If we stopped all emissions, of all GHGs and aerosols, what would be removed first are the aerosols. The sulfate cooling offset is estimated at 1.1 W/m2 so their loss would lead to a strong warming influence. The black carbon is estimated by IPCC at about 0.4-0.5 and by Ramanathan and others to be twice that. Their loss would lead to a less positive forcing, so, if all these emissions stopped, the net would be a small warming influence. Stopping all emissions, of course, tropospheric ozone warming influence would also end over months. And then methane influence would go down over decades. So, one would tend toward a lessened warming influence. And some, but not a lot of the CO2 would be taken up. So, stopping all forcing does reduce the warming influence.
If you want to see a graph of the effects of ending all GHG emissions (the tables have information on aerosols), go to a recent proceedings paper I have posted at http://www.climate.org/PDF/MacCracken_Erice.pdf, where you will also see my views about how to utilize the different time scales to promote an agreement between developed and developing nations at http://www.climate.org/topics/climate-change/maccracken-proposal-north-south -framework.html These notes are all about forcings, as the forcing will determine the climate that the world heads toward. The ocean slows the transition to equilibrium. If you want to see what is, in effect, a geoengineering set of simulations by the modeling groups of the world, look at the graph of the IPCC projections of temperature. One sees the results for the various SRES scenarios, but the yellow/orange line shows the results for holding all concentrations and aerosol loadings constant. Holding CO2, N2O, and halocarbon concentrations constant requires some very large percentage reduction in their emissions; for methane the cutback is much less. But cutting CO2 emissions by 80-90% to keep its concentration constant will surely lead to a sharp reduction in SO2 emissions, and so a very sharp reduction in their cooling influence, and perhaps in black carbon and its somewhat smaller warming influence, meaning that to hold the aerosol burden constant, there must be substantial emissions of aerosols/aerosol precursors (just what is being discussed for geoengineering, except in the troposphere). You can see that about 0.5 C further warming goes on, and this is the oceans catching up to the land. Mike MacCracken On 11/1/09 12:34 PM, "John Gorman" <[email protected]> wrote: > > I think the point is as follows: > > If we fix the CO2 at say 2 times preindustrial then the net forcing will not > instantly get the global temperatures up to their long term steady state. > The oceans will lag. > > It sounds as if you are thinking of the net forcing which has resulted in > the temperature rise for the land has gone away-but it hasn't in the case > you have quoted. The CO2 level will stay constant for centuries even if all > emissions stop today. > > There was a very recent post or link on this recently which quoted 3deg for > doubling of CO2 in the short term but 6deg long term. This link, which I > cant find just now, used data from some much earlier time when the doubling > had already resulted in almost completely ice free poles. This is presumably > what will happen now if we get to doubling and don't do something about it. > The Arctic is melting now. It isn't going to stop melting just because we > stop increasing the temperature. So there is a temperature inertia or lag > due to ocean heat capacity but an even bigger one due to ice cap latent heat > of melting. > > john gorman > > > ----- Original Message ----- > From: "John Nissen" <[email protected]> > To: <[email protected]> > Cc: "geoengineering" <[email protected]> > Sent: Sunday, November 01, 2009 1:56 PM > Subject: [geo] Re: Jamais Cascio-- on the problematic idea of 350 > > >> >> >> Hi all, >> >> Jamais Cascio is described as an "environmental futurist" and has >> written a book with the title "Hacking the Earth" [1]. It's great that >> somebody is pointing out the implication of the 350 ppm target! >> >> But he shares a very common scientific belief which I do not understand: >> >> "(Even more troubling: even if we stopped all anthropogenic carbon >> sources immediately, we'd still see continued warming for at least >> decades, possibly longer, simply from the thermal inertia of the >> oceans. Absent a radical step, we're guaranteed to see at least >> another degree or two of warming, no matter what we do.)" >> >> >> With global warming, the land and atmosphere warm faster than the >> oceans. If emissions stopped overnight, the oceans would still be >> warming up, thus cooling the atmosphere, rather than warming it. Thus >> the thermal inertia of the oceans would drag down the global temperature >> (mean of surface temperatures over the globe). Am I right? >> >> Cheers, >> >> John >> >> [1] http://www.lulu.com/content/6048806 >> >> -- >> >> Dan Whaley wrote: >>> You will appreciate this one Greg... >>> >>> http://www.fastcompany.com/blog/jamais-cascio/open-future/350 >>> >>> 350 >>> BY Jamais CascioTue Oct 27, 2009 at 2:55 PM >>> 350 parts-per-million is the carbon limit. How will we get back there? >>> >>> 350.org >>> >>> It may be odd to focus a political movement on a relatively obscure >>> bit of science, but a world-wide push to limit concentration of >>> atmospheric carbon dioxide to 350 parts-per-million made a big splash >>> last week, with rallies and gatherings all over the planet focusing on >>> drilling this number into the public consciousness. The number comes >>> from work done by (among others) NASA's James Hansen, looking for >>> potential climate "tipping points." 350ppm for CO2 is a safe limit-- >>> get too much beyond it, and the dangers multiply. >>> >>> It's an audacious goal, for reasons of both communication and science. >>> >>> In terms of communication, while a simple meme like "350" or "350ppm" >>> fits nicely on protest signs and bumper stickers, it's a term without >>> much context for the vast majority of the populace. In and of itself, >>> that's not a problem; however, it can make a visceral connection to >>> the concept more difficult. Activists adopting the 350 meme will need >>> to match rhetoric with education, to make the number meaningful. >>> Again, not impossible, but likely an ongoing challenge. >>> >>> The scientific audacity with the 350 meme comes from a single, simple >>> fact: current concentration of atmospheric CO2 is roughly 385ppm. That >>> is, we already exceed the 350 limit, and most climate scientists say >>> we'll be hard-pressed to keep from going over 450ppm by the middle of >>> the century. And carbon dioxide takes centuries to cycle out of the >>> atmosphere--even if we stopped all anthropogenic sources of CO2 right >>> this minute, we'd still see too-high concentrations for years to come. >>> >>> (Even more troubling: even if we stopped all anthropogenic carbon >>> sources immediately, we'd still see continued warming for at least >>> decades, possibly longer, simply from the thermal inertia of the >>> oceans. Absent a radical step, we're guaranteed to see at least >>> another degree or two of warming, no matter what we do.) >>> >>> If this sounds like I think the 350 movement is a bad idea... I don't. >>> I rather like the simplicity of the meme, and the target is--if >>> difficult--smart. It's not saying "let's keep things from getting too >>> much worse," it's saying "let's make things better." That's the kind >>> of goal I like. >>> >>> But getting back to 350ppm requires more than a rapid cessation of >>> anthropogenic sources of atmospheric carbon. It requires an >>> acceleration of the processes that cycle atmospheric CO2. Planting >>> trees is an obvious step, but it's slow and actually doesn't do enough >>> alone. We'll also need to bring in more advanced carbon sequestration >>> techniques, such as bio-char. The combination of the two would likely >>> bring down atmospheric carbon levels, given enough time. >>> >>> Unfortunately, we may not have enough time. >>> >>> If efforts to eliminate carbon emissions continue to happen at a pace >>> most generously described as "leisurely," we will almost certainly >>> face a situation where we approach and even pass critical tipping >>> point concentrations. Ocean thermal inertia means that climate >>> benefits from emission cessation won't be seen for decades. There's a >>> very real scenario where finally get it right, both cutting out >>> anthropogenic emissions and sequestering megatons of carbon via plants >>> and bio-char ... and still face terrible environmental consequences, >>> simply because we didn't act fast enough. >>> >>> That's where we start to talk about much more radical, and potentially >>> dangerous, steps. Geoengineering to hold temperatures down is one; to >>> meet the 350ppm goal, we will likely also start looking at large-scale >>> methods to sequester carbon, such as with triggered algae blooms. >>> >>> 350ppm is an audacious goal, but one worth striving for. But its >>> challenge comes not just in the effort to eliminate anthropogenic >>> carbon emissions around the world--a massive endeavor alone--but also >>> in figuring out how to remove the extra carbon already there. I hope >>> that the 350 leaders have thought through the implications of what >>> that means. >>> >>> [Images: "Organized Spelling B" by Wade in Da Water on Flickr, >>> Creative Commons Licensed; "Summer Bloom in the Baltic Sea" by NASA >>> Visible Earth] >>>> >>> >> >>> >> > > > > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "geoengineering" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/geoengineering?hl=en -~----------~----~----~----~------~----~------~--~---
