To understand how Carbon Dioxide (CO2) is contributing towards global warming, we need to start with how the planet is heated by the sun. Because it is so far away, light from the sun takes around 8 minutes and 20 seconds to reach the Earth, and makes a journey through our atmosphere to the ground. It first has to get past the clouds, as these can reflect the sun’s rays back out into space. Other large spaces of white such as glaciers and snow covered fields will also reflect sunlight back (that’s why it is good to wear white in the summer to keep cool). Therefore around 70% of the energy makes it past the clouds, and down to the Earth’s surface. The energy that makes it to the ground heats up the oceans, buildings and the ground. Then a proportion of energy is radiated back out into space. The rest is trapped on Earth by particles in the atmosphere like water vapour, methane particles and CO2 molecules.
All of the above is known as the greenhouse effect, and if you have ever been in a garden greenhouse, you will know that they trap in a lot of heat to help the plants stay healthy throughout colder times.
The way in which CO2 contributes towards the greenhouse effect, is that CO2 is one of the greenhouse gasses and can absorb radiation given off by the earth. The radiation from the sun is in wavelengths shorter than 4,000 nanometers, however the radiation reflected by earth objects back out to space have a wavelength of more than 4,000 nanometers. CO2 is good at absorbing radiation with wavelengths of 4,000 or more, and so it traps the heat in. We need a certain amount of CO2 in the atmosphere to keep the earth warm (otherwise it wouldn’t be habitable), but too much could see us getting too warm, and causing serious issues. This phenomenon is called ‘Global Warming’.
Current levels of CO2 in the atmosphere are around the 400 parts per million mark, which is a 40% increase since the industrial revolution. This higher level of CO2 has been linked to an increase in the temperature of the earth, and has said to be a contributing factor towards freak weather conditions and disasters.
What’s clear is that we need to reduce our CO2 emissions for the sake of future generations, and we can turn to any number of renewable technologies to do so.
Because light takes 8 minutes 20 seconds to reach Earth, during sunset, when the bottom of the sun is sitting on the horizon, the top of the sun has actually already dipped below the horizon line.