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. Moreover, there > > > > must be a point where the oceans are also largely saturated and take > > > > up little more CO2. However, the point where climate sensitivity does > > > > reduce to close to zero, might not be reached before we're all fried > > > > and the oceans are nigh on dead. If that brief extrapolation makes > > > > sense, has anyone attempted to estimate where those limits might be? > > > > > What has jumped out at me from these replies is the Wasdell paper. He > > > > is highlighting the distinction between the Charney and ESS approaches > > > > to the quantification of climate sensitivity. This is not an academic > > > > peer-reviewed paper although he does refer to several but if he is > > > > correct that climate sensitivity now looks like it might be closer to > > > > 10degC rather than 3degC, that should send alarm bells ringing that I > > > > certainly don't hear. Is that because ESS is not yet sufficiently > > > > robust for it to replace Charney; simply because the material has yet > > > > to be published, or because even though CS might be three times higher > > > > than previously thought, the time lag before the equilibrium is > > > > reached is such that things won't warm up that much faster in the > > > > short term and therefore no one's too concerned about it yet? > > > > > But if ESS does provide a more accurate valuation of CS and it is > > > > about 10degC, what policy implications might that have for the timing > > > > of geoengineering deployments? > > > > > Robert Chris > > > > > On Feb 20, 9:48 pm, Ken Caldeira<[email protected]> > > > > wrote: > > > >> The attached papers are relevant. > > > > >> On Mon, Feb 20, 2012 at 11:32 AM, David Mitchell< > > [email protected]>wrote: > > > > >>> From paleoclimate data with a geologic time-scale, climate > > sensitivity may > > > >>> be ~ 2.7 times larger than the Charney value of ~ 3 deg. C ( climate > > > >>> feedback factor 0.75 deg. C/W m2; characteristic of the fast > > feedbacks in > > > >>> GCMs) based on a recent paper from Jeff Kiehl: > > > >>> Kiehl, J., 2011: Lessons from Earth's Past. Science, Vol. 331, 14 > > Jan., > > > >>> 158-159, DOI: > > ... > > 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.
