Most of the energy from the Sun passes through Earth ’ s atmosphere . Some of the purple and blue light is scattered by nitrogen molecules – which is why our sky looks blue . Most of the remaining shortwave energy ( ultraviolet and visible violet ) is absorbed by the Earth , warming it up .
Some of the longer wavelengths are reflected off the Earth and back out into space . It ’ s important that this happens , or the planet could overheat , but , if too much heat escaped , the temperature could drop too low to sustain life .
So what keeps our planet at the right temperature ?
The answer is greenhouse gases , including water vapour , methane , nitrous oxide and carbon dioxide . They work the same way as the glass in a greenhouse , helping to trap warmth . We need the correct amount of these gases to keep the temperature stable .
Want to have a positive impact on the environment ?
Check out Random Acts of Green ( RAOG ), a free app that helps you to reduce the amount of greenhouse gases ( GHG ) released by your actions . You can earn points for choosing to walk , eating meat-free for a day , refusing single-use plastic and lots of other challenges from everyday life . It shows you that small changes can add up … and recording them really helps you to make permanent changes in your life .
The most important greenhouse gas is carbon dioxide ( CO 2 ). The atmospheric concentration of CO 2 has increased by about a third since the Industrial Revolution , but the biggest changes have happened since 1950 . Humans have caused some of this by cutting down trees and clearing land for both agriculture and building . A major contributor has been the burning of fossil fuels ( crude oil , coal and gas ) to power vehicles , buildings and machinery .
When we burn fossil fuels , their carbon ( C ) combines with the oxygen ( O ) in the air to make CO 2 . The more people there are on the planet , and the more stuff we all consume , the more we burn fossil fuels . This makes more CO 2 , which can trap more heat in the atmosphere . This process has lots of names , including the human enhanced greenhouse effect , global warming , climate change , the climate crisis and the climate emergency .
Climate change is much more complex than just a temperature rise , and it ’ s caused by more factors than just CO 2 levels . You can read more about it at the Young People ’ s Trust for the Environment : https :// ypte . org . uk / learn .
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Words : Sarah Bearchell . Illustration : Nick Taylor