I have seen previous articles that noted this soot had an effect, but only a minor one.
 John Burton

Has this study of the effect of soot been peer reviewed or commented on by any climatologists?
It has been reported for years that soot has an effect, but is believed to have only a minor effect.
John Burton

At the time Ramanathan stated that the net heating effect within mid-tropospheric brown clouds were contributing a net heating effect - not a net shading effect. Instead of the two components canceling out each other's effects, soot's net heating effect exceeds that of its shading effect and the higher reflectivity of sulfates. One factor may be that the hotter rising clouds of soot segregate themselves away from the whiter, cooler sulfates where their effect is enhanced and self-propelling.

The general effects of aerosol-ladened brown clouds had already been observed to disrupt the formation of low-level rain clouds, actually reducing both regional cloud-top albedo (reflective heat-rejecting cloud tops) as well as surface-cooling shading from rain clouds.

In August 2006, however, Ramanathan's team took their field data and applied them to climate models. Not only were high-level brown clouds found culpable for HALF of regional warming anomalies formerly blamed on CO2 but the brown clouds were generally responsible for 40 percent of the warming over the vast Pacific (30 percent of the Earth's surface).

What has added grist to the counter-mill of so-called climate skeptics is that Ramanathan's team was making direct observations in situ, running sorties of small robotic planes at various altitudes sampling atmospheric chemistry and temperature - the significance being that direct empirical data apparently contradicted many climate models as well as the public proclamations of the IPCC and pro-environment politicians. For once the climate skeptics had a real chink in the empirical armor of climatology and global politics. All the other speculations on the effects of solar activity, dyssynchrony in the Vostok paleo ice samples, etc., were piffle compared to the Scripps Inst. team's discovery.

The significance of this discovery shouldn't be understated, however, because it still turns the world's attention to both sustainable development and international cooperation. The bulk of global soot pollution is still from itinerant farmers working the land via slash and burn farming as well as fueling their cook stoves with wood. This isn't to blame the itinerant poor but to consider what the industrialized West can do to help them replace their use of wood as cook fuel and subsidize better agricultural methods. The answer, paradoxically, may be to encourage them to use petroleum-based cooking fuels and fertilizers (made from natural gas), bio-char black carbon and other soil amendments.

For that to be feasible, however, methane, kerosene and gasoline prices will need to become more economical to itinerant farmers through both subsidies and sustained conservation efforts (fuel efficiencies & energy use cutbacks). This again turns the focus on the industrialized nations to mitigate their petroleum throughput.

As Ramanathan famously stated, this does seem to provide a way out of a very broad conundrum, because the results of soot abatement are immediate realized - as opposed to the 15 - 25 year atmospheric half life of methane or the 40 - 50 year half life of atmospheric CO2.

The results will also provide other positive synergistic results: Deforestation near temperate and tropical glaciers has decimated the microclimate recharge effect of forests acting as an atmospheric watershed. Likewise the mid-tropospheric air-borne soot strata directly sully and heat both temperate and tropical glacial packs (in the Himalayas, in the American Rockies and famously on Kilimanjaro). Mitigating the use of arboreal cook fuels and itinerant slash-and-burn agriculture will both mitigate climate change and help reclaim now-vanishing glacial watersheds. Likewise flooding problems in low-lying areas like Bangladesh largely stem from upstream deforestation that results in worsening watershed flooding downstream.

Likewise we can foresee another benefit of soot-reduction being the reclamation of Arctic and sub-Arctic glaciers as well as tundra conditions (a potential source of methane under run-away thaw conditions). The Arctic has suffered terribly from the snow-darkening heating effects of soot deposition - up to 25 percent of the past century's warming can be attributed to the Arctic melt-off, and up to 90 percent of that has been due to soot. Due to the nature of westerly winds, most of the current soot deposition in the Arctic is borne from S.E. Asia, along with a fair amount from Russian oil fields and the rest from industrialized N. American and Europe.

I hope that helps.

--leebert