15 Carbon Dioxide in Prehistoric times CO2 levels in the early Cenozoic Era (~65 Myr ago) were 4 to 5 times higher than they are today. Some have speculated that the uplift of the Tibetan plateau resulted in increased weathering and a draw down of atmospheric CO2 levels bringing us into our present ice age state.
16 Climate and the carbon cycle have many time scales of interest.
17 The last Glacial Maximum occurred around 18,000 years ago
19 Preindustrial levels of CO2 were 280 ppm and remained so until ~1800 Preindustrial levels of CO2 were 280 ppm and remained so until ~ Present values are around 383 ppm a 37% increase over preindustrial times. There has been a 70 ppm increase since
26 Because of long time delays for the carbon cycle, drastically different scenarios yield very similar results for a 20 year time horizon, but drastically different result for a 50 to 100 year time horizon.
27 Recent results suggest that world wide emissions of carbon from fossil fuel use is growing at a rate corresponding to the largest projected emission scenario suggested by the 2001 IPCC report.
28 For the past 30 to 35 years emissions have been closely linked to population.