Final answer:
The IPCC AR4 projections predict increased precipitation in the inner tropics and decreased precipitation in the subtropics by 2100, with varied impacts on global population centers and storm events.
Step-by-step explanation:
The IPCC AR4 multi-model climate projections suggest a nuanced future for global precipitation patterns due to climate change. Within the inner tropics (0 to 10 n/s), there is an expectation of increased precipitation, which is likely to contribute to more intense rainfall events. This projected increase in precipitation is due to raised atmospheric water vapor content, increased evaporation rates, and shifting wind patterns. However, the same projections indicate a decrease in precipitation for the subtropics (10 to 25 n/s), leading to more frequent and severe drought conditions in these regions. Changes in storm events are also expected, with stronger winds and more precipitation associated with tropical storms.
Major population centers such as New York, Bogotá, and Manila are expected to experience increases in precipitation, posing various challenges like flooding and strained infrastructure. Conversely, metropolitan areas like Delhi, Lagos, and São Paulo may face severe water shortages and challenges with drinking water and agricultural water supply due to predicted decreases in precipitation.