“Titanium dioxide could scatter sunlight and cool Earth, scientist says.“
And as an added bonus would reduce crop yields and make solar “power” even less useful than it is now 
Spritzing a sunscreen ingredient into the stratosphere could help counteract the effects of global warming, according to scientists behind an ambitious new geoengineering project.
The plan involves using high-altitude balloons to disperse millions of tons of titanium dioxide—a nontoxic chemical found in sunscreen as well as in paints, inks, and even food.
Once in the atmosphere, the particles would spread around the planet and reflect some of the sun’s rays back into space.
About three million tons of titanium dioxide—spread into a layer around a millionth of a millimeter thick—would be enough to offset the warming effects caused by a doubling of today’s atmospheric carbon dioxide levels, according to project leader and chemical engineer Peter Davidson.
This idea is not new. Among others, a Finnish professor of meteorology proposed a similar scheme already some 15 years ago (probably not the first one, either) and proposals along the same lines pop up every once in a while. Incredible that people who get hysteric over a few ppms of CO2, the lifeblood of all flora, are ready to inject stuff in the atmosphere with completely unpredictable consequences to the whole Earth. Just look at what PInatubo did to the global climate! The really scary thing is that some politicians may take these schemes seriously.
Ehrlich, et al, want to kill 6 billion humans.
As I’ve posted here before, the US Navy patented airborne dispersion of TiO2 pigment in 1974 for this purpose. As geoengineering it is really a very cheap option – one A380 could put about 800 t/d of dispersed pigment into the stratosphere if they had the right groundbased logistical support (quickly reloading 100 t of pigment into a plane in micronisable form would be the main difficulty. Above 10,000 m the half life of such particles is about 2 years, which is good because you need less to get the effect than SO2 and if it causes any problems you just stop and wait for it to rain out. So 3 Mt/a of pigment (about half world production) would need as few as 15 big planes.
The tiny problem with this whole idea is that the world, as it happens, hasn’t warmed for the last 15 years, and very little of the warming in the 20thC was due to CO2. So the whole thing is a complete waste of time and money. Which is why I dropped work on it in 2006, and went back to my day job, heh!
Interesting Bruce of Newcastle. There’s another way of cheaply dispersing reflectants into the stratosphere, put the sulfur back into jet fuels. For a financial consideration airlines will alter their flight plans to suit deposition needs (passengers could get cheaper fares for the inconvenience of longer flights than necessary) and you could selectively concentrate sunshields to “protect” say coral reefs in the case of El Niño ocean surface warming.
Of course the big problem with screwing with the climate is that everyone’s mileage varies – the same climatic conditions that deliver drought to eastern Australia and Indonesia also deliver good rains to America’s parched southwest. Who gets to say what conditions are desirable at a given moment? If you do try to make changes to conditions and someone else suffers drought/flood/crop failure/pimples on the belly/whatever is compensation then owed? How would we ever untangle that?
Yes, good idea, except you don’t really want the corrosion of the engines…
The main issue with SO2 or sulfuric acid is getting the right droplet size (of resulting H2SO4). But it’d be a whole lot cheaper than pigment if you can get it into the stratosphere. You’d think you’d need a much bigger tonnage as rutile TiO2 has the highest known refractive index. TiO2 pigment is also already designed off the shelf to have maximum diffraction (particle size 0.24 um), which is necessary for good quality paint. Car paint for example is only ~30 particles ‘deep’, yet you see no tinge of steel-grey showing through such a thin layer as those 30 particles have fully scattered the incident light. TiO2 is also pretty harmless – painters usually don’t take many precautions when removing old paint by power sanding.
It looks like about 250 million t of jet fuel gets used annually. From what I’ve seen, based on Pinatubo and IPCC’s estimates for CO2 sensitivity, about 4 Mt/yr of sulfur would need to be burnt in the low stratosphere, which means you need something like 2% S in all commercial jet fuel burnt on the planet, probably much more.
I like the warmist climate scientists who say sulfur emissions from China stopped the world from warming (they use this argument to ‘correct’ for the expected warming caused by the supposed high 2XCO2 value). The logical answer in that event would be to remove the limit for sulfur in coal for power stations, and turn off the flue gas desulfurisation units. Not only would that ‘stop’ (nonexistent) CAGW, but would actually save money on alkali costs and waste disposal. But for some reason they hate it whenever I mention this.
Who gets to say what conditions are desirable at a given moment?
Yes. It’d be a different question if CAGW was real, but it isn’t.
In total agreement about the absence of need Bruce of Newcastle.
If you were to find a need to selectively reduce insolation then I don’t think you’d require anything like 4 Mt/yr sulfur – basically you’d want to tweak the tropical belt where you get the most bang for your buck and you’d only want to treat regions within a few hundred miles of the west continental coast, for example, to ‘protect’ susceptible corals and displace excessive precipitation occurring to the east of the target zone. Selectively cooling (less-warming?) ocean regions could be effective in manipulating trade wind strengths and even timing so you can influence the presence/absence of precipitation concentration around the globe.
Perturbing atmospheric circulation, however, is a recipe for litigation from greenies and everyone with ills real or imagined.
Influencing insolation and precipitation is an intriguing concept but we are a long, long way from understanding the atmosphere and climate sufficiently to attempt doing it.
The main reason I like governments talking about it is that they’ll never agree an ‘ideal’ temperature/precipitation regime and so will never get around to doing anything at all (my preferred option for governments with a mind to control the weather).
I was basing on Robock et al 2009 (link). As to local vs global use my thought was a green government could just lay out the stuff on meridian 30W and 150E and thumb their nose at everyone else. Although the Russians might object with slight violence, since I secretly suspect Mr Putin would rather like some global warming. Siberia would be much nicer.
Sorry I shouldn’t give these people ideas…or give you a hard time