An official website of the United States government.

We've made some changes to EPA.gov. If the information you are looking for is not here, you may be able to find it on the EPA Web Archive or the January 19, 2017 Web Snapshot.

Climate Action Benefits Report

Frequent Questions about CIRA

General information:

Methods and Process:

Interpreting the Results:


General Information

What is the CIRA project?

The Climate Change Impacts and Risk Analysis (CIRA) project quantifies physical effects and economic damages under multiple climate change scenarios. The goal of this work is to estimate climate change impacts to multiple U.S. sectors (e.g., human health, infrastructure, and water resources) and what damages may be avoided or reduced under different future global emissions scenarios. Consistent socioeconomic, emissions or concentrations scenarios, and climate inputs facilitate comparison of projected impacts across all sectors in a world with and without global reductions in greenhouse gas emissions. CIRA advances the estimation of climate change damages by bridging the gap between climate modeling and economic effects, presenting both physical and monetized damages. 

The analyses in this project represent an EPA-led collaborative modeling effort that includes analytical teams within the federal government and scientists from a number of academic institutions and consulting firms. The peer-reviewed products estimate specific impacts categorized into six broad sectors: health, infrastructure, electricity, water resources, agriculture, and ecosystems. Importantly, these analyses estimate only some of the impacts of climate change, and are therefore an incomplete picture of the total benefits to the United States of reducing global greenhouse gases (GHGs).

What are the CIRA publications?

There are several components to the CIRA effort, including publications. 

A 2015 report, Climate Impacts in the United States: Benefits of Global Action, summarizes multiple analyses that quantify the physical effects and economic damages of climate change under two global GHG emission scenarios.

The most recent product is the draft Avoiding and Reducing Long-term Risks of Climate Change: A Technical Report for the Fourth National Climate Assessment. This draft 2017 Technical Report summarizes and communicates the results of the second phase of modeling under the CIRA project, and is primarily intended to inform the congressionally mandated fourth National Climate Assessment (NCA4) of the U.S. Global Change Research Program (USGCRP), which in turn is scheduled for publication in late 2018. The draft 2017 Technical Report is currently undergoing peer review.

Multiple analyses which form the underlying methods and results of the CIRA project have also been peer reviewed in the scientific literature, including a special issue of Climatic Change entitled, “A Multi-Model Framework to Achieve Consistent Evaluation of Climate Change Impacts in the United States.”[1]

What are the differences between the 2015 and 2017 reports?

The results in the 2017 draft Technical Report (Avoiding and Reducing Long-term Risks of Climate Change: A Technical Report for the Fourth National Climate Assessment) build off the CIRA framework developed for the 2015 report (Climate Change in the United States: Benefits of Global Action).[2] However, the modeling framework, including underlying assumptions and inputs, has been updated in the 2017 Technical Report to be consistent with USGCRP-recommended scenarios for use in NCA4, such that these CIRA results may more easily serve as inputs to NCA4. As a result of using different scenario frameworks, and alternative or enhanced methodologies for some sectors, differences exist in the magnitude of results reported in 2017 Technical Report compared to those found in the 2015 report.[3]

In addition to updating the modeling framework, the 2017 Technical Report expands or enhances several sectoral models and includes multiple new sectoral impacts not included in the 2015 report. The Technical Report also incorporates several additional advancements and improved estimates of the costs, benefits, and effectiveness of adaptation options for several sectors, all of which are outlined in the section on Advancements in the CIRA Framework. Future CIRA work will likely expand the coverage of sectoral impacts, leverage improved economic methods for valuing impacts, explore the effectiveness of adaptation in more sectors, and expand the consideration of how impacts are distributed across different socioeconomic populations.

Are the CIRA reports scientific assessments, like the National Climate Assessment?

No, there is a difference. Climate change science assessments, such as those by the Intergovernmental Panel on Climate Change (IPCC) and U.S. Global Change Research Program (USGCRP), look across a larger body of scientific literature to develop consensus conclusions about the state of climate change science. The CIRA project, on the other hand, is narrowly focused analysis designed to answer the targeted question of what the physical and economic damages of climate change will be in the U.S under different climate scenarios.

Top of Page

Methods and Process

What scenarios are used in the CIRA project?

In the 2017 draft Technical Report, the CIRA results presented assess the risks to the U.S. in a future with moderate climate change (lower global atmospheric GHG concentrations, or Representative Concentration Pathway RCP4.5) and a future with severe climate change (higher global atmospheric GHG concentrations, or RCP8.5). As this report is designed to inform the development of NCA4, the selection of scenarios and projections has been made consistent, to the maximum extent possible, with the USGCRP inputs to the forthcoming assessment. These inputs have the benefits of being well-known and commonly used by others in the climate change impacts modeling community.

The CIRA results presented in the 2015 report also consider two (high and low) emissions scenarios, but these differ from the most recent draft report.

Importantly, the CIRA scenarios provide illustrations for analytical comparison and do not represent specific policies.

What is the precision of the results?

While projecting decades into the future involves uncertainty, the CIRA analyses show a substantial difference between GHG emission scenarios. Using peer-reviewed methods, the estimates in the reports provide insights to the direction and magnitude of climate change impacts and the benefits (avoided impacts) to the U.S. of global GHG reductions. However, none of the estimates reported should be interpreted as definitive predictions of future impacts at a particular place and time. Instead, the intention is to produce estimates of future effects using the best available climate data and methods, which can then be revisited and updated over time as the science and/or modeling continues to advance.

How are the CIRA reports peer reviewed?

Both the 2015 and the draft 2017 CIRA reports build on multiple layers of independent peer review. First, the underlying datasets used throughout the project are established, peer-reviewed sets of information. Second, the methods and results of the underlying climate change impacts analyses are individually peer reviewed in scientific journals, including a special issue of Climatic Change entitled, “A Multi-Model Framework to Achieve Consistent Evaluation of Climate Change Impacts in the United States.”[4, 5] Finally, the summary reports themselves undergo external, independent peer review to ensure that the content accurately reflects the science, appropriately summarizes the results, and clearly communicates the methods and conclusions of the underlying papers. The draft 2017 report is currently undergoing this independent external peer review process.

How are the positive effects of climate change on the U.S. considered?

The CIRA analyses evaluate both negative as well as positive effects of climate change. Overall, positive effects are substantially outweighed by the negative effects of unmitigated climate change. For instance, the projected increase in deaths due to more frequent extremely hot days is estimated to be much larger than the projected decrease in deaths due to fewer extremely cold days. 

How does CIRA consider adaptation to climate change?

The 2017 Technical Report includes analysis of the costs, benefits, and effectiveness of adaptation options for several sectors, including extreme temperature mortality, infrastructure (roads, bridges, and rail), winter recreation, and coastal property. This not only allows for improved estimates of climate change impacts and economic costs, but contributes to the knowledge base to inform responses at national, regional, and local levels. 

Top of Page

Interpreting the Results

Does the CIRA project cover all climate change impacts?

No. The CIRA project describes certain important impacts of climate change, but many others are not included due to data availability and resource constraints. In addition, for some sectors, only part of the impact or damage is included in the estimate. For example, for wildfires, only the costs associated with suppressing them and reducing fuels are included in CIRA, while other damages (e.g., health effects from decreased air quality or water contamination, property damages, or loss of recreational space) are not. The primary geographic focus of CIRA is on the contiguous U.S., with most of the sectoral analyses excluding Hawai’i, Alaska, and the U.S. territories. Lastly, the results do not quantify the additional benefits to air quality and health that would stem from the co-control of traditional air pollutants along with GHGs (both are emitted from many of the same sources). Including these would further increase the benefits by a significant amount.

Does CIRA estimate avoided impacts from any specific policy, including EPA actions?

No. The CIRA analyses examine plausible scenarios to illustrate potential impacts and damages of alternative future climates. They do not evaluate any specific domestic or global climate policy. Though the CIRA reports do not make policy recommendations, they are designed to inform strategies to enhance effective resiliency and protect human health, investments, and livelihoods.

Does CIRA consider costs of reducing GHG emissions?

No. CIRA does not constitute a cost-benefit assessment of climate policy. The project only addresses analytical gaps focused on the impacts and damages to the U.S. of illustrative climate scenarios. There are multiple policy approaches that could be undertaken to achieve any particular emissions reduction target or concentration pathway, but the CIRA reports do not discuss those approaches nor the costs of implementing any particular policy. There is a robust literature on climate mitigation costs, such as the IPCC’s Working Group III’s contribution to the Fifth Assessment Report: Climate Change 2014: Mitigation of Climate Change.

Top of Page

References

1. Martinich, J., J. Reilly, S. Waldhoff, M. Sarofim, and J. McFarland, Eds. 2015. Special Issue on “A Multi-Model Framework to Achieve Consistent Evaluation of Climate Change Impacts in the United States.” Climatic Change, 131: 1-181.

2. EPA. 2015. Climate Change in the United States: Benefits of Global Action. United States Environmental Protection Agency, Office of Atmospheric Programs, EPA 430-R-15-001.v

3. In addition, damages were presented in $2014 in the 2015 report and are presented in $2015 in the Technical Report.

4. Martinich, J., J. Reilly, S. Waldhoff, M. Sarofim, and J. McFarland, Eds. 2015. Special Issue on “A Multi-Model Framework to Achieve Consistent Evaluation of Climate Change Impacts in the United States.” Climatic Change, 131: 1-181.

5. See also the list of research citations in Section A2 of Appendix A in the 2017 Technical Report and Section B “Literature Underlying the CIRA Project” in the Technical Appendix of the 2015 CIRA report.