The other problem with 100-year GWPs is that they tend to hide all that can be done with the short-lived species (black carbon, methane, ozone precursors), so what we really need to do is to use both 20 and 500+ year GWPs. Use of 100-year GWPs covers up both of the important tails.
Mike On 11/20/09 2:49 PM, "Greg Rau" <[email protected]> wrote: > Thanks, David. I agree. Failure to appreciate long term effects and ocean > acidification impacts, together with questionable/opaque discounting schemes > has I believe resulted in CO2 mitigation being greatly undervalued by the > economists and this is significantly undermining policy and political will. > Regards, > Greg > >> Greg >> >> GWP's by design ignore all climate impacts beyond 100 years. >> >> This has real consequences as it makes methane look relatively more important >> that it should be, and it also overweight's the beneficial impacts of biomass >> sequestration in some calculations. >> >> While some traditional economists may assume that discounting allows them to >> ignore any impact beyond 100 years, this GWP formula has long been a point of >> contention as most of us do value the future of the planet beyond 100 years. >> >> Adopting a 100 year analysis horizon, as the IPCC generally does, takes our >> eye off the long term consequences of dumping fossil carbon in the >> atmosphere. The risk of sea level rise look much less serious if one only >> looks a century out. >> >> Scientific understanding about the long term impacts of fossil emissions is >> decades old (see Jim Kasting's old papers for example), popular realization >> of these facts is long overdue. >> >> Cheers, >> David >> >> >> >> From: Greg Rau [mailto:[email protected]] >> Sent: November 16, 2009 1:23 PM >> To: [email protected]; [email protected] >> Subject: Re: [geo] Re: Rejected - a simple argument for SRM geoengineering >> >> In light of recent modeling results on the lifetime of CO2 in the atmosphere, >> I am concerned that the current time-integrated (not instantaneous) GWP >> estimate for CO2 has been underestimated and hence GWP's of other gases (esp >> short-lived gases) relative to CO2 have been overestimated. E.g., Eby et >> al., 2009: >> http://*ams.allenpress.com/perlserv/?request=get-abstract&doi=10.1175%2F2008J >> CLI2554.1 >> show that 20-30% of excess emissions of CO2 and 60-70% of the subsequent >> CO2-caused surface air temp anomally exists 10,000 years after emission. >> Isn't this (or is this?) a far larger total time-integrated GW effect than a >> mass equivalent emission of CH4? Experts please set me straight. >> Thanks, >> Greg >> >>> Agreed, one has to consider a time period, so assume one takes a day that >>> when injected there is no decay over this period-so it might as well be a >>> second of time one takes-so virtually instantaneous. And I'll assume >>> linearity on methane absorption and logarithmic for CO2. >>> >>> So, for methane, humans have caused an increase of roughly 1000 ppb which >>> converts to about 3 GtCH4, and this causes a forcing of about 0.5 W/m**2 (at >>> the tropopause) per IPCC. >>> >>> For CO2, we know that a doubling (so we'll say from 300 to 600 ppm so we are >>> in the range of interest) causes a forcing of about 3.6 W/m**2 (at the >>> tropopause). So, 300 ppm of CO2 in the atmosphere is roughly 600 GtC or 2200 >>> GtCO2 (and global warming potential is done for CO2, I believe. >>> >>> So, if we take the ratio of forcing to mass for CH4 divided by the ratio of >>> forcing to mass for CO2, we get a rough estimate of the instantaneous GWP, >>> so >>> >>> [0.5/3]/[3.6/2200] equals roughly 100 >>> >>> for the ratio at t=0 (so allowing for no decay) of the radiative forcing >>> caused by a unit mass of CH4 added to the atmosphere to a unit mass of CO2 >>> added to the atmosphere. >>> >>> Not exact, but plausible. >>> >>> Mike >>> >>> >>> >>> >>> On 11/16/09 3:42 AM, "Peter Read" <[email protected]> wrote: >>> John, Andrew >>> Re "BTW, does anybody know the _immediate_ warming potential of methane?" >>> Someone will correct me no doubt but my understanding is that warming is a >>> rate process measured in W/m^2 >>> So "instantaneous" [[== "immediate"?]] warming is an incorrect concept >>> Unless it continues for a second, a week, a year, 25 years, for whatever, no >>> warming takes place. >>> So it is necessary to multiply by a duration to get joules/m^2 >>> It's how many joules get into the low albedo meltwater on top of Greenland's >>> ice that decides how much gets melted each year to fall down crevasses and >>> lubricate the eventual collapse of large areas of ice into the oceans. >>> Meaning that the integral [[roughly]] under the CO2 level curve is what >>> matters [multiplied by the warming potential over that period] when it >>> comes to measuring threats of Greenland's collapse >>> So the key issue is duration - how long elevated greenhouse gas levels last >>> and how to get them down. >>> Think that's right >>> Peter >>> >>> ----- Original Message ----- >>> >>> From: John Nissen <mailto:[email protected] >>> <mailto:[email protected]> >>> > >>> >>> To: [email protected] >>> >>>> Cc: geoengineering <mailto:[email protected] >>>> <mailto:[email protected]> > >>>> >>>> Sent: Monday, November 16, 2009 6:18 PM >>>> >>>> Subject: Re: [geo] Re: Rejected - a simple argument for SRM geoengineering >>>> >>>> >>>> >>>> Hi Andrew, >>>> >>>> You say: "I don't oppose John's argument, but the evidence on the severity >>>> of the problem is far from conclusive." I disagree. >>>> >>>> The methane presents a very real risk - because of the uncertainty on >>>> timing combined with the potential size of methane discharge - perhaps >>>> even enough to cause thermal runaway due to positive feedback, as is >>>> thought to have happened in the past [1]. Risk management involves >>>> identifying events and assessing them in terms of their likelihood and >>>> magnitude of impact [2]. Thus something with a small likelihood (such as >>>> rapid massive methane excursion) can have a high risk, if the magnitude of >>>> impact is sufficiently large (and you can't get much larger than thermal >>>> runaway). >>>> >>>> It is possible that much or most of the methane trapped in frozen >>>> structures has built up over hundreds of thousands of years. There is >>>> little sign of massive methane discharge in the ice record. In fact >>>> methane seems to track the temperature even better than CO2 [3]. >>>> >>>> But of course methane discharge is not the only high risk event - there is >>>> also the Greenland ice sheet disintegration. >>>> >>>> BTW, does anybody know the _immediate_ warming potential of methane, as >>>> opposed to the 20 year value (72), 100 years (25) or 500 years (7.6)? The >>>> lifetime is only 12 +/- 3 years. See [4]. >>>> >>>> Cheers, >>>> >>>> John >>>> >>>> [1] http://**en.wikipedia.org/wiki/Clathrate_gun_hypothesis >>>> <http://**en.wikipedia.org/wiki/Clathrate_gun_hypothesis> >>>> >>>> [2] http://**en.wikipedia.org/wiki/Enterprise_risk_management >>>> <http://**en.wikipedia.org/wiki/Enterprise_risk_management> >>>> >>>> [3] http://**answers.yahoo.com/question/index?qid=20090329215018AAxqYFk >>>> <http://**answers.yahoo.com/question/index?qid=20090329215018AAxqYFk> >>>> >>>> [4] http://**en.wikipedia.org/wiki/Greenhouse_gas >>>> <http://**en.wikipedia.org/wiki/Greenhouse_gas> >>>> >>>> --- >>>> >>>> Andrew Lockley wrote: >>>> At present the likely methane excursion is far from clear. Further, it is >>>> also unclear how quickly the total excursion will occur. The excursion >>>> rate is highly significant due to the short life of methane in the >>>> atmosphere. The methane ends up as CO2, in itself a major issue. >>>> However, the CO2's likely effect is nothing compared to the devastating >>>> temperature spike which may result from a sudden methane excursion. >>>> >>>> >>>> I don't oppose John's argument, but the evidence on the severity of the >>>> problem is far from conclusive. We need much more research into: >>>> >>>> 1) The methane reservoir in clathrates and permafrost >>>> >>>> 2) The size of potential methane sources currently frozen as organic >>>> detritus >>>> >>>> 3) The likely changes to the GWP of methane in future atmospheres, as the >>>> levels of hydroxyl radicals etc. shift over time and as a direct result of >>>> methane excursion. Recent research on this asks more questions than it >>>> answers. >>>> >>>> >>>> >>>> My personal feeling is that the range of likely outcomes is from a >>>> significant amplification of AGW, right up to a 'Great Dying' sized >>>> mass-extinction event when we come within a sneeze of sterilising the >>>> entire planet. I'd be tempted to bet on the latter, but I wouldn't be >>>> around to collect the winnings, so I'll keep my wallet in my pocket. >>>> >>>> >>>> >>>> My suggestions is that geoengineers look at ways to clean up the methane >>>> from the atmosphere, and then lock down the resulting carbon. My guess is >>>> we've got about 50 years to do this, but virtually no time at all if the >>>> methane can't be dealt with once it's in the atmosphere. Therefore, I'd >>>> support John out of precautionary principle-based reasoning. >>>> >>>> >>>> >>>> A >>>> >>>> >>>> 2009/11/15 jim woolridge <[email protected]> >>>> >>>> Nice one, John; the train of argument is clear (of limpid clarity, in >>>> fact!) The problem is that the people and institutions addressed are >>>> in the business of politics, the art of the possible, rather than in >>>> the business of logical evaluation. They hear what you are saying and >>>> must see the validity of it. But politically what is true and what is >>>> doable do not always coincide, as we all know from as many examples as >>>> one cares to ennumerate. >>>> >>>> We have to keep hammering away at the arguments, to the point at which >>>> they are generally understood and accepted, and also keep on >>>> politicking in the sure and certain hope that eventually the >>>> acceptance of the arguments and the cowardice/caution/horse sense/ >>>> opportunistic careerism of the politicos will achieve the right kind >>>> of intersection. In the next year or so (& wouldn't it be a great >>>> help to have the environmental NGOs on board.) >>>> >>>> >>>> >>>> On Nov 12, 10:51 pm, John Nissen <[email protected]> wrote: >>>>> > It is incredible. It is so obvious. >>>>> > >>>>> > 1. Global warming is driven largely by atmospheric CO2 according to the >>>>> > concentration above its pre-industrial level; and >>>>> > >>>>> > 2. After emissions are stopped it could take millenia for the >>>>> > concentration to fall back to that level, because the effective >>>>> lifetime >>>>>> > of some of that excess CO2 is many thousands of years. >>>>>> > >>>>>> > Therefore: >>>>>> > 3. Drastic emissions reduction, even to zero overnight, cannot and >>>>>> will >>>>>> > not stop the Arctic continuing to warm for decades. >>>>>> > >>>>>> > Therefore: >>>>>> > 4. The Arctic sea ice will continue to retreat, accelerating the >>>>>> warming >>>>>> > due to the albedo effect. >>>>>> > >>>>>> > Therefore: >>>>>> > 5. The permafrost will continue to thaw releasing increasing >>>>>> quantities >>>>>> > of methane, a potent greenhouse gas, potentially adding many degrees >>>>>> to >>>>>> > global warming; and >>>>>> > >>>>>> > 6. The Greenland ice sheet will become increasingly unstable, >>>>>> > potentially contributing to an eventual sea level rise of 7 metres. >>>>>> > >>>>>> > Therefore: >>>>>> > 7. To avoid these two catastrophes, we need to cool the Arctic >>>>>> quickly >>>>>> > enough to save the Arctic sea ice; and >>>>>> > >>>>>> > 8. Probably the only feasible way to do this is through solar >>>>>> radiation >>>>>> > management (SRM) geoengineering. >>>>>> > >>>>>> > 9. SRM is not a last resort, it is needed now to cool the Arctic. >>>>>> > >>>>>> > It is incredible that people do not seem to follow this train of logic - >>>>>> > it is so obvious. >>>>>> > >>>>>> > Yet when I challenged a panel of geoengineering experts to refute this >>>>>> > argument, the response was that geoengineering (even just to cool the >>>>>> > Arctic) was too dangerous - not that the argument was false! [1] >>>>>> > >>>>>> > So we continue to hear politicians and their advisers claiming that >>>>>> > emissions reduction alone can be sufficient to keep the planet safe. >>>>>> [2] >>>>>> > >>>>>> > And we continue to hear geoengineering experts saying that >>>>>> > geoengineering should only be used as a last resort. [3] >>>>>> > >>>>>> > How can this mindset be changed quickly, to avoid leaving >>>>>> geoengineering >>>>>> > too late? >>>>>> > >>>>>> > John >>>>>> > >>>>>> > P.S. Apologies to those who have heard this all before and accept the >>>>>> > logic as self-evident. >>>>>> > >>>>>> > [1] This challenge was put to the panel at the launch of the Royal >>>>>> > Society geoengineering report, on September 1st, with response from >>>>>> the >>>>>> > team leader and panel chairman, Professor John Shepherd. >>>>>> > >>>>>> > [2] For example at the geoengineering hearing at the House of >>>>>> Commons, >>>>>> > November 2008. >>>>>> > >>>>>> > [3] For example at the congressional hearing on geoengineering, >>>>>> November >>>>>> > 2009. >>>>> >>>>> -- >>>>> >>>>> 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] >>>>> <mailto:geoengineering%[email protected] >>>>> <mailto:geoengineering%[email protected]> > . >>>>> For more options, visit this group at >>>>> http://**groups.google.com/group/geoengineering?hl= >>>>> <http://**groups.google.com/group/geoengineering?hl=> . >>>>> >>>>> >>>>> >>>>> -- >>>>> 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= >>>>> <http://**groups.google.com/group/geoengineering?hl=> . >>>> >>>> >>>> >>>> >>>> -- >>>> 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= >>>> <http://**groups.google.com/group/geoengineering?hl=> . >>>> >>>> >>>> >>>> >>>> >>>> >>>> >>>> No virus found in this incoming message. >>>> Checked by AVG - www.**avg.com >>>> Version: 8.5.425 / Virus Database: 270.14.67/2505 - Release Date: 11/15/09 >>>> 19:50:00 >>>> >>>> -- >>>> 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= >>>> <http://**groups.google.com/group/geoengineering?hl=> . >>> -- >>> 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=. >> >> -- >> 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=. > > > -- > 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=. > -- You received this message because you are subscribed to the Google Groups "geoengineering" group. 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