The greenhouse effect

Heat from the sun shines onto the Earth. Short-wave solar radiation passes through the greenhouse gases, heats the earth and is re-radiated back into space as long-wave infra red – some of this is absorbed by the greenhouse gases in our atmosphere. It passes through a blanket of gases in our atmosphere.

Some of the heat energy is reflected back into space. Some of the heat energy is absorbed by the blanket of gases.

The ‘greenhouse’ gases are essential to life on Earth The ‘greenhouse’ gases are essential to life on Earth. Without them heat energy would escape back into space. Earth would be a very chilly place with an average temperature of -18°C ! Greenhouse gases include methane, nitrous oxide, water vapour and carbon dioxide.

The gases work a bit like glass in a greenhouse to trap in warmth. The greenhouse gases help to keep the temperature of the earth in balance. This process is called the GREENHOUSE EFFECT. The gases work a bit like glass in a greenhouse to trap in warmth. But the earth is getting warmer and warmer. WHY? The greenhouse effect works a bit like the glass in a greenhouse to trap in warmth. The key difference, however, is that the glass ‘traps’ in the heated air, while the greenhouse gases ‘absorb’ radiation.

Human activities are creating more greenhouse gases including carbon dioxide, CO2. As we burn more fossil fuels, for example, the blanket of greenhouse gases becomes thicker. Examples of fossil fuels – oil, coal, gas. Human activities, such as burning more fossil fuels or cutting down forests, increase the ‘concentration’ of greenhouse gases in our atmosphere.

More greenhouse gases in the atmosphere mean that more heat energy is absorbed. We call this increase in the temperature of the earth ‘global warming’.

R. A. Rohde (www.globalwarmingart.com/wiki/Carbon_Dioxide_Gallery) Graph: R. A. Rohde (www.globalwarmingart.com/wiki/Carbon_Dioxide_Gallery) What do you deduce from this graph?

“Human activities over the last 100 years, particularly the burning of fossil fuels, have caused a rapid increase in carbon dioxide and other greenhouse gases in the atmosphere. Before the industrial age, these gases had remained at near stable concentrations for thousands of years..... The rapid warming observed since the 1970s has occurred in a period when the increase in greenhouse gases has dominated over all other factors. ” Intergovernmental Panel on Climate Change, IPCC Fourth Assessment Report: Climate Change, 2007

“Models and observations show warming in the lower part of the atmosphere (the troposphere) and cooling higher up in the stratosphere.... If an increase in solar output had been responsible for the recent climate warming, both the troposphere and the stratosphere would have warmed... Such considerations increase confidence that human rather than natural factors were the dominant cause of the global warming observed over the last 50 years.” Intergovernmental Panel on Climate Change, IPCC Fourth Assessment Report: Climate Change, 2007

Think about ways that you could reduce your carbon footprint and be part of the climate-change solution! Eleven of the last twelve years have been the hottest since records started in 1858. Eleven of the last twelve years have been the hottest since records started in 1858. (The Royal Society, Climate Change controversies: a simple guide available at www.royalsoc.ac.uk (accessed June 2007))

The world’s top 10 warmest years on record have occurred since 1998. (Records began in 1858) Eleven of the last twelve years have been the hottest since records started in 1858. (The Royal Society, Climate Change controversies: a simple guide available at www.royalsoc.ac.uk (accessed June 2007))

CALL TO ACTION Caritas Australia is working with many more communities to help people affected by climate change. But Pope Francis also reminds us that Governments and every person need to be kind and fair to everyone and to our planet! “Humanity still has the ability to work together in building our common home.” [13]

What can we do? We can choose simpler and more sustainable ways to live our life. For example, we can: Reduce the amount of waste we produce, and make sure to reuse and recycle too Switch to renewable energy sources Take public transport, walk, run, cycle… Plant trees Turn off lights when not in use What other things can you think of? Photo credits: Erin Johnson

Credit Adapted from a resource produced by CAFOD