Sunday, June 11, 2006

Business was not usual (continued)

Jim Hansen, in his testimony to the Senate Committee on Energy and Natural Resources (btw he testified four times on essentially the same topic between November 1987 and 1989) said:

For the future, it is difficult to predict reliably how trace gases will continue to change. In face, it would be useful to know the climatic consequences of althernative scenerios. So we have considered three scenarios for future trace gas growth, shown on the next viewgraph.

Scenerio A assumes the CO2 emissions will grow 1.5 percent per year and that CFC emissions will grow 3 percent per year. Scenerio B assumes constant future emissions. If populations increase, Scenerio B requires emissions per capita to decrease.

Scenerio C has drastic cuts in emissions by the year 2000, with CFC emissions eliminated entirely and other trace gas emissions reduced to a level where they just balance their sinks.

These scenarios are designed specifically to cover a very broad range of cases. If I were forced to choose one of these as most plausible, I would say Scenario B. My guess is that the world is now probably following a course that will take it somewhere between A and B
Of course, as we have seen in the previous post, atmospheric methane (CH4) concentrations have leveled off starting in 1990 and the Montreal Protocols are actually reducing the mixing ratios of the CFCs.

In testimony to the House Energy and Power Subcommittee Hansen made the following recommendations for immediate action:
I think we could take some steps now to reduce the rate of growth of the greenhouse effect. Chlorofluorocarbons, which destroy ozone, as well as cause 20 percent of the greenhouse effect, could be phased out entirely over an appropriate period of time. The manufacturers agree that there are or will be substitutes for the chlorofluorocarbons.

Also, we should increase our energy efficiency, because CO2 causes 55-60 percent of the greenhouse effect. There's a lot of room for improved efficiency. It would have other benefits, independent of the greenhouse effect, especially on our balance of payments deficit. How to get at that problem is, of course, a major difficulty and that's something you can address better than I can. I know that there are major ways that we could improve our energy efficiency.

Finally, I think we should discourage deforestation and encourage reforesetation, because that would not only reduce atmospheric CO2, but also preserve the habitat for innumerable, valuable biological species. The impact of these kinds of steps on the short run is going to be relatively small, but it's very important, because it would change the direction in which the greenhouse effect is headed. Instead of the sharp, upward ramp that we're on now, it could put us on a more manageable course on the longer term, over the next several decades.
Before anyone gets crazy, the "CO2 causes 55-60 percent of the greenhouse effect", clearly refers to the forcing, not the total greenhouse effect.


Anonymous said...


Darling Lubos, would you care, for example, to point to a map of the world 55 million years ago, and if you can, how confident are you of its accuracy

Posted by: Eli Rabett | June 9, 2006 07:10 PM


Dear Darling, sure. What you ask for is essentially the 4th picture at

this page.

I am 90% certain that at least 90% of the area agrees with reality (land vs. ocean). The reason why I am so certain is that the continental drift (have you heard of it?) has been rather uniform in the recent era, and 55 million years is a "recent era" in the science of continental drift. Geologists who actually study these questions are reconstructing the continents more than 1 billion years ago, 20 times more than what you find impossible because you don't understand physics behind it.

You should look into Wikipedia for various supercontinents such as Pangaea. A lot is known about them.


EliRabett said...

Sweet Lubos, unless your car has a bumper sticker demanding Gondwanaland be reunited, you are a mere chickenhawk on the matter. However, this is progress given that you have never admitted having less than 100% certainty on anyting. Perhaps you are reaching the emotional age of five. Happy birthday.

Anonymous said...

Lubos said: "You should look into Wikipedia for various supercontinents such as Pangaea. A lot is known about them."

Ah, yes, "Wikipedia", the Oracle.

Isn't that the encyclopeadia that allows anyone to change anything?

I wonder what they have to say about string theory. Undoubtedly that it actually has something to do with reailty.

ncdave4life said...

Four times?!? I'd never heard that!

This is the transcript of his June 23, 1988 testimony to the U.S. Senate Committee on Energy and Natural Resources:

He never mentioned CFCs that day.

Do have, or know where to find, the other three transcripts?

ncdave4life said...

I found the other three transcripts (Nov. 9, 1987; July 7, 1988; May 8, 1989), and I've added links to them here:

Interestingly, Hansen's 11/9/1987 testimony contradicts the paper!

The 1988 paper says, "Scenario A assumes that growth rates of trace gas emissions typical of the 1970s and 1980s will continue indefinitely; the assumed annual growth averages about 1.5% of current emission..."

But in his 11/9/1987 testimony he said, "Scenario A assumes the CO2 emissions will grow 1.5 percent per year and that CFC emissions will grow 3 percent per year."

(Note: 11/9/1987 was just 24 days after the Montreal Protocol's adoption; it's impossible to imagine Hansen was unaware of it. So he obviously know CFC emissions would decline, when he testified that day.)

So, the obvious question is: did they model CFC emissions increasing at +3%/year (per the 1987 testimony), or at +1.5%/year (per the 1988 paper)?

More than nine months elapsed between the two. So maybe they revised the Scenario A parameters and re-ran the model before publishing the paper? Do you know whether they did?