Introduction to Greenhouse Gas Emissions

​​What does a concentration of 416 ppm mean?

When measuring gases (like carbon dioxide), the term "concentration" is used to describe the proportion of a gas by volume in the air. One part per million (by volume) is equal to one volume of a given gas in a million volumes of air:

So, here it’s:    416 / 1,000,000

How greenhouse gases warm the earth

• Absorbing energy from the sun
• Slowing the rate at which the energy escapes to space

What are the ways in which greenhouse gases differ from each other?

The two main ways in which these gases differ from each other are their ability to:

• Absorb energy (radiative efficiency)
• How long they stay in the atmosphere (lifetime)

How long do greenhouse gases stay in the air?

CO2 gas can actually stay in the atmosphere for thousands of years rather than 100 years

• Methane gas has a GWP of 28 to 36 times that of the CO2 equivalent. This is because methane absorbs much more energy than CO2 - but lasts about 10 years in the atmosphere.
  
  
• Nitrous Oxide has a GWP of 265- 298 times the CO2 equivalent and remains in the atmosphere for more than 100 years on average.
  
  
• The three main categories of Chlorofluorocarbons and their cousins are the worst - with GWPs thousands or tens of thousands of times the CO2 equivalent. This is because for a given mass, they trap substantially more heat than CO2.