Climate Update
Feb. 2nd, 2007 03:43 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
marcusmarcusrcThe summary for policymakers of the IPCC Fourth Assessment Report (the biggest climate document of the last five years, both in size and importance) was just released today.
"Most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations."
Two nice graphs: pg. 16 (SPM-2): Forcing changes since 1750: Anthropogenic contributions: 0.6 to 2.4 W/m2 (uncertainty mainly due to interactions between aerosols and clouds). Change in solar forcing: 0.06 to 0.3 W/m2. pg. 18 (SPM-4): Comparing models run with "just natural" forcing and "all forcings" to observations, showing how the last half century of warming is not explained without human influences. (this is a qualitative comparison: there are of course more quantitative measures of attribution behind this)
For the most part the report attempts to put probability ranges on all the reported numbers (rather than just reporting ranges, as in the third assessment report).
Projected temperature change for the next century: 1.1 to 6.4 degrees C (without probability, since they still don't quantify probabilities for emissions scenarios) (compare to 0.6 degrees C for 1900 to 2000). Sea level rise: 18 cm to 59 cm (compare to about 17 cm for 20th century). This does not include Greenland/Antarctica, which could add another 10 to 20 cm or more, but the melting processes of these ice sheets are still poorly understood.
It is also "likely" that we will see both more droughts and more heavy precipitation events, and more intense tropical cyclones in the 21st century.
Discussion also available at realclimate.
Note that the summary is based on a report that is fully drafted but "embargoed", and will not be released until April. The science in the full report is set, and won't change, but there may be minor edits and wording changes. The summary itself still needs some editing (I've noticed a few typoes), but apparently once it was "hammered out" by scientists and politicians to be as understandable as possible while still accurately reflecting the draft chapters they wanted to release it as quickly as possible.
Note that it seems like most people think that this report has been somewhat "conservative" in its statements.
In other climate news, Prof. Lindzen of MIT appeared on Larry King along with Bill Nye the science guy. Sadly, in the short clip I watched (the first couple minutes of the show), Lindzen repeated one ridiculous skeptic canard, namely "it hasn't warmed in the past 8 years" because 1998 was as warm as any year since. Claiming that this indicates that there isn't a warming trend makes about as much sense as saying on June 8th, "hey, it was warmer on June 1st than it is today. Therefore, there isn't a warming trend! I bet it won't be any warmer in August than now!" Lindzen is probably the best scientist among the "climate skeptic" population, but this kind of statement among others is why I've lost any respect for him. It is also odd that a 4 person panel would consist of 2 "skeptics" and 2 "mainstreamers" where the skeptics are a climatologist and an economist and the mainstreamers are a weather channel host and a TV science guy - why didn't they get a mainstream scientist or economist on the show? Why did the show have to "evenly represent" two sides of view that are totally not evenly represented in the real world? etc.
"Most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations."
Two nice graphs: pg. 16 (SPM-2): Forcing changes since 1750: Anthropogenic contributions: 0.6 to 2.4 W/m2 (uncertainty mainly due to interactions between aerosols and clouds). Change in solar forcing: 0.06 to 0.3 W/m2. pg. 18 (SPM-4): Comparing models run with "just natural" forcing and "all forcings" to observations, showing how the last half century of warming is not explained without human influences. (this is a qualitative comparison: there are of course more quantitative measures of attribution behind this)
For the most part the report attempts to put probability ranges on all the reported numbers (rather than just reporting ranges, as in the third assessment report).
Projected temperature change for the next century: 1.1 to 6.4 degrees C (without probability, since they still don't quantify probabilities for emissions scenarios) (compare to 0.6 degrees C for 1900 to 2000). Sea level rise: 18 cm to 59 cm (compare to about 17 cm for 20th century). This does not include Greenland/Antarctica, which could add another 10 to 20 cm or more, but the melting processes of these ice sheets are still poorly understood.
It is also "likely" that we will see both more droughts and more heavy precipitation events, and more intense tropical cyclones in the 21st century.
Discussion also available at realclimate.
Note that the summary is based on a report that is fully drafted but "embargoed", and will not be released until April. The science in the full report is set, and won't change, but there may be minor edits and wording changes. The summary itself still needs some editing (I've noticed a few typoes), but apparently once it was "hammered out" by scientists and politicians to be as understandable as possible while still accurately reflecting the draft chapters they wanted to release it as quickly as possible.
Note that it seems like most people think that this report has been somewhat "conservative" in its statements.
In other climate news, Prof. Lindzen of MIT appeared on Larry King along with Bill Nye the science guy. Sadly, in the short clip I watched (the first couple minutes of the show), Lindzen repeated one ridiculous skeptic canard, namely "it hasn't warmed in the past 8 years" because 1998 was as warm as any year since. Claiming that this indicates that there isn't a warming trend makes about as much sense as saying on June 8th, "hey, it was warmer on June 1st than it is today. Therefore, there isn't a warming trend! I bet it won't be any warmer in August than now!" Lindzen is probably the best scientist among the "climate skeptic" population, but this kind of statement among others is why I've lost any respect for him. It is also odd that a 4 person panel would consist of 2 "skeptics" and 2 "mainstreamers" where the skeptics are a climatologist and an economist and the mainstreamers are a weather channel host and a TV science guy - why didn't they get a mainstream scientist or economist on the show? Why did the show have to "evenly represent" two sides of view that are totally not evenly represented in the real world? etc.
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no subject
Date: 2007-02-04 04:45 pm (UTC)(for comparison, I think the European Trading System carbon price peaked at about $100/ton, and is back down to less than $10/ton now. I _so_ wish I could have figured out some way to make money off the fact that everyone in my lab was 90% certain that the $100/ton price was totally off base)
Anyway, to sum up: I really do think it is worth spending some significant but not economy-crushing amount of resources on emissions mitigation now in order to reduce climate impact in the future, despite projected economic growth of possibly unimaginable magnitude. Of course, I admit that given that I've chosen to spend the last N years studying the topic, it would be hard for me to reach the conclusion that those N years were wasted because the climate problem isn't worth worrying about... but I'm trying to be as rational and unbiased as I can manage...
no subject
Date: 2007-02-04 05:29 pm (UTC)I tend to agree with you in the broadest sense, that we should be doing something about climate change. I think the only reason I started debating at all was because it sounded like you were being a bit flip about the idea of discounting. I expect it sounds a bit silly on TV, but most things do.