John Nissen, I might recommend Susan Solomon's recent paper. http://www.pnas.org/content/early/2009/01/28/0812721106.full.pdf
A key paragraph: Global average temperatures increase while CO2 is increasing and then remain approximately constant (within +/-0.5 °C) until the end of the millennium despite zero further emissions in all of the test cases shown in Fig. 1. This important result is due to a near balance between the long-term decrease of radiative forcing due to CO2 concentration decay and reduced cooling through heat loss to the oceans. It arises because long-term carbon dioxide removal and ocean heat uptake are both dependent on the same physics of deep-ocean mixing. Sea level rise due to thermal expansion accompanies mixing of heat into the ocean long after carbon dioxide emissions have stopped. For larger carbon dioxide concentrations, warming and thermal sea level rise show greater increases and display transient changes that can be very rapid (i.e., the rapid changes in Fig. 1 Middle), mainly because of changes in ocean circulation (18). Paleoclimatic evidence suggests that additional contributions from melting of glaciers and ice sheets may be comparable to or greater than thermal expansion (discussed further below), but these are not included in Fig. 1. Dan On Nov 1, 5:56 am, John Nissen <j...@cloudworld.co.uk> wrote: > 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 geoengineering@googlegroups.com To unsubscribe from this group, send email to geoengineering+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/geoengineering?hl=en -~----------~----~----~----~------~----~------~--~---
