Other big sources include rice cultivation and oil production. Then there are those troublesome CFCs, like the freon you need for your air conditioner and now have to buy from a guy who smuggles it from Mexico. Once considered warming gases, CFCs were then reappraised as cooling gases, and now are considered to be doing something, though nobody's sure what. CFCs are entirely of human origin. Adding a further complication is a likely source of warming that lies outside the reach of people, cows and even the Earth itself.
Many people are certainly worried.
Other sources see coastal flooding from melting ice caps. They predict growing problems with pests, disease and violent weather from changes in the climate. A worst-case scenario has the climate changing to such an extent that it passes a point of no return and renders the Earth essentially uninhabitable. But not everybody agrees that even already-hot equatorial regions face catastrophe from a warming planet. A Heartland Institute report suggests that increased atmospheric CO2 is just what the botanist ordered when it comes to keeping crops happy and healthy.