This comes from Joe Romm's blog post:

Our  understanding of basic climate science is so strong now that the U.S. National Academy of Sciences concluded its recent review of climate science, saying it is a “settled fact” that “the Earth system is warming and that much of this warming is very likely due to human activities.”  Last year, Time magazine reported on a comprehensive new review paper of “100 peer-reviewed post-IPCC studies” in an article titled, “Report: The Case for Global Warming Stronger Than Ever” noting:

By looking at a wide range of observations from all over the world,  the Met Office study concludes that the fingerprint of human influence on climate is stronger than ever. “We can say with a very high significance level that the effects we see in the climate cannot be attributed to any other forcings [factors that push the climate in one direction or another],” says study co-author Gabriele Hegerl of the University of Edinburgh.