By warning a graduating class of doctors to reject “faith-based science,” Mr. Bloomberg yesterday signaled yet again that he plans to use his second term to take the national stage.

The mayor railed against letting “ideology get in the way of truth,” and singled out creationism, global warming, and stem cell research as topics where science is under attack.

Mr. Bloomberg’s views on these issues – and on other topics he’s taken on over the last few months – barely register outside the five boroughs. But after winning re-election by a record margin, Mr. Bloomberg, a billionaire, is becoming increasingly vocal and eager to address controversial topics.

“It boggles the mind that nearly two centuries after Darwin, and 80 years after John Scopes was put on trial, this country is still debating the validity of evolution,” Mr. Bloomberg told graduating medical students at Johns Hopkins University in Baltimore, where he earned his bachelor’s degree.

Mr. Bloomberg combined two of his favorite topics, science and education, when he criticized school districts in Kansas and Mississippi that want to teach “intelligent design,” the theory that human life cannot be explained solely by evolution. He said schools would be “condemning these students to an inferior education” by promoting faith over settled science.

In the last year alone, Mr. Bloomberg has donated $100 million to Johns Hopkins. According to a published report, much of that was to go to stem cell research. The Bloomberg name is plastered on buildings all over campus and the school of public health is named for the mayor outright, so it was no surprise that he was invited to speak.

Mr. Bloomberg, who does not have a formal medical background, spoke to the new doctors while an actual doctor who leads the National Institutes of Health, Elias Zerhouni, gave the commencement address to undergraduates.

Science is just the latest national topic Mr. Bloomberg has chimed in on. He has already staked out positions on gun control, immigration, and abortion over the past few months. With every speech he delivers on a national topic, he raises the specter that he is interested in higher office. He also distances himself from the Republican Party’s conservative base.

The mayor’s comments on the evolution versus intelligent design debate drew criticism from the Discovery Institute, a Seattle-based think tank that advocates teaching evolution not as dogma, but as one scientific theory.

“I wish his science was as good as his humor,” the institute’s president, Bruce Chapman, said after reading a copy of Mr. Bloomberg’s speech. “I don’t believe in ‘faith-based science,’ but since when is it wrong to criticize a scientific theory based on evidence?”

A spokesman for Agudath Israel of America, Rabbi Avi Shafran, had a similar take. “To raise fundamental and as-yet unanswered questions about nature does not devalue science. It ennobles it. Nor does it cheapen theology. On the contrary, it is its very essence.”

The deputy director for the National Center for Science Education, Glenn Branch, commended Mr. Bloomberg and said he was in line with the scientific establishment, which has fought challenges to teaching human evolution as an authoritative theory in the classroom.

“It’s not as though he’s flying in the face of the established scientific consensus,” Mr. Branch said. “Bloomberg’s view is at one with the National Academy of Sciences, which is the nation’s most prestigious scientific organization. It is also one with the American Association for the Advancement of Science, with the Royal Society of London, and with dozens of other major scientific organizations.”

In December, a federal judge in Pennsylvania ruled that teaching intelligent design was unconstitutional largely because it promotes religion. That case involved the Dover school system.

According to a transcript of the speech, Mr. Bloomberg criticized the federal government for restricting funding for new stem cell lines, saying the dried up funding options would put the burden for research squarely on the private sector.

“Was there anything more inappropriate than watching political science try to override medical science in the Terry Schiavo case?” he said. “I’ve always wondered which science those legislators who have created their own truths will pick when their families need life-saving medical treatment.”

Just as Vice President Gore’s movie about global warming is opening, Mr. Bloomberg warned students about the growing movement to debunk the reality of climate change.

There are, however, many who believe that there is no real evidence that human behavior has played a role in hurricanes, floods, tsunamis, and other weather-related events and that environmental changes are simply cyclical.

A spokesman for the Republican National Committee, Aaron McLear, said: “While we remain supportive of Mayor Bloomberg, we recognize that we will not always agree on every issue.”

Mr. Bloomberg has donated money to the national party and he had New York host the party’s convention for the last presidential election.

The interim dean at Baruch College’s school of public affairs, David Birdsell, said Mr. Bloomberg was clearly using his office as a bully pulpit on a national scale.

“If you look at what Bloomberg is calling attention to in this speech, it is clear that he is attacking national issues,” Mr. Birdsell said.

“He certainly sounds like a person who at least during these remaining three years wants to use the mayoralty to shape a national conversation, if not a national candidacy,” he said.