160,000 BP - Global Warming
Many scientists fear that rising levels of so-called "greenhouse gases" from the burning of fossil fuels and other human activities will cause global warming, with potentially grave consequences for human agriculture and society. One of the clearest signs that elevated levels of greenhouse gases can result in warming comes from an ice core taken near the Russian Vostok station in Antarctica. This graph tracks temperature and atmospheric levels of carbon dioxide (CO2) and methane (CH4) from the present back to about 160,000 years ago. (This represents about 11,350 feet of ice accumulation.) The graph clearly shows how a rise in gases will mean a rise in global temperature (though whether rising gases trigger rising temperatures, or vice versa, remains unknown). Also note that (though the graph, which has data up to two decades old, does not show this), at about 360 parts per million, the amount of CO2 in the atmosphere today far exceeds levels at any time in the past 160,000 years—indeed, in the past few million years. For those worried about global warming, this is a sobering statistic.
Graph data taken from:
Barnola, J. M., D. Raynaud, Y. S. Korotkevich and C. Lorius, 1987, Vostok ice core provides 160,000-year record of atmospheric CO2, Nature, 329, 408-414.
Chappellaz, J., J.-M. Barnola, D. Raynaud, Y. S. Korotkevich and C. Lorius, 1990, Atmospheric CH4 record over the last climatic cycle revealed by the Vostok ice core, Nature, 345, 127-131.
Jouzel, J., C. Lorius, J. R. Petit, C. Genthon, N. I. Barkov, V. M. Kotlyakov and V. M. Petrov, 1987, Vostok ice core: a continuous isotope temperature record over the last climatic cycle (160,000 years), Nature, 329, 403-407.
Lorius, C., J. Jouzel, C. Ritz, L. Merlivat, N. E. Barkov and Y. S. Korotkevich, A., 1985, 150,000-year climatic record from Antarctic ice, Nature, 316, 591-595.