35 percent of U.S. adults now see global warming as an "imminent" threat, up from 32 percent in 2017 and 24 percent in 2015, according to this national Reuters/Ipsos poll taken Nov. 29-Dec 10. More than half (57 percent) also think global warming is caused by "human activity" or "mostly human activity", according to the survey, up from the 47 percent who attributed it to human activity in a similar poll in 2012. And 69 percent said in the poll that the U.S. should work with other nations to curb climate change, including 64 percent of Republicans and 80 percent of Democrats. That marks a decline from 72 percent in a similar poll in 2017.