Waskita Adijarto

Dalam 2000 tahun terakhir, bumi pernah mengalami zaman yang lebih hangat, yaitu zaman 'Medieval Warm Period' atau 'Perioda Pertengahan Hangat' , dan juga zaman yang lebih dingin yaitu 'Little Ice Age' atau 'Zaman Es Kecil'.

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Sumber: http://gcrio.org/CONSEQUENCES/winter96/article1-fig1.html
Figure 1 Example of regional variations in surface air temperature for the last 1000 years, estimated from a variety of sources, including temperature-sensitive tree growth indices and written records of various kinds, largely from western Europe and eastern North America. Shown are changes in regional temperature in° C, from the baseline value for 1900. Compiled by R. S. Bradley and J. A. Eddy based on J. T. Houghton et al., Climate Change: The IPCC Assessment, Cambridge UniversityPress, Cambridge, 1990 and published in EarthQuest, vol 5, no 1, 1991.