Washington, D.C. ? President-elect Barack Obama’s selection Saturday of a Harvard physicist and a marine biologist for science posts is a sign he plans a more aggressive response to global warming than did the Bush administration.

John Holdren and Jane Lubchenco are leading experts on climate change who have advocated forceful government action. Holdren will become Obama’s science adviser as director of the White House Office of Science and Technology Policy. Lubchenco will lead the National Oceanic and Atmospheric Administration, which oversees ocean and atmospheric studies and does much of the government’s research on global warming.

Holdren also will direct the president’s Council of Advisers on Science and Technology. Joining him as co-chairs will be Nobel Prize-winning scientist Harold Varmus, a former director of the National Institutes of Health, and Massachusetts Institute of Technology professor Eric Lander, a specialist in human genome research.