PRAGUE — The organizers of next Saturday's Live Earth concerts hope that the entire world will hear a crystal clear message: Climate change is the most critical threat facing the planet. Planned by former U.S. Vice President Al Gore, Live Earth will be the biggest, most mass-marketed show of celebrity activism in history.

But making global warming the world's top priority means that we shuffle other major challenges down our "to do" list. Some climate change activists actually acknowledge this: Australian author Tim Flannery recently told an interviewer that climate change is "the only issue we should worry about for the next decade."

Tell that to the 4 million people starving to death, to the 3 million victims of HIV/AIDS, or to the billions of people who lack access to clean drinking water.