Ever since earth formed some 4.5 billion years ago, heat-trapping gases have kept the atmosphere warm.
A few see natural variation as more central to global warming than heat-trapping gases.
But it is a major component of heat-trapping greenhouse gases in the atmosphere.
Oil and coal are the main source of carbon dioxide, the dominant heat-trapping gas.
It had been known since 1960 that humans were increasing the amount of heat-trapping greenhouse gases in the atmosphere.
According to the models, the buildup of heat-trapping greenhouse gases is largely responsible.
Carbon dioxide, the main heat-trapping gas, comes primarily from the burning of fossil fuels.
The United States government still needs to regulate emissions of heat-trapping greenhouse gases.
Some scientists blame heat-trapping gases, like carbon dioxide, produced from burning coal and oil.
The president has said that more research is needed before the administration can even consider mandatory restrictions on heat-trapping greenhouse gases linked to global warming.
