It's rigorous work. Agriculture has more players than the energy sector, and figuring out the climate impact of food production isn't as easy as it is with a lump of coal. "It's very tricky to know the carbon footprint of a hamburger," said Jonathan Foley, executive director of the California Academy of Sciences. "We know exactly the carbon footprint of a gallon of gas."
Then there is the political dynamic. If the push-back from the energy industry (and its lawyers and lobbyists) over increased regulation tied to climate change is any sign, a similar fight with agribusiness (and its lawyers and lobbyists) will be long and arduous.
The road to a warmer world is papered over with clever ideas that are politically impractical, such as a 2011 paper suggesting that CO2 be taxed where fossil fuel is extracted. Just two weeks ago, scientists reported how for the price of its highway system (in today's dollars), the U.S. could have all the renewable power it wants on a modern electrical grid. Neither is likely to happen any time soon, if ever.