In Chapters 3 and 4, we described the issue of global warming pointing out that the Earth has not warmed since 1998, explaining why the media now refer to the problem as climate change, and that there is a weak linear relationship between temperature anomalies and CO2 levels. In the last few years news stories have appeared that seem to cast doubt on the entire theory. To measure the effect on public opinion several surveys have been conducted by Pew Research Center. Approximately 1,000 American adults were asked the following question in March 2012 and March 2013.

How serious a problem is global warming? The responses are:

1. Very serious

2. Somewhat serious

3. Not too serious

4. Not a problem

Is there sufficient evidence to infer that the proportion of American adults who believe that global warming is a very serious problem decreased between 2012 and 2013?