HP representatives delivered a paper, "Design of farm waste-centered demand-driven supply side infrastructure for data centers," at the 2010 ASME International Conference on Energy Sustainability. The paper described how a dairy farm with 10,000 head of cattle could supply a megawatt (MW) of electricity. 1MW (a million watts) is sufficient to run a typical data center, with enough left over to supply some of the power required to run the farm. In return, the heat produced by the data center can be used for other purposes, such as improving the process of extraction to increase the yield of methane. According to the United Nations, methane from livestock accounts for 20% of greenhouse gases produced worldwide. Methane is twenty times more potent as a greenhouse gas than carbon dioxide; recent calculations indicate that methane may be responsible for 30% of global warming since the 1750s. Converting methane to energy rather than letting it dissipate into the atmosphere mitigates that effect. In a discussion of methane's influence on climate change, NASA climatologist Drew Shindell said, "If we control methane, which the U.S. is already starting to do, then we are likely to mitigate global warming more than one would have thought, so that's a very positive outcome"