Global warming period
A global warming period is an epoch or age (usually of several centuries) in which the absolute surface average temperature of the earth is rising or reaches a peak (see global warming). There have been several such periods in recorded history, alternating with global cooling periods:
- AD 0-300 - the Roman Warm Period, when surface water temperature was as warm as the present
- AD 600-850 - a surface water temperature warming of ~3.0°C
- the Medieval Warm Period: fluctuations of 0.5-1.0°C until AD 1200
- AD 1700 to the present, SWT increased by 1.75C (the Modern Warm Period)
Needless to say, these periods of global warming were interspersed with periods of global cooling.
Various theories have been put forth to account for these temperature fluctuations. Some scientists even disagree sharply about whether such periods have existed worldwide. For instance, Michael Mann portrays global temperatures as dropping steadily over the last 1,000 years, essentially denying the existence of the Medieval Warm Period. McIntyre and McKendrick claim that Dr. Mann doctored his statistics intentionally to produce a Hockey Stick graph, possibly to justify the Kyoto protocol.