1.   But many climatologists said it marked a substantial move forward in understanding forces that have warmed the earth and are likely to continue warming it.

2.   Fewer than half the emissions, scientists believe, remain airborne to warm the earth.

3.   If greenhouse gas emissions are not reduced, the United Nations scientific panel has consistently said, atmospheric concentrations will continue to rise and warm the earth further.

4.   Is human activity warming the earth?

5.   Meanwhile, a strengthening March sun warms the earth, generating updrafts and downdrafts of air.

6.   This veil-like type of cloud allows sunlight in to warm the earth and traps some of the rising heat before it can radiate into space.

7.   Most prevalent among those greenhouse gases, whose growing concentration in the atmosphere is believed to be warming the earth, is carbon dioxide from burning fossil fuels.