AVOIDING DANGEROUS CLIMATE CHANGE

The document establishes that limiting global warming to 2°C requires stabilizing atmospheric heat-trapping gases at or below 450 ppm CO2eq, which necessitates a global cumulative emissions budget of 1,700 GtCO2eq for 2000–2050. For the United States, this translates to a cumulative budget of 160 to 265 GtCO2eq, requiring emissions to be reduced by at least 80 percent below 2000 levels by 2050. The analysis finds that most federal legislative proposals fail to meet these targets, with only the Global Warming Pollution Reduction Act (S. 309) and the Safe Climate Act (H.R. 1590) remaining within the upper budget limit.

• To maintain a reasonable chance of limiting global average temperature increases to 2°C above pre-industrial levels, the concentration of heat-trapping gases must be stabilized at or below 450 parts per million CO2equivalent (ppm CO2eq). This target provides a roughly 50 percent chance of staying below 2°C and a 67 percent chance of staying below 3°C.
• Achieving the 450 ppm CO2eq stabilization target requires limiting worldwide cumulative emissions to approximately 1,700 gigatons (Gt) CO2eq between 2000 and 2050. Industrialized nations' share of this budget is approximately 700 GtCO2eq, requiring them to reduce emissions by an average of 70 to 80 percent below 2000 levels by 2050, assuming emissions peak in 2010.
• The United States' specific cumulative emissions budget for 2000–2050 is estimated between 160 and 265 GtCO2eq, depending on whether the allocation is based on population, GDP, or current emissions share. To meet this, the U.S. should reduce emissions by at least 80 percent below 2000 levels by 2050, necessitating an average annual reduction of 4 percent starting in 2010.
• An evaluation of U.S. federal climate policy proposals indicates that only the Safe Climate Act (H.R. 1590) and the Global Warming Pollution Reduction Act (S. 309) would keep cumulative emissions below the upper budget limit of 265 GtCO2eq. Other proposals, including the Low Carbon Economy Act (S. 1766) and the Climate Stewardship Act (H.R. 620), would exceed this limit.

APA

Union of Concerned Scientists (2007). AVOIDING DANGEROUS CLIMATE CHANGE. https://www.ucs.org/sites/default/files/2019-10/emissions-target-fact-sheet.pdf

Chicago

Union of Concerned Scientists. AVOIDING DANGEROUS CLIMATE CHANGE. 2007. https://www.ucs.org/sites/default/files/2019-10/emissions-target-fact-sheet.pdf.

Wikipedia

{{cite report |author=Union of Concerned Scientists |title=AVOIDING DANGEROUS CLIMATE CHANGE |date=2007 |url=https://www.ucs.org/sites/default/files/2019-10/emissions-target-fact-sheet.pdf |access-date=23 October 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{unionofconcernedscientists2007avoiding, author = {{Union of Concerned Scientists}}, title = {{AVOIDING DANGEROUS CLIMATE CHANGE}}, institution = {Union of Concerned Scientists}, year = {2007}, url = {https://www.ucs.org/sites/default/files/2019-10/emissions-target-fact-sheet.pdf}, urldate = {2026-10-23}, note = {Indexed by Climate Insights Directory} }