Changes

As far back as temperature records can be reconstructed, periods of global warming and global cooling have alternated; see [[ice age]]s and [[interglacial warming]].

As far back as temperature records can be reconstructed, periods of global warming and global cooling have alternated; see [[ice age]]s and [[interglacial warming]].

In the  modern period of global warming, a slight increase of {{temperature|0.8|1.4}} has been measured at weather stations throughout the world, since around 1850, when organized records began to be kept. Since this happens to correlate with increases in [[carbon dioxide]], many have speculated about their possible relationship.  Despite this, there is no completely proven model explaining the rise in global temperatures.

In the  modern period of global warming, an increase of {{temperature|0.8|1.4}} has been measured at weather stations throughout the world, since around 1850, when instrumental measurements began to be taken and organized records began to be kept. Although only a small increase in absolute terms, the temperature increase is unprecedented within at least the last 14,000 years according to the reconstructions by Viau et al. (2006) <ref>http://www.citeulike.org/user/kmcolo/article/618203 Viau et al. (2006) 'Millennial-scale temperature variations in North America during the Holocene' in Journal of Geophysical Research, 111</ref> Since this happens to correlate with increases in [[carbon dioxide]], many have speculated about their possible relationship.  Despite this, there is no completely proven model explaining the rise in global temperatures.

==Controversy==

==Controversy==