And some additional context:
These ERF numbers for aerosols are the result of a host of processes in
GCMs (and in the real world) and aren't a simple setting. In really simple
models they are though. In those really simple models it's trivial to run
all sorts of different values at once so a lot of studies run millions of
runs which scope out the uncertainty in aerosol forcing, climate
sensitivity and ocean heat uptake. They then plot the 'cone of uncertainty'
for some variable. Typically this forms the input to various economic
models as the results of the simple models aren't that interesting on their
own.
On Friday, 4 March 2016 09:57:29 UTC-5, p.j.irvine wrote:
>
> Hi,
>
> To put this in perspective the IPCC AR5 found:
>
> The magnitude of the aerosol forcing is reduced relative to AR4. The RF
> due to aerosol–radiation interactions, sometimes referred to as direct
> aerosol effect, is given a best estimate of –0.35 (–0.85 to +0.15) W m–2,
> and black carbon (BC) on snow and ice is 0.04 (0.02 to 0.09) W m–2. The ERF
> due to aerosol–radiation interactions is –0.45 (–0.95 to +0.05) W m–2. A
> total aerosol–cloud interaction5 is quantified in terms of the ERF concept
> with an estimate of –0.45 (–1.2 to 0.0) W m–2. The total aerosol effect
> (excluding BC on snow and ice) is estimated as ERF of –0.9 (–1.9 to –0.1)
> W m–2. The large uncertainty in aerosol ERF is the dominant contributor
> to overall net Industrial Era forcing uncertainty. Since AR4, more aerosol
> processes have been included in models, and differences between models and
> observations persist, resulting in similar uncertainty in the aerosol
> forcing as in AR4. Despite the large uncertainty range, there is a high
> confidence that aerosols have offset a substantial portion of WMGHG global
> mean forcing. {8.3.4, 8.5.1, Figures 8.15, 8.16}
>
> this 2.5 Wm-2 is considerably outside that estimated range. Given that
> this paper makes no comparison with observations, I'd take this high
> estimate with a pinch of salt as it's model-specific.
>
> On Thursday, 3 March 2016 17:17:02 UTC-5, Andrew Lockley wrote:
>>
>> Poster's note : a significant negative forcing we're going to be missing
>> once solar power kicks in at scale
>>
>> http://onlinelibrary.wiley.com/doi/10.1002/joc.4613/abstract
>>
>> International Journal of Climatology
>>
>> The updated effective radiative forcing of major anthropogenic aerosols
>> and their effects on global climate at present and in the future
>>
>> Authors
>> Hua Zhang,
>> Shuyun Zhao,
>> Zhili Wang,
>> Xiaoye Zhang,
>> Lianchun Song
>>
>> 25 January 2016
>> DOI:10.1002/joc.4613
>>
>> ABSTRACT
>>
>> The effective radiative forcing (ERF), as newly defined in the
>> Intergovernmental Panel on Climate Change's Fifth Assessment Report (IPCC
>> AR5), of three anthropogenic aerosols [sulphate (SF), black carbon (BC),
>> and organic carbon (OC)] and their comprehensive climatic effects were
>> simulated and discussed, using the updated aerosol-climate online model of
>> BCC_AGCM2.0.1_CUACE/Aero. From 1850 to 2010, the total ERF of these
>> anthropogenic aerosols was −2.49 W m−2, of which the aerosol–radiation
>> interactive ERF (ERFari) and aerosol–cloud interactive ERF (ERFaci) were ∼
>> −0.30 and −2.19 W m−2, respectively. SF was the largest contributor to the
>> total ERF, with an ERF of −2.37 W m−2. The ERF of BC and OC were 0.12 and
>> −0.31 W m−2, respectively. From 1850 to 2010, anthropogenic aerosols
>> brought about a decrease of ∼2.53 K and ∼0.20 mm day−1 in global annual
>> mean surface temperature and precipitation, respectively. Surface cooling
>> was most obvious over mid- and high latitudes in the northern hemisphere
>> (NH). Precipitation change was most pronounced near the equator, with
>> decreased and increased rainfall to the north and south of the equator,
>> respectively; this might be largely related to the enhanced Hadley Cell in
>> the NH. Relative humidity near surface was increased, especially over land,
>> due to surface cooling induced by anthropogenic aerosols. Cloud cover and
>> water path were increased, especially in or near the source regions of
>> anthropogenic aerosols. Experiments based on the Representative
>> Concentration Pathway (RCP) 4.5 given in IPCC AR5 shows the dramatic
>> decrease in three anthropogenic aerosols in 2100 will lead to an increase
>> of ∼2.06 K and 0.16 mm day−1 in global annual mean surface temperature and
>> precipitation, respectively, compared with those in 2010.
>>
>
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