Public concern about climate change in the U.S. is at an all-time high, according to a new Gallup survey – although not too high. Forty-five percent of the poll’s respondents say they worry about global warming “a great deal,” while 62 percent believe its effects are already occurring. Overall, 68 percent of participants – the highest level reported yet – said they believe climate change is driven by human activities, while 29 percent attribute it to natural causes and 3 percent had no opinion.

Still, these findings are up from a previous high in 2007, when a similar poll found that 41 percent of respondents worried greatly about climate change. Between then and now, American concern about global warming actually declined for four years and has only been on the rise again since 2011.

Similarly, the percentage of Americans who believe climate change is already happening previously peaked at 61 percent in 2008 and then declined until 2011.

The reasons for this dip and recovery are unclear from the survey results, but previous research has suggested that public concern about climate change may be linked to the state of the economy. From 2008 to 2010, the U.S. was suffering in the Great Recession – and in times of economic downturn, Americans may be less likely to worry about global warming.