Established by the World Meterological Organization and the U.N. Environment Programme, IPCC assesses a range of information on human-caused climate change. Nobel Peace Prize winner, IPCC includes a number of reports.
This U.N. agency focuses on "Earth's atmosphere, its interaction with oceans, the climate it produces, and resulting distribution of water resources." The site is somewhat hard to navigate. Use the dropdown menus on the homepage to target an area of interest.
State site provides links to climate-change research, California's Global Warming Solutions Act, figures and charts on California's greenhouse gas inventory, and more. It is part of the California Environmental Protection Agency's Air Resources Board.
Overviews of Evidence, Causes, Effects, etc. with related references. Key websites, videos and images. Even a widget so you can keep track of climate change. From NASA (National Aeronautics and Space Administration).
This site, from the National Oceanic and Atmospheric Administration (NOAA), bills itself as the "World's largest collection of climatic data." The free data includes comparative climatic data, wind data, storm data. You can download monthly climate statistics for all stations in California. Some fee-based information, such as climate maps, is low-cost.
The U.S. Dept. of Agriculture's climate change site includes links to its full reports on the effects of climate change on agriculture, biodiversity, and land and water resources, as well as report updates on specific topics.
Research-quality global climate modeling that can run on personal computers. With the software, design experiments and run simulations. The EdGCM Project, which includes exercises on global warming, is supported by the National Science Foundation and NASA.
The Pew Center "provides research, analysis and recommendations for federal, state, and international policies related to climate change." Links to reports are organized chronologically and by topic: environmental impact, economic, solutions. The Pew Center also analyzes legislation.
RealClimate describes itself as "a commentary site on climate science by working climate scientists for the interested public and journalists." News and discussions provide insight into the latest thinking and research. The dozen or so topic areas include greenhouse gases, climate modeling, and oceans.