The "Keeling curve" showing CO2 measurements at Mauna Loa, Hawaii, shows that concentrations of CO2 have reached approximately what level, in parts per million (PPM)?
A) 1,000 ppm
B) 400 ppm
C) 350 ppm
D) 200 ppm
E) 100 ppm

Question

Quizplus · Accepted Answer

The "Keeling curve" shows that concentrations of CO2 have reached approximately 400 parts per million (PPM). This is considered a significant and concerning increase, as preindustrial levels were around 280 ppm.

The "Keeling Curve" Showing CO2 Measurements at Mauna Loa, Hawaii