What do greenhouse gases do to warm the atmosphere?

Answer 1

Yes. By definition they affect the temperature: that's why they're called "greenhouse" gases: they emit thermal radiation.

Greenhouse gases are gases in an atmosphere that absorb and emit radiation within the thermal infrared range. Greenhouse gases greatly affect the temperature of the Earth; without them, Earth's surface would be on average about 33°C (59°F) colder than at present. (from Wikipedia)

What you're likely asking is whether MAN-MADE greenhouse gases are causing the Earth's temperature to increase. This is a hotly (pun intended) debated topic. Turning again to wikipedia:

The 2007 assessment report compiled by the IPCC noted that "changes in atmospheric concentrations of greenhouse gases and aerosols, land cover and solar radiation alter the energy balance of the climate system", and concluded that "increases in anthropogenic greenhouse gas concentrations is very likely to have caused most of the increases in global average temperatures since the mid-20th century".

Answer 2

When the sun's solar radiation enters the earth, absorbed by the ozone layer, some heat radiation is allowed to escape back into space but gases like CFCs, Halons, Carbon dioxide, Nitrous oxide and Methane, trap the rest. Because of this, more and more heat radiation is getting trapped in the earth and that is resulting in the heating of our atmosphere.

Answer 3

There has always been a natural greenhouse effect, without which the world would be some thirty degrees colder than it is today. This occurs because greenhouse gases such as water vapour, carbon dioxide, methane and ozone absorb heat energy being re-radiated from the earth and prevent it escaping into space.

What is now happening is that human activities, such as burning fossil fuels, are increasing the atmospheric concentration of carbon dioxide. The level of carbon dioxide in the atmosphere has increased from a long-term pre-industrial level of 260-280 parts per million (ppm) to the present level of around 400 ppm, more than a 35 per cent increase. The more carbon dioxide, the more pronounced the greenhouse effect and the higher global average temperatures go.

Answer 4

Greenhouse gases like water vapour, carbon dioxide and methane absorb infrared heat rising from the warm earth. The heat is held in the atmosphere instead of escaping into space.

We need the greenhouse effect to keep us warm. However, too much greenhouse gas is now causing an enhanced (or accelerated) greenhouse effect which is causing global warming.

Answer 5

Greenhouse gases remain in the atmosphere for a long time. They cause the temperature to rise because the sun's harmful rays can get through the ozone layer of the atmosphere.

Answer 6

Greenhouse gasses absorb infrared radiation from the earth, which is heated by the sun), and radiate it out again. Some of it escapes into space while some is sent back toward the earth.

Answer 7

Greenhouse gases in the atmosphere capture heat rising from the surface of the earth and prevent it escaping into space. Thus the atmosphere is warmed.