Global warming has so many implications for industries and government, besides being an environmental issue, that there are powerful forces on all sides trying to convince us of one reality or another. You can only know the truth by digging it up for yourself. Here are some helps in that direction.
1. I just finished reading "The discovery of Global Warming" by Spencer Weart. (Harvard Univ. Press, 2003) This is an account of the history of the subject, written from an expert viewpoint, but fairly balanced. Weart is the director of the Center for History of Physics at the American Institute of Physics--great credentials. This is a great book, but won't tell you details of the science, just how various evidence has fit together over time. It's quite an eye-opener. Only a year old, it is already out of date on technical grounds. You can probably check out this book in a college library, I did.
2. A big sticking point among some "professionals" has been the publications of John Christy (U. of Alabama, Huntsville) which have shown no warming trends in satellite measurements of atmospheric temperature. His measurements have been a great comfort to the present Republican administration, which abandoned the Kyoto agreements that the U.S. had helped to forge. Christy's work is now being seriously challenged by two recent publications that show large warming trends based on satellite data. (If interested, I think you can get a recent Christy paper on-line: John R. Christy et al. "Update on Microwave-based Atmospheric Temperatures from UAH" 15th Symposium on Global Change and Climate Variations. 2003) Christy has a web site: email@example.com. Following are the challenging references.
3. Qiang Fu et el., "Contribution of Stratospheric Cooling to Satellite-inferred Tropospheric Temperature Trends" Nature 429, 55-58 (6 May 2004). Fu says that Christy overlooked the influence of tropospheric cooling in his calculations. He makes the correction, and finds a large warming trend. This appears to be a hot topic right now. Hard copies of this issue may not have reached library shelves yet, but a helpful librarian can download the paper for you.
4. Menglin Jin, "Analysis of Land Skin Temperature Using AVHRR Observations" Bul. of the American Meteorological Soc. (BAMS) April, 2004, p. 587-600. Jin analyzes satellite data to obtain earth surface temperature. He also shows a large warming trend. This is a major paper, lots of references. Most of the figures are in color, good luck getting it copied.
Final word: It can be shown logically that a warming earth does not necessary cause the upper troposphere to get warmer, as Christy would argue. I will provide this in a future post.