How changes to the carbon cycle affect global climate

Carbon dioxide is essential in the earth’s atmosphere to produce a planet habitable for life. Its capacity to absorb short-wave solar radiation has generated a temperature suitable for life to develop at this distance from the sun.

However, anthropogenic (human) activity, particularly since the start of the Industrial Revolution, has resulted in increasing amounts of CO2 being released and a reduced capacity for natural systems to absorb it into other stores.

Fossil fuels are naturally sequestered stores of carbon accumulated over millions of years and locked away in sub-surface strata for yet more millions of years.

But exploiting them and burning them in large quantities for the past 200 years, human activity is effectively taking carbon from a long-term store of the slow carbon cycle, and creating a huge input into the fast carbon cycle.

The input of CO2 into the atmosphere from the burning of coal, oil and gas is faster than natural processes can remove it. There is evidence that plant growth increases with higher atmospheric CO2 levels, but only to a point and this levels off quite rapidly.

Oceans have absorbed the bulk of human-generated CO2, but that rate is also thought to be slowing as phytoplankton thrive in cooler water and by rising ocean temperatures, their photosynthesis is reduced. In addition, increasingly acidic seas make it more difficult for molluscs and shell-forming marine creatures to extract the bicarbonate ions they need to convert into calcium carbonate.