During millions of years the atmosphere has remained the same. It can change when, for example, when ashes and hot gases erupt from an active volcano. This can block sunlight for years or cause temperatures to change. 

In the past centuries people have also caused great changes in the atmosphere.  

  • More and more grazing animals produce methane gas.
  • Fossil fuels like coal, oil or gas produce carbon dioxide which leads to the greenhouse effect. This gas makes the atmosphere denser and it traps the heat.  
  • CFCs that come from air conditioning, spray cans or burning plastic get into the atmosphere and endanger the ozone layer.
  • Sulfur dioxide and nitrogen oxide are emitted into the atmosphere by industries and cars. These gases can combine with water in the air and produce what is called acid rain. It pollutes lakes and damages buildings and other structures.



air pollution caused by cars in Prague

Air pollution caused by cars in Prague
Image: Martin Vorell, Public Domain 




 

Words

  • acid rain = rain that has chemicals in it and can damage the world around us  
  • block = keep out
  • carbon dioxide = gas that is produced when we breathe out or when carbon is burned
  • cause = lead to
  • century = a period of a hundred years
  • CFC = chlorofluorocarbons = a gas that damages the ozone layer; it is in refridgerators an spray cans 
  • combine = to get together with
  • damage = destroy, harm
  • dense = many objects that are close together, in a small area
  • emit = to send out
  • endanger = to put in danger
  • erupt = to break out with a lot of power
  • fossil fuels = energy like coal or oil that is produced by dead animals and plants in millions of years 
  • graze = animals eat grass in the fields
  • methane = a gas that you cannot smell or see; it can be burned to give heat
  • nitrogen oxide = when you combine nitrogen and oxygen
  • pollute = to make air, water etc.. dirty so that we cannot use it
  • remain = stay
  • spray can = can from which you can spray paint onto things
  • sulpher dioxide = a gas that is very poisonous 
  • trap = keep something in the same place and not let it out