How to Avoid Dangerous Climate Change

The report argues that to avoid dangerous climate change, the U.S. must reduce emissions by at least 80% below 2000 levels by 2050. This target is derived from a global stabilization goal of 450 ppm CO2eq, which provides a medium chance of limiting global warming to 2°C. The authors calculate a U.S. cumulative emissions budget of 160 to 265 GtCO2eq for 2000–2050 and warn that delaying reductions until 2020 would double the required annual reduction rate from 4% to 8%. An assessment of then-current federal bills found that only the Global Warming Pollution Reduction Act (S. 309) and the Safe Climate Act (H.R. 1590) were consistent with the upper limit of the proposed U.S. emissions budget.

• Stabilizing atmospheric concentrations of heat-trapping gases at or below 450 ppm CO2eq is identified as the upper limit for policies seeking to avoid dangerous climate change, as it offers a medium chance (approximately 50%) of limiting the global average temperature increase to 2°C above pre-industrial levels.
• To maintain a reasonable chance of limiting warming to 2°C, cumulative global emissions for the period 2000–2050 must not exceed approximately 1,700 gigatons (Gt) CO2eq, requiring global emissions to drop 40 to 50 percent below 2000 levels by 2050.
• Industrialized nations must reduce their emissions by 70 to 80 percent below 2000 levels by 2050, with a cumulative emissions budget of 600 to 700 GtCO2eq for the 2000–2050 period, assuming their emissions peak in 2010 and developing nations' emissions peak between 2020 and 2025.
• The United States should reduce its emissions by at least 80 percent below 2000 levels by 2050, with a cumulative emissions budget for 2000–2050 estimated between 160 and 265 GtCO2eq depending on whether the allocation is based on population, GDP, or current emissions share.
• Delaying the start of U.S. emissions reductions from 2010 to 2020 would double the required average annual reduction rate from 4 percent to approximately 8 percent to stay within the 265 GtCO2eq budget.
• Among federal proposals considered in 2007, only the Global Warming Pollution Reduction Act (S. 309) and the Safe Climate Act (H.R. 1590) required reductions consistent with the upper limit of the U.S. cumulative emissions budget (265 GtCO2eq).
• Global warming of 2°C to 3°C above pre-industrial levels is linked to severe risks, including the potential extinction of 20 to 30 percent of species and the destabilization of the Greenland and West Antarctic ice sheets, which could raise sea levels by 12 to 40 feet.

APA

Luers, A. L., Mastrandrea, M. D., Hayhoe, K., & Frumhoff, P. C. (2007). How to Avoid Dangerous Climate Change. Union of Concerned Scientists. https://www.ucs.org/sites/default/files/2019-10/emissions-target-report.pdf

Chicago

Luers, Amy L., Michael D. Mastrandrea, Katharine Hayhoe, and Peter C. Frumhoff. How to Avoid Dangerous Climate Change. Union of Concerned Scientists, 2007. https://www.ucs.org/sites/default/files/2019-10/emissions-target-report.pdf.

Wikipedia

{{cite report |last1=Luers |first1=Amy L. |last2=Mastrandrea |first2=Michael D. |last3=Hayhoe |first3=Katharine |last4=Frumhoff |first4=Peter C. |title=How to Avoid Dangerous Climate Change |publisher=Union of Concerned Scientists |date=September 2007 |url=https://www.ucs.org/sites/default/files/2019-10/emissions-target-report.pdf |access-date=23 October 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{luers2007how, author = {Luers, Amy L. and Mastrandrea, Michael D. and Hayhoe, Katharine and Frumhoff, Peter C.}, title = {{How to Avoid Dangerous Climate Change}}, institution = {Union of Concerned Scientists}, year = {2007}, month = sep, url = {https://www.ucs.org/sites/default/files/2019-10/emissions-target-report.pdf}, urldate = {2026-10-23}, note = {Indexed by Climate Insights Directory} }