Opinion writer
Here are the highlights from President Obama's 2015 State of the Union speech, including zingers on climate change and calls for tax reform. (Nicki DeMarco/The Washington Post)

There was a time when President Obama barely mentioned climate change in major speeches. But if he hadn’t touched on the issue in Tuesday’s State of the Union Address, it would have been perhaps the most dishonest omission of his presidency. His Environmental Protection Agency is in the process of enforcing landmark rules on greenhouse gas emissions. In Beijing last year, he struck a unexpected deal committing the United States to emissions cuts over the next decade. Who cares about a bunch of new proposals that the GOP Congress will ignore? This is what the president is actually doing.

It was good thing, then, that he not only mentioned the issue, but also delivered a ringing defense of global warming science — an explanation for why he is determined to act and a rebuke of those who would end his climate program.

I’ve heard some folks try to dodge the evidence by saying they’re not scientists; that we don’t have enough information to act.  Well, I’m not a scientist, either.  But you know what – I know a lot of really good scientists at NASA, and NOAA, and at our major universities. The best scientists in the world are all telling us that our activities are changing the climate, and if we do not act forcefully, we’ll continue to see rising oceans, longer, hotter heat waves, dangerous droughts and floods, and massive disruptions that can trigger greater migration, conflict, and hunger around the globe….

That’s why, over the past six years, we’ve done more than ever before to combat climate change, from the way we produce energy, to the way we use it…. And that’s why I will not let this Congress endanger the health of our children by turning back the clock on our efforts. I am determined to make sure American leadership drives international action.

This is a lot better than what the country had from its presidents before. Polling shows that most Americans are concerned about climate change but put the issue far down on their priority lists. The first task is to elevate the issue. Obama did not do that at the beginning of his presidency. He’s finally catching up near the end.

Obama’s legacy won’t be established by some grand new program for reinvigorating the middle class, miraculously passed by a GOP Congress in the fourth quarter of his term. Much of the next two years are going to be about entrenching domestic policies Obama established during the last several — a time marked by economic sluggishness and foreign messes, yet also by a burst of policy accomplishment, particularly on health care for lower-income Americans and on global warming.

But after making a case for his record, Obama should have told Congress what it needs to do on climate. At some point, lawmakers will have to pass a global warming policy tailored to reduce carbon dioxide emissions. As it is, the Obama administration has to rely on the cumbersome Clean Air Act to mandate greenhouse gas cuts, and there’s no plan for what happens after the next decade or so. The president should have at least made the case for a stable, efficient and long-term policy, such as a carbon tax.

Given the GOP Congress’s stance on the issue, the immediate result might only have amounted to a few Americans thinking about the issue with a little more depth. But on an issue of such importance, that’s worth it.