The changes in the two groups in which it's chiefly occurred are striking ones. Last year leaned Republicans by 72-25 percent believed the Earth was warming; today it's 55-43 percent. Conservatives last year divided by 69-28 percent on the question; today, by contrast, it's 56-41 percent. Combining these groups – that is, among conservative Republicans – a bare majority now says global warming is not occurring, the only group in which more than half says so.
Looking back another year, to spring 2007, shows changes that also are disproportionately among conservatives and Republicans. In this comparison, belief that global warming is occurring has dropped by 21 points among conservatives vs. 7 points and 5 points, respectively, among liberals and moderates; and by 18 points among leaned Republicans vs. 7 points among leaned Democrats.
WHY? – Policy preferences could hold a clue as to why these changes have occurred. Conservatives and Republicans broadly oppose proposed government measures to deal with climate change. A heightened sense that such changes may be coming, particularly since the Obama administration took office, may encourage more people in these groups to express disbelief that global warming is occurring in the first place.
Data in this survey show, as expected, that belief that global warming is occurring predicts support for measures to deal with it. But the reverse also is true: Views on government measures to address climate change predict belief in whether it's occurring. Directionality is difficult to establish, and may well run both ways. In any case, including one of these variables when predicting the other in a statistical model increases the model's explanatory power.
In further evidence, belief that global warming is occurring has fallen since summer 2008 entirely among people who oppose cap and trade and who oppose unilateral action by the United States. Among their policy opposites, belief has held steady.
The change in views among conservatives and Republicans has occurred even as scientific consensus and the urgency of warnings about the impact of a warmer Earth have increased. Previous research, however, has shown that conservatives and Republicans simply are less disposed to accept those warnings as reliable.
SERIOUSLY? – Among people who believe climate change is occurring, there again are ideological and partisan differences on its seriousness. Three-quarters of conservatives in this group say it's a serious problem now, 9 and 13 points fewer than the number of moderates and liberals who say so. The partisan gap is wider: Among Republicans who think it's happening, 63 percent call it serious; that jumps to 82 percent of independents and 90 percent of Democrats.
ACTION/BELIEF – As noted, belief that global warming is occurring, and that it's a serious problem, are the strongest independent predictors of support for government action in general, and a cap-and-trade law in particular.