.

Best, James

Perhaps we should just agree that Hansen would be well-served in the future to simply point out that:

a) Temperature has followed the curves of B and C
b) However, neither scenario provides a good representation of actual emissions paths underlying the scenarios
c) But perhaps they (by accident) B and C got GHG forcing about right

Thanks!