Gases trapped in ice cores show the dramatic impact that human
activities have had on the planet since the Industrial Revolution.
The first graph reveals how atmospheric carbon dioxide, methane, and
nitrous oxides from coal- and oil-burning power plants, cars, and
other fossil-fuel-burning sources have climbed along with the world
population, with as yet unknown effects on the climate system.
The second graph displays similar results with sulfates and
nitrates. Sulfates, which originate primarily in coal-fired power
plants, started rising around 1900. (This rise is partially
attributed to increased volcanic activity in the Caribbean around
the turn of the century; other volcanic eruptions—represented
by large spikes in the graph—can be seen at numbers 1, 2, and
3.") Nitrates didn't begin to climb significantly until after 1950,
when cars and oil-powered plants appeared in a big way. Scientists
credit the leveling off in sulfates and nitrates at the graph's far
right—that is, the most recent period—to a less-polluted
atmosphere after the 1972 U.S. Clean Air Act went into effect.Data in gases graph from:
Etheridge, D.M., Pearman, G.I., and Fraser, P.J., 1992, Changes in tropospheric methane between 1841 and 1978 from a high accumulation rate Antarctic ice core, Tellus, Ser. B, 44, 282-294. (CO2 and CH4)
Keeling, C.K., Adams, J.A., Ekdahl, C.A., and Guenther, P.R., 1976, Atmospheric carbon dioxide variations at the South Pole, Tellus, 28, 552-564. (direct measurements)
Machida, T., Nakazawa, T., Fujii, Y., Aoke, S. and Watanabe, O., 1995, Increase in atmospheric nitrous oxide concentrations during the last 250 years, Geophys. Res. Lett., 22, 2921-2924. (N20)
McEvedy, C. and Jones, R., 1978, Atlas of world population history, Penguin. (world population)
Data in particulates graph from:
Mayewski, P.A., Lyons, W.B., Spencer, M.J., Twickler, M.S., Buck, C.F. and Whitlow, S., 1990, An ice core record of atmospheric response to anthropogenic sulphate and nitrate, Nature 346(6284), 554-556.