Climate engineering seems like a better bet than massive political/economic change across the entire world in advance of clear harm. It is relatively easy (but

Climate engineering seems like a better bet than massive political/economic change across the entire world in advance of clear harm. It is relatively easy (but still difficult in an absolute sense) to get support in sufficiently rich countries to handle clearly demonstrated, immediate threats — clean air, clean water, removal of litter, etc. These also tend to have relatively low costs, and the costs they do impose tend to be on large industries which also have pricing power to pass it along. There have definitely been successful global environmental actions. The CFC/Ozone thing was probably the most clear; it was a pretty substantial and demonstrable harm, and the costs of switching were relatively low. (It was painful for fire suppression, since halon is still superior to alternatives, and did require a lot of special stuff around auto air conditioners, but it was basically industries which could pass along costs.) Acid rain/sulfur dioxide/etc was a lot harder because it crossed jurisdictional boundaries, but within the US it was at least pretty easy to use the federal level. Hasn’t worked as well with China... CO2 has the problems of an indirect link between the pollution and harms (merely raising CO2 in the air is fine; the issue is science showing a few levels downstream this is a problem, and it isn’t as clear as most other forms of pollution.). It is also much more fundamentally tied to economic activity, and alternatives have much higher costs (including higher forms of other pollution due to decreased efficiency...), and is pretty widely distributed across consumers and smaller businesses. As well, a lot of the problem is the 3-4B people living at a lower standard of living who if they industrialize the same way will make 50% reductions in the other 3-4B pretty meaningless. I’d rather bet on climate engineering.