geplukt van wikipedia:
"Five hundred million years ago carbon dioxide was 20 times more prevalent than today, decreasing to 4-5 times during the Jurassic period and then slowly declining with a particularly swift reduction occurring 49 million years ago.[21][22] Human activities such as the combustion of fossil fuels and deforestation have caused the atmospheric concentration of carbon dioxide to increase by about 35% since the beginning of the age of industrialization.[23]
Up to 40% of the gas emitted by some volcanoes during subaerial eruptions is carbon dioxide.[24] It is estimated that volcanoes release about 130-230 million tonnes (145-255 million tons) of CO2 into the atmosphere each year. This is about a factor of 1000 smaller than the sum of the other natural sources and about factor of about 100 smaller than the sources from human activity. Carbon dioxide is also produced by hot springs such as those at the Bossoleto site near Rapolano Terme in Tuscany, Italy. Here, in a bowl-shaped depression of about 100 m diameter, local concentrations of CO2 rise to above 75% overnight, sufficient to kill insects and small animals, but warm rapidly when sunlit and disperse by convection during the day.[25] Locally high concentrations of CO2, produced by disturbance of deep lake water saturated with CO2 are thought to have caused 37 fatalities at Lake Monoun, Cameroon in 1984 and 1700 casualties at Lake Nyos, Cameroon in 1986.[26] Emissions of CO2 by human activities are currently more than 130 times greater than the quantity emitted by volcanoes, amounting to about 27 billion tonnes per year.[27]"
500 miljoen jaar geleden was het CO2-gehalte 20x hoger. Dat vind ik best extreem. Lag dat grote gehalte aan continue vulkanische activiteit (over een hele lange periode)?
Laatste punt: de continenten zoals we ze nu kennen dateren van minder dan 10 miljoen jaar geleden. Kunnen we stellen dat het CO2-niveau en temperatuur nooit eerder zo hoog waren? Ik weet niet hoever men kan terugkijken via het onderzoek van zuidpoolijs etc.
Grts
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