That last one is the key to this whole thing. We have been dumping all three of these greenhouse gases into the atmosphere at a rate of billions of tons per year for the past century, and that’s upset the natural balance of the planet.
We’re heating up, and it’s our damn fault.
And there’s more: Obviously, if we do nothing, just go about business as usual, things will continue to get worse. But even if we improve, cut back on CO2 emission, things will still continue to get worse for quite some time.