The question, to be answered over the next four years, is whether he can succeed where so many of his predecessors failed.
The president-elect presented his energy and environmental team yesterday, a group with a strong record in energy and environmental reform.
The very nature of the announcement suggests the enormity of the changes ahead. Energy and the environment are often seen as separate files, managed by separate departments and agencies.
For the incoming administration, however, energy and the environment are one and the same.
The nomination also reflected Mr. Obama's strong determination to make energy/environment a linchpin of his economic recovery plan, even as the United States reverses course, becoming a leader, rather than a laggard, in the fight against global warming.
"We can seize boundless opportunities for our people," Mr. Obama said at a news conference yesterday. "We can create millions of jobs, starting with a 21st-century economic recovery plan that puts Americans to work building wind farms, solar panels and fuel-efficient cars."
While in the fight against global warming, "America will lead not just at the negotiating table; we will lead, as we always have, through innovation and discovery, through hard work and the pursuit of a common purpose."
To fulfill that purpose, Mr. Obama has chosen as his energy secretary Steven Chu, who in 1997 won the Nobel Prize in Physics. In recent years Mr. Chu has shifted the focus of his research to the search for new and environmentally friendly alternatives to fossil fuels.
Mr. Obama has picked Lisa Jackson, until recently head of environmental protection for the New Jersey government, as head of the Environmental Protection Agency. It's a controversial choice.
Ms. Jackson's supporters praise her competence and approachability, but environmental groups claim she is too close to business interests.
"While Ms. Jackson has a compelling biography, little of what occurred during her 31-month tenure commends her for promotion," stated Jeff Ruch, executive director of Public Employees for Environmental Responsibility. "Under her watch, New Jersey's environment only got dirtier, incredible as that may seem."
Carol Browner, who ran the EPA during former president Bill Clinton's tenure, is slated to become a so-called "climate czarina" within the White House, co-ordinating energy/environmental initiatives across government departments. And Nancy Sutley, a senior adviser to Mr. Obama's transition team, and former assistant to Ms. Browner, will chair the White House Council on Environmental Quality.
The appointments signal nothing less than a 180-degree reversal in the energy and environmental policies of the United States.
Under an Obama administration, the government will embrace the scientific consensus that the planet is warming dangerously through man-made increases in greenhouse-gas emissions.
To combat the problem, and to lessen U.S. dependence on foreign oil and gas, automobile manufacturers will be pressed to improve mileage and broaden their range of hybrid and electric cars; homeowners and businesses will receive financial incentives to insulate and otherwise improve energy efficiency; there will be billions to upgrade the energy grid; billions more for wind farms and solar-power generation.
What Mr. Obama did not specify was whether his plans for greater energy efficiency include the use of more environmentally controversial sources of power, such as nuclear energy or investments in so-called clean-coal technology. (Critics assert that there is no such thing.)
The money for all this will come from the economic stimulus package being prepared for Congress, now expected to run as high as $1-trillion (U.S.) over two years.
The question is whether any of these measures will do any real good. World governments are struggling to come up with a new treaty by December of next year as a successor to the Kyoto accord on global warming.
But the U.S. never ratified the agreement; other countries, including Canada, failed to meet their targets, and China and India, major producers of greenhouse gasses, object to any measures that might slow their burgeoning economies.
And whether any environmental measures would create new jobs in time to alleviate the effects of the recession is equally problematic.
Still, the appointments confirm Mr. Obama's determination to move the U.S. in an entirely new direction. He is committed to instituting a national cap-and-trade system to force reductions in carbon-dioxide emissions from industry and coal-fired power plants, regardless of its impact on an already troubled economy.
The supply-side economist Arthur Laffer, a strong critic of Mr. Obama's policies, believes an effective cap-and-trade system will cost the U.S. economy more than four percentage points of lost growth.
Nonetheless, unlike in previous administrations, the incoming Congress appears tilted in favour of enacting such legislation. Mr. Obama is likely to get his revolution, for better or for worse.
The pressing question for Canadians is whether and how federal and provincial governments should try to catch up to a United States that, under its new president, vows to lead the world in energy and environmental reform.