A new Rasmussen Reports national telephone survey of 1,000 likely U.S. voters finds that 60 percent consider global warming at least a somewhat serious problem. That’s the lowest level of concern since February of last year but still generally consistent with findings in regular surveys since 2009.

Thirty-six percent don’t share that concern. The latest findings include 38 percent who regard global warming as a very serious problem and 16 percent who say it’s not at all serious.

When it comes to the causes of global warming, voters are now evenly split: 42 percent think it is caused primarily by long-term planetary trends, while 41 percent now blame human activity. While it’s only by one point, this is the first time the number blaming planetary trends has surpassed those blaming human activity since April 2012. Since early 2009, the number of people blaming global warming on humans has ranged from 33 percent to 47 percent, while the number blaming long-term trends has ranged from 35 percent to 50 percent.

But when asked how much more they are willing to pay each year in higher taxes and utility costs to generate cleaner energy and fight global warming, 48 percent of voters say nothing at all. That’s largely unchanged from previous surveys. Another 23 percent are only willing to spend $100 more a year. Slightly fewer (21 percent) are willing to pay more than that, with five percent (5 percent) saying they’d be willing to spend $1000 a year or more to help fight global warming.

Thirty-seven percent of all voters think Americans are being selfish by putting their economic concerns ahead of the fight against global warming, tying the highest level measured since 2009. A plurality (47 percent) still disagrees, while 17 percent are undecided.

However, even 22 percent of those who think Americans are being selfish for putting their economic concerns ahead of fighting global warming are not willing to pay any more in taxes and utility costs. One-quarter (25 percent) of this group is only willing to pay $100 more per year.