Seeing as we can all agree that global warming is definitely real, it's probably a good idea to start doing something about it. Making slight changes to our lifestyle is obviously a ridiculously thing to suggest, so let's move on to more realistic schemes like global weather modification through controlled atmospheric aerosol release, which might actually be affordable.
While releasing aerosols into the atmosphere sounds like a bad thing (and it very well may be, in the long run), we know that it's an effective way to cool the planet down in the short term since we can measure the effect every time a major volcano erupts. For example, the 1991 eruption of Mt. Pinatubo added about 20 megatons of sulfur dioxide to the upper atmosphere, which lowered the average summer temperatures of Northern Europe by about four degrees Fahrenheit.
A recent study in Environmental Research Letters took a look at ways that it might be possible for humans to achieve something similar without having to set off an actual volcano, and there are a bunch of ideas that look like they might work for an amount of money that's easily achievable within the next few years. Here are some ideas, based on delivering several megaton of aerosols into the atmosphere at a sufficiently high altitude:
Modifying a fleet of Boeing 747s for high altitude flight and aerosol delivery would cost just $1.1 billion per year. We'd only need 14 of them, and we could buy used ones on the cheap. However, they max out at about 45,000 feet. Going higher (up to 65,000 feet) would require a fleet of 28 supersonic B-1 bombers at a cost of nearly $5 billion, and for extreme high altitude delivery, we'd need to spend $8.4 billion on 133 F-15s that could "zoom-climb" up to 85,000 feet.
For the most effective high altitude aerosol deployment, another option would be a new, purpose-built aircraft. The estimated cost for an aircraft capable of releasing five megatons of aerosols at 100,000 feet would be just under $10 billion, but that's a lot more cargo at a much higher altitude than current aircraft, making for a more effective system.
For heavy cargo lifting and long duration operations, airships could be a good way to go. Hybrid lift helium airships that can deliver one megaton per year of aerosols to 100,000 feet would cost about $2 billion per year.
Rockets are an obvious way to get to high altitudes, and the researchers took a look at a concept vehicle that would use "rocket engines or motors to boost a vehicle and payload to altitude. At apogee, wings are deployed to increase the vehicle's lift-to-drag coefficient to allow it to glide at altitude and disperse payload. Once dispersal is completed, the wings retract to allow it to descend quickly." Cool idea, but it would be about a hundred times more expensive than a less exotic system at an estimated $390 billion per year.
Yes, guns. Why not just shoot aerosols into the atmosphere packaged inside exploding artillery shells fired out of an Iowa-class battleship's 16'' Mark 7 naval gun? Sounds like fun to me, but the overall cost would be nearly $140 billion, or $20 billion if the guns were modernized to fire shells electromagnetically (sweet!). Also, the study notes that "these new gun technologies are unlikely to be available for non-military uses for some time to come." Bummer.
We've looked at this pipe idea before: you'd take a hose, attach it to a big balloon, send the balloon up to into the air, and then pump aerosols through the hose. Unfortunately, we don't yet have the materials that we'd need to get this to actually work at the necessary altitudes, but getting us there might cost between $4 and $10 billion.
Mind you, this study was not paying any attention to the effectiveness of these methods at climate modification, just the potential cost. And really, it seems fairly cheap. As the authors of the study point out:
To put these cost in perspective, the costs of climate damages or of emission mitigation are commonly estimated to be 0.2-2.5% of 2030 global GDP equivalent to roughly $200B to $2000B per year. Our estimates of the cost of delivering mass to the stratosphere--likely to be the most substantial part of the cost of SRM deployment--are less than 1% of this figure.
Again, the preferred method of dealing with climate change is to tackle the root causes, but if we can't get together to manage that, concepts like these might need to be put into practice to keep our environment stable.