Arizona has an area of 113,998 sq. mi. (295,252 sq. km.), with inland water comprising 364 sq. mi. (942.8 sq. km.). The state’s average elevation is 4,100 ft. (1,250 m.) above sea level, with a range in elevation from 70 ft. (21 m.) above sea level on the Colorado River to 12,633 ft. (3,850 m.) on Humphrey’s Peak. The state has a variety of elevation regions, with the high plateau in the northeast with elevations of 5,000-7,000 ft. (1,524-2,134 m.), a mountainous region running in a diagonal from the southeast to the northwest ranges from 9,000 to 12,000 ft. (2,7433,656 m.), and in the southwest the land is primarily made up of desert interspersed with low mountains.
The climate is dependent on the elevation, with warm summers and mild winters, except in the high plateau, which has cool summers and cold winters. The air is generally dry and clear with a relatively low humidity (August humidity in Phoenix is 38 percent, Flagstaff 55 percent, Winslow 46 percent, and Yuma 33 percent) and much sun. Precipitation is governed by elevation and seasons.
Average annual precipitation on the high plateau is approximately 10 in. (.25 m.) Summer rain early July to mid-September comes from moisture-bearing wind from the southeast source in the Gulf of Mexico. Air masses from the Gulf of Mexico and Gulf of California, which release moisture while rising over the southeastern mountains.
Flood conditions are infrequent, mostly flash flooding from thunderstorms in July and August. Air currents from November through March are strongly from the Pacific in the high mountains; cold air masses come from Canada in the central and northern parts of state bringing heavy snow accumulations (sometimes reaching 100 in. or more). The highest temperature recorded in the state was 128 degrees F (53.3 degrees C), in Lake Havasu City on June 29, 1994, and the lowest temperature recorded in the state was minus 40 degrees F (minus 40 degrees C), in Hawley Lake on January 7, 1971. Annual lake evaporation is 80 in. in the southwest and 50 in. in the northeast corner.
The warm climate allows Arizona to produce vegetables for winter supply, and crops such as wheat and corn. Mining for copper, coal, sand, and gravel are important to the economy. A 1992 Colorado River Compact required 8.23 million acre ft. of water to be released every year to Nevada, California, and Mexico. In 2002, the crisis between farmers who own most of the water rights to the Colorado River and California cities downriver occurred.
The federal government ruled that California had to stick with the water allotment provided for in the compact and had to divide it equitably. The federal government further stipulated that water provided for in the compact was only excess water. Coal-powered steam, nuclear power, and some hydroelectric plants provide electricity. The Glen Canyon Dam generates hydroelectric power and created Lake Powell.
Arizona’s climate has changed over the centuries. The ancient native peoples began farming the area in approximately 1500 b.c.e., and optimum rainfall increased arable farmland and drew a larger population. A Medieval climate anomaly in the southwest during the 8th and 12th centuries caused hardship.
While climate models vary on the amount of temperature increase possible with unmitigated global warming, Arizona’s temperature could increase as much as 6.75 degrees F (3.75 degrees C) by the end of the century. The potential risks include: decreased water supplies from decreased snow pack in the mountains, thereby reducing summer flow in Arizona streams; increased risk for wildfires; changes in food production as temperatures rise beyond the tolerance level of crops; more extreme fluctuations in precipitation levels across the region (heavier rainfall and flooding events in winter, and summer drought conditions); change in rain pattern to downpours with the potential for flash flooding; and health risks of certain infectious diseases from water contamination; disease-carrying vectors such as mosquitoes, ticks, and rodents; and heat-related illnesses. The recent drought and intense wildfire seasons in Arizona are consistent with what climatologists expect will occur more frequently as global warming continues. A study by an Arizona and New Mexico team examined charcoal residues of ancient forest fires. During colder climate periods, smaller, less damaging fires occurred and during warmer climate periods, severe, stand-clearing fires occurred. Based on these data, global warming may cause more severe forest fires.
Based on energy consumption data from the U.S. Energy Information Association in 2007, Arizona’s total CO2 emissions from fossil fuel combustion in 2004 was 96.16 million metric tons of CO2, made up of contributions from: commercial 2.04, industrial 4.62, residential 2.20, transportation 36.07, and electric power 51.22. Arizona committed to lowering its greenhouse gas emissions to 2000 levels by 2020, and 50 percent below 2000 levels by 2050. Arizona instituted a requirement that 1.1 percent of the state’s energy come from renewable sources by the end of 2007.
In February 2005, Arizona established the Climate Change Advisory Group. Arizona holds member status with the Western Regional Climate Action Initiative, in which the partners will set an overall regional goal for reducing greenhouse gas emissions and design a market-based mechanism to help achieve that reduction goal.
Arizona joined the Climate Registry, a voluntary national initiative to track, verify, and report greenhouse gas emissions, with acceptance of data from state agencies, corporations, and educational institutions beginning in January 2008. The state’s solar energy program issues a tax credit to individuals for installing a solar or wind energy device at an Arizona residence.