Climate Change and Agriculture

The severity and pace of climate change in the 21st century is presenting an unprecedented challenge.1 Current global surface temperatures are now about 0.6°C higher than the average for the last century. This increase is consistent with model predictions of the effects of rising atmospheric concentrations of carbon dioxide (CO2) and other GHGs, which are (potentially) a result of human activity. Also in line with the same model simulations, the observed warming is greater at higher latitudes — particularly in the northern hemisphere, where most landmasses are located — than in the tropics. At the same time, extreme-temperature events are becoming more frequent, causing increasing damage to ecosystems, agriculture, and human health. Such worrisome trends will intensify in this century if emissions of anthropogenic GHGs continue to follow a business-as-usual scenario, with global atmospheric surface temperatures predicted to rise by at least 4°C by 2100. Moreover, the hydrological cycle will strengthen because of increased rates of evaporation from land and sea surfaces. As a result, rainfall may increase in the tropics and at higher latitudes, while decreasing over large continental interiors, with critically water-scarce areas of the world expected to become drier and hotter. More frequent climate extremes will increase the incidence and intensity of droughts and flood events worldwide. Finally, a sea-level rise will put millions of people at risk, presenting a significant challenge for rural, low-lying areas in many poor, developing countries.