Scientists from over 130 countries now agree with 90 percent certainty that global warming is the result of human activities. Released today by the Intergovernmental Panel on Climate Change (IPCC), volume one of the Fourth Assessment Report (AR4) is the first comprehensive global appraisal of climate change since 2001. The AR4 reflects major advances in climate modeling and data collection compared to the IPCC's third report, resulting in more precise predictions at a higher level of confidence.
The Intergovernmental Panel on Climate Change
The IPCC was formed in 1988 by the United Nations Environment Programme (UNEP) and the World Meteorological Organization (WMO) to address growing concerns about potential global warming. Through the collaboration of thousands of international scientists and governments, the IPCC objectively assesses scientific, technical and socio-economic information and publishes its landmark Assessment Reports, released every five to six years. The AR4, titled Climate Change 2007, will be released in four phases throughout 2007, representing a six-year evaluation of the most up-to-date and peer-reviewed scientific literature available worldwide. The second volume, reporting on climate impacts and adaptation, will be launched on April 6.Changes in Temperature, Sea Level and Northern Hemisphere Snow Cover
Source: IPCC, 2007. Climate Change 2007: The Physical Science Basis, Summary for Policymakers
Major Findings
The first volume of the AR4, The Physical Science Basis, describes observed past climate trends, makes future predictions, and assesses progress in understanding the human contribution to climate change. The report uses terminology of "very likely" and "likely" to reflect a 90 percent and 66 percent likelihood of occurrence respectively. A few of the major findings include:
- Average surface temperature has increased by 0.74°C since 1906, with 11 of the past 12 years ranking among the 12 warmest since modern records began in 1850. Arctic temperatures have increased at nearly twice the global average rate.
- Global temperatures will "likely" increase by 2 to 4.5°C (3.6 to 8.1°F) if atmospheric concentrations of greenhouse gases double from pre-industrial levels (280 ppm in 1750 versus 379 ppm today). Scientists are over 99 percent certain that most land areas will experience warmer and more frequent hot days and nights.
- Sea level will "likely" rise by 28 to 58 centimeters by the end of the century due to thermal expansion and glacier melt. This prediction is narrower than the range of 9 to 88 centimeters predicted by the 2001 report.
- Upward trends in extreme hot weather are "very likely" to continue, leading to more intense and longer lasting droughts over a larger geographic area.
- It is "likely" that the observed increase in intense tropical cyclone activity will continue through the 21st century.
Urgent Action Needed
Observed changes in the atmosphere, oceans, and ice caps show undeniably that the world is warming. Furthermore, the AR4 predicts that these trends will continue for centuries, even if we are able to control global greenhouse gas emissions. This does not imply, however, that nothing can be done--the extent and severity of the impact will greatly depend on the speed with which both preventative and remedial actions are taken.
RELATED LINKS:
Summary of Climate Change 2007: The Physical Science Basis
The United Nations Framework Convention on Climate Change (UNFCCC)
NASA's Global Change Master Directory
Carbon Dioxide Information Analysis Center
World Resources Institute's Climate Analysis Indicators Tool
EarthTrends
Climate and Atmosphere Searchable Database
Data Table: Global Climate Trends 2005
Data Table: Carbon Dioxide Emissions by Source 2005
October 2006 Monthly Update: Fossil Fuel Consumption and Its Implications
News Post: Business and Environmental Group Alliance Calls for Legislation to Reduce U.S. Emissions
News Post: Drought in Indonesia Could Intensify with Global Warming
