This graphic shows the relationship between atmospheric carbon dioxide levels and average global temperature during the last 400,000 years. This data comes from air bubbles trapped in Antarctic ice. As the ice shelf formed hundreds of thousands of years ago, ancient air was trapped between snowflakes and compressed into tiny bubbles as the ice thickened. Isotopes of the atoms in the trapped air bubbles tell us what the average global temperature was.
The red line shows how much carbon dioxide was in the atmosphere for a given time in history. Likewise, the yellow line shows average global temperature, as recorded by oxygen isotopes in the bubbles. Carbon dioxide traps heat in the atmosphere, preventing it from radiating into space. Over the millenia, carbon dioxide levels have risen and fallen in a 100,000 year cycle. Each peak in carbon dioxide is matched by a rise in temperature a few years later, and each trough in carbon dioxide causes a corresponding decrease in temperature.
In the past 400,000 years, global carbon dioxide levels have never risen above 300 parts per million, or 0.30%, until about 1960. More recent Antarctic ice core drills dating back 650,000 years show the same ebb and flow in the carbon dioxide cycle, whose levels also have never risen above 300 parts per million. Since the beginning of the Industrial Revolution in the mid-1800s, global carbon dioxide levels have been rising, reaching 300 parts per million in 1960, and rising steadily until today. In 2005, earth's atmosphere contained 370 parts per million of carbon dioxide, or 0.37%. People are responsible for the earth's highest carbon dioxide levels in at least 650,000 years from things like airplanes, power plants, cars and trucks, factories, furnaces, and anything else that burns oil, gas, or coal. By the year 2100, carbon dioxide levels will be double what they are today, over 0.70%.
As humans increase carbon dioxide levels, the historical evidence trapped in those ice cores tells us that global temperatures will rise. It takes a few years for the extra heat to accumulate, because the atmosphere is very large and slowly builds momentum. The temperature will rise in time, however. Average global temperature has been increasing over the past few decades; nearly all climatologists tell us the rise is due, at least in part, to the increasing concentration of carbon dioxide in the atmosphere.
As you look at this graph, note how the earth's average temperature is already warmer than it has been for most of the last 400,000 years. The lowest points on the yellow lines were during ice ages, when the earth was covered by sheets of ice several miles thick from the poles halfway to the equator. That's the difference between the earth's mild climate today and the earth's harsher climate during the ice ages when snow falls in the summertime and never melts. If that much increase in the yellow line can produce so much change in climate, then as carbon dioxide levels rise more than they have in 650,000 years and the earth warms a corresponding amount, imagine the impact of that significant warming on our climate.
Be a force of change. Drive a hybrid vehicle. Write your congress-person and ask them to support limits on carbon dioxide emissions and the Kyoto Protocol. Don't waste energy. Demand change. Thank you.
