A new survey revealed that the number of Americans doubting the occurrence of climate change has increased by seven percent just between April and November 2013.

Anthony Leiserowitz, lead author of the study and a director of the Yale Project on Climate Change Communications at Yale University, and his colleagues surveyed 830 Americans about their beliefs and opinions regarding climate change or global warming.

The results revealed that 63 percent of the overall population of Americans believes that there is climate change and 53 percent are concerned about its consequences.

However, the percentage of Americans saying they "don't know" if it is happening decreased by six percent from 20 percent in April 2013. The findings suggest that many who previously answered they "don't know," now believes that global warming is not really happening.

 "People who prior said 'don't know' are increasingly saying they don't believe it," Leiserowitz told LiveScience.com.

Additionally, 47 percent of Americans believe that climate change is a result of careless human activities, while 37 percent believe that it is a result of natural climate fluctuations.

The respondents were also categorized into six distinct groups called "The Six Americas Segments." They were sorted out based not on their demographics but on their beliefs and concerns regarding climate change.

Of the respondents, 16 percent are "alarmed," meaning they strongly believe that global warming is happening and they are concerned about it. The "concerned," who sees climate change as a threat to others and the future generations, but not for them accounts for the 27 percent.

The "cautious," who are likely to believe climate change is real, but are not certain occupies 23 percent of the whole population. The "disengaged," or those who disregard the issue, make up about five percent.

On the other end of the spectrum, those who do not believe that there is climate change, or the "dismissive," and those who are "doubtful" if it is happening or not, comprises about 15 percent and 12 percent of the population, respectively.

See complete report here.