No one can look out the window and deny climate change is occurring. The impact of man is the arguable point. Climate changes by the minute, day, years and eon. Not gonna stop until the sun makes the earth a little puff of space dust.
As for secondhand smoke, of course it is a negative for many if just for the odor and eye irritating haze. And it certainly affects those with other health problems. Again, there is nothing positive about tobacco smoke or smoke from the campfire or exhaust vents on factories or the kimchi buried in the neighbor's yard, rotting away. Sorry, should have written aging or fermenting. No! Rotting is the correct word. There are some who enjoy such, most do not.
Smoking is a selfish diversion. We shouldn't be so dismissive of the effects of secondhand smoke if only because of the fact that some do not wish to be exposed to it. It's akin to vulgar language in the presence of ladies and children and other anti-social behavior. There is a reason that many years ago smokers did not smoke in public. Clubs and back rooms sufficed. Or out in the middle of the south forty.