Gather sources from non-partisan websites. Typically the easiest way to identify those sites is to see if they end with ".edu" or ".gov." Though this does not necessarily indicate that the information is infallible, it does suggest a greater degree of accuracy than sites that end with ".com," ".net" or even ".org." For example, identify and use sources such as the Environmental Protection Agency's Climate Change page, the House of Representative's Energy Independence and Global Warming Committee's page or Stanford University's Solar Center's Global Climate Change site (See Resources). In addition to representing the most up-to-date, non-partisan research on the issue of global warming and climate change, these sites also provide additional links and resources.
Contact the physical science departments at local colleges or universities in your area. Often researchers within physical science departments such as biology, chemistry or even the multidisciplinary department of environmental science will be able to comment on the most current research on global warming, as well as provide you with potential article, book and website bibliographies that you were unable to at a library or online.
Avoid biased sources by substantiating your research against non-partisan sources like those listed in the Resources section. Hot-button issues like global warming tend to generate a lot of biased and polemical writing that people attempt to pass off as "scholarly." Sometimes the bias is obvious, as with the constant back and forth between Al Gore and his detractors regarding his film "An Inconvenient Truth." Other times, however, you will not be able to spot bias as easily as you can in his film and in the critical comments of his film. Again, compare information across sources. Frequently repeated facts and statements are more likely to be accurate.
Continue researching and substantiating in an ongoing effort to stay on top of the topic. A topic as pressing and contemporary as global warming is sure to generate continuously changing research and information.