Carter appeared as a witness before the 2009 select committee on climate policy of the Parliament of Australia, and testified before the United States Senate on the issue of human-caused climate change. He appeared in the media speaking for the Nongovernmental International Panel on Climate Change (NIPCC), a contrarian report backed by The Heartland Institute, a free-market think tank opposed to climate change responses. He was a contributor and reviewer of their 2009 report "Climate Change Reconsidered", and lead author of the 2011 interim report.