https://www.sciencedaily.com/releases/2019/06/190617164642.htm
https://www.anthropocenemagazine.org/2019/06/feeding-cows-seaweed-could-reduce-their-methane-emissions/
Including 1% of a particular type of seaweed in cow feed reduces cow-emitted methane by 75% or more. The active ingredient is
bromoform. Methane is far more potent as a greenhouse gas than CO2 (37X more). Some reading I've done suggests that in the US, livestock's climate change effect is on the same order as the transportation sector. A chemist tells me that bromoform should be easy to synthesize, as an alternative to growing millions of tons of this type of seaweed. Since bromoform is probably something like 0.1% or less of seaweed, maybe the feed only has to be 0.001% bromoform, or the bromoform gets added to feed by the farmer.
Anyway, I am quite optimistic about the power of technology to address climate change, whether the climate change situation is as, more, or less serious as some think. Solar + wind + wave + energy storage, electric vehicles, seaweed for cows, carbon capture, even geo-engineering in space. I don't think we (humans) need to do everything necessary right now, just make a good start and then figure out how much and how to do more as we better understand how much more is needed.