Effective and affordable ways to curb climate change exist — what’s uncertain is whether governments have the political will to implement them. So says the latest study by the U.N. Intergovernmental Panel on Climate Change, which was released yesterday in Accra, Ghana. A key step will be to reduce the world’s reliance on oil and to shift to renewable energies, the reports says. The report also cites nuclear power as an option because it has low greenhouse gas emissions, although enviros remain adamantly opposed to it for safety reasons. The report isn’t hopeful, however, that the necessary changes will occur anytime before 2020.