Update, Sept 5, 2012: The answers have been posted, but the site cannot handle the traffic. Scientific American has posted the candidates’ answers here. I have not studied them yet, but according to a press release,
Notable highlights include a shift in Romney’s policy toward climate change away from his more recent position of “My view is we don’t know what’s causing climate change on this planet…” back toward his view in June of 2011 when announcing his run for president. However Romney’s ideas about what to do about the problem are not clear. They contrast with Obama’s, who says he has specifics plans and is taking specific steps such as doubling fuel economy standards, but who was unable to get a cap-and-trade bill through congress.
Shawn Otto, the founder of ScienceDebate, further adds, “Some of the questions aren’t fully answered when they become politically difficult and others could really benefit from followup discussion.…”
… but Congress refuses.* See here for the presidential edition and here for the congressional edition of the questions. The presidential campaigns’ responses will be published here. Science Debate is an “independent citizens’ initiative” sponsored by the American Association for the Advancement of Science, the National Academies, and others.
* Well, OK, Representatives Henry Waxman and Chris Van Hollen have responded to the questions, so 2/535 = 0.0037, or about 0.4 %, which is close enough to 0 for my taste. Besides, John Boehner refused outright.