But only 55% of Americans believe it to be human-caused. From the actual report [^1]:

> A majority of Americans (55%) understand that global warming is mostly human-caused. By contrast, only about one in three (32%) think it is due mostly to natural changes in the environment.

The remaining 13% presumably answered "don't know" -- so there's at least some hope of reaching up to 68%.

However, even if that 13% is won over, there's still another big barrier to meaningful legislation: Anthropogenic skepticism is over-represented in congress.[^2] Every state gets 2 senators regardless of population, and the more populous states tend to already have senators that believe it is caused by humans.

[1]: https://climatecommunication.yale.edu/wp-content/uploads/201... [2]: https://www.theguardian.com/environment/2015/jan/22/us-senat...