Working Group III: "Mitigation of Climate Change"

Growing Greenhouse Emissions

Working Group III issued its part of the 2007 report, focusing on mitigation of future climate change, on May 4, 2007.

It found that growth in worldwide emissions of greenhouse gases was about 70 percent 1970 to 2004. * (WGIII Summary for Policymakers/SfP, page 3)

It included key increases at these rates:

  • Energy supply sector — 145 percent.
  • Transportation — 120 percent.
  • Industry — 65 percent.
  • Land use and forestry — 40 percent. (WGIII SfP, page 3)

The authors concluded that various policies, not all directly addressing climate change, have cut greenhouse emissions, but have "not yet been large enough to counteract the global growth in emissions." (WGIII SfP, page 3)

Until 2030

Looking ahead until 2030, the authors' assessment included these points:

  • Using current mitigation policies and related practices, global emissions of greenhouse gases will continue to grow. * (WGIII SfP, page 9)
  • An assortment of studies have found "substantial economic potential" for mitigating emissions "that could offset this growth or reduce emissions below current levels." * (WGIII SfP, page 15)
  • Technologies and practices that are currently commercially available — and projected to be commercialized before 2030 — were identified for economic sectors including energy supply, transportation, buildings, industry, agriculture, forestry and forests, and waste. (WGIII SfP, page 10)
  • Costs and associated reductions in economic growth were projected for strategies aimed at stabilizing carbon dioxide, the principal greenhouse gas, in the atmosphere at various levels. (WGIII SfP, page 11)
  • Studies indicate costs may be substantially lower with policies that use revenues from carbon taxes or emission permits to promote low-carbon technologies or reform existing taxes. (WGIII SfP, page 11)
  • Lifestyle and consumption changes stressing conservation can help build "a low-carbon economy that is both equitable and sustainable." (WGIII SfP, page 12)

After 2030

Beyond 2030, the authors' conclusions included:

  • Stabilizing greenhouse gases in the atmosphere would require emissions to peak and then continue to decline. * (WGIII SfP, page 15)
  • Various post-2030 stabilization levels are attainable by using "a portfolio of technologies that are currently available and those that are expected to be commercialised in coming decades." * (WGIII SfP, page 16)
  • Scenarios to achieve lower stabilization levels "put more emphasis on the use of low-carbon energy sources, such as renewable energy and nuclear power, and the use of CO2 capture and storage." (WGIII SfP, page 16)

* These statements were ranked as "high agreement, much evidence" in the WGIII report. This represented the top levels for both agreement and evidence in this working group's system for expressing relative uncertainty. WGIII authors did not assign specific agreement/evidence rankings to other statements noted here. (WGIII SfP, page 23)

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