Reactions between rocks, rain and carbon dioxide in the atmosphere have helped to stabilize the climate throughout Earth’s history, but they won’t help prevent our carbon emissions from causing severe warming, a new study shows. However the results could help us find better ways to trap CO2 and slow climate change.
Over a million years on Earth, gas emissions from volcanoes should have nearly tripled the concentration of carbon in the atmosphere and ocean. Such an increase in CO2 should have caused my higher temperatures. Instead, the climate has remained relatively stable and allowing liquid water to persist and life to flourish.
This stability is mostly due to removal of CO2 by the weathering process, says Susan Brantly at Pennsylvania State University. Basically, this starts when CO2 gas reacts with rainwater to form carbonic acid, which dissolves rock such as limestone. This rock erosion causes the production of soluble minerals and bicarbonate – a dissolved form of carbon. These products are then washed into the oceans, where they form carbonate minerals that eventually lock the carbon away in rock.
Previous research has shown that chemical weathering may speed up in higher temperatures, taking more CO2 out of the atmosphere and thus acting to control the climate, like a thermostat. Brantley and her colleagues wanted to determine if this was always true.
With all this data, the researchers were able to determine that chemical weathering is only particularly temperature sensitive in areas with high rainfall and high rate of rock erosion due to this rainfall. This means that natural rock weathering is too slow to counteract the vast amounts of CO2 being released by human activities.