Carbon Dioxide - Seasonal Cycles

This is an exam style question suitable for GCSE chemistry making use of real data sets showing carbon dioxide concentrations at Mauna Loa, a volcano on the island of Hawai'i in the Northern Hemisphere.

©The Royal Meteorological Society. All rights reserved.

~ 1 hour
KS4

Preparation

Download the document below and follow the step by step to share contextual information with students

What you need

Curriculum links

  • Biology
  • Chemistry

Location

  • Indoors

Step by step

The questions in the document support students to explore the idea that there is a seasonal cycle in carbon dioxide in the atmosphere, because plants take up carbon dioxide during photosynthesis in the spring and summer, which is then released back into the atmosphere when plants die and leaves rot in the autumn and winter.

Carbon dioxide is a well mixed gas, meaning that the data recorded at Mauna Loa is representative of the Northern Hemisphere, and that at the South Pole is representative of the Southern Hemisphere.

The seasons are out of phase with each other – when it is summer in the Southern Hemisphere, it is winter in the Northern Hemisphere.

As there is far less vegetation in the Southern Hemisphere than in the Northern Hemisphere, the seasonal cycle is much smaller.

Students may notice that there could also be a human element to the cycle – we burn more fossil fuels in the winter than in the summer (and there are also fewer people in the Southern Hemisphere).

The correct answer for the mean is 416.1 parts per million.

As well as the seasonal cycle, the graph provided shows the increase in atmospheric carbon dioxide since 1958. This increase is because of the emissions of carbon dioxide by human activities including land use change including deforestation, burning fossil fuels and cement production. 

Mount Loa