There was bleak, though not unexpected, news coming out of the World Meteorological Organization yesterday. Average levels of carbon dioxide in the atmosphere had reached 400 parts per million (ppm) in the early months of 2015, a rise of 43 percent over pre-Industrial levels (when we were at 278 ppm). While the atmospheric concentration ebbs and flows with the seasons, WMO officials say the planetary average is expected to remain above 400 ppm beginning in 2016. This is especially worrisome since many scientists contend that concentrations need to stay well below 400 ppm in order to avoid major disruptions to the earth’s climate – hotter temperatures, more extreme weather events, sea level rise and consequences for all living things.

This report comes just a few weeks before representatives of 190 countries are due to meet in Paris to work on an international treaty to reduce greenhouse gases. The United Nations Conference on Climate Change (COP21 – November 30-December 11) provides a teachable moment on the challenges of reaching an accord that all countries can endorse. Energy use varies widely around the globe, leading less developed countries to place the blame for climate change squarely on the shoulders of more industrialized countries. Meanwhile, tropical rainforests (the lungs of the earth) are being clear-cut and burned in Brazil and Indonesia, removing a vital carbon sink. The effects of climate change will be felt everywhere, but some countries are especially vulnerable to sea level rise, droughts, floods, hurricanes and monsoons.

Our new lesson, Carbon Crunch, illustrates the competing interests of different countries as our atmosphere and climate changes. Have students read about the concept of a “carbon budget” and discover how different countries compare in their vulnerability (and coping ability) to future climate trends. The lesson is one of six featured on our new interactive website, www.WorldPopulationHistory.org. The site also features a population map with overlays to show changes in carbon emissions, land use and vital statistics around the globe as the population has changed since the pre-Industrial times. The lesson puts today’s science in and social perspective and engages secondary students in today’s headlines.