A list of puns related to "Radiative Forcing"
The CO2 radiative forcing term is often modelled as
Ξ F=k ln(c/c0),
where k in AR3 is 5.35 (page 358 in the "WG1 physical basis").
Now in a 2015 Nature article by Feldmann "Observational determination of surface radiative forcing by CO2 from 2000 to 2010", the radiative effect of CO2 was observed to be 0.2 W/m2 over the decade for 2000-2010(see Figure 4), during which CO2 increased from 370ppm to 392 ppm.
This is 30% lower than what the IPCC model states:
Ξ F=5.35* ln(392/370) = 0.309 W/m2.
To approximate the result of the Nature article, the parameter k should have been reduced to ~3.6:
Ξ F=3.6* ln(392/370) = 0.207 W/m2.
Feldmann and co-authors appear to not have noticed or commented that the radiative forcing they found was low in their paper.
ECS can be split into pre-feedback climate sensitivity and a post-feedback gain factor, and the radiative forcing of CO2 is a factor in pre-climate sensitivity.
Thus a reduced radiative forcing estimate by 30% would mean that ECS estimates from IPCC models should be reduced by 30% as well.
This recently submitted paper also seems to support the idea that estimate of CO2 radiative forcing used by IPCC should be reduced.
Does anyone know how to make an apples to apples comparison of "how far along" we are in terms of the RCPs? Is the current GHG concentration "ahead" or "behind" schedule compared to say RCP8.5, and by how much?
Values in Table 2 of https://www.esrl.noaa.gov/gmd/aggi/aggi.html for Total Radiative Forcing are larger than the historical numbers at http://www.iiasa.ac.at/web-apps/tnt/RcpDb/dsd?Action=htmlpage&page=compare by about 50% in 1980.
Of course these aren't directly comparable as the NOAA paper is just converting concentrations with constants and ignoring feedbacks. So I suspect the main difference is water vapour feedback perhaps? The RCP database notes that total concentration exludes mineral dust and the effect of land albedo, however.
The difference between the two measures of total radiative forcing decreases with time and if you extrapolate from the 4 points of overlap it would be about 32% today. Applying this ratio seems to suggest that we doing (a little bit) better in 2018 than RCP8.5 forcing by 2020 was projected to be. Does this sound about right? I had it in my head that we'd been emitting worse than RCP8.5 for quite some time now but maybe that was a few years ago and we've actually started turning away from this pathway a bit?
2000 ppb for methane. It is more potent then CO2 by a factor of 86, from what I have read. It has increased from 750 to 2000 ppb. Surely it would warm the globe more. Couldn't find any real sources, giving the temperature equivalent, so I would be thankful if an awnser and perhaps correction to my thinking would come up.
I need a very basic formula that relates Greenhouse Gas (GHG) concentrations and radiative forcing (RF). I need this formula in order to create a basic model relating RF, GHG, and surface temperature anomalies for a project. If anyone can point me in the right direction, let me know. I have been having trouble finding cited equations.
Thanks!
Recently I've been trying to make sense of aerosol radiative forcing and I am having trouble distinguishing the important papers that have been published since AR5 from the less influential ones. Could you guys point out some of the papers which have been published during the past 5 years that I should definitely read? For example IPCC's SR15 references the following three articles cited below, but I still feel my knowledge is woefully incomplete. Any suggestions would be appreciated.
due to anthropogenic emission changes during the period 1990-2015. Atmospheric
Chemistry and Physics, 17(4), 2709β2720, doi:10.5194/acp-17-2709-2017.
volcanic eruptions. Nature, 546(7659), 485β491, doi:10.1038/nature22974.
aerosol emissions. Geophysical Research Letters, 45(2), 1020β1029,
doi:10.1002/2017gl076079.
Can anyone here knowledgeable in climate science chime in and provide any feedback on why "clear-sky" studies like this can or can't be used in the manner described below? Any help much appreciated.
The CO2 radiative forcing term is often modelled as
Ξ F=k ln(c/c0),
where k in AR3 is 5.35 (page 358 in the "WG1 physical basis").
Now in a 2015 Nature article by Feldmann "Observational determination of surface radiative forcing by CO2 from 2000 to 2010", the radiative effect of CO2 was observed to be 0.2 W/m2 over the decade for 2000-2010(see Figure 4), during which CO2 increased from 370ppm to 392 ppm.
This is 30% lower than what the IPCC model states:
Ξ F=5.35* ln(392/370) = 0.309 W/m2.
To approximate the result of the Nature article, the parameter k should have been reduced to ~3.6:
Ξ F=3.6* ln(392/370) = 0.207 W/m2.
Feldmann and co-authors appear to not have noticed or commented that the radiative forcing they found was low in their paper.
ECS can be split into pre-feedback climate sensitivity and a post-feedback gain factor, and the radiative forcing of CO2 is a factor in pre-climate sensitivity.
Thus a reduced radiative forcing estimate by 30% would mean that ECS estimates from IPCC models should be reduced by 30% as well.
This recently submitted paper also seems to support the idea that estimate of CO2 radiative forcing used by IPCC should be reduced.
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