[breck]

Yeah this seems like the obvious thing.

If everyone stopped mowing their lawns for 20 years and let trees run wild instead, would that make a dent?

What about that plus turn half of our roads into parks?

Anyone got a link to a good open source interactive simulator?

[sbierwagen]

In 2016, the US burned 728 million tons of coal: https://www.ucsusa.org/resources/how-coal-works

That's one country, for one year. The world has been burning coal for more than a century. To get back to preindustrial CO2 levels, all that coal needs to be unburned and buried again. That's the scale of the problem.