NOAA Earth Systems Research Laboratory (ESRL)

The National Climate Assessment was released on May 6, 2014. The Southwest chapter (Chapter 20) documents critical climate change impacts to the region’s coasts and forests, and projects increased risks to water resources reliability, agriculture, and public health. The chapter notes the special vulnerabilities of native nations and U.S.-Mexico border cities, due to high rates of poverty, and low tax bases for generating resources needed to develop and improve infrastructure, such as safe roads and water treatment and distribution. The chapter also points to adaptive responses by state and local governments, water utilities, forest managers, and federal agencies, to reduce the impacts of current and future changes. The chapter gives an example of how the region can reduce its production of heat-trapping greenhouse gases through adjustment of energy sources used in the generation of electricity, while also reducing water use. See http://nca2014.globalchange.gov/report/regions/southwest.

The Southwest Chapter for the National Climate Assessment was based on The Assessment of Climate Change in the Southwest United States, a technical input report published in May 2013. The technical input report is a summary and synthesis of the past, present, and projected future of the region’s climate, examining what this means for the health and well-being of human populations and the environment throughout the six Southwestern states—Arizona, California, Colorado, Nevada, New Mexico, and Utah—an area that includes vast stretches of coastline, an international border, and the jurisdictions of more than one hundred Native nations. This year, results from this report were distributed through presentations, publications, and media coverage throughout the Southwest.

Several recent studies estimate that the future streamflow of the Colorado River will decline due to drought and climate change. However, estimates from these projections range from less than 10% to a 45% decline by 2050. This cross-RISA research team explored why this large range exists and suggested ways that scientists and other stakeholders could apply these projections for future research and adaptation efforts.

Although the projections show drastically different amounts of streamflow reduction, it is still evident across all studies that Colorado River streamflow will be reduced due to climate change. Additionally, current reconstructions of the worst possible drought for the Colorado River are underestimates of the severity and duration of drought that has occurred, and that could occur, in the Colorado River Basin.

The Southwest is one of the most sensitive regions of the U.S. to climate change and variability. It is essential to understand the full scope of climate variability and change in the Southwest and how to communicate in ways that enable effective decision mak­ing. The goals of this project are to (1) lead efforts to communicate about climate variability and change to decision and policy makers in, and relevant to, the Southwest, and (2) make climate knowledge useful for stakeholder understanding and decision making.