Could There Be No Net Human Impact on Earth's Temperature?

Powerline, with the help of those hacked emails, points out that the sulfur dioxide sent into the air by China and India may be canceling out the warming created by carbon dioxide emissions:

Your prediction for 2009 is very interesting...and I would expect the analysis you have done is correct. But, I have one nagging question, and that is how much SO2/sulfate is being generated by the rising emissions from China and India.... While I understand there are efforts to get much better inventories of CO2 emissions from these nations, when I asked a US EPA representative if their efforts were going to also inventory SO2 emissions (amount and height of emission), I was told they were not. So, it seems, the scientific uncertainty generated by not having good data from the mid-20th century is going to be repeated in the early 21st century (satellites may help on optical depth, but it would really help to know what is being emitted).

That there is a large potential for a cooling influence is sort of evident in the IPCC figure about the present sulfate distribution--most is right over China, for example, suggesting that the emissions are near the surface--something also that is, so to speak, 'clear' from the very poor visibility and air quality in China and India. So, the quick, fast, cheap fix is to put the SO2 out through tall stacks. The cooling potential also seems quite large as the plume would go out over the ocean with its low albedo--and right where a lot of water vapor is evaporated, so maybe one pulls down the water vapor feedback a little and this amplifies the sulfate cooling influence.

Now, I am not at all sure that having more tropospheric sulfate would be a bad idea as it would limit warming--I even have started suggesting that the least expensive and quickest geoengineering approach to limit global warming would be to enhance the sulfate loading.... Sure, a bit more acid deposition, but it is not harmful over the ocean.... Indeed, rather than go to stratospheric sulfate injections, I am leaning toward tropospheric, but only during periods when trajectories are heading over ocean and material won't get rained out for 10 days or so.

In any case, if the sulfate hypothesis is right, then your prediction of warming might end up being wrong. I think we have been too readily explaining the slow changes over past decade as a result of variability--that explanation is wearing thin. I would just suggest, as a backup to your prediction, that you also do some checking on the sulfate issue, just so you might have a quantified explanation in case the prediction is wrong.

Otherwise, the Skeptics will be all over us--the world is really cooling, the models are no good, etc.

Sulphur dioxide, like carbon dioxide, is emitted as a result of industrial activity. Unlike carbon dioxide, it is actually a pollutant. But whereas carbon dioxide tends to warm, sulphur dioxide tends to cool, and MacCracken suggests that SO2 emissions from China and India may well be offsetting the temperature impact of CO2. The net effect of human activity, therefore, may be much closer to neutral than the alarmists have been claiming.