It is now virtually certain that Australia and the world will experience significant climate change over the next century, as a result of human-caused emissions of carbon dioxide (CO2) and other greenhouse gases. This note is a brief discussion of the projected effects of climate change on agriculture, under ‘business as usual’ conditions in which global concentrations of CO2 grow steadily and under the assumption that a global mitigation effort successfully stabilises global concentrations of CO2 and slows the climate change. Both global effects and effects on Australian agriculture are considered, with a particular focus on irrigated agriculture in the Murray–Darling Basin.