Dear Robert, You wrote originally looking for help disputing a “skeptic,” and I hope it hasn’t been lost upon you that there sometimes seems to be almost as much disagreement within the climate community itself as between such “skeptics” and climate scientists. Indeed, the outcome of such internal disagreement could eventually be even more important for our fate than disputes with those who ultimately have little or no concern for science whatsoever.
Perhaps the largest internal struggle in climate science regards methane. That is why David Archer recently wrote his strongly titled “Much Ado about Methane,” which Ken called one of the best recent pieces on methane emissions. I personally thought it was one of the most poorly conceived pieces of climate science from within the climate community, and the group AMEG – the Arctic Methane Emergency Group, formed from this Google geoengineering group – is still quite concerned with rebutting this piece of writing. I immediately started my own ongoing series in response, called Methane in the Twilight Zone, in which I address Archer’s “Much Ado” in some detail (particularly in Episode 2), and promptly received a private note of thanks from someone at the top of the climate heirarchy at NASA, specifically for those parts concerning Daivd Archer’s recent writing. So, you can see that there is, unfortunately, considerable disagreement on this! The reason, of course, is that methane feedbacks could potentially upend much of the worldview of many scientists, and could radically impact this topic of “non- linearity of climate sensitivity,” as well as the current state of the climate. You ask about Wasdell’s “ESS,” and about how it should impact considerations of geoengineering, but one of the greatest problems today is that this kind of “high-sensitivity” view, or any recognition that there could potentially be powerful tipping points at relatively short time scales, should impact both geoengineering policy AND emissions policy (particularly, in terms of advantaging and prioritizing immediate and large reductions of anthropogenic methane emissions). In terms of other things I noted within your various exchanges, the best recent work from NASA, now with a half-decade of pretty robust research behind it, suggests that the methane forcing is TWO THIRDS of CO2’s (added RF since industrialization, that is), not one third, as stated – thus, the recent human methane forcing is about twice as large as imagined at the time of the IPCC TAR, for example (exclusive of any earlier impacts on methane humans might have had). Further, in terms of whether there is evidence of increased methane releases in the arctic, I’ve printed below the NOAA data from Barrow, Alaska for a given day from the most recent year available, 2010. Methane spiked to 2230ppb that day there. The question is really just what and where the precise source is, not that it is increasing and doing so quite rapidly. By the way, you said something at the beginning about reducing the CO2 GWP – but by definition, CO2’s GWP is always one, as perfect a numerical translation of monotheism as one could create, I guess..... Cheers, Nathan Methane at Barrow, Alaska on 9/11/10 BRW 2010 09 11 05 1909.11 6.13 .C. BRW 2010 09 11 06 1937.95 11.47 .C. BRW 2010 09 11 07 1952.57 5.80 .C. BRW 2010 09 11 08 1957.61 6.80 .C. BRW 2010 09 11 09 1935.10 4.13 .C. BRW 2010 09 11 10 1946.28 7.73 .C. BRW 2010 09 11 11 1976.60 7.42 .C. BRW 2010 09 11 12 1982.51 5.45 .C. BRW 2010 09 11 13 1989.94 3.03 .C. BRW 2010 09 11 14 1995.60 4.68 .C. BRW 2010 09 11 15 2009.41 3.65 .C. BRW 2010 09 11 16 2016.25 5.74 .C. BRW 2010 09 11 17 2039.49 8.05 .C. BRW 2010 09 11 18 2046.90 10.47 .C. BRW 2010 09 11 19 2039.67 3.53 .C. BRW 2010 09 11 20 2042.08 5.24 .C. BRW 2010 09 11 21 2058.38 7.64 .C. BRW 2010 09 11 22 2073.26 2.98 .C. BRW 2010 09 11 23 2074.07 21.03 .C. BRW 2010 09 12 00 2067.34 13.10 .C. BRW 2010 09 12 01 2005.53 1.39 .C. BRW 2010 09 12 02 1988.98 12.67 .C. BRW 2010 09 12 03 1965.76 4.13 .C. BRW 2010 09 12 04 1984.17 10.82 .C. BRW 2010 09 12 05 1956.75 4.72 .C. BRW 2010 09 12 06 1941.76 4.05 .C. BRW 2010 09 12 07 2051.73 112.21 .C. BRW 2010 09 12 08 2230.78 30.93 .C. BRW 2010 09 12 09 2181.13 35.70 .C. BRW 2010 09 12 10 2087.70 26.63 .C. BRW 2010 09 12 11 1968.64 30.33 .C. BRW 2010 09 12 12 1928.62 8.78 .C. For comparison, here is the same day on the first year of records there, 1987 (note that it is not just lower, but also closer to the global average at the time): BRW 1987 09 11 05 -999.99 -99.99 *.. BRW 1987 09 11 06 1797.62 7.26 .C. BRW 1987 09 11 07 -999.99 -99.99 *.. BRW 1987 09 11 08 1814.18 18.15 .C. BRW 1987 09 11 09 -999.99 -99.99 *.. BRW 1987 09 11 10 -999.99 -99.99 *.. BRW 1987 09 11 11 1802.12 4.90 .C. BRW 1987 09 11 12 1803.20 8.48 .C. BRW 1987 09 11 13 1814.01 20.46 .C. BRW 1987 09 11 14 -999.99 -99.99 *.. BRW 1987 09 11 15 1772.95 4.86 .C. BRW 1987 09 11 16 -999.99 -99.99 *.. BRW 1987 09 11 17 1775.05 2.50 .C. BRW 1987 09 11 18 -999.99 -99.99 *.. BRW 1987 09 11 19 1766.73 0.65 .C. BRW 1987 09 11 20 -999.99 -99.99 *.. BRW 1987 09 11 21 -999.99 -99.99 *.. BRW 1987 09 11 22 -999.99 -99.99 *.. BRW 1987 09 11 23 -999.99 -99.99 *.. BRW 1987 09 12 00 -999.99 -99.99 *.. BRW 1987 09 12 01 -999.99 -99.99 *.. BRW 1987 09 12 02 1768.09 1.55 ... BRW 1987 09 12 03 -999.99 -99.99 *.. BRW 1987 09 12 04 -999.99 -99.99 *.. BRW 1987 09 12 05 1782.46 1.00 ... BRW 1987 09 12 06 1776.73 1.12 ... BRW 1987 09 12 07 -999.99 -99.99 *.. BRW 1987 09 12 08 1822.97 10.56 .C. BRW 1987 09 12 09 -999.99 -99.99 *.. BRW 1987 09 12 10 1772.28 11.62 .C. BRW 1987 09 12 11 -999.99 -99.99 *.. BRW 1987 09 12 12 1774.90 4.82 .C. On Feb 22, 4:23 pm, Robert Chris <[email protected]> wrote: > Ken > > May I have your permission to quote your paragraph 'On the other hand > the Romans ...' in my PhD thesis. > > This is about as good an exposition of the challenge of > intergenerational equity arsing from climate change that I could hope > to find and perfectly demonstrates the paradox of framing climate > change as an intergenerational problem. We want to do right by them, > but who is them, the centennial them or the millennial them? Why do > we assume that all future generations have the same interests, or if > we don't, on what basis do we favour one against another? Why do we > tacitly assume that any future world with dramatically fewer people > would somehow not be as desirable as one with more or less the same > number as now? The problem is that interesting as these and many > related questions are, they don't have easy answers that the whole > world will buy into as a basis for action. So framing climate change > as an intergenerational problem introduces a slew of intellectual > challenges of the same order of complexity as the physical climate > science itself and create an Everest to climb before action can be > agreed. How much easier if we forgot about the future and just agreed > amongst ourselves that the intrinsic indecency of fouling our nest and > squandering scarce resources is a sufficient reason for immediate > action. Is that too much to ask? > > That's a little polemical. Hopefully it won't come out like that in > the thesis. > > This thread has gone off in a direction I hadn't anticipated when it > started. Many thanks to those who have contributed. Don't let me > stop you if you want to continue. > > Robert > > On Feb 22, 4:38 pm, Ken Caldeira <[email protected]> > wrote: > > > > > Both amounts and rates of change are important to estimating climate damage. > > > If we were turning the Earth into the Cretaceous over millions of years, > > that is not a problem. If we are doing it in centuries, that is a problem. > > > So, if we are talking about near-term damage from climate change, the > > Charney sensitivity is the most relevant factor. > > > If we are talking about long-term damage from a changed climate, then the > > Earth System sensitivity becomes relevant. > > > I don't think God made the Earth with the perfect climate and that any > > cooling or warming is inherently bad. I do think the Earth is full of stuff > > that is adapted to the current climate and that climate change is damaging. > > So, I am more concerned with rates of change than absolute amounts of > > change. > > > On the century scale of concern to most policy makers, rates and amounts of > > change are closely linked. > > > On the other hand, if the Romans had discovered fossil fuels and had a > > fossil-fueled industrial revolution, they would have maximized their net > > present value and we would be here two millennia later with rising seas, > > acidified oceans, melting ice caps, diminished biodiversity, etc, finding > > little solace in the fact that they followed the path their economists told > > them was economically optimal. So, even the period with disruptive climate * > > change* could last thousands of years and Earth System sensitivity becomes > > relevant on these time scales. However, once climate change stabilizes at a > > new level, it is not clear to me that the changed climate itself is in any > > fundamental sense worse than what we started out with. > > > From a policy perspective, this distinction between changing climate and a > > changed climate is of little interest, because the prescription is the same > > in both cases: *Stop using the atmosphere as a waste dump. > > * > > > On Wed, Feb 22, 2012 at 3:30 AM, Robert Chris <[email protected]> wrote: > > > Tom > > > > Thanks for persevering with me. I think I do now understand that the > > > relationship between climate sensitivity and radiative forcing is > > > linear and that between climate sensitivity and atmospheric > > > concentration of GHGs is logarithmic, as is that between the forcing > > > and concentrations. I think my confusion had been that climate > > > sensitivity is routinely referenced to a doubling of CO2 > > > concentrations from the 280ppmv pre-industrial level without always > > > making it explicit that it is the doubling not the additional 280ppmv > > > that is crucial. > > > > Getting back to my skeptic’s argument that global warming isn’t a > > > problem because the incremental global warming asymptotically > > > approaches zero as the atmospheric concentration increases, in effect > > > a form of negative feedback, it seems this is a case of the wrong > > > conclusion being arrived due to a partial understanding of the issue. > > > While it may be the case that the warming does reduce logarithmically > > > as concentrations increase, my understanding, confirmed by Ken’s > > > remarks is that this doesn’t happen until we’re living in a toaster, > > > if indeed we’re living at all. > > > > However there is an additional relationship that seems to me to be > > > equally important, that between CO2 emissions and atmospheric CO2 > > > concentrations. At present it is largely assumed that this > > > relationship is also linear with about 50% of emissions ending up in > > > the atmosphere and the other 50% being sequestered primarily in the > > > hydrosphere. But if the capacity of the hydrosphere in particular to > > > absorb CO2 reduces (also logarithmically?) as saturation is > > > approached, it must follow that atmospheric concentrations would rise > > > exponentially unless emissions are correspondingly reduced. In other > > > words in a BAU emissions scenario we could see runaway increases in > > > atmospheric CO2 concentration which may have increasingly little > > > effect on global warming for the reasons discussed above but would > > > imply perilous ocean acidification. Moreover, if ocean saturation of > > > CO2 reduces as the water temperature rises, this effect would be > > > accelerated by global warming. > > > > Which brings me to my final question. If my understanding of these > > > dynamics is now more or less correct, when I revert to my skeptic, is > > > there some research upon which I can rely which specifies the > > > quantitative dimensions of these variables? By how much would mean > > > surface temperatures have risen (or at least such rises be committed) > > > before the incremental global warming from incremental emissions > > > became negligible? What would atmospheric concentrations of CO2 have > > > to be before ocean uptake of CO2 reduced to a trickle and what state > > > would the oceans be in by then? For example might we be on the verge > > > of an anoxic event? > > > > Finally, I should like to revert to my home territory and pick up on a > > > point Ken made regarding the ESS v. Charney approaches to the > > > computation of climate sensitivity. It is noteworthy that the > > > considerably higher equilibrium temperatures implied by ESS apparently > > > do not merit more decisive action in the short term because the > > > additional factors which ESS takes into account only operate over > > > millennial timescales. This implicitly places reduced moral value on > > > our very distant descendants, in effect a form of time preference > > > applied to human life > > > > There is nothing inherently wrong with taking such a normative > > > position if it is done transparently but I wonder whether it should be > > > made explicit so that those who are concerned with the moral > > > implications of climate change and in particular its intergenerational > > > dimensions can engage in the debate. If intergenerational equity > > > considerations were policy significant (which I do not assume to be > > > the case), very different policy outcomes might be arrived at if > > > climate sensitivity were understood to be a multiple of its current > > > assumed value of ~3degC. > > > > Robert > > > > On Feb 22, 12:20 am, Tom Wigley <[email protected]> wrote: > > > > Chris, > > > > > I'm sure others will cover this, but there is apparently still some > > > > confusion in your mind. > > > > > The point, as I mentioned in my original email, is that the climate > > > > sensitivity in its fundamental definition does not refer to CO2. It is > > > > the equilibrium surface temperature change per unit of radiative > > > > forcing. > > > > > As it happens, the forcing for CO2 (as noted by others) is logarithmic > > > > in concentration. In other words, there is the same forcing for any > > > > doubling of CO2 concentration -- from 300 to 600 ppm, or 500 to 1000 > > > > ppm, or 700 to 1400 ppm, etc. > > > > > Because of this we often "define" the sensitivity as the equilibrium > > > > surface temperature change for a CO2 doubling. Note that the sensitivity > > > > is NOT linear in terms of CO2 concentration. It is only linear as a > > > > function of radiative forcing. > > > > > Climate models, of course, take this fully into account. Furthermore, > > > > sophisticated climate models do not specify how the climate sensitivity > > > > varies as conditions change. These variations are internally generated > > > > based on the fundamental physics that is in the models. > > > > > Tom > > > > > ++++++++++++++++++++++++++++++++++ > > > > > On 2/21/2012 8:35 AM, Robert Chris wrote: > > > > > > Ken > > > > > > Thanks for replying to my email. You were right. The Google Group > > > > > worked much quicker than I'd anticipated. > > > > > > There's quite a lot of technical material here for a humble social > > > > > scientist to digest. On a quick scan the message I get is that the > > > > > forcing is logarithmic but climate sensitivity is linear because of > > > > > compensating feedbacks in the climate system. Although it does seem > > > > > to me that if the forcing is logarithmic there must come a point where > > > > > the absorptive capacity of the GHGs is so small that incremental > > > > > emissions will not produce any more global warming. > > ... > > read more » -- 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.
