This image of the Earth's atmosphere was taken by astronauts aboard the International Space Agency in November. The camera was pointed west shortly after sunset, producing a panorama of clouds, land masses and ocean water. Image Credit/NASA

Nearly one in three likely U. S.voters considers global warming a “very serious” issue, according to a newly released survey. In all, 64 percent believe the rise in temperature is at least a “somewhat serious” problem, according to Jan. 7 poll results provided by Rasmussen Reports.

The 30 percent who support the “very serious” notion represent the highest level in 2 1/2 years, according to Rasmussen.

The telephone survey of 1,000 likely voters was conducted Jan. 3-4. The results include a plus or minus 3 percent error rate and a 95 percent confidence level.

Global warming is a rise in the heat trapped in the Earth’s atmosphere attributed to increases in the emission of carbon compounds and other greenhouse gases by either natural or manmade sources. Experts worldwide continue to debate how much human activity contributes to the rise and whether regulations on carbon emissions would slow or reduce the increase.

Here is a link to a recent NASA study.

The latest Rasmussen poll found that likely voters are sharply divided on who is to blame. Forty percent say humans, 39 percent blame planetary processes. Eight percent say there are other causes.

Voter sentiment on that front is essentially changed from January 2011.

Two years ago, a similar Rasmussen poll measured those who blame human activity at 37 percent and those who blame planetary processes, at 50 percent. Then, five percent blamed other causes.

There is a more noticable shift from 2008. An April Rasmussen poll found that 47 percent of likely voters believe human activity is to blame. Thirty-four percent blamed nature, and eight percent pointed to other reasons.