Climate’s Urgent Repair

The energy needed as well as the resources to build a shield would be immense and can only be afforded by very few. Meaning we are back to the basic reality that J.L. Talked about in his book the revenge of Gaia. 80% of Humanity will perish one way or the other and there is no nice way to put it or to sugar code this. A shield is unrealistic and even if successful can only save and protect less then 5% of Humanity. In addition, those 5% wont be those we want to save either. I do not think that pumping another chemical into the air will help us, SO2 does react and can change it self with as well as the balance in it self in ways we can not predict at this point. Stop eating Fish and leave the ocean alone for a century will be far cheeper and safer. Then the Ocean can absorb the CO2 as well as filter other chemicals. Fish by them self could help a lot here as well as some forms of plankton.

We need to stop trying to sugar cote the problem and face reality.

http://my.nowpublic.com/environment/revenge-gaia-humanity-under-attack

Indeed amyjudd the shield option is at this moment the best solution very cost effective compared to the other solution sucking CO2 out of the atmosphere. As you can see from the attached diagram it is a one time operation that covers the whole globe for a long period of time.

Paschen sorry, I don't agree with you, the proposed SO2 shield is meant to cover the globe entirely and not only 5% as you may think. The only drawback for SO2, which is equal to volcanic ash, is that it could cause drought in unwanted areas. But alternatives are under development. If Earth's temperatures do rise the oceans' temperatures too, that will realease CO2 instead of absorbing it! It is a real feasible and realistic option without sugar cote.

Did you ever go near a Volcano, SO2 will kill you eventually.

Sulfur dioxide (also sulphur dioxide) is the chemical compound with the formula SO2. It is produced by volcanoes and in various industrial processes. Since coal and petroleumoften contain sulfur compounds, their combustion generates sulfur dioxide. Further oxidation of SO2, usually in the presence of a catalyst such as NO2, forms H2SO4, and thus acid rain.[1] This is one of the causes for concern over the environmental impact of the use of these fuels as power sources.

It will eventually come back down as Sulfur dioxide is an intermediate in the production of sulfuric acid, being converted to sulfur trioxide, and then to oleum, which is made into sulfuric acid. Sulfur dioxide for this purpose is made when sulfur combines with oxygen. The method of converting sulfur dioxide to sulfuric acid is called the contact process. Several billion kilograms are produced annually for this purpose.

Wish means people will have to protect them self and that only 5% can afford. SO2 affects the Heard bonds Oxygen meaning we deplete the atmosphere of more oxygen and reduce it another one or two percent wish would cause death for most mammals. 

The O has to come from some where, to bind with the S. We are already losing Oxygen and reducing our levels dangerously, we can not afford to lose more. It is a Chemical equation and all things in Nature need to be balanced out as well as in Chemistry. 

SO2 + 2 H2S → 3 S + 2 H2O  It does also react with other Atoms SO2 + Cl2 → SO2Cl2 Creating some nasty chemicals. 

SO2 is a pollutant and toxic as well as Chemical that reacts with all other Chemical or atoms.

But Paschen the sulphur dioxide once brought in the stratosphere reacts with water and other molecules to form sulphate particles the same stuff as volcanic ash. In a volcanic outburst the sulphate for 90% falls direct on earth surface without sorting any cooling effect apart from the one you described. Contrary to the cooling effect once brought in the stratosphere by plane or weather balloons. I do agree this is likely not the nicest solution, but at the moment no other alternative is available, and it is better to undertake the yet best option than doing nothing at all. Remember: D-Day is coming up on us very fast!

Further Crutzen pointed out that the amount of SO2 you'd need to lower temperatures significantly is surprisingly small—nowhere near the 20 million tons that Pinatubo released, much of which was wasted near the ground where it had no effect on temperatures.

Besides: Scientist Keith is working on designing particles that are more efficient at cooling than sulfates, but without the side effects. Because sulfates tend to settle on the ground after a few months, they'd need to be replenished regularly. Keith's engineered particle would absorb the sun's energy unevenly, causing one side to heat more quickly than the other and to drift upward. Such a particle might be released on the ground and rise up on its own accord. It might be built in such a way that it rises higher than the ozone layer—to the mesosphere, 100 kilometers up—where it would reflect light but leave the ozone intact. For safety reasons, these particles could also have preordained lifetimes. "It's something we're developing," he says. "It may not work. But it's almost certain that if engineers put their minds to this, something could be made to work better than sulfates."

The most devastating side effect could be political. Success in lowering temperatures—or even the knowledge that scientists had the means to do so—might decrease the political will to make costly emissions cuts. Not even the most zealous advocate of geo-engineering argues for using it in lieu of cutting and capturing carbon. Using geo-engineering to keep temperatures artificially low while carbon levels continued to rise would be doubling down the risk of rapid warming should the air-cooling project suddenly stop, or need to be halted, for any reason.

The sulphur in Petroleum is in Europe eliminated and the rest of the world could do the same. Nevertheless it is recommended to use synthetic diesel fuel that no sulphur at all contains.