Changes in the carbon cycle over time, to include natural variation (including wild fires, volcanic activity) and human impact (including hydrocarbon fuel extraction and burning, farming practices, deforestation, land use changes).

Changes in the carbon cycle over time In this section: You must understand: The changes to carbon cycle over time, to include natural variation and human impact. Student must be able to describe, explain, analyse and comment on factors leading to change including: wild fires, volcanic activity, hydrocarbon fuel extraction and land use changes

The graph shows a mirroring pattern High temperatures are associated with higher levels of Co2 Recent rise in Co2 – Due to anthropogenic changes which means level surpass 400PPMV An increase in Co2 in the atmosphere enhances the greenhouse effect which then increases the temperatures Lower levels of Co2 reduces the effectiveness of the greenhouse effects which leads to global cooling Both examples of positive feedback mechanisms Carbon dioxide levels can trigger temperature change although temperature change also has massive impacts on Co2 levels in the atmosphere.

Wildfires Can be started naturally by lightening strikes Despite being restricted to tiny parts of the surface, they can have regional impacts 1997-8 and in 2003, Indonesia had lots of wild fires that burnt out of control for months Smoke spread across south-east Asia Released large amount of Co2 into the atmosphere – noticeable strike in carbon emissions Turned forests into a carbon source (compared to a carbon sink) – combustion returns carbon back to the environment

Volcanic activity Returns carbon that has been trapped in the lithosphere for millions of years During Palaeozoic era (542-251 million years ago), volcanoes were much more active than they were today Carbon dioxide was therefore emitted into the atmosphere, where it remained for a very long time. At present, volcanoes emit between 130 and 180 million tonnes of Co2 each year, by comparison, human activities release 30 billion tonnes as a result of burning fossil fuels Volcanoes also erupt lava, which contains silicates that will slowly weather. This converts carbon dioxide in the air to carbonates in solution. In this way, carbon dioxide is absorbed very slowly from the atmosphere.

Assess the extent to which natural factors impact the carbon cycle over time. (20 marks)