John, I have no doubt that, from the perspective of many extant species and less-fortunate humans, we are indeed in dire straits.
If I were convinced that stratospheric aerosols would work as advertised and that there would be no unforeseen or unanticipated repercussions, and that some sort of democratic process could be devised to give the overall effort political legitimacy, then I would be in favor of early deployment of such schemes. However, I am confident that were such systems deployed, there would be surprises. Maybe the surprise would be how well it works and how everyone the world over greets the project with such a high degree of appreciation. On the other hand, the surprise could be that things go rather wrong, exacerbating international friction, leading to economic disruption, wars, etc. Before such systems would be deployed, I would hope that the risk-benefit balance would be very clearly tipped in the direction of benefit. I just do not think we are there yet. Best, Ken ___________________________________________________ Ken Caldeira Carnegie Institution Dept of Global Ecology 260 Panama Street, Stanford, CA 94305 USA +1 650 704 7212 [email protected] http://dge.stanford.edu/labs/caldeiralab @kencaldeira On Sat, Jul 23, 2011 at 12:08 AM, John Nissen <[email protected]>wrote: > Hi Ken, > > You take a fundamentally different view of the Earth System and > geoengineering. I see the Earth System as in an extremely precarious state > and geoengineering as absolutely necessary to nudge the system back into a > state that allows continued habitation of the planet by ourselves and our > offspring. Do you really think that we can survive the century simply by > reducing carbon emissions? If we wait for some dramatic event, like > disappearance of Arctic sea ice, as an "emergency" sufficient to justify > geoengineering, don't we risk leaving geoengineering too late? > > For me, geoengineering is like chemotherapy when a vital organ has cancer, > or like fire-fighting when parts of the burning building contain > explosives. You start tackling the problem as quickly as you possibly can, > concentrating on the critical parts. > > John > > --- > > > On Fri, Jul 22, 2011 at 4:02 PM, Ken Caldeira <[email protected]> wrote: > >> Two points: >> >> I am not opposed to scientists making prescriptive statements in their >> roles as citizens. >> >> However, I am opposed to prescriptive statements (statements about what we >> should do) in peer-reviewed scientific papers. >> >> I think science is about establishing objective facts about the world. As >> citizens, we take these facts and our values and make judgments about what >> we should do. >> >> I am 100% in favor of Jim Hansen making prescriptive statements. I would >> just prefer that he not do it in the context of a peer-reviewed scientific >> paper. >> >> Science cannot tell us what to do. It can give us information which we can >> use to make decisions. >> >> If the science gets mixed up with politics in peer-reviewed scientific >> publications, I think it ends up weakening the credibility of the entire >> scientific publication process (since statements whose truth value cannot be >> empirically established are obviously getting past reviewers). >> >> I should say that the worst in this respect are the economists, who insist >> that they should be regarded as a science while simultaneously trying to >> tell us what we should be doing. >> >> --- >> >> On deployment of some sort of solar reflection system: all of our model >> results indicate that a high co2 world with deflection of some sunlight >> would be more similar to a low co2 world than is a high co2 world without >> deflection of sunlight. >> >> So, do I think that direct environmental damage from greenhouse gases >> could be diminished by deploying such a system? Yes, probably although I am >> not 100% certain of this. >> >> Do I think near-term deployment will reduce overall risk and improve >> long-term well-being? Of this I am less certain, as it is hard to predict >> the various sociopolitical, as well as environmental, repercussions that >> might occur. >> >> Ken Caldeira >> [email protected] >> +1 650 704 7212 >> http://dge.stanford.edu/labs/caldeiralab >> >> Sent from a limited-typing keyboard >> >> On Jul 22, 2011, at 16:38, John Nissen <[email protected]> wrote: >> >> >> >> Dear Ken, >> >> I've already looked at this interesting paper [1], from Jim Hansen and >> Mikiko Sato - but I'd not read before of his conjecture about rate of ice >> mass loss doubling per decade, producing many metres of sea level rise this >> century. But the implication is that the situation can be saved simply by >> reducing fossil fuel emissions! Is that the prescription that you are >> complaining about? Wouldn't a well-considered prescription be welcome from >> somebody as eminent as Prof Hansen? Geoengineering for example! I don't >> see a way out of our predicament without it. Do you, Ken? >> >> Does Hansen accept that 90% sea ice could be gone as soon as at end summer >> 2016? (BTW, I've another reference to this date we've been arguing about >> [2].) >> >> Hansen seems to dismiss methane as always producing less forcing than CO2: >> >> "*This sensitivity has the merit that CO2 is the principal GHG forcing >> and perhaps the only one with good prospects for quantification of its >> long-term changes.*" (page 15) >> >> However the paper is relevant to the methane issue in several ways. One >> argument, which I've heard from Jeff Ridley, is that there is no sign of a >> methane excursion at previous interglacials* such as end-Eemian, when it was >> hotter, so we don't need to worry about having an excursion now. Hansen >> shows that it was never hotter than it is now (in Holocene) by more than one >> degree. >> >> Elsewhere Hansen points out that the current rate of global warming is >> much higher than it has been for millions of years. Andrew Lockley suggests >> it's higher than even it was at the PETM some 55.8 million years ago, when >> temperatures rose about 6 C [3]. That rate of change is important, because >> of methane's short lifetime. The increasing speed of change implied by >> Hansen's climate sensitivity is thus relevant to methane. >> >> A further way that the paper is relevant to methane is because of climate >> sensitivity to radiative forcing. The paper suggests various alternative >> values that could be taken - see [1] table 1. If we get over 2 W/m-2 from >> methane, then that certainly takes us over the danger line of 2 degrees >> global warming, using his argument. >> >> Cheers, >> >> John >> >> * During the past 800,000 years, methane never rose much above 700 ppb >> until recently, see [1] figure 2 >> >> [1] Full paper <http://arxiv.org/ftp/arxiv/papers/1105/1105.0968.pdf> >> http://arxiv.org/ftp/arxiv/papers/1105/1105.0968.pdf >> >> Abstract here: >> <http://arxiv.org/abs/1105.0968v3>http://arxiv.org/abs/1105.0968v3 >> >> [2] <http://www.bbc.co.uk/news/science-environment-13002706> >> http://www.bbc.co.uk/news/science-environment-13002706 >> >> [3] >> <http://en.wikipedia.org/wiki/Paleocene%E2%80%93Eocene_Thermal_Maximum> >> http://en.wikipedia.org/wiki/Paleocene%E2%80%93Eocene_Thermal_Maximum >> >> --- >> >> On Thu, Jul 21, 2011 at 11:07 PM, Emily < <[email protected]> >> [email protected]> wrote: >> >>> Hi, >>> >>> here is a recent paper from Jim Hansen,including some figures I've read >>> before, which stunned me: >>> >>> "In the early Pliocene global temperature was no more than 1-2°C warmer >>> than today, yet sea level was 15-25 meters (50-80 feet) higher." >>> >>> best wishes, >>> >>> Emily. >>> >>> >>> *Paleoclimate Implications: Accepted Paper and 'Popular Science'* >>> >>> >>> "Paleoclimate Implications for Human-Made Climate Change" has been >>> reviewed, revised in response to the referee's suggestions, and accepted >>> for publication in "Climate Change at the Eve of the Second Decade of >>> the Century: Inferences from Paleoclimate and Regional Aspects: >>> Proceedings of Milutin Milankovitch 130th Anniversary Symposium" (Eds. >>> A. Berger, F. Mesinger and D Šijački), Springer. >>> >>> This final version has also been published in arXiv:1105.0968v3 >>> [physics.ao-ph] >>> <<http://columbia.us1.list-manage.com/track/click?u=0ebaeb14fdbf5dc65289113c1&id=fbefcc8464&e=60a7483168> >>> http://columbia.us1.list-manage.com/track/click?u=0ebaeb14fdbf5dc65289113c1&id=fbefcc8464&e=60a7483168 >>> > >>> >>> A__'popular science' summary >>> <<http://columbia.us1.list-manage.com/track/click?u=0ebaeb14fdbf5dc65289113c1&id=d3b93e0894&e=60a7483168> >>> http://columbia.us1.list-manage.com/track/click?u=0ebaeb14fdbf5dc65289113c1&id=d3b93e0894&e=60a7483168 >>> > >>> of the paper, intended for lay audience, is available. >>> >>> Thanks especially to reviewer Dana Royer for helpful comments, >>> foundations and NASA program managers for research support, and a number >>> of people for comments on an early draft of the paper, as delineated in >>> the acknowledgements. >>> >>> Jim Hansen >>> >>> -- >>> You received this message because you are subscribed to the Google Groups >>> "geoengineering" group. >>> To post to this group, send email to <[email protected]> >>> [email protected]. >>> To unsubscribe from this group, send email to >>> <geoengineering%[email protected]> >>> [email protected]. >>> For more options, visit this group at >>> <http://groups.google.com/group/geoengineering?hl=en> >>> http://groups.google.com/group/geoengineering?hl=en. >>> >>> >> -- >> You received this message because you are subscribed to the Google Groups >> "geoengineering" group. >> To post to this group, send email to <[email protected]> >> [email protected]. >> To unsubscribe from this group, send email to >> <geoengineering%[email protected]> >> [email protected]. >> For more options, visit this group at >> <http://groups.google.com/group/geoengineering?hl=en> >> http://groups.google.com/group/geoengineering?hl=en. >> >> > -- You received this message because you are subscribed to the Google Groups "geoengineering" group. 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