# Presentation: 228074

## Impacts of Climate Change on the United States:What Do We Know?

***Presented to:***
**5th State and Local Climate Change Partners’ Conference**
***Presented by:***
**Joel B. Smith**
**Stratus Consulting Inc.**
**November 22, 2002**

## There Have Been Many Studies on Climate Change Impacts on the United States

**EPA Report to Congress 1989**
**EPRI analyses 1999 and 2001**
**U.S. National Assessment, 2000**
**Pew Center series**
**Union of Concerned Scientists series**

## I’ll Present a Brief Overview of Impacts

**We have reasonable confidence about some of the large scale changes**
**I feel we can draw some conclusions about the vulnerability of different sectors of the economy, natural resources, and regions**
**At a state and local level there is much more uncertainty**
**mainly because of uncertainty about climate change at the state and local level**

## OUTLINE

**Limitations**
**Relative changes in temperature and precipitation**
**National impacts**
**Regional impacts**
**Conclusions**

## Key Limitations 

**There are many critical uncertainties about climate change impacts, including**
**Regional climate change**
**Biophysical relationships, e.g., CO****2**** fertilization**
**Adaptation **
**Societal development**
**Omitted impacts, e.g., tourism**
**Rapid or catastrophic changes in climate or impacts**

## Average Estimated Temperature Changes for 15 GCMs 

- Summer (Jun - Jul - Aug)

- Winter (Dec - Jan - Feb)

- Source: Wigley, 1999.

**Average Estimated Temperature Changes for 15 GCMs **

## Average Estimated Precipitation Changes for 15 GCMs

- Source: Wigley, 1999.

**Average Estimated Precipitation Changes for 15 GCMs**

## OVERVIEW OF IMPACTS

**National Impacts**
**Regional Impacts**

## Natural Ecosystems Are Relatively Vulnerable

**Natural Ecosystems Are ****Relatively Vulnerable**

## Societal Systems Are Sensitive but Have High Adaptive Capacity

**Societal Systems Are Sensitive but Have High Adaptive Capacity**

## Seasonality of Runoff in Snowmelt Basins Will Change

- Source: Gleick and Frederick, 1999.

**Seasonality of Runoff in Snowmelt Basins Will Change**

## Water Resources Will See Changes in Flooding and Droughts

**Water Resources Will See Changes in Flooding and Droughts**

## Difference in Vulnerability between Societal Sectors and Natural Ecosystems

**Societal sectors, particularly in a developed country, such as the United States, have high adaptive capacity. Function of:**
**Wealth**
**Technology**
**Sound institutions**
**Access to information**
**In contrast, natural ecosystems have limited ability to adapt to climate change and are further hampered by society and development.**

## Regional Vulnerabilities Vary

**Regional Vulnerabilities Vary**

## Low-Lying Coastal Areas Are at Greatest Risk

- Source: U.S. National Assessment, 2000.

## Regional Results Vary Considerably

**Regional Results Vary Considerably**

## Southern Regions at Greater Relative Risk

**Sea level rise**
**Loss of competitiveness in agriculture and forestry**
**Greater health risks**
**As long as public health sector is strong, impacts should be minimized**
**Potential for reduced water supplies**
**Particularly in arid areas**
**Higher energy demand**
**Loss of biodiversity — greatest diversity in southern areas**

## Northern Regions May Have Mixed Effects

**Low lying coastal areas at risk**
**Change in ecosystems and reduced biodiversity**
**Higher risk of heat stress **
**Increases in agricultural and forestry production**
**Reduced energy demand**
**Key point: *****Gains are transient, i.e., benefits will start to decline***

## Conclusions

**Many sectors are sensitive**
**Society has high adaptive capacity that can minimize many effects**
**Differences in vulnerabilities across sectors**
**Differences in vulnerabilities across regions**
**Natural ecosystems are highly vulnerable**

## For Additional Information

**U.S. EPA **
**www.epa.gov/globalwarming/**
**U.S. National Assessment:**
**http://www.usgcrp.gov/usgcrp/nacc/default.htm**
**Pew Center on Global Climate Change**
**http://www.pewclimate.org/projects/index_environment.cfm**
**Union of Concerned Scientists**
**http://www.ucsusa.org/global_environment/global_warming/****index.cfm**