Building on his February State of the Union pledge to bypass Congress if necessary, Obama unveiled a list of executive actions that he can take using his own special authority as president.
They include reining in carbon emissions from existing power plants, promoting and developing new sources of renewable energy, protecting America from the worst effects of extreme weather, and spearheading a new global green deal.
Obama also dealt with the controversial issue of the Keystone XL pipeline which environmentalists say will cement his environmental legacy as the 44th president of the United States: "Our national interest will be served only if this project does not significantly exacerbate the problem of carbon pollution. "
In the words of Van Jones, former White House green jobs adviser:
"I think the president gave a very encouraging wink and a nod to environmentalists on this issue. I think that if I were the head of TransCanada, I would have my head in my hands, and that if I were Bill McKibben I would have my fist in the air after that speech."
The pipeline hopes to transport dirty fuel from the Canadian tar sands down to refineries in New Mexico. Such oil releases three to four times more carbon emissions than conventional fossil fuels because it requires huge amounts of energy to both extract and transport.
In fact, if we are to burn all of that oil, it will raise global temperatures by a further 0.4 degrees Celsius. That marks half of the warming already experienced by our planet.
The State Department, which is responsible for carrying out an environmental review of the pipeline, upset environmentalists in March when it concluded that the pipeline will not accelerate global greenhouse gas emissions. It is due to issue its final review over the next few months, with Obama expected to make his ultimate decision on the matter later this year.
The president's most significant move perhaps was his decision to bypass Congress to draw up new carbon limits for power plants. At present, they generate around 40 percent of America's greenhouse gas emissions: "Power plants can still dump limitless carbon pollution into the air for free. That's not right, that's not safe and it needs to stop."
The White House hopes to propose the new rules by next summer, and finalize them by 2015. This will roll out a timetable that will rein in those emissions by the time Obama leaves office in three years time.
The speech won widespread praise from the environmental community and fellow Democrats. Former U.S. Vice President Al Gore described the address as the best speech on climate by any president, while the executive director of the Sierra Club Michael Brune praised Obama for "the change Americans have been waiting for on climate. President Obama is finally putting action behind his words."
In spite of the political deadlock that has dogged his second term, Obama said that he was still willing to work across the political aisle, but will not tolerate attempts to deny the science behind climate change. "We don't have time for a meeting of the flat earth society," the president said to great applause.
As can be expected, the plan ran into fierce opposition from the coal sector and Republicans, with John Boehner, the speaker of the House dismissing the very idea as "absolutely crazy."
But, the president pushed back, arguing that such a view reflects a "fundamental lack of faith in American business and American ingenuity". Moving to renewables will serve as "an engine for growth for decades to come".
In fact, most voters see such a black and white distinction between "jobs" on the one hand and "the climate" on the other as being far too simplistic. And, according to a February Pew survey, most Americans reject the notion that environmental regulations "will hurt the country's economic recovery and destroy jobs."
In the words of Bob Ward from the Grantham Research Institute on Climate Change:
"The question now is whether moderate Republicans will have the courage to break from the extreme political ideology that has straitjacketed them in denial of the scientific evidence. President Obama clearly wants the US to offer international leadership on climate change. It is time for Congress to share his ambition."
Only time will tell how much of Obama's vision can translate into reality as it will invariably be met by a string of legal and political challenges. As Van Jones points out: "It's going to take two years to produce the rules and then probably five years to litigate it so that is a big chunk of time."
Nevertheless, the most important point is that America finally has a climate rescue action plan which marks such a sea change unto itself.
After attending the international climate talks at the start of his first term, the president has been noticeably absent in more recent years. But, Obama has now vowed to spearhead a new global green deal which will set the planet on a more positive course than its current trajectory which according to the World Bank will usher in four degrees celsius of warming by 2060.
The president will also continue to forge new bilateral agreements with other big carbon emitters such as China and India.
The speech comes just a few weeks after he signed a landmark deal with China's Xi Jinping to stamp out highly polluting HFC's from air conditioners and refrigerators.
The world's most populous nation has already overtaken the U.S. to become the world leader in the clean energy race. But on Tuesday, Obama said that America was now heading back into the race to win that mantle back.
With the world's two largest economies and carbon polluters taking tougher action to rein in greenhouse gases at home, the prospects of a coordinated global deal in 2015 look much brighter compared to recent years. According to analysts, strong domestic action must precede any successful effort at the international level.
In the words of Lord Nicholas Stern, author of a landmark paper on the economics of climate change:
"China has been moving very strongly on this issue both in its current five-year plan and in preparations for the 13th five-year plan. There would be tremendous benefits if China and the United States could together show real international leadership on this issue."
If Obama and Xi can both fulfill their promises for a cleaner tomorrow powered by green energy, our world will finally be heading towards a low carbon future which our children's children will be able to enjoy. As Nobel Peace Prize winner Wangari Maathai once said: "In the course of history, there comes a time when humanity is called to shift to a new level of consciousness, to reach a higher moral ground. That time is now."