Climate change is already affecting the American people in far-reaching ways. So begins an extensive report issued by the U.S. Global Change Research Program on May 6, 2014.
The Global Change Research Act of 1990 requires that Congress and the president should be presented every four years with an assessment of the effects of climate change on the United States, so a team of more than 300 experts assembled the report from peer-reviewed science and observations. It contains 12 key findings, the first of which notes that climate is changing globally and that change is apparent in the United States.
Among the changes is an increase in temperature, as illustrated in the image above. Since consistent record-keeping began in 1895, the average temperature in the United States has increased by 1.3 to 1.9 degrees Fahrenheit (0.8 to 1.1° Celsius), and most of that change has happened since 1970. The warmest year on record for the United States was 2012.
Scientists also observed precipitation changes. On average, precipitation has increased since 1900, but some areas have gotten drier. The map above shows how much precipitation changed between 1991 and 2012 compared with the average precipitation observed between 1901 and 1960.
If warming continues, climate models project that wet areas will continue to get wetter while dry areas will get drier. The changes will include more frequent downpours, floods, droughts and heat waves. In fact, heavy rainfall events already have become more common throughout the United States, while heat waves and droughts have become more frequent and intense, particularly in the West.
Additional findings discuss the impacts of climate change on a variety of sectors, including human health, infrastructure, water quality and availability, agriculture, ecosystems, and the ocean. The report also looks at actions being taken to prepare for impacts and to mitigate future changes. To download a copy of the report, visit http://nca2014.globalchange.gov.