John, David, list etal:
1. You have correctly quoted Dr. Hansen below for 6 degrees as his
best guess on climate sensitivity (the temperature increase expected with a
doubling in CO2). But that was a 2008 paper. Today, he has revised downward,
and is using the range 3-4 degrees as a better estimate. A denier reading
this list has pointed me today (for a different reason) to a more recent Hansen
paper:
Hansen, James, Makiko Sato, Gary Russell, and Pushker Kharecha. "Climate
sensitivity, sea level and atmospheric carbon dioxide." Philosophical
Transactions of the Royal Society A: Mathematical, Physical and Engineering
Sciences 371, no. 2001 (2013): 20120294.
http://rsta.royalsocietypublishing.org/content/371/2001/20120294.full.pdf+html
Reading the last several pages is a good place to start.
2. With his new preferred range of 3-4 degrees for a CO2 doubling,
you still get over a 2 degree C rise, which is what this conversation with
David is about, using your method of computation below. I had rather seen a
logarithm in there - but I think you have made your point to David.
3. I am still leaning to Hansen's and your 6 degree number as being
more appropriate - for two reasons. The effects of modern aerosols still seems
not to have been well handled - due to lack of data on their real levels and
locations. Secondly, the 3-4 degree range is always listed as fast-feedback.
I think early Arctic ice disappearance is not assumed. This topic is way out of
my area of competency, so I hope others can chime in.
4. Hansen is extremely supportive of your position. I think a better
reference to his views than either your cite or mine is this for his law-suit
brief (because it has been written for a less scientifically literate audience
than he usually writes for):
http://charlietebbutt.com/files/ScienceAmicusBrief.pdf
5. Likely that 350 will not be enough; the target of 2 degrees C is
outdated. Proof is what is happening to the Arctic. My reading of Neven's
blog is that experts are expecting new record lows for area, extent, volume,
and thickness - because this was a much warmer Arctic winter than a year
previous. 2016 for essentially zero September ice again looks distinctly
possible - not 2080.
Ron
On Mar 16, 2014, at 2:43 PM, John Nissen <[email protected]> wrote:
>
> Hi David,
>
> I said that the level of CO2 had to be reduced if the world was to have a
> chance of keeping below 2ºC warming. Perhaps the simplest way to show this
> is to use the climate sensitivity calculations of Prof Hansen [1] and then
> look at the current level of CO2 equivalent from Prof Prinn [2]. I admit
> being shocked when I did the maths!
>
> Hansen says:
>
> "Equilibrium sensitivity 6°C for doubled CO2 is relevant to the case in which
> GHG changes are specified. That is appropriate to the anthropogenic case,
> provided the GHG amounts are estimated from carbon cycle models including
> climate feedbacks such as methane release from tundra and ocean sediments."
>
> Now while we currently have 400 ppm CO2, the additional greenhouse gases
> bring it up to 478 ppm equivalent (CO2e) according to Prinn, so we are not so
> far from doubling of CO2e, which would produce 6ºC warming as equilibrium
> temperature according to Hansen. In fact, we are 198 ppm over the
> pre-industrial level of 280 ppm.
>
> 198 / 280 * 6ºC = 4.24ºC.
>
> This means we've already put enough greenhouse gases into the atmosphere to
> produce a 4.24 degrees C equilibrium temperature, even with no further
> increase in greenhouse gases.
>
> Clearly we will have to suck CO2 out of the atmosphere faster than we are
> putting it into the atmosphere! We also have to think about reducing CO2
> because of ocean acidification. Carbon dioxide removal (CDR) using
> geoengineering techniques, is essential. This should be ramped up ASAP.
>
> AMEG proposes a target of CO2 reduction to below 350 ppm in 20 years, ramping
> up the CDR continuously over that period. The CDR will probably require a
> combination of: (i) CCS for all fossil fuel power stations, (ii) improved
> forest management, (iii) improved agricultural practice such as biochar, and
> (iv) improved CO2 absorption in the sea using kelp and photosynthesising
> algae such as diatoms. The CDR should be funded by a levy on carbon taken
> out of the ground, preferably at the point of extraction thus avoiding the
> problem of taxation further down the supply chain.
>
> Cheers,
>
> John
> Chair AMEG (Arctic Methane Emergency Group)
>
> [1] http://arxiv.org/ftp/arxiv/papers/0804/0804.1126.pdf
>
> [2]
> http://oceans.mit.edu/featured-stories/5-questions-mits-ron-prinn-400-ppm-threshold
>
> --
>
> On 16/03/2014 13:19, Hawkins, Dave wrote:
>>
>> John,
>>
>> You say--
>> the level of CO2 in the atmosphere has to be reduced if the world is to have
>> any chance of keeping below 2 degrees C warming.
>> If you are referring to today's level of CO2 in the atmosphere, what
>> paper(s) can you point to that support this conclusion?
>>
>> As for the FOE comments about geoengineering, I think it is worth noting
>> that FOE says it opposes only one form of geoengineering, SRM, and appears
>> to be primarily concerned about one form of SRM, stratospheric particle
>> injection.
>>
>> David
>>
>>
>> Sent from my iPad
>>
>> On Mar 16, 2014, at 4:50 AM, "John Nissen"
>> <[email protected]<mailto:[email protected]>> wrote:
>>
>> Hi all,
>>
>> FoE says the WG2 report on climate impacts will be published on March 29th
>> and the WG3 report on "pathways to avoid dangerous climate change" will be
>> published on April 11th.
>>
>> To quote from the WG3 summary by FoE:
>>
>> "It is still possible to reduce global carbon pollution fast enough and deep
>> enough to make 2 degrees of global warming unlikely and provide a small
>> chance of avoiding 1.5 degrees of warming, but only by making far-reaching
>> socio-economic changes."
>>
>> This is complete twaddle and wishful thinking by people whose solidarity is
>> clearly with the "egalitarians" (see posting by Dan Kahan on polarities).
>> It is twaddle because the level of CO2 in the atmosphere has to be reduced
>> if the world is to have any chance of keeping below 2 degrees C warming.
>> There is no way that some vague collection of "socio-economic changes" can
>> reduce the CO2 in the atmosphere as required. Only geoengineering can do
>> this.
>>
>> It is also twaddle because the situation in the Arctic is completely
>> ignored. Best scientific evidence points to a vicious cycle of warming and
>> melting in the Arctic as albedo is lost. The only way to break this cycle,
>> and halt the slippery slide into complete Arctic meltdown, is to cool the
>> Arctic.
>>
>> The sooner that IPCC accepts geoengineering as a logical necessity for both
>> CO2 removal and cooling the Arctic, the sooner that the twin dangers from
>> excess CO2 and Arctic overheating will be accepted by politicians and
>> society at large. The talk of geoengineering will make everyone aware that
>> the situation we find ourselves in is already dangerous - really dangerous.
>>
>> The only sensible "pathways to avoid dangerous climate change" must involve
>> geoengineering to remove CO2 and geoengineering to cool the Arctic. The
>> pathway proposed by WG3 is suicidal lunacy.
>>
>> Cheers, John
>>
>>
>>
>>
>> On Sat, Mar 15, 2014 at 12:34 AM, Oscar Escobar
>> <[email protected]<mailto:[email protected]>> wrote:
>> IPCC AR5 WG2 report - advance briefing
>>
>> Intergovernmental Panel on Climate
>> Change (IPCC)
>> Fifth Assessment, Working Group 3 report
>> Questions and answers in advance of publication
>>
>> http://www.foe.co.uk/sites/default/files/downloads/advance-briefing-ipcc-report-climate-mitigaton-45694.pdf
>>
>> (Excerpt)
>> Reasons to be worried
>>
>> Although the WG3 report will show that the potential to cut carbon pollution
>> sufficiently to
>> make 2 degrees warming unlikely exists, it will also illustrate the very
>> significant
>> socio-economic changes that are needed to do so. Currently the political
>> will to make these
>> changes, for example reducing fossil fuel use or reducing inequalities
>> between and within
>> countries, is sorely lacking.
>>
>> Because of current and past failures to reduce carbon pollution it is not
>> surprising that the
>> IPCC has investigated geoengineering options. However, by doing so it
>> potentially
>> normalises these approaches alongside energy efficiency, renewables, etc.
>> The risks of
>> particularly solar radiation management are very high and this will need to
>> be made clear.
>>
>> What are others likely to say?
>>
>> It is likely that climate deniers will identify the high costs of mitigation
>> whilst ignoring the
>> considerable benefits which outweigh the costs.
>> It is also possible that right-wing think tanks and the media focus on the
>> potential for
>> geoengineering as a potentially low cost response to climate change,
>> particularly regarding
>> the extremely risky strategy of injection of aerosols into the stratosphere
>> as a form of solar
>> radiation management.
>>
>> Friends of the Earth is opposed to the deployment of solar radiation
>> management.
>> There is also the danger that some commentators also reject all negative
>> emissions
>> technologies in addition to rejecting solar radiation management.
>> This is simplistic and could create opposition to development of necessary
>> technologies
>> to remove carbon pollution from the atmosphere (e.g. air capture of carbon
>> utilising carbon capture and storage).
>>
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