This is an exercise to check your ability to handle units in equations and to manipulate energy quantities. The daily food energy intake for an adult is often taken to be 2000 Calories. Global cloud cover depends positively on atmospheric humidity. Absorbed solar radiation depends negatively on planetary albedo. Evaporation from the Earth's surface depends positively on global temperature.
Atmospheric humidity depends positively on evaporation from the Earth's surface.
Global temperature depends positively on absorbed solar radiation. Planetary albedo depends positively on global cloud cover. In the little known country of Erlichia, the human population is growing at 2.8 percent per year. With economic and agricultural development, water use per person in Erlichia is increasing at a rate of 4 percent per year. Because Erlichia is an arid country in sub-Saharan Africa, it is difficult to find new supplies of water and, because of the need to build dams and drill deeper wells, the environmental impact of acquiring each liter of water is increasing at a rate of 3.2 percent per year.