7. Changes in the carbon cycle

How is natural climate change a physical explanation for changes in the carbon cycle?

• The quaternary geological period from 2.6million years ago to now shows fluctuations between glacial and interglacial periods

• Carbon and temperatures often rise and fall in line with each other so it’s difficult to decide whether higher temperatures cause more carbon or the other way around

What happened between the 1600’s and 1800’s and what do scientists believe about it?

• A little ice age where the Thames would freeze up for up to 2 months per year

• Scientists believe this was a volcanic eruption where ash and sulphur blocked out the sun causing a cooling effect

• This reflects solar radiation back into space allowing ice sheets to grow due to the high albedo

• However, scientists disagree on when the eruptions were and some scientists just argue there was decreased radiation from the sun

How can cold conditions impact carbon stores?

• Chemical weathering processes may be more active because cold water holds more CO2

• Forest coverage may be less as soil is frozen affecting photosynthesis

• Less water would flow as it may be locked up as snow and ice on land

• Less carbon would be in the soil store as decomposers would be less effective

How can warm conditions impact carbon stores?

• Melting permafrost increasing the greenhouse effect as methane is released

• Ocean warming can decrease the solubility of CO2 in water releasing it into the atmosphere

Explain how the Earth’s eccentricity (1st Milankovitch cycle) can change the carbon cycles?

• This is the shape of the Earth’s orbit around the sun

• Usually the orbit is circular however sometimes it is more elliptical which may mean cooler conditions in the Northern Hemisphere

• Glaciers may form which will help to store carbon in the glaciers and oceans

Explain how the Earth’s axial tilt (2st Milankovitch cycle) can change the carbon cycles?

• Smaller axial tilt may promote the growth of ice sheets as the Earth is tilting further away from the sun

Explain how the Earth’s precession (3rd Milankovitch cycle) can change the carbon cycles?

• This is the Earth’s wobble as it spins on the axis

How are wildfires a physical contributor to changes in carbon cycle?

• Transfer carbon from biosphere to atmosphere. They can encourage the growth of plants long term.

• 2013 Indonesian fire saw combustion turning the forests from a carbon sink into source

• Wildfires may be started on purpose and may cause destruction of homes or health conditions

How volcanic activity is a physical contributor to changes in carbon cycle?

• Ash and sulphur dioxide have a cooling effect reflecting sunlight away from the Earth eg: Pinatubo 1991 which caused a dip in global temperatures for a year or 2

• 100-300million tonnes of carbon is released from volcanos per year

• Short term cooling, long term warming