Plows, Plagues, and Petroleum: How Humans Took Control of Climate by a career climatologist claims that anthropogenic global warming began some 6,000 years ago with the discovery of agriculture, and that the methane production which began with rice paddies in India and Asia is the mechanism that is holding back the onset of the next ice age.
He also notes that the overall trend is planetary cooling. There was no permanent ice cap at all until the one formed in Antarctica some 14 million years ago. The first ice age (a Northern hemisphere phenomenon only; there isn't enough land in the south) occurred 2.75 million years ago. There were 40-50 ice ages over the next 1.8 million years, with no permanent arctic ice during the warm periods. The length of the cycle more than doubled 900,000 years ago, from around 41,000 years to about 100,000 years. It is only during this latter period, less than a million years, that there has been permanent ice in the arctic.
I've never seen these claims anywhere else but Ruddiman at least makes a calm and reasoned argument for them, which is in sharp contrast to the shrill hysteria of the OwlGore apostles.
There is no science, none at all, which quantifies the human contribution to climate change. And there is no science, none at all, which quantifies the benefits to be gained from any of the proposed remedial measures (like Kyoto). The hubris of those who think they can significantly change the course of cosmic events like climate change rivals the hubris of King Canute and his royal edict commanding the tides.