Overview of the 2013 US National Climate Assessment, with special reference to impacts of climate change on ecosystems, hydrology, and urban areas of the Southwest

Background/Question/Methods

The 2013 United States National Climate Assessment (NCA) evaluated the current and projected future impacts of global climate change on eight US regions (including the Southwest), seven sectors, and eight issues that cut across sectors or geographic regions. Of particular relevance to the Southwest, the assessment included land-use and cover change; energy, water, and land; urban infrastructure and vulnerabilities, and impacts on the lands and resources of native peoples as cross-sectoral issues. Each chapter drew on technical input received from hundreds of scientists from academia, non-governmental organizations, business, and government, reflecting the most current research findings in each area. The US Global Change Research Program, which coordinated the NCA, has organized a network including many of these contributors that is intended to draw upon their expertise to sustain and update the assessment over the long term. For this presentation, I provide an overview of the NCA and draw from the chapters mentioned above to synthesize impacts relevant to the intersection of ecosystems, hydrologic systems, and urban areas of the Southwest.

Results/Conclusions

In January 2013, the 60-member NCA Development and Advisory Committee released the NCA report for public comment (comment period ended in April 2013), with 30 chapters written by 240 authors. The report makes a strong statement with overwhelming evidence that climate is changing and affecting people of the US. Yet the impacts of climate change can be difficult to assess against a background of other globally prevalent and mainly anthropogenic changes that interact with climate change. In the Southwest in particular, the enormous interannual variability in climate and rapid urbanization (with attendant changes in hydrologic systems) confound attempts to attribute observed changes to global climate change. As examples, I contrast 1) the changes in streamflow expected due to climate change with changes already observed under urbanization, and 2) the impact of the urban-wildland interface on fire frequency with increases attributed to climate change. A conceptual model for impacts of interacting multiple stressors associated with urbanization, hydrologic change, and climate change on ecosystems will be presented. Knowing how to untangle such interactions of multiple anthropogenic changes will be useful in adaptation planning and mitigation strategies.