In a recent story of mine regarding CPRS polling, commenter “Blue_green” asked:
Possum — It would be interesting if you could plot a correlation between ‘against cprs’ and ‘global warming is exaggerated’ for each demographic. I wonder if they are consistent or if some just want another climate policy (just not the CPRS).
That is a mighty fine idea. The results have some pretty profound implications.
Our only small problem is that we don’t have enough observations in the Morgan poll breakdowns to look at the relationship between generic global warming scepticism and disapproval levels of the CPRS legislation for any given age group or voting block — with only three periods of observation for any and every demographic cohort, it wouldn’t really tell us much.
Yet, what we can do is use those various cross-tab cohorts as observations themselves in a broader look at the national relationship between the CPRS and beliefs in global warming.
Morgan asks two questions in its CPRS and global warming polling series — the data that we’ll use here. The first is “Which of the following is closest to your view about global warming? Do you think: Concerns are exaggerated; if we don’t act now it will be too late; it is already too late?“, while the second question is a generic “do you approve or disapprove of the CPRS legislation” type affair. We have answers to these questions for three periods of time from the same respondent sample — August 2009, November 2009 and January 2010.
What we can do is not only look at whether the change in beliefs on global warming correlates to any changes in support for the CPRS, but we can also look at the size of any such effect.
Before we start though, we need to state the obvious — correlation is not causation without good cause.
Yet here, we have pretty good reason for cause. Before we even look at the data, we would expect that as the proportion of people that believe “if we don’t act now it will be too late” on global warming increases, the proportion of people that approve of the CPRS would increase as a result.
Similarly, we would also expect that as the proportion of the population that believes global warming “concerns are exaggerated” increases, the proportion of the population that disapproves of the CPRS would likewise increase.
First up, we’ll use just the result of the age breakdowns since it covers the the full spectrum of population and has no demographic overlap. Morgan runs cohorts that are 14-17 years, 18-24 years, 25-34 years, 35-49 years and 50+ years. If we chart the responses of each of these groups to CPRS approval rates and “if we don’t act now it will be too late”, we get:
The relationship here is statistically significant. As we can see, as the proportion of the population that believes “if we don’t act now it will be too late” increases, it walks hand in hand with an increase in the proportion of the population that approves of the CPRS.
It does so at a level where for every 1% increase in the proportion of the public that believes in the need for action now, the proportion of the population that approves of the CPRS increases, on average, by 1.0098% — let’s just call it 1% as well. This relationship explains 67% of the variation in the change in approval levels of the CPRS.
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