The Guardian has a poll of Copenhagen Conference participants.
Most of those who responded expect a global mean temperature increase over the next century in excess of 3 C . About 5.5 F globally; well over 10F, presumably , in continental interiors and the Arctic.
What do you think? Pick a number.
Image: NASA
"What do you think a safe peak CO2 concentration is?"
ReplyDeleteWell if I have to pick a number, how does Hansen's 350ppm figure sound?
Sorry, but that is the wrong question. The more critical question is, "When will we see large scale transfer of heat to the ice sheets?" Thus, the correct question is: "When will the temperature of seawater in contact with the base of the WAIS exceed 0C?" For that number I would say the odds are even that it will happen - before 2020. I would even go out on a limb and say that the odds of it happening by 2015 were as high as 10%. Surprised? Were you also surprised at the Larson collapse in 2002? Or, the Wilkins in 2009? Or, the Wordie?
ReplyDeleteDefine "safe". Already by 1958 CE, with CO2 at 315 ppm, the last mainland remnants of the Laurentide Ice Sheet had melted (in the 30s and 40s); Greenland was just beginning to melt; Swiss glaciers were in retreat at about 4 m/yr.
ReplyDeleteIn 1850 CE, with CO2 concentrations at 288 ppm. Swiss glaciers stopped advancing.
Sounds as if (ignoring methane) close to 290 ppm is "safe".
Under "Open thread" (but I didn't know which number we were supposed to pick!)...
ReplyDeleteThis is another plain speaking point from IPCC author Andrew Weaver (again!):
Over the years I have given numerous presentations on the science of global warming. Midway through I show a graph that demonstrates that no matter what trajectory our greenhouse gas emissions follow, the projected global warming over the next two decades is about 0.2C per decade. This is the level of global warming to which we must adapt, regardless of our emissions trajectory. By the end of the century, (however), things are very different and the world our grandchildren inherit profoundly depends on the choices we make today. Global warming is fundamentally a question of intergenerational equity.
Consequently, political leaders who take bold steps to implement policies to limit these emissions are doing so for future generations. The politicians will not see the climatic consequences of their decisions within their political lifetime.
So when asked what I believe to be the most important thing an individual can do to combat global warming, I invariably respond that they should support those who have the political courage and moral fortitude to implement the difficult, yet essential policies required to deal with it. When asked about the greatest obstacle to change, I point to shameless political opportunism and gimmicks designed to score cheap political points and votes in a desperate attempt to get elected.(N.B. the BOLD edits/adds are mine because I had to re-read that first paragraph to catch it first time around...)...
A little background. Canada has two provincial governments that have introduced (can ya believe it!?) the dreaded "carbon taxes"... There is an election in British Columbia right now that is devolving into a referendum on the issue... Weaver is weighing in, recognizing that the world is watching... (as they were in the last Canadian fed election)...
The somewhat fringe BC Reform Party has adopted a lovely href="http://www.reformbc.net/reform-logo-2.gif">We 'heart' CO2 logo for the campaign... sigh...
Anyway, what I liked about Weaver's piece was the candid discussion of the disconnect between the 2 several decades of climate outcomes and current action... the contrast between the "term" of today's politicians and the future beneficiaries...