Question

What conclusion can you make about how the carbon dioxide level has changed over time?

The level has not changed.
The level of CO2 has declined.
The level of CO2 has risen.
The level has reached its maximum.

Answer 1

This is an interesting question, but over the passage of time CO2 levels have risen due to CO2 emissions from cars, humans, and factorys as well as other sources.

Answer 2

The right answer is The level of CO2 has risen.

Since 1750, the concentration of carbon dioxide (CO2) has steadily increased in the atmosphere, from 280 ppmv before the industrial age to 381 ppmv in 2006. This increase has accelerated since the mid-1960s and continues to accelerate. Between 1970 and 1979, it was 1.3 ppmv per year, between 1980 and 1999 around 1.55 ppmv per year, and between 2000 and 2006 it was 1.9 ppmv per year.

Three factors explain this acceleration:

- an increase in carbon emissions, which exceeds the most pessimistic forecasts,

- an inversion of the evolution of the "carbon emission / economic growth" ratio,

- a reduction in the efficiency of natural carbon sinks.