A month before the 2008 presidential election, sociologists Riley Dunlap and Aaron McCright (of Oklahoma State and Michigan State, respectively) published a prescient study on the rapidly growing partisan gap on issues of environmental and climate protection.

They concluded by speculating that a win by Sen. John McCain, an outspoken climate champion, could represent "a sea change among Republican Party leadership on the issue of climate change," whereas an Obama victory "could see Republican trends toward increased skepticism continue for the next several years."

Well, we know how that turned out.

Now Dunlap and McCright (along with Oklahoma State’s Jerrod Yarosh) have updated their study, giving us a fresh look at public opinion on climate change at the end of the Obama era.

The findings are dismal, if not very surprising: Polarization only accelerated after 2008, the gap between the parties is wider than ever, and the trend shows no sign of stopping.

The large and growing partisan gap on climate change

Let’s look at some charts from the study, and then we’ll have a think about what it means for US politics.

First, here’s a chart showing how League of Conservation Voters (LCV) scores, which track the voting records of members of Congress, have changed over time.

As you can see, environmental issues were reasonably bipartisan back in the 1970s. The parties began to drift apart in 1980, and then more sharply when Bill Clinton became president in 1992. In 2008, when Obama took office, there was another lurch, and now Republicans in Congress are very close to unified in opposition to all environmental legislation.

So, yes, polarization among US federal legislators has most definitely grown more extreme, to near-comical levels.

But what about public opinion? For that, we shift over to Gallup, which has been asking a set of climate-related questions pretty consistently since the late 1990s. It has the best longitudinal data available.

Here are responses to a question about whether the effects of climate change have already begun:

The partisan gap grows in the 2000s and then widens further in 2008. Democratic answers fluctuate, but overall they trend higher (though not yet reaching the heights of 2007, when Al Gore’s movie came out). Republicans never again reach their peak of 2007, or their even higher peak of 1997.

Are changes in climate mostly due to human activity?

Again, the partisan gap grows wider in 2008, with Democratic numbers rising and Republican numbers never reaching their 2001 peak.

Do you personally worry about climate change?

The lines on this one look somewhat different, obviously shaped by the financial crisis, which left little room for additional worries. The size of the gap peaks in 2007, but remains large.

And so on through various other climate questions. The authors sum up the size of the gaps over time:

On every question, the partisan gap grew between 2001 and 2008, and grew again (with one exception, where it remained steady) from 2008 to 2016.

What’s more, the gap between self-identified conservative Republicans and liberal Democrats is far larger than the above numbers indicate, sometimes reaching into the 60s. And it’s the committed partisans who are most likely to vote and wield influence over policymakers.

Taking these trends at face value, it looks like the GOP is going be under continuing pressure to keep climate skepticism central to Republican orthodoxy, at least for the foreseeable future.

Hopes for reducing polarization are mostly forlorn

There are three sources of hope for reducing polarization in the short term. Dunlap et. al. shoot them all down.

The first is education — better informing the public about climate science. The much-derided "information deficit model" has proven a failure in practice. "Two decades of news coverage and educational campaigns since 1997 have produced only modest increases in Americans’ belief in the reality and human cause of climate change, with gains among Democrats often offset by declines among Republicans," the authors write.

The second is better "framing," pitching climate to conservatives in terms more likely to appeal to their values — climate as a national security threat, or an economic opportunity, or a threat to God’s covenant. However, dozens of studies have found small or negligible effects from these strategies. "The evidence so far gives little basis for optimism," they conclude.

The third is personal experiences with extreme weather events, which, it is often hoped, will drive home the reality of climate change. But what evidence exists shows that such experiences have little-to-no effect on climate beliefs, especially among committed partisans. People interpret their experiences through their preexisting worldviews. "Again," Dunlap et. al. write, "the evidence thus far does not provide much support for optimism."

Why is polarization so resistant to change?

The reason increasing polarization on climate change remains so resilient is that it’s not really about climate change. The issue has been swept up in a much larger, broader trend of polarization in US politics (which I have written about before). As Americans sort themselves into camps, both ideologically and geographically, political orientation becomes more and more a matter of identity — or as sociologist Arlie Russell Hochschild called it in her excellent account of white working-class communities in Louisiana, "deep story."

Skepticism toward climate change and hostility toward climate policy have been yoked to conservative identity. To reject them is to risk rejecting that identity and harming the social relationships that come with it. And most people have much stronger commitment to their core identity than they do to any individual political issue.

Once an issue has been yoked to our core identities, we stop reasoning like scientists (gathering evidence, seeing where it leads) and start reasoning like lawyers (start with a conclusion, work backward to build a case). Yale psychologist Dan Kahan calls it "motivated reasoning"— "the unconscious tendency of individuals to process information in a manner that suits some end or goal extrinsic to the formation of accurate beliefs." In this case, the "end or goal" is preserving commitments core to identity.

Studies show that a college education and a self-identified understanding of the issue both tend to raise Democrats’ concern over climate change, but the same factors have no effect, sometimes even a negative effect, on a Republican’s concern. Why? Because Democrats, for basically tribal reasons, are likely to be open to the idea that climate change is a problem. Republicans, for basically tribal reasons, are unlikely to be open to the idea. A committed Republicans is apt to learn more about climate change in order to bolster the skeptical case.

Core identity commitments are extremely difficult to dislodge. Insofar as they shift, the change tends to originate inside the tribe.

The forlorn hope of focusing on clean energy

Many people (myself included) have noted that, despite their partisan opposition to climate action as such, pluralities and sometimes even majorities of Republicans favor many policies that would have the effect of reducing carbon emissions — local pollution regulations and clean energy support, especially. Perhaps there’s hope there?

Dunlap and crew say no:

[A]s Lilliana Mason and other political analysts note, individuals can hold relatively moderate positions on many issues and yet be strong partisans committed to keeping the other party out of office. Thus, as long as rank-and-file Republicans vote for conservative candidates, and those candidates remain steadfast in opposition to climate change action, the former’s receptivity to climate-friendly policies remains almost irrelevant—for the Congress they help elect will be highly unlikely to give such policies any consideration.

This is an important point to understand. Even someone with moderate opinions on particular issues is subject to the growing influence of "negative partisanship."

In a 2015 paper, political scientists Alan Abramowitz and Steven Webster showed that "since 1992 and especially since 2008 … growing proportions of strong, weak and leaning party identifiers have come to perceive important differences between the parties and to hold extremely negative opinions of the opposing party. This has led to sharp increases in party loyalty and straight ticket voting across all categories of party identification."

Even self-identified moderates, centrists, and independents tend to vote like partisans these days.

And parties have shifted toward parliamentary-style discipline. If you vote for a Republican, even if you have moderate inclinations on clean energy and pollution regulations, even if the particular Republican you vote for has such inclinations, what you get is the party. And the party, institutionally speaking, is united against climate action.

(The inverse is not quite as true yet of Democrats, on climate anyway. There are still holdouts in coal and heavy manufacturing states.)

Political parties are generally shaped by a few core commitments, the concerns of big donors, and the influence of organized, engaged constituencies. The GOP’s core ideological opposition to taxes and regulations, its big fossil fuel donors, and its most intense constituencies are all pushing it strongly toward skepticism, denial, and opposition on climate policy.

What to do?

This is all a bit depressing and hopeless. What to make of it?

Most of all, it clarifies the stakes of the 2016 elections (if additional clarity was needed). The continued hyper-polarization around climate change means it matters very, very much for climate policy which party controls Congress and the presidency for the next four years.

"Whether, and how, individual Americans vote this November," Dunlap et. al. write, "may well be the most consequential climate-related decision most of them will have ever taken."

But do we have to accept that we’re stuck with partisan polarization in the world’s richest country, toward the biggest challenge our species has ever faced? Is there nothing that can cleave climate off from the culture war, from the role it now plays in conservative identity?

Longtime readers know I’m very, very skeptical toward most such efforts. But I’ll discuss a few thoughts along those lines in a subsequent post, which will address the question of just how Republican sentiment on decarbonization might be shifted.