There is significant scientific debate about the extent and causes of climate change.
The IPCC's Fourth Assessment Report (2007) declared the evidence for human-caused warming 'unequivocal' - the strongest language the body had used. The same year, Al Gore and the IPCC shared the Nobel Peace Prize for climate communication.
What changed?
When the IPCC published its Fourth Assessment Report in February 2007, the language was the strongest the body had used. Human warming of the climate was ‘unequivocal.’ The probability that human activity was the dominant cause of observed warming since the mid-twentieth century was assessed at greater than 90 percent. The report synthesized the work of thousands of scientists across more than a hundred countries and represented a broader, deeper evidentiary base than any previous assessment.
That autumn, the Nobel Committee awarded the Nobel Peace Prize jointly to the IPCC and Al Gore, whose documentary An Inconvenient Truth had reached theaters in 2006 and had been widely screened in schools. The combination, a Nobel Prize and a major popular film, brought climate science to public attention in a way that no scientific paper had managed. For a period in 2007, it was difficult to have missed the message.
But the message had competition. The fossil fuel industry’s campaign to manufacture scientific doubt had succeeded in embedding climate skepticism as a partisan position in American politics. Cable news channels regularly presented climate scientists and industry-funded skeptics in ‘both sides’ segments, assigning equal weight to positions with vastly unequal scientific support. Online communities distributed talking points about temperature plateaus, solar cycles, and the unreliability of climate models. Some of these arguments were technically sophisticated; none represented the mainstream scientific view.
For a student graduating in 2007, whether they understood climate science as settled or contested depended significantly on which media they consumed, where they lived, and what their school had taught. In schools using IPCC-aligned materials with confident teachers, the message was reasonably clear. In schools where teachers felt uncertain or where political pressure discouraged direct statements about scientific consensus, the impression was often of ongoing debate. The scientific community had spoken clearly; the transmission of that clarity to the classroom remained incomplete.
