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In addition to the natural carbon cycle comes anthropogenic (human) emissions through the combustion of fossil fuels like coal and oil products.
Organic material that rots, or burning of paper, wood and other material also release CO2.
Some of the oil-exporting countries in the Middle East and the USA have the world record in CO2 emissions with more than 20 tonnes of CO2 per person per year.
Average emissions per capita in Europe is roughly 10 tonnes. Global average is 3,9 tonnes.
CO2 is responsible for approximately 55% of the human induced enhanced greenhouse effect, and has an "adjustment time" of more than 100 years.
Annual increase of atmospheric CO2 is about 0.5-1%.
  1. The cycles

    In previous times, 300-400 million years ago, the amount of CO2 in the atmosphere was much higher than today, giving our planet a very different climate compared to that of our times. Through natural cycles, this huge amount of carbon was over the eons stored in long term storage in the form of coal and oil a very long time before humans appeared on Earth.

    We are now experimenting with recreating the jurassic climate by moving huge amounts of carbon from long-term storage to rapid carbon cycles.
    We might actually manage to recreate climate as it was 150-250 million years ago.
    The pre-Jurassic climate was much warmer than today, with no snow and glaciers at the poles, bathing temperature at the North pole, sea level up to maybe 300 meters higher, and very different ecological habitats, many of them rather hostile to the present human civilisation.
    This very warm climate existed, even if the solar input at that time was more than 10% weaker than today.

    Nature needed about 200 million years to move large amounts of carbon-containing greenhouse gases from the atmosphere into the ground. Human civilisation now puts it back into the atmosphere using less than 200 years.

    Multimedia om jordas klima (Forskning .no)

    Understanding Earth's Deep Past:
    Lessons for Our Climate Future (National Academic Press)

    Carbon release, global warming now and in the ancient past

    Carbon release 10 times faster than in the past: PETM 55 million years ago

    Graphic by UNEP/GRID-Arendal:
    Climate graphics library (UNEP/GRID-Arendal

    Read more:
    Carbon, carbon everywhere (UNEP/GRID-Arendal