Is the planet warming?
Yes. Every one of the hottest 15 years on record has occurred since 1980. The hottest five have been since 1997.
The world's average surface temperature increased by about 0·7°C over the 20th century. (By average we mean the average of air temperatures near land surfaces, and sea surface temperatures.) The World Meteorological Organization announced that 2005 was the hottest year on record in the northern hemisphere.
Records, which go back to 1861, show the rate of change has varied a lot. For example, most of the warming occurred during two periods, 1910 - 1945 and 1976 - 2000 (source: Intergovernmental Panel on Climate Change).
The three fastest-warming regions on the planet in the last two decades have been Alaska, Siberia and parts of the Antarctic Peninsula. Continents in the northern hemisphere have warmed the most. Computer models suggest this trend will continue.
