Scientists now know that Earth's climate has been much more stable and far warmer during the last 10 000 years than at any other time in the last 100 000 years. This remarkable stability has allowed human society to flourish. Even so, there have been changes in climate over this period, with far-reaching effects.

A vast sheet of ice more than 1.5 km thick covered what is now Vancouver at the peak of the last ice age 16,000 years ago. Climate warmed rapidly at the end of the ice age, melting ice sheets and creating more habitable conditions.

Global temperature change over 10000 years (Source: Mann et al., 1999, Environment Canada)

Did you know?
9000 years ago, average temperatures in southern British Columbia were 1° to 2° C warmer than today.

Did you know?
Vikings settled Greenland during a warm period, when climate was much like it is today-the so-called 'Medieval Warm Period' between 1000 AD and 1200 AD. Climate cooled in the thirteenth and fourteenth centuries, forcing Vikings to abandon their Greenland settlements.
Europe experienced unusually cold weather during the 'Little Ice Age,' which began in the thirteenth century and ended in the late 1800s.

How can we be sure that the warming of the last two decades is not related to the natural rhythm of climate?

References

Folland, C.K., Karl, T.R., and Vinnikov, K.Ya., 1990: Observed climate variations and change; in Climate Change: the IPCC (Intergovernmental Panel on Climate Change) Scientific Assessment, Cambridge University Press, p.195-238.

Mann, M.E., Bradley, R.S., and Hughes, M.K., 1999: Northern hemisphere temperatures during the past millennium: inferences, uncertainties, and limitations; in Geophysical Research Letters v. 26, no. 6, p. 759-762.