President Obama delivers his State of the Union address to a joint session of Congress on Capitol Hill on Tuesday. Vice President Biden and House Speaker John A. Boehner (R-Ohio) listen in the background. (AP Photo/Mandel Ngan)

In his State of the Union address, President Obama made what are surely his strongest statements yet about climate change -- at least for a State of the Union speech. "No challenge  --  no challenge  -- poses a greater threat to future generations than climate change," he warned, proceeding to launch into a three paragraph sally that included some serious mockery of the recent Republican "I'm not a scientist" talking point.

The president also strongly emphasized the strength of the science on climate change, cited six years of progress by his administration, and warned that "I will not let this Congress endanger the health of our children by turning back the clock on our efforts."

He may be responding with such force precisely because the threat is now so great.

“The president is speaking out more often and forcefully than ever about climate in part because the science indicates increasingly serious threats to our economy and security,” said Paul Bledsoe, a former Clinton White House climate adviser and now a senior fellow at the German Marshall Fund. “But Obama also now sees climate as a key political wedge issue, contrasting his view of Republican willingness to deny facts and put the American people in harm’s way with his own efforts to literally help save the planet.”

Indeed, a new Washington Post poll suggested that on climate change, the public prefers Obama's ideas to those of the Republican Congress by 45 percent to 28 percent.

So-called "climate hawks" have been enraptured by the new Obama on climate, but the approach is really less than two years old. In his first term, Obama had tried two other approaches that we've almost forgotten already -- reframing his way around the issue, and ignoring it entirely -- before starting a more aggressive approach in his second.

The "Green Jobs" Era


A scene from the "green jobs" era: Obama tours the manufacturing facilities of Cree, a leading manufacturer of energy-efficient LED lighting, on June 13, 2011, in Durham, N.C. (AP Photo/Carolyn Kaster)

It's hard to remember now, but the administration's initial message on climate change often skirted the unavoidably scientific issue of change itself. Believe it or not, in his 2011 State of the Union address, Obama omitted the term "climate" entirely.

This was the "green jobs" era, as we struggled to re-emerge from the economic collapse and the administration reportedly adopted a strategy of trying to pass a cap-and-trade bill not by emphasizing the dire threat of climate change, but rather, with a positive economic message about how innovation in the clean energy industry would help the recovery.

The approach is fairly understandable, in light of the context: Everyone was terrified about the economy, and climate policies were being attacked as job killers. Still, for those who know the climate issue well, there was always something rather unsatisfying about this approach. Of course clean energy is a good thing, but the urgency of an energy transition is pretty hard to sell without understanding that we literally have a very limited number of gigatonnes of carbon that we can still put in the atmosphere without risking climate chaos.

The "Climate Silence" Era


A scene from the "climate silence" era: Republican presidential nominee Mitt Romney listens to President Obama speak during the third presidential debate at Lynn University on Oct. 22, 2012, in Boca Raton, Fla. (AP Photo/Pool photo by Rick Wilking)

Matters arguably got even worse as the 2012 election got into full swing. Before long Obama, Mitt Romney and the major TV news media alike were being accused of collective strategy of "climate silence."

On Obama's part, after the cap-and-trade push failed in Congress, it hardly helped that he didn't have a major climate accomplishment to talk about. As for Romney, the former Massachusetts governor had to prove his conservative bona fides -- talking about climate change was definitely not going to help.

In part as a consequence -- but rather amazingly nonetheless -- the climate issue never even came up in a 2012 presidential debate. Obama did break the "silence" in his 2012 Democratic National Convention speech, however, as he played to the base there.

"Climate change is not a hoax," Obama said on that occasion. And then he continued with a tone that presaged today's climate Obama: "More droughts and floods and wildfires are not a joke. They are a threat to our children's future."

The "Future Generations" Era


The "future generations" era begins: President Obama speaks about climate change at Georgetown University in Washington on June 25, 2013, wiping his brow from the heat. (AP Photo/Charles Dharapak)

But after getting reelected, something really changed for Obama. We began to hear murmurs that he considered his legacy to very much depend on addressing climate change. And then in a major speech on a sweltering June 2013 day at Georgetown, Obama did what the climate hawks had long demanded. He let it rip. He laid out the science of climate change and why nobody who takes that science seriously could ignore a problem of this magnitude.

"I refuse to condemn your generation and future generations to a planet that’s beyond fixing," Obama said -- and announced that his Environmental Protection Agency would be going ahead on regulating carbon emissions from power plants without any law from Congress on the matter.

So we're now in the present -- with Obama constantly emphasizing that what matters is the future. And standing up for science itself. It took a long time -- but precisely because (as Obama once said) "climate change is not a hoax," it was ultimately the message that had to win out.