Why does global warming remain controversial despite the scientific consensus on climate change? In this talk, I will first argue that fundamental structures and techniques of climate research — such as the ongoing re-examination and renanalysis of historical data — play a substantial part in keeping climate knowledge controversial. Next I will discuss three climate controversies of the last 15 years: (1) putative discrepancies between temperature retrievals from satellite instruments and from radiosondes, (2) the "hockey stick," and (3) a supposed warm bias in the US historical climate network. In conclusion I'll speculate a bit about the future of climate science in an age when blogs and independent "audits" are challenging traditional peer review systems, even as the prospects for international climate negotiations and carbon-neutral energy futures seem to be dim.