Which activity releases carbon that was stored underground for millions of years?
AnswerBurning fossil fuels
Fossil carbon is ancient; biological carbon cycles on short timescales.
Science · Facts & stats
Carbon facts & stats
7 fact-checked facts about cutting carbon, one counted kilogram at a time, each with the reason behind it. 5 more are in today's round and join this page after it closes.
The basics
Which transport choice has the lowest carbon per passenger-kilometre?
AnswerWalking or cycling
Human power emits essentially nothing per km; a solo car trip emits roughly 150 to 250 g CO₂ per km.
Going deeper
Roughly how many tonnes of CO₂ does the average American emit per year?
AnswerAbout 14 to 16 tonnes
US per-capita emissions are about 14 to 16 t CO₂ a year, around three times the global average (Global Carbon Project).
Scope 1, 2 and 3 emissions are a framework from which standard?
AnswerThe GHG Protocol
The Greenhouse Gas Protocol splits emissions into direct (1), purchased energy (2) and value chain (3).
How much CO₂ does burning one US gallon of gasoline release?
AnswerAbout 8.9 kg
The EPA figure is 8,887 grams of CO₂ per gallon of gasoline.
Expert level
The 'social cost of carbon' is used by governments to estimate what?
AnswerThe economic damage caused by one extra tonne of CO₂
It puts a dollar value on future damages per tonne so that policies can weigh costs and benefits.
Direct air capture plants remove CO₂ from the air using what?
AnswerChemical sorbents or solutions that bind CO₂
DAC uses solid sorbents or liquid solvents to capture CO₂, then heat to release and store it; it is still expensive and small-scale.
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