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Thermal maximums

Global paleogeographic reconstruction of the Earth during an ice-free period in the late Cretaceous 90 million years ago.

Ron Blakey, NAU Geology

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The Cenozoic Era: Climate in the last 65 Million Years Last Updated on 2010-12-18 00:00:00 The most extreme climate event of the modern era (the Cenozoic—65 Ma to the present) was the Late Paleocene Thermal Maximum, which occurred at around 55 Ma. [1] Apparently, deep-sea temperatures were warming gradually when methane hydrates (ice containing CH4) in seafloor sediments melted and belched massive amounts of CH4 into the atmosphere. [2] Addition of this greenhouse gas to the already high levels of CO2 (approximately 0.2%) triggered a global warming of 5°C to 7°C over about 10,000 years. [3] Recovery was slow, taking over 100,000 years from the onset of the event. Support for this interpretation derives from the gradual decline in ?18O and ?13C values during the Paleocene (evident in drill core samples from deep-sea bed sediments), interrupted by a precipitous drop in both measures; the drop in ?18O values reflects a temperature spike, whereas that in... More »
Glacier Last Updated on 2010-05-08 03:07:36 Introduction to Glaciation     Various types of paleoclimatic evidence suggest that the climate of the Earth has varied over time. The data suggest that during most of the Earth's history, global temperatures were probably 8 to 15° Celsius warmer than they are today. However, there were periods of times when the Earth's average global temperature became cold; cold enough for the formation of alpine glaciers and continental glaciers that extended in to the higher, middle and sometimes lower latitudes. In the last billion years of Earth's history, glacial periods have started at roughly 925, 800, 680, 450, 330, and 2 million years before present (B.P.). Of these ice ages, the most severe occurred at 800 million years ago when glaciers came within 5 degrees of the equator. The last major glacial period began about 2,000,000... More »