The document discusses the Medieval Warm Period between approximately 900-1300 AD. It provides evidence from historical records of warmer conditions in parts of the world during this period compared to later centuries. Climate data from central England and temperatures in Europe are discussed. While some regions like China were cooler, other areas like South Japan and Western Europe experienced warmer temperatures during this time compared to after 1300 AD, known as the Medieval Climate Optimum. There is debate around the extent and causes of warming, with more evidence needed to fully understand natural variability compared to potential human influences on climate.

1. GEOG5426 Megadrought II

2. MEDIEVAL
WARM
PERIOD

4. Professor Hubert H. Lamb University of East Anglia

5. Climate Research Unit University of East Anglia

6. And multifarious evidence of a meterological
nature from historical records in various parts of
the world from the Arctic to New Zealand... has
been found to suggest a warmer epoch lasting
several centuries between about A.D. 900 or
1000 and about 1200 or 1200.”
“
Lamb 1965. The early medieval warm epoch and its sequel.

8. Mildness or severity of
winter weather
Raininess or drought in
July and August
Winter severity index
High summer wetness
index
DJF temperature (°C)
JA precipitation
(% of average)

9. Temperatures prevailing in central England, 50-year averages Lamb, 1965

10. Summer temperatures prevailing in central England, 50-year averages Lamb, 1965

11. A prevailing warm epoch with dry anticyclonic character,
especially in summer, in temperate Europe between
about 1000 and 1300 A.D. appears to be confirmed.”
“
Lamb 1965. The early medieval warm epoch and its sequel.

12. Intergovernmental Panel on Climate Change
Climate Change: The IPCC Scientific Assessment
1990

13. Schematic diagram of global temperature variations since the last thousand years. IPCC 1990

14. The do ed line nominally represents
conditions near the beginning of the
twentieth century.”
“
Schematic diagram of global temperature variations since the last thousand years. IPCC 1990

15. Chapter 7. Observed Climate Variation and Change. IPCC 1990.
The late tenth to early thirteenth centuries (about
AD 950-125) appear to have been exceptionally
warm in western Europe, Iceland and Greenland
(Alexandre 1987, Lamb 1988). This period is known
as the Medieval Climatic Optimum. China was,
however, cold at this time (mainly in winter) but
South Japan was warm (Yoshino, 1978).”
“

16. The problem is confounded by numerous studies that
have used the term “Medieval Warm Period” for any
climatic anomaly that occurred at some time in the
historical Medieval period (500 to 1500 A.D.)—even if
the record is unrelated to temperature.
Bradley et al, 2003, Science
“

17. The warmest 30-year periods prior to AD 1970. Bradley et al., 2003

18. The balance of evidence does not point to a High
Medieval period that was as warm as or warmer than
the late 20th century. However, more climate records
are required to explain the likely causes for climate
variations over the last millennium and to fully
understand natural climate variability, which will
certainly accompany future anthropogenic effects on
climate.
Bradley et al, 2003, Science
“

19. Goosse et al., 2006
solar irradiance
volcanic forcing
CO2 concentration
forest cover
aerosol load

20. Goosse et al., 2006
Solar irradiance

21. Goosse et al., 2006
Volcanic forcing

22. Goosse et al., 2006
CO2 concentration

23. Goosse et al., 2006

24. The term “Medieval Warm Period”, of limited meaning at
hemispheric scale, nonetheless thus appears reasonable
as applied specifically to summer European temperatures,
the region the term was originally applied to.”
“
Goosse 2006. The origin of the European “Medieval Warm Period”.

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