This incorporates both public and private expenditures. The total costs of adaptation in agriculture is based on 1) the costs of R&D, including costs of extension, and 2) physical capital expenditures both in terms of climate change and in terms of future evolutions in population and corresponding food requirements (McCarl, 2007). The "business as usual" scenario assumes no climate change. Two climate change scenarios assume: i) no mitigation (SRES A1) or ii) some mitigation (SRES B1).