who has some idea what he's talking about.

It's not a simple problem. E.g. http://irina.eas.gat...6/Andreae2005.pdf - an article from Nature in 2005:

(Sorry about the extraneous CRs.)

Climatic effects of aerosols

In the first IPCC report7, climate change was considered to be driven predominantly by anthropogenic GHG emissions. Aerosol effects on climate were mentioned, but our knowledge was considered inadequate to estimate their magnitude, or even sign. Since then, the number of aerosol-caused climate effects considered and the estimates of their cumulative magnitude have steadily grown. All aerosol types (sulphates, organics, mineral dust, sea salt, and so on) intercept incoming sunlight, and reduce the energy flux arriving at the Earth’s surface, thus producing a cooling8. Some aerosols (for example, soot) absorb light and thereby warm the atmosphere, but
also cool the surface. This warming of atmospheric layers may also reduce cloudiness, yielding another warming effect. In addition to these ‘direct’ radiative effects, there are several ‘indirect’, cloud mediated effects of aerosols, which all result in cooling: more aerosols produce more, but smaller, droplets in a given cloud, making it more reflective. Smaller droplets are less likely to coalesce into raindrops, and thus the lifetime of clouds is extended, again increasing the
Earth’s albedo. Finally, modifications in rainfall generation change the thermodynamic processes in clouds, and consequently the dynamics of the atmospheric ‘heat engine’ that drives all of weather and climate. The recent tremendous growth in knowledge of the climatic effects of aerosols, along with the emergence of
the likelihood of positive feedbacks between climate and the carbon cycle9,10, have transformed the orderly picture of climate change of the early 1990s, dominated by GHG warming, into a complex mix of opposing effects11,12.

[...]

The SRES emissions scenarios25 used in the IPCC-TAR all suggest that aerosol emission by the middle of this century will be near or below present levels. Because aerosols are very short-lived in the atmosphere—lifetimes of days compared with decades for the greenhouse gases—they do not accumulate and the burden is
almost proportional to the emissions. Consequently, as we clean up our vehicles and smokestacks to provide cleaner air and improve air quality, the aerosol loading of the atmosphere will decrease. Even population growth and increasing industrialization in the developing countries will do little to change this outcome. We are already in the process of revising downward our projections of aerosol emissions from China and other developing countries, as they are introducing
cleaner technology faster than had been anticipated a decade or so ago. Because of the rapidly growing knowledge of the very serious health effects of aerosols28 we expect that regulatory efforts will act to reduce aerosol emissions even more rapidly than anticipated when the SRES scenarios were developed.

[...]

We have run the simple model on to 2100 for a range of scenarios from the IPCC’s Special Report on Emissions Scenarios (SRES, see Box 2) (Figs 2 and 3). We find that a large uncertainty range of temperature increase is predicted for 2100, and that even by 2050, the model runs with strong historical aerosol cooling predict a
temperature rise from 1850 of as much as 2.2 8C. The implied high climate sensitivities are within the range of sensitivities inferred by recent observational approaches. Analyses of the probability distribution of climate sensitivities that can be deduced from climate observations suggest that there is a significant
probability that the true climate sensitivity is in excess of 4 K (refs 5, 6), and maybe as high as 10 K. Recent analyses of the palaeoclimatic record also suggest fairly high climate sensitivity20,21.

When we include the uncertainty caused by the choice of emission scenarios, we find that the range considered most plausible in IPCC-TAR (2.3–4.9 8C from 1850–2100) can be obtained only for aerosol forcings considerably weaker than predicted by current
forward models (Fig. 3), which tend to estimate the sum of aerosol forcings to be in the range 21 to 22Wm22 (refs 11, 12, 16, 17).
Ominously, Fig. 3a shows temperature increases in excess of 6 8C for the climate sensitivity implied by the central estimate of aerosol forcing (21.5Wm22), and for all but the most optimistic emission scenario. Such an enormous increase would be comparable to the temperature change from the previous ice age to the present.
Furthermore, the overall uncertainty is dominated by climate sensitivity and hence historical aerosol forcing: Fig. 3a shows that the warming range for a given scenario (for example, 2.5–7.9 K for scenario A2) is greater than the range across scenarios for a given climate sensitivity (6.8–9.6 K at its widest).

Part of the reason for this extraordinary sensitivity of future projections to the historical aerosol forcing is due to the impact of the carbon cycle feedback on projected CO2 levels (Fig. 3b). The extent to which the land carbon cycle amplifies future CO2 increase depends critically on climate sensitivity (Fig. 4). [...]

Too little is known about the amounts of SO2 needed, the effects introducing such amounts into the atmosphere, and the interactions of those aerosols with other important actors in the atmosphere to think that it should be pushed as a "simple" solution to anthropogenic climate change. What we do know about aerosols is that they are bad for lakes and forests (e.g. acid rain) and lungs.

Isn't it interesting how pundits who aren't experts like to claim that things are so cheap and simple when they fit their biases?

Cheers,
Scott.