Comments 1 to 6:

1. ubrew12 at 02:34 AM on 24 May, 2016

   The article 'Far from turning a corner, Global CO2 emissions still accelerating' contains a graph showing current CO2 at 400ppm and 'CO2+nonCO2 GHGs' at 500ppm.  This second line may hit 560ppm (a doubling from pre-Industrial 280ppm) within the decade.  Am I correct in assuming we are, within the decade, essentially 'locked in' to the equilibrium climate sensitivity of 1.5C to 4.5C?  If so, this seems a critical argument to start making.

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2. bozzza at 19:47 PM on 25 May, 2016

   No, those numbers only apply to carbon emissions !

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3. ubrew12 at 01:50 AM on 26 May, 2016

   Thanks for responding.  However, at around 1850,  CO2 and CO2+nonCO2-GHG's are at the same Pre-Industrial value: 280ppm.  Which value applies today?  CO2 or CO2+nonCO2-GHG's?  I'm sure the Infrared Radiation doesn't discriminate: the latter applies to climate sensitivity calculations.  Hence, 560ppm within 10-20 years.  Here's the relevant graph from the article: 

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4. Tom Curtis at 04:52 AM on 26 May, 2016

   ubrew12 @1&3, if you wish to determine the effect of human activities on climate, you should include all effects including the cooling effects of aerosols and albedo changes for LUC.  Doing so shows a total current anthropogenic forcing of about 2.1 W/m^2, not the 3.1 obtained by looking at WMGHG alone as you are doing.  What is more, as is apparent on this graph, the forcing is rising steadily, not accelerating:

    

   You may think that is unreasonable in that the aerosol effects will wash out of the atmosphere fairly rapidly in the event that we cease anthropogenic emissions (which is correct), but equally, if we cease anthropogenic emissions non-CO2 well mixed GHG will rapidly decompose, and CO2 will be fairly rapidly be taken up by the ocean until ocean/atmosphere equilibrium is reached.  The upshot is that the long term climate effects are best determined by considering CO2 alone, and allowing for the effects of the CO2 cycle.  For the short term effects, however, there is no substitute for looking at all forcings, including the negative anthropogenic forcings. 

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5. ubrew12 at 11:45 AM on 26 May, 2016

   Tom Curtis@4: That sounds reasonable.  The reason to exclude nonCO2-GHG's in an 'equilibrium climate sensitivity' calculation is their relative impermanence once 'action is taken'.  But that liability turns into an asset for sun-shading aerosol pollutants, since it is now their shading capability that is impermanent, not IR blocking.  So we should follow CO2 alone for an idea of future IR blocking-induced heating, but understand that once aerosols rain out an additional heating will incur.

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6. MA Rodger at 19:28 PM on 26 May, 2016

   ubrew12 @5,

   I think it worth adding a couple of points or so.

   Firstly, the NOAA/ESRL Annual Greenhouse Gas Index is looking at the atmospheric content not emissions. So the trends in their numbers will be affected by natural pertubations. I think this results in an exaggerated rise, an additional acceleration, over the last couple of decades since 1990 or 2000.

   Secondly, if we do accept that acceleration in the AGGI numbers continues, it woud suggest the 2xCO2(e) level arrives in 20 years. But note, as well as being exaggerated by natural events, that underlying acceleration also assumes we continue to grow FF use as we did since 1990 or 2000. I don't see that happening.

   Thirdly, I agree that CO2 is the true devil because a significant proportion of it it will be with us for millenia. (It's likely destination will surely be our decendents using their technology to remove it rather than allow it to, for instance, send Greenland into melt-down.) Yet, I feel there is the potential for tackling SO2 emissions without tackling the positive forcings. Turning off coal-use or more effective/widespread scrubbing could easily see SO2 emissions massively reduced. Indeed the current trends are down. Sadly this is not so for the big GHGs.

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