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32 comments on Houston ASPO Day 2 part 2

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mdsolar on October 22, 2007 - 4:13pm Permalink | Subthread | Comments top

Heading Out,

It is a great opportunity to have both Kharecha and Rutledge in the same room. NASA GIS has done some models (taking off from Hansen's alternative scenario) that are more similar to Dave's model while Dave's use of the earlier estimate of what may constitute a dangerous carbon dioxide concentration could need so revision. Was there any back and forth on this?

Thanks,

Chris

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Liz on October 22, 2007 - 6:40pm Permalink | Subthread | Parent | Comments top

Presumably Rutledge's model, just like the IPCC's, doesn't include any positive feedback effects such as the permafrost melting and sea ice thawing, both already underway and (in the permafrost case at least) in danger of creating runaway warming. Therefore I find it hard to give it much credence.

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mdsolar on October 22, 2007 - 10:51pm Permalink | Subthread | Parent | Comments top

NASA GIS atlernative and Dave's model are both emissions scenarios that are substantially below BAU. Since emissions still appear to dominate the build up of carbon dioxide in the atmosphere, one can justify taking this approach. An alternate and not very revealing approach is to ask how much feedback is happening now based on the atmospheric carbon dioxide record:

Mauna Loa measurements of the annual change in the concentration of carbon dioxide in the atmosphere (thin solid line) together with fossil fuel emissions (thick solid line) and various extrapolations. A linear extraoplation (short-dashed line) reaches dangerous climate change (450 ppm) near the year 2035 (where the line thickens). This and the exponential extrapolation (dot-dashed line) are fits minimizing Chi^2 in linear are log space respectively. The other two lines attempt to match these at the beginning and end of the measurements. They have the functional form of time to the power of time (triple-dot-dashed line) and a Gaussian (long-dashed line). The data point for 2007 is a guesstimate.

More on the plot here.

The way I see it, some pretty spectacular feedbacks are allowed by the data to be underway, but this is because the data are not very constraining. We do not understand fully where our extra emissions go or how negative feedbacks might behave. Can newly exposed Arctic waters absorb more carbon dioxide for example? Is there growing biological fecundity that is acting as an overall sink that is soaking up our accelerated emissions? But, the possibility of soon to be dominate positive feedbacks is a real worry even if we can't yet measure their effect in this manner.

Chris

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FMagyar on October 23, 2007 - 6:28am Permalink | Subthread | Parent | Comments top

"Can newly exposed Arctic waters absorb more carbon dioxide for example? Is there growing biological fecundity that is acting as an overall sink that is soaking up our accelerated emissions?"

This doesn't sound too good:

http://www.sciam.com/article.cfm?articleID=C92C3262-E7F2-99DF-30FA22A938...

"Carbon dioxide levels in the atmosphere continue to rise thanks to dirtier economies and a weakening in natural systems' ability to remove the greenhouse gas"

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mdsolar on October 23, 2007 - 11:20am Permalink | Subthread | Parent | Comments top

I agree that carbon sinks that have played a major role so far may be saturating. The two highlighted in your link, southern oceans and mid-latitude land plants are very important sinks. I expect that sources, such as tundra rot, could be overwhelming. Yet, the Mauna Loa data seem to hold their course just now while emissions jump. Part of the point of the figure is that a number of atmospheric build up scenarios could be consistent with the data. So, and apparent holding of course may not be all that meaningful. There is a possiblity of new sinks too. Northward expansion of boreal forests might go faster than anticipated just as Arctic sea ice loss has gone faster. To me, the safe concentration of carbon dioxide in the atmosphere is the pre-industrial level.

Chris

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mdsolar on October 23, 2007 - 11:30am Permalink | Subthread | Parent | Comments top

I forgot to say that US emissions of carbon dioxide were down 2.2% in 2006 coincident with the largest jump in electricity prices is 25 years. The price jump was a result of the transition to deregulation. While the market is not working yet to reduce electricity prices, it might be reducing emissions a little.

Chris

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Heading Out on October 22, 2007 - 9:07pm Permalink | Subthread | Parent | Comments top

Not much, it tended to focus more on Dave Rutledge's work.

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mdsolar on October 22, 2007 - 11:03pm Permalink | Subthread | Parent | Comments top

Sounds like Dave knew his audience better too. Thanks,

Chris

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32 comments on Houston ASPO Day 2 part 2

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