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World Bank Study
Figure 3.2. Annual simulated mean precipitation changes (mm) for the a, b) near future (2015–2039) and c, d) end of the 21st century (2075–2099) for 60-km and 20-km resolutions
Source: Figure generated under the Memorandum of Understanding (MOU) between the MRI and the World Bank. Note: Areas statistically significant at 95 percent level are hatched. Hatched areas only appear in the 60-km resolution, since only that one could be compared with the ensemble of GCMs. There was only a single run in the 20-km resolution. Therefore, the results obtained from it could not be compared with other results.
Extreme Precipitation Events
Global warming is not only expected to change the mean conditions of climate variables but also to increase the amplitude and frequency of extreme events. Understanding where these changes in extremes will take place is important for recognizing where adaptation measures are needed. Two distinct impacts can be identified: (i) changes in heavy precipitation (measured through the maximum total in five days, denoted as RX5D, in millimeters), and (ii) days without rain (measured through the number of consecutive dry days). These two extreme indexes for precipitation were calculated to illustrate changes in precipitation extremes over Peru. Figure 3.3 shows the projected changes in the heavy precipitation in comparison with today, at both 60-km and 20-km resolutions for the near future and end of the century. The model suggests that there will be an increase of heavier downpours throughout Peru, leading to an increased likelihood of floods and reduced stability of streamflows. As seen in the figure, the model projects even greater increases in heavy precipitation by the end of the century at a higher resolution (20 km). Overall, the largest rainfall intensification is found over the northwestern coast and the Andean Cordillera.