the main claim put forward in the movie An Inconvenient Truth that the earth is getting warmer as a result of human activities is largely based on one particular graph, depicting the variation in temperature compared to the levels of carbon dioxide in the atmosphere over the last 1,000 years.
naturally, this particular graph was subject to a great deal of controversy.
"Not only has the data been under the microscope, but the way that the data is represented has been minutely dissected... An article published by the conservative think tank the Heartland Institute calls the slide in Gore’s film, “A triumph of data manipulation.” Among other criticisms, the article claims that you can’t tell whether warmer temperatures precede or follow the rises in levels of carbon dioxide and that the scale along the vertical “y” axis is not clearly labeled. Rarely has an example of design been subjected to such intense scrutiny at every level from so many sources.".
an alternative graph was offered by critics of global warming in an attempt to show that temperatures are not, in fact, on the rise.