Two respected voices articulate where the climate debate stands.

In an interesting bit of symmetry, two highly admired figures in their respective spheres have simultaneously issued pronouncements on climate change that illustrate the seismic shifts under way in the larger public debate.

Commentary

One of those shifts is on the political landscape. It was reaffirmed this week after long-time moderate-conservative Republican Senator Senator Richard Lugar was defeated by a Tea Party challenger in the Indiana Republican primary. The dwindling number of moderate Republicans who hold elective office probably nodded grimly in agreement after reading Senator Lugar’s concession statement which included this:

Republicans cannot admit to any nuance in policy on climate change. Republican members are now expected to take pledges against any tax increases. For two consecutive presidential nomination cycles, GOP candidates competed with one another to express the most strident anti-immigration view, even at the risk of alienating a huge voting bloc.

Lugar went on to decry the increasing partisanship of both major political parties, but he zeroed in on the various ideological pledges that Republican officeholders are now routinely expected to accept. (He hasn’t always done so, and that’s seen as being one big reason for his primary defeat.) But Lugar’s reference to the current Republican stance on climate change may have even been charitable. For rejection of climate science and any climate legislation has now become part of GOP doctrine.

The Republican Party’s hardened position reflects, or perhaps reinforces, the attitudes of Republican voters who are now increasingly suspicious of climate science and dismissive of climate change. This development has undoubtedly widened the partisan gap on climate issues, leaving little political space for constructive (much less nuanced) debate on climate change.

Meanwhile, on the scientific landscape, NASA climate scientist James Hansen has just published an op-ed in The New York Times that also defines, and some might say narrows, the parameters of debate. He writes:

The global warming signal is now louder than the noise of random weather, as I predicted would happen by now in the journal Science in 1981. Extremely hot summers have increased noticeably. We can say with high confidence that the recent heat waves in Texas and Russia, and the one in Europe in 2003, which killed tens of thousands, were not natural events — they were caused by human-induced climate change.

Some climate scientists vehemently dispute such unequivocal, sweeping claims.

Additionally, Hansen repeats his “game-over” predictions for the world’s atmosphere if Canadian oil sands are fully developed, leading New York University faculty member and science journalist Dan Fagin to tweet: “Respect Hansen a lot, but hate his #climate lingo. Not a game, and it’s not over, no matter what happens w/#tarsands.”

Nonetheless, Hansen’s latest pronouncements on recent extreme weather events and oil sands dovetail with the prevailing opinions of high profile and influential voices in the climate concerned community. In effect — and because of his stature — Hansen’s rhetoric in his Times column amplifies larger memes in the media that have come to shape climate discourse.

So Republicans have their narrative, and they appear to be sticking with it. And on the science landscape, if Hansen’s marker in the Times is any indication, the “game over” and extreme weather narratives are becoming equally established.

Regardless of whose narrative prevails — the Republican dismissal of climate change or the climate community’s ratcheting up of alarm — there can be no doubt that each serves a political purpose. Where that leaves the ultimate political and policy outcome remains clouded.