Well, Irv, thanks for your response but you didn't answer the question. The article in your link is interesting, but also doesn't answer my question. In fact, the guy says: "There’s nothing particularly magic about the number 400, (ppm CO2). But for environmental scientists and advocates grappling with the invisible, intangible threat of rising carbon dioxide levels in the atmosphere, this symbolic target has served as a clear red line into a danger zone of climate change. "
Enough, herbu! I answered your question and a few others too. I am not a climatologist and I really don't know the significance of 400 PPM, and I'm not bought into the Green Deal human life on earth will end bullshit.
Quite interesting he calls it an "intangible threat" and a "symbolic target". That tells me he doesn't know either.
People are advocating some extreme measures to "save the planet". Let's stop all coal burning, gasoline powered cars and airplanes, and implement a carbon tax. Pretty serious measures. So why is my question so hard to answer?
If we immediately stopped ALL coal burning in the USA, exactly what benefit would we realize? And at what price? Once we understand the benefit and cost, we can make an intelligent decision. Until then it's just emotion or politics. Same question for other actions. What if all cars averaged 50mpg? Benefit and cost? And if you can't define the benefit, how can you say the cost is acceptable? That is my problem with all the global warming talk. Unless you can express the problem and solution in numbers, you cannot logically argue your case. BTW, numbers about how much levels have risen or how fast they are rising may be interesting, but mean nothing unless you understand what they mean.
If we stopped all coal burning:
1. There would be a lot less mercury in the environment.
2. There would be less particulate air pollution.
3. Most coal mines would close, which would be a big environmental benefit.
So, yeah, I don't like coal power plants.
As for all cars averaging 50mpg, you get less air pollution, less fossil fuel consumption (and the production of fossil fuels of all types is a dirty business),and you'll achieve a lower cost per mile of driving, so the amount of driving per person will increase, so traffic will get worse. (Basic macro economics.)
And, FWIW, as I've already stated, I am not in favor in any way of costly programs to quickly eliminate fossil fuel burning by some arbitrary date. But for a lot of reasons I am in favor of reducing reliance on fossil fuels as soon as the market and the technologies reasonably allow. I think the risk from global warming is high, but since the US is only 15% or less of all fossil fuel consumption in the world, I am absolutely not in favor of up-ending the US economy when even our complete elimination of fossil fuel consumption would only buy a few years of CO2 savings.