What Causes Climate Change?
The primary cause of the current climate change is burning of fossil fuels, which releases large amounts of carbon dioxide into the atmosphere. Globally, over 30 billion tonnes of carbon dioxide from fossil fuels are emitted annually. It would take over 1 trillion new trees every year to take in that much carbon dioxide.
Carbon dioxide is a very stable gas, and it can remain in the atmosphere for centuries. Carbon dioxide in the atmosphere retains heat, and as carbon dioxide increases in the atmosphere, more heat is retained, warming the Earth and affecting the energy flows that affect temperature, winds and precipitation around the globe.
Human civilization developed during a relatively stable climate period in the past several thousand years when Earth’s atmosphere typically contained about 280 parts per million of carbon dioxide, and levels fluctuated within a range controlled by natural processes, including the cycling of carbon among animals, plants, and the atmosphere, soils, and oceans. Earth’s species and ecosystems developed and were highly adapted to those conditions.
In the 18th century, humans began to burn coal, and later oil and natural gas in large quantities. This fossil carbon, that had been sequestered for millions of years, was suddenly released into the atmosphere, disrupting the balance in the carbon cycle. Atmospheric carbon dioxide levels began to increase, and are now above 400 parts per million and still rising.
Other gases, including methane, nitrous oxide, the chemicals used in refrigeration and in many industrial processes, also contribute to atmospheric warming, but carbon dioxide is by far the most important.