Though the majority of Americans believe that global warming is actually occurring, many do not understand the reasons behind it, suggests new research released Thursday.

According to a study by Yale University researchers, 63 per cent of U.S. citizens believe that global warming exists. However, only 57 per cent know what the greenhouse effect is and only 45 per cent recognize the impact of carbon dioxide in trapping the earth's heat.

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The greenhouse effect involves the trapping of the sun's heat by gases in the earth's atmosphere, such as carbon dioxide, nitrous oxide and methane.

And 50 per cent of Americans understand that global warming is the result of human activities.

In a national online survey conducted by Knowledge Networks between June 24 and July 22, 2010, 2,030 Americans aged 18 and older were queried about their knowledge of global warming.

The poll reveals that almost half of Americans — 49 per cent — incorrectly believe that the space program contributes to global warming, and that the hole in the ozone layer, toxic wastes, aerosol spray cans, volcanic eruptions, the sun and acid rain also play a role.

Seventy-five per cent of those surveyed said they would like to know more about the phenomenon and 75 per cent believe that schools should teach children about the issue.

The study's margin of error was plus or minus two per cent, 19 times out of 20.