Before we start discussing strategies to mitigate emissions, let’s address a fundamental question: How Do We Measure CO2 Emissions?
Let’s start with the fundamental unit used globally for measuring CO2 emissions, the tonne. You’ll probably notice right away that we wrote ‘tonne’ rather than ‘ton.’ Why is that? Both “ton” and “tonne” are units of weight, but a “ton” is a British and American measure, while a “tonne” is a metric measure.
A “tonne” is equal to 1,000 kg. In the US it may be referred to as a “metric ton”.
You should be careful when using the word “ton”, as there are two different types – British and American. The British ton (also used in other countries that have the Imperial system of weights and measures) is equal to 2,240 pounds or 1,016.047 kg. It is sometimes referred to as the “long ton”, “weight ton” or “gross ton”. The North American ton (only used in the United States and Canada) is equal to 2,000 pounds or 907.1847 kg. It is sometimes referred to as the “short ton” or “net ton”.1Harward, B. (2012, January 23). The difference between “ton” and “tonne”. Common Mistakes in Business English. https://blog.harwardcommunications.com/2012/01/23/the-difference-between-ton-and-tonne/
Units for CO₂ Emissions
When you are reading text about CO2 emissions, or looking at graphs or data charts with emissions data, you can assume that t = tonne = metric ton. And sometimes you will see people write ‘ton’. In this case, they most likely mean ‘metric ton’ and are just dropping ‘metric’ for shorthand. Let’s review some numbers and units you may see as you read about CO2 emissions.
a metric tonne = 1 t = 1,000 kg
1 Mt = 106 t = 1 megatonne
1 Gt = 109 t = 1 gigatonne
In these lessons, when discussing the mass of CO2, all references to ‘t’ mean metric ton (tonne).