1. Topic 5.2
The greenhouse effect

2. Estimated major stores of carbon on the Earth
5.2.1 The Carbon Cycle
Carbon exists in many forms:
Atmospheric gases (CO2 and methane)
Dissolved CO2 in aquatic ecosystems
Organic carbon in living organisms
Carbon deposits in the lithosphere, as minerals (carbonates) or fossil fuels.
Estimated major stores of carbon on the Earth
What are the sources of atmospheric CO2?
What is the sink of atmospheric CO2?
Which processes return C to the lithosphere?
Respiration, Decomposition, Diffusion, burning of fossil fuels (combustion)
Producers and fossil fuels - photosynthesis, some diffusion into aquatic systems
Decomposition of organic matter, marine deposits of carbonates

3. 5.2.1 The Carbon Cycle

4. 5.2.2 Analyse the change in concentration of atmospheric CO2 using historical records

5. 5.2.2 Analyse the change in concentration of atmospheric CO2 using historical records
These measurements indicate a rise in annual average atmospheric CO2 concentrations, from parts per million by volume (ppmv) in 1992 to ppmv in 2006, or an increase of almost 1.75 ppmv per year, on average.

6. 5.2.3 Relationship between CO2 and other
gases and the enhanced greenhouse effect

7. 5.2.3 Relationship between CO2 and other
gases and the enhanced greenhouse effect

8. 5.2.3 Relationship between CO2 and other
gases and the enhanced greenhouse effect.
Elevated levels of greenhouse gases are strongly correlated with an enhanced greenhouse effect:
As levels of CO2, methane, water vapour and oxides of nitrogen increase, more radiation is reflected back to Earth instead of being lost to space.
Although we see correlation, where do scientist find the evidence for a causal relationship?

9. 5.2.3 Relationship between CO2 and other
gases and the enhanced greenhouse effect.
The focus on CO2 is understandable because it remains in the atmosphere for extended lengths of time, it is produced in huge quantities and it is familiar and easy to communicate its importance to the public.
Which gases in the table have the potential to cause the most damage?

10. 5.2.4 Outline the precautionary principle
So they key issue is this: we suspect that human activity leads to climate change. We are still collecting data to support (or refute) this hypothesis, and the evidence is growing stronger and stronger that anthropogenic climate destabilisation is true. In the meantime, should we wait for more evidence before taking action or should we take preventative and remedial measures now, in order to get a ‘head start’?

12. 5.2.5 Evaluate the precautionary principle

14. 5.2.6 Consequences of a global temperature rise on arctic ecosystems.
Increased rates of decomposition of detritus previously trapped in permafrost,
Expansion of the range of habitats available to
Temperate species,
Loss of ice habitat,
Changes in distribution of prey species affecting higher trophic levels
Increased success of pest species, including pathogens