On the one side, we've got greenhouse gases that are pulling the system towards a warmer state, on the other hand, we've got particles from pollution that are cooling it down.
NARRATOR: In other words, while the human greenhouse effect has produced 2.6 to three watts of extra energy for every square meter of the Earth, global dimming has subtracted about 1.5 watts, so, more than half the warming effect of our greenhouse emissions has been masked by the cooling effect of particle pollution.
Perhaps this is why, despite a large rise in the concentration of greenhouse gases, until recently, the temperature rise has been hard for most of us to notice.
PETER COX: We're going to be in a situation, unless we act, where the cooling pollutant is dropping off while the warming pollutant is going up. CO2 will be going up and particles will be dropping off, and that means that we'll get an accelerated warming. We'll get a double whammy. We'll get reducing cooling and increased heating at the same time, and that's, that's a problem for us.