Uncertainty analysis for estimates of the first indirect aerosol effect

Chen, Y.; Penner, Joyce E.

doi:10.5194/acp-5-2935-2005

Cited by 115 publications

(69 citation statements)

References 48 publications

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“…At atmospheric pressures where low cloud typically occurs (800-950 mb), zonal mean annual average all-sky CDNC are 50-250 cm −3 (Fig. 5), a range in agreement with previous simulations (e.g., Chen and Penner, 2005).…”

Section: Aerosol Indirect Effectsupporting

confidence: 80%

“…Figure 7 shows the annual average zonal mean AIE due to carbonaceous combustion aerosol. At latitudes between 35 • S and 55 • N we calculate a zonal mean radiative effect at the top of the atmosphere as large as −1.5 W m −2 (when we assume smaller sized carbonaceous combustion particles) in agreement with Chen and Penner (2005).…”

Section: Aerosol Indirect Effectsupporting

confidence: 64%

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Global cloud condensation nuclei influenced by carbonaceous combustion aerosol

et al. 2011

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Abstract. Black carbon in carbonaceous combustion aerosol warms the climate by absorbing solar radiation, meaning reductions in black carbon emissions are often perceived as an attractive global warming mitigation option. However, carbonaceous combustion aerosol can also act as cloud condensation nuclei (CCN) so they also cool the climate by increasing cloud albedo. The net radiative effect of carbonaceous combustion aerosol is uncertain because their contribution to CCN has not been evaluated on the global scale. By combining extensive observations of CCN concentrations with the GLOMAP global aerosol model, we find that the model is biased low (normalised mean bias = −77 %) unless carbonaceous combustion aerosol act as CCN. We show that carbonaceous combustion aerosol accounts for more than half (52-64 %) of global CCN with the range due to uncertainty in the emitted size distribution of carbonaceous combustion particles. The model predicts that wildfire and pollution (fossil fuel and biofuel) carbonaceous combustion aerosol causes a global mean cloud albedo aerosol indirect effect of −0.34 W m −2 , with stronger cooling if we assume smaller particle emission size. We calculate that carbonaceous combustion aerosol from pollution sources cause a global mean aerosol indirect effect of −0.23 W m −2 . The small size of carbonaceous combustion particles from fossil fuel sources means that whilst pollution sources account for only onethird of the emitted mass they cause two-thirds of the cloud albedo aerosol indirect effect that is due to carbonaceous combustion aerosol. This cooling effect must be accounted for, along with other cloud effects not studied here, to ensure that black carbon emissions controls that reduce the high number concentrations of fossil fuel particles have the desired net effect on climate.

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Section: Aerosol Indirect Effectsupporting

confidence: 80%

Section: Aerosol Indirect Effectsupporting

confidence: 64%

Global cloud condensation nuclei influenced by carbonaceous combustion aerosol

et al. 2011

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“…However, our approach and our choice of updraught velocities have been shown to provide a good approximation of mean CDNC (Fountoukis et al, 2007;Pringle et al, 2009;Karydis et al, 2011). As with many other aerosol activation schemes (e.g., Chen and Penner, 2005;Roelofs et al, 2006), the employed scheme does not account for droplet collision-coalescence (i.e. no droplet loss rate), thus CDNCs are shown at cloud-base altitude.…”

Section: Treatment Of Aerosol Activation and Model Evaluationmentioning

confidence: 99%

Importance of tropospheric volcanic aerosol for indirect radiative forcing of climate

et al. 2012

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Abstract.Observations and models have shown that continuously degassing volcanoes have a potentially large effect on the natural background aerosol loading and the radiative state of the atmosphere. We use a global aerosol microphysics model to quantify the impact of these volcanic emissions on the cloud albedo radiative forcing under pre-industrial (PI) and present-day (PD) conditions. We find that volcanic degassing increases global annual mean cloud droplet number concentrations by 40 % under PI conditions, but by only 10 % under PD conditions. Consequently, volcanic degassing causes a global annual mean cloud albedo effect of −1.06 W m −2 in the PI era but only −0.56 W m −2 in the PD era. This non-equal effect is explained partly by the lower background aerosol concentrations in the PI era, but also because more aerosol particles are produced per unit of volcanic sulphur emission in the PI atmosphere. The higher sensitivity of the PI atmosphere to volcanic emissions has an important consequence for the anthropogenic cloud radiative forcing because the large uncertainty in volcanic emissions translates into an uncertainty in the PI baseline cloud radiative state. Assuming a −50/+100 % uncertainty range in the volcanic sulphur flux, we estimate the annual mean anthropogenic cloud albedo forcing to lie between −1.16 W m −2 and −0.86 W m −2 . Therefore, the volcanically induced uncertainty in the PI baseline cloud radiative state substantially adds to the already large uncertainty in the magnitude of the indirect radiative forcing of climate.

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“…The aerosol burden calculation, the cloud fraction, and the representation of the preindustrial aerosol state (size distribution and mass concentration) are the main sources of uncertainty. Chen and Penner (2005) warn about the use of off-line simulations that could cause additional sources of uncertainty since they use a monthly average aerosol number concentration and argue for a fully coupled GCM, which would give a better estimate of the interactions between aerosols, clouds and radiation.…”

Section: Déandreis Et Al: Radiative Forcing Estimates Of Sulfate mentioning

confidence: 99%

“…Chen and Penner (2005) have analysed the uncertainty in the estimation of the first indirect aerosol effect due to emissions, chemical transport model, aerosol size distribution, cloud nucleation parameterization, and different clouds properties. The aerosol burden calculation, the cloud fraction, and the representation of the preindustrial aerosol state (size distribution and mass concentration) are the main sources of uncertainty.…”

Section: Déandreis Et Al: Radiative Forcing Estimates Of Sulfate mentioning

confidence: 99%

Radiative forcing estimates of sulfate aerosol in coupled climate-chemistry models with emphasis on the role of the temporal variability

et al. 2012

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Abstract. This paper describes the impact on the sulfate aerosol radiative effects of coupling the radiative code of a global circulation model with a chemistry-aerosol module. With this coupling, temporal variations of sulfate aerosol concentrations influence the estimate of aerosol radiative impacts. Effects of this coupling have been assessed on net fluxes, radiative forcing and temperature for the direct and first indirect effects of sulfate.The direct effect respond almost linearly to rapid changes in concentrations whereas the first indirect effect shows a strong non-linearity. In particular, sulfate temporal variability causes a modification of the short wave net fluxes at the top of the atmosphere of +0.24 and +0.22 W m −2 for the present and preindustrial periods, respectively. This change is small compared to the value of the net flux at the top of the atmosphere (about 240 W m −2 ). The effect is more important in regions with low-level clouds and intermediate sulfate aerosol concentrations (from 0.1 to 0.8 µg (SO 4 ) m −3 in our model).The computation of the aerosol direct radiative forcing is quite straightforward and the temporal variability has little effect on its mean value. In contrast, quantifying the first indirect radiative forcing requires tackling technical issues first. We show that the preindustrial sulfate concentrations have to be calculated with the same meteorological trajectory used for computing the present ones. If this condition is not satisfied, it introduces an error on the estimation of the first indirect radiative forcing. Solutions are proposed to assess radiative forcing properly. In the reference method, the coupling between chemistry and climate results in a global average increase of 8 % in the first indirect radiative forcing. This change reaches 50 % in the most sensitive regions. However, the reference method is not suited to run long climate simulations. We present other methods that are simpler to implement in a coupled chemistry/climate model and that offer the possibility to assess radiative forcing.

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Uncertainty analysis for estimates of the first indirect aerosol effect

Cited by 115 publications

References 48 publications

Global cloud condensation nuclei influenced by carbonaceous combustion aerosol

Global cloud condensation nuclei influenced by carbonaceous combustion aerosol

Importance of tropospheric volcanic aerosol for indirect radiative forcing of climate

Radiative forcing estimates of sulfate aerosol in coupled climate-chemistry models with emphasis on the role of the temporal variability

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