The pontiff urged lawmakers at a joint meeting of Congress to balance concern for those living in poverty with protection from environmental deterioration, which he said was "caused by human activity." (AP)

It was not Pope Francis's way to be explicit in his calls to action when addressing Congress on Thursday. He touched briefly on a number of topics that roil within American politics. On abortion, he said that the Golden Rule reminds us of "our responsibility to protect and defend human life at every stage of its development." On same-sex marriage, that "[f]undamental relationships are being called into question, as is the very basis of marriage and the family." He encouraged Congress to keep the poor in mind, to reject the death penalty and to question the sale of deadly weapons. He suggested that Congress -- and through them, all of us -- remember our immigrant roots and to respond to immigrants "in a way which is always humane, just and fraternal."

Only once, though, did he call Congress to specific action. "I am convinced," Francis said, "that we can make a difference, and I have no doubt that the United States – and this Congress – have an important role to play." The subject: climate change.

"I call for a courageous and responsible effort to 'redirect our steps,'" he said, quoting his encyclical on the subject, "and to avert the most serious effects of the environmental deterioration caused by human activity. ... Now is the time for courageous actions and strategies, aimed at implementing a 'culture of care' and 'an integrated approach to combating poverty, restoring dignity to the excluded, and at the same time protecting nature.' ... In this regard, I am confident that America’s outstanding academic and research institutions can make a vital contribution in the years ahead."

On every other topic, the Pope pointed indirectly at the path he'd recommend. On climate change, he called Congress to do something concrete.

But Congress has probably never been less likely to heed that call.

The last time Congress considered major legislation aimed at curtailing the greenhouse gas emissions that contribute to the warming climate was in President Obama's first year in office. The proposal was a "cap and trade" bill that would have set limits on how much heavy carbon dioxide producers could emit and created a marketplace on which allowances for excess production could be traded. Your coal plant is producing more CO2 than it's supposed to? Buy credits from a plant that is producing less than it's allowed. The idea would set an overall amount of pollution -- and provide market-based rewards for producing less. It's a system similar to what was implemented to curtail acid rain under the administration of George H. W. Bush.

Thanks to a combination of the faltering economy, bad political choices and Republican opposition, the bill passed the House only to be abandoned in the (then-Democratic) Senate. In short order, the fight on Capitol Hill became about health care, and the topic faded.

That moment was an important one. Climate change had come to national attention following Al Gore's documentary, "An Inconvenient Truth," which also galvanized opposition to taking action to combat the problem. Gore's film was released in 2006, right before Gallup polling found Americans were becoming more likely to consider the threat of climate change to be "exaggerated."

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At the same time, Americans were more likely to prioritize the health of the economy over environmental protection, in part because the effects of the economic collapse were still rippling across the country. Opponents of the cap-and-trade bill called it "cap-and-tax," implying a heavy cost for normal Americans. That same argument is common today.

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Where Americans once favored prioritizing the environment by a 2-to-1 margin, it's now about an even split.

What's more, climate change has been subsumed into America's political polarization. Maps of acceptance of climate change mirror maps of congressional representation. A 2014 study found that climate change was more polarized on partisan lines than abortion or the death penalty. The gap between the parties on climate was 47 points, to 26 points for abortion and 25 on the death penalty. Polling has repeatedly shown that conservative Republicans are the most likely to be skeptical of the need to address climate change.

Republicans, conservative or not, now have more clout than they have had in a long time on Capitol Hill. The House has as big a majority as it's had at any point since the 1930s, and the Senate majority for the party is more than enough to block unwanted legislation. Each of those House members and a good number of the senators faces reelection next year and a primary process before that. Few, it's safe to assume, will be willing to risk their political careers on a risky climate bill. (A group of 11 Republicans did recently sign a resolution that offers a tepid call for climate action. It is not expected to go anywhere.)

In short: No deal, Francis. When the pope first produced his climate encyclical, we offered skepticism that it would make a difference. That skepticism still holds, even after the pope's unprecedented personal appeal in front of the full federal representation of the United States. It was the only topic on which he broke from his preferred style of referring obliquely to the change he wanted to see. But that forcefulness by-Francis-standards isn't likely to make a dent at all.

From his private meeting with President Obama to giving the first-ever papal address before a joint session of Congress, Pope Francis did not shy away from politics during his three-day stop in Washington, D.C. (Julie Percha/The Washington Post)