Thanks for the comments.

Hopefully, I never said “temperature reduction”! I always try to indicate that my number represents a “savings” from where the global temperature would have otherwise had been without a particular action. Thus, it is not an actual lowering of the temperature by some teensy amount, but a tiny slowing of the rate of warming which would otherwise occur to that point in time. No one–or at least I hope not–is talking about actually reducing global temperatures by emissions reductions. That ain’t going to happen. You are correct, for that to occur, emissions need to go to virtually zero (or below) and then we need to wait—probably a long time!

-Chip

The most which can be said about the effects of a partial emissions rate reduction, such as that committed to by CA or that proposed for the US, is that (given your assumptions) they would reduce temperatures below what they would otherwise have been without the emissions reductions. That does not translate to a reduction in absolute terms.

Global average temperature reductions in absolute terms (given your assumptions) would require not only a total cessation of AGW emissions, but also some reduction in the atmospheric concentration of GHG.

I do not believe it is realistic to begin discussing temperature reductions until the driving force for temperature increases (given your assumptions) has been eliminated. Based on the IEA estimate of ~$45 trillion to reduce emissions by 50% by 2050, we are somewhere north of $100 trillion from worrying about reducing global average temperatures in absolute terms.

You might go ahead and buy the champagne now, but I wouldn’t worry about chilling it or breaking out your champagne flutes quite yet.

Ed

Thanks for the question. Here is a short answer.

Greenhouse gases in the atmosphere control a certain amount of the earth’s surface temperature. Fewer greenhouse gases produce lower temperatures, more greenhouse gases produce higher temperatures. Humans have been adding greenhouse gases to the atmosphere, thus the global average surface temperature should be rising. And, in fact, it is.

Don’t get me wrong, natural variability is also at play, but it is acting on top of the impact of the growing greenhouse gas concentrations. Sometimes it acts to quicken the rate of warming (for example, throughout the 1990s), other times it acts to lessen the rate of warming (for example, so far this century)–but it is not responsible, to my best understanding, for the majority of the observed rise in global surface temperatures for the past 30 years or so.

-Chip

Yes, I did the calculation that came up with the 0.02ºF for the global temperature “savings” of California reducing its emissions to zero. It is important to understand, as Ed Reid suggests in his comment, that this represents more the tiny influence that California has on the global climate through its greenhouse gas emissions than it does an exact value. As such, we should focus less on its precision and more on its overall magnitude…which is minuscule. As different assumption are used about climate sensitivity, future global emissions, etc. the 0.02ºF number could change a bit, but it would never change enough to make California have a useful role in changing the global climate by altering its emissions rate.

I have done similar calculations for some of the U.S. climate bills that have been introduced in the past to reduce total U.S. carbon dioxide emissions. You can see the results of these calculations in an article posted over at World Climate Report. The numbers for the whole U.S. aren’t very impressive either…it will take large scale global action.

-Chip

Nobody calculated that figure; or, if someone did, they “screwed up”.

Assuming that increasing atmospheric CO2 concentrations are driving increases in global average temperature, a US reduction of 80% by 2050 would not reduce global average temperature by 0.02F (or at all, actually), all other things held equal. China is currently increasing its annual CO2 emissions by 10% per year; that is, it is increasing global annual CO2 emissions by 2% per year. An 80% reduction in US emissions over 40 years (2% per year) would be offset by the Chinese increases within 5 years.

The contribution of the California reduction “wish”, on a global level, would be the rough equivalent of a single spot of “yellow snow” in the Rockies in a blizzard.

If AGW is an issue, it is a global issue, amenable only to a global solution. Anything less is doomed to failure.

Further, the 80% number is meaningless, since it might slow, but would not stop, AGW. Atmospheric CO2 concentrations began increasing in ~1750, when global annual CO2 emissions were approximately 1/2000th of current levels. Logically, halting the increase would require reducing global annual emissions to below the level at which the atmospheric concentration began to increase, even assuming that the global CO2 sinks are as effective as they were in ~1750. That would translate to an ~ 99.95% reduction in global annual CO2 emissions, which would would require a total elimination of fossil fuel combustion emissions, either through capture and sequestration or cessation of fossil fuel combustion. It would also require reductions in human and domesticated animal populations, since both contribute CO2 and CH4 emissions to the GHG totals. (Think population controls and a vegan diet.)

I went back to your previous posting about California and found a statement that by 2050, temperatures would be reduced by less than 0.02 degree F. Did you calculate this figure or are you quoting another source?

I’ve been seeking similar information for the U.S. if 80% reduction by 2050. Is there a standard forumla to be used to calculate temp reduction if CO2 emissions are reduced by certain amount? Or, is there a web source that lists the actual temp reductions based on specific policies? Thanks.

C3H Editor, http://www.c3headlines.com

The reports don’t confirm a darn thing other than that the continued blind implementation of AB32 is bad for California. As the self proclaimed “leader” on the issue, California would lead better simply by taking a “time out” to suspend implementation, allow the economy to recover, and understand how others might act (one major leg of AB32 is the Western Climate Initiative, which appears to be splitting apart.) The economic impacts of implementation have been discussed here and elsewhere (and, no surprise, CARB believes the net is positive, other analyst find net costs)—but that was done way before the economy tanked, when fuel was high-priced, and capital was readily available (note most of the “solutions” are capital intensive in exchange for future savings…supposedly.) There is NO problem created by a two or three year delay. Who knows, maybe everybody will get off their high horse and learn something–like the definintion of “scenario.”