Some atmospheric CO2 is natural. For example, before the Industrial Revolution, there were about 280 parts per million (ppm) of CO2 in the atmosphere, and during most of the past 800,000 years, CO2 fluctuated between about 180 ppm during ice ages and 280 ppm during interglacial warm periods. Since the Industrial Revolution, though, the amount of CO2 has dramatically increased. Currently, the increase is 100 times faster than that when the last ice age ended, according to the National Oceanic and Atmospheric Administration (NOAA).