During the Medieval Warm Period, wine grapes were grown as far north as England, where growing grapes is now not feasible and about 300 miles (500 km) north of present vineyards in France and Germany. Grapes are presently grown in Germany up to elevations of about 1800 ft (560 m), but from about 1100 to 1300 AD, vineyards extended up to about 2500 ft (780 m), implying that temperatures were warmer by about 2–2.5°F (1–1.4°C). Wheat and oats were grown around Trondheim, Norway, suggesting that the climate was about 2°F (1°C) warmer than present (Fagan, 2007).
Oxygen
isotope data from the GISP2
Greenland ice core clearly show a prominent MWP (Fig. 21.8 ) between 900 and 1300 AD. It was followed by global cooling and the beginning of the Little Ice Age
Summer sea surface temperatures near Iceland (Sicre et al., 2008 ).
One example among many is the study of
tree rings in China (Fig. 21.10; Liu et al., 2011).
Comparison of Greenland temperatures, the Bermuda Rise sea surface temperatures (SST) (Keigwin, 1996), and west African and a sea surface temperature (deMenocal
et al., 2000) for the last 2500 years. LIALittle Ice Age; MWPMedieval Warm Period. Solid triangles indicate radiocarbon dates.