Oxygen isotopic ratios in the dating of ice cores

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However, they provide no direct analogue for the future because the ice core era contains no periods with concentrations of CO2 comparable to those of the next century.O ensures that it passes more readily into the liquid state than water vapour made up of the lighter oxygen isotope (Dansgaard, 1961).Its concentration is now much more than double its pre-industrial level.This is mainly due to the increase in emissions from sources such as rice fields, ruminant animals and landfills, that comes on top of natural emissions from wetlands and other sources.

Ice cores provide direct information about how greenhouse gas concentrations have changed in the past, and they also provide direct evidence that the climate can change abruptly under some circumstances.It is believed that the warmings out of glacial periods are paced by changes in Earth’s orbit around the Sun, but the tiny changes in climate this should cause are amplified, mainly by the resulting increase in CO, and by the retreat of sea ice and ice sheets (which leads to less sunlight being reflected away).Looking at the warming out of the last glacial period in detail, we can see how remarkably closely Antarctic temperature and CO that was not accompanied by an increase in temperature.Ice core measurements allow us to extend this way back into the past.In an Antarctic core (Law Dome) with a very high snowfall rate, it has been possible to measure concentrations in air from as recently as the 1980s that is already enclosed in bubbles within the ice.

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