1.3.3 Effects of the Carbon Cycle

Question 1

Effects of the carbon cycle on the atmosphere and climate

Answer 1

• The carbon cycle affects the amount of gases containing carbon (e.g. CO2 and methane) in the atmosphere. These are greenhouse gases – they trap some of the Sun’s energy, keeping some of the heat in and keeping the planet warm.
• As the concentrations of greenhouse gases in the atmosphere increase (e.g. due to changes in the carbon cycle caused by human activities such as deforestation and the burning of fossil fuels) temperatures are expected to rise. This is climate change.
• Changes in temperature across the globe will affect other aspects of the climate, for example, more intense storms are predicted.

Question 2

Effects of the carbon cycle on the land

Answer 2

• The carbon cycle allows plants to grow – if there was no carbon in the atmosphere, plants could not photosynthesise. If there was no decomposition, dead plants would remain where they fell and their nutrients would never be recycled.
• Changes in the carbon cycle can reduce the amount of carbon stored in the land, for example, warmer temperatures caused by global warming are causing permafrost to melt. This releases carbon previously stored in the permafrost into the atmosphere.
• An increase in global temperatures could also increase the frequency of wildfires.

Question 3

Effects of the carbon cycle on the oceans

Answer 3

• As part of the carbon cycle, carbon dioxide is dissolved directly into the oceans from the atmosphere.
• CO2 in oceans is used by organisms such as phytoplankton and seaweed during photosynthesis and by other marine organisms to form calcium carbonate shells and skeletons.
• Increased levels of CO2 in the atmosphere can increase the acidity of the oceans because the oceans initially absorb more CO2. This can have adverse effects on marine life.
• Global warming can also affect oceans. For example, organisms that are sensitive to temperature (e.g. phytoplankton) may not be able to survive at higher temperatures, so their numbers decrease. This means that less CO2 is used by them for photosynthesis, so less carbon is removed from the atmosphere.
• Warmer water is also less able to absorb CO2, so as temperatures rise the amount of CO2 that could potentially be dissolved in the sea decreases.