Final Climate Change Report Raises Red Flags for the Future

November 21, 2007

The Intergovernmental Panel on Climate Change (IPCC) has issued the final report from its fourth assessment on climate change. Its previous assessment reports were issued in 1990, 1995, and 2001. The new "synthesis" report, which summarizes the results from three working groups that were issued earlier this year, is described by the executive director of the United Nations Environment Programme as "essential reading for every person on the planet who cares about the future." Also described as a "pocket guide for policymakers," the report underlines the urgent need to reduce greenhouse gas emissions, while also noting that societies must step up efforts to adapt to the changing climate.

In short, the report concludes that the climate is definitely warming, and that most of the warming over the past 50 years was very likely caused by greenhouse gas emissions from human activities. As a result, greenhouse gas emissions have very likely contributed to rising sea levels and are likely to have contributed to changes in wind patterns. With global greenhouse gas emissions expected to increase in the next few decades, the report anticipates increasing impacts on health; water and food supplies; ecosystems; and coastal areas. Particularly dire impacts are expected in Africa and Asia. And while the sea level rise from thermal expansion is expected to be significant over a time period of many centuries, there is a possibility that dynamic processes in ice sheets seen in recent observations, but not fully assessed in the report, could lead to a more rapid rise in sea levels.

On the bright side, the report concludes that there is great potential to reduce greenhouse gas emissions over the coming decades using a wide range of technologies, including energy efficiency and renewable energy. According to the report, achieving the reductions will require the institution of the proper incentives and the removal of market barriers. As noted in the report, by 2050 the costs of taking this action correspond to slowing the average global growth in gross domestic product by less than 0.12%. Meanwhile, the impacts of climate change are very likely to impose net annual costs that will increase over time, but there is great uncertainty as to how large those costs will be and how they will be distributed over the globe. See the UNEP press release and the full IPCC report (PDF 6.4 MB). Download Adobe Reader.