Mass Units - (n.)

When dealing with the enormous quantities of carbon discussed in global climate change studies, scientists use the following units:

tonne: a unit of weight equal to 1000 kg (103 kg).

kt: kilotonnes; equal to 1000 tonnes or 106 kg.

GtC: gigatonnes of carbon; 1 GtC is equal to 109 tonnes of carbon or 1012 kg. 3.7 Gt carbon dioxide will give 1 GtC. To give you an idea how big this unit is: in 1997 the total supply of petroleum for the USA (including imports) was approximately 1 Gt per year.

TgC: teragrams of carbon or 1012 grams of carbon.

PgC: petagrams of carbon or 1015 grams of carbon; 1 PgC is equal to 1 Gigatonne of carbon.