Below is a graph of atmospheric CO₂ levels measured at Mauna Loa Observatory, Hawai’i.

Explain the observed changes in atmospheric CO₂ concentration from 1960 to 2005.

Outline the precautionary principle.

(from 1960–2005) atmospheric CO₂ concentration increases/strong positive trend / increase between 1960–2005 of 65 ppm/figures to that effect;
CO₂ released by human activities contributes to the increase;
examples of human activities e.g. combustion of fossil fuels / deforestation;
seasonal/annual fluctuations (do not prevent long-term increase);

some human-induced change can be very large/perhaps catastrophic;
those responsible for the change must prove it will cause no harm before proceeding;
appropriate (environmental/medical etc.) example e.g. companies must immediately reduce emission of greenhouse gases even though proof of human impact on global warming is still debated;
is reverse of historical practice / previously those concerned about change had to prove it will do harm to prevent such changes from going ahead / paradigm shift;

Few candidates gained three marks. The increasing trend of atmospheric CO₂ was commonly given with the combustion of fossil fuels as the reason. Sometimes, there was no explanation at all. Many candidates reported the seasonal/annual fluctuations in the trend.

It was clear that many candidates had never heard of the precautionary principle and guessed at the answer. Conversely, there were candidates who wrote terrific answers which got at the heart of the answer, i.e. that those responsible for change must prove it will cause no harm before proceeding. Good examples were limited.