Is 4 tonnes of CO2 a year a lot?

4 tonnes of CO2 by group

Percentile is the share of the world's people who emit less than this a year. “1 in X” counts the rarer side: people at or beyond this value above the median, at or under it below. Percentiles are estimated from a normal distribution with mean 4.7 t and SD 2.8 t, which understates the long right tail.

What this means

• Absorbing 4 tonnes takes about 180 trees growing for a full year, at the 45 trees per tonne our carbon test uses. The rule of thumb is generous; trees are slow and offsets are a crowded market.
• The closest national average is Sweden at 3.8 t. An American averages 14.5 t, an Indian 1.9 t, so 4 tonnes is 2.1 times the Indian figure.
• Country figures are territorial emissions divided by population: power stations, cement works and all, not a household's shopping. A personal calculator counts consumption and misses imports. Neither is precise to the tonne.
• Emissions are skewed, with a long tail of frequent flyers and large houses. A normal curve is a rough fit, and the richest 10% of people cause about half of all emissions.

Questions

Is 4 tonnes of CO2 a year a lot?

4 tonnes a year is more than 40% of the world's people emit, against a global mean of 4.7 tonnes per person. That is close to the world mean, though far above India or Brazil.

What is the average carbon footprint per person?

About 4.7 tonnes of CO2 a year worldwide. Australia averages 15.1 t, the United States 14.5 t, Germany 7.9 t, the United Kingdom 5.5 t, Sweden 3.8 t and India 1.9 t (Our World in Data, territorial emissions).

How many trees offset 4 tonnes of CO2?

About 180 trees absorbing for a year, at 45 trees per tonne. Put differently, one tree would need 180 years. Planting is cheap; the carbon stays out of the air only as long as the trees stand.