Grounding the airliners actually noticeably reduces cloud cover and hence increases warming. Scientists took advantage of the post 9/11 lull in air traffic to do some studies on it as it wasn't something they'd ever get real data on otherwise.
That is not 100% correct. Reducing cloud cover would not increase global warming, In fact it might actually do the opposite. Cloud cover actually keeps all of the C02, waper vapor, and other green house gases inside the atmopshere, much like a greenhouse, which warms the earth. During a cloudy night It traps in the earth's geothermal and infared heat which is why it is hotter during cloud cover at night time. Instead of these green house gasses being dispersed higher into the atmosphere they get trapped into the lower atmosphere causing higher scales of global warming.
In turn, reducing clouds may be better for the atmosphere. Depending on where the earth is positioned to the sun.
However, cloud seeding, while being tested, doesn't do very much in the overall atmosphere. To effect the atmopshere of a small town. Chemicals would have to be spreyed onto an intire town much like how they put out forest fires, you would obviously be able to see it happening. A stream of chemicals at 20,000+ feet would not reach human consumption, or be enough cunsumption to have deterimintal effects. That is why this conspiriacy is for idiot loons. The best form of cloud seeding today would be exploading nuclear bombs into the atmopshere. Notice how big that actually is, while only effecting people who were near it. You would have to detonate 100s or 1000s of nuclear bombs all over the world for it to have a major effect. That is the size of the clouds we are talking about here and the wind patterns that would carry them.
Volcanoe creation would take an enournous amount of energy. I LOL at people who think humans could create any type of real volcanoe. When you realize how powerful the earth cores and energy of geothermal heat, along with the movement of continental shelfs take an enormous amount of energy. One 1000s of times greater than a nuclear bomb.
This is why cloud cover from an astroid or Volcanoe killed the dinosours. Plants could not grow due to no sun light, in turn that killed the C02 and oxygen levels of the earth. Dinosours couldn't eat dead plants, which killed those populations and the carnavors could not eat them so they died out. During intense cloud cover, you would be freezing during the day, and hot during the night, depending on the earths position to the sun, (EI time of season. ) non the less, all the rest of the CO2 and water vapor would dispearse causing the earth to get colder and colder until these chemicals freeze, causing an ice age. We most likely got out of the ice age by a tremendous amount of heat from the earth over time. This broke the cloud barriers and allowed to the sun to help grow plants again. Once the earth reached sustainable CO2 and oxygen levels, the earth was able to prosper and thrive again. So in this case the sun did increase warming due to help of regainment of C02 in the atmosphere.
Global warming is simply due to the effect of green house gases in the atmopshere. So if you have an abundance of cloud cover with high C02 rates, you would be in a product of global warming.
So my final question is, why would anyone want this to happen to earth, realizing that it would inevitably kill them as well? There is no "winning" or gaining power in the circumstance.
