What are greenhouse gases?
Greenhouse gases are gases such as carbon dioxide, methane and water vapor which are present in our atmosphere and capable of trapping heat.
How do greenhouse gases warm the planet?
We have to keep in mind that the Earth’s atmosphere, water mass, surface and ecosystems constantly interact with each other, behaving much like a living community.
Weather and climate result from the interaction of this living community with solar energy, which is why understanding this interaction is so important for us.
Before reaching the Earth’s surface a portion of solar energy is absorbed, reflected or scattered back to space by clouds and other atmospheric particles. On average, only about half of the sun’s radiation actually reaches the surface of the Earth where it is absorbed by land, oceans, and vegetation. Due to the absorbed solar radiation these then heat, causing them to radiate energy back into space.
When the Earth’s surface radiates energy back into space, gases such as carbon dioxide, methane and water vapour in the atmosphere, absorb a large portion of this energy. These gases then warm up and re-radiate energy back to the Earth’s surface where it is again absorbed, causing additional heating of the ground surface, which then once again radiates energy back into the atmosphere, repeating the cycle again and again.
In this way, the atmosphere maintains a higher surface temperature than the Earth would have without an atmosphere. This process is called the greenhouse effect.
Why are greenhouse gases good for us?
Earth would be a lot colder, and quite inhospitable, if greenhouse gases in the atmosphere did not exist, so this greenhouse effect is actually beneficial to us.
So what’s the problem with greenhouse gases?
Analysis of ice cores clearly shows a relationship between atmospheric methane and carbon di0xide levels and global temperatures. The higher the concentration of these gases, the warmer the planet.
Ice cores show that carbon dioxide levels now are greater than over the past six hundred fifty thousand years and that they have risen thirty percent over the last hundred and fifty years alone.
Today carbon dioxide levels are more than four hundred parts per million, far above carbon dioxide levels ever registered since human beings evolved.
This enormous rise has taken place in a very short time.
Shorter ice cores from Antarctica and Greenland have shown that between 1000 AD and the mid-1800s Carbon Dioxide levels remained fairly constant at about two hundred ninety parts per million.
Since then Carbon Dioxide levels have been steadily rising in pace with the industrial revolution and accompanied by a steady rise in global temperatures.
Analysis of air bubbles trapped in ice sheets also indicates that methane is more abundant in the Earth’s atmosphere now than at any time during the past four hundred thousand years and that methane concentrations in the atmosphere have increased by more than one hundred and fifty percent since 1750.
Studies have shown that methane is about twenty times as effective as carbon dioxide at trapping heat in the atmosphere.
Because carbon dioxide and methane levels have increased spectacularly since the industrial revolution we can be pretty certain humans are to blame for a large part of this dramatic increase in atmospheric greenhouse gases, which is disturbing the natural interaction of Earth’s ecosystems, causing the temperature to rise above its natural balance.