Climate Change and Drought Impacts
Most expectations are that climate change will, in general, increase the frequency and severity of droughts worldwide (Kundzewicz et al. 2007; Meehl et al. 2007). However, the specific effects of climate change on regional and local droughts provide another challenge for drought early warning systems for several reasons (Hayes et al. 2011). First, Milly et al. (2008) highlighted how the past climate may not represent the best analog for the future. Second, recent climate trends do not necessarily reflect future projections. Third, future drought projections are going to reflect, in part, the projections being made for both temperature and precipitation (see Chapter 11). While temperature projections are more uniform and understood, the projections of precipitation are not as uniform and have higher uncertainty on both spatial and temporal scales.
Drought early warning systems will ultimately have to be able to account for how the local and regional characteristics of the hydrological cycle will be affected by climate change. This will have major implications for sectors susceptible to drought, including agriculture and water supply and management. Both rain-fed and irrigated agriculture could see drought impacts on production, particularly because of increased water deficits during summer growing months, even if they actually receive more precipitation than they do at present. The reason for this, of course, would be due to increased temperature, increased evapotranspiration, and possibly more days in between precipitation events. Projected reductions in general runoff, and in the runoff generated by snowpack and glaciers, would reduce water availability for the agricultural sector in areas where these reductions occur, resulting in greater vulnerability to drought impacts on agriculture (Backlund et al. 2008; Kundzewicz et al. 2007; Meehl et al. 2007). The overall global impact on agriculture is likely to be extremely variable and dependent on factors such as the local environmental and socioeconomic conditions (Eitzinger et al. 2009).