Evidence > Temperature and CO2
Global temperature and carbon dioxide (CO2) levels tend to move together. The graphs, of the data from the past 800,000 years, show this clearly.
Collecting the data
Scientists have gone to Antarctica and drilled deep into the ice. By examining bubbles of air trapped in this ice, they have been able to see what has happened in Antarctica over the last 800,000 years. Scientists can determine the CO2 levels in the atmosphere over this vast stretch of time, and deduce the atmospheric temperatures.
Presenting the data
On the left of the graphs, we have the situation 800,000 years ago. As we move right, we see how CO2 and temperature varied between then and 1950. The concentration of carbon dioxide in the atmosphere is in parts per million (ppm). You cannot see the recent rise in CO2 levels to 400 ppm, because 100 years is too small to be seen on the graph.
The most recent ice-age ended about 20,000 years ago. This is on the far right of the graphs, where both the temperatures and CO2 levels are low. During this ice age about half of North America was covered by an ice sheet up to 3 kilometres deep.
You can see that over these 800,000 years, there are about ten temperature peaks. For those short periods, the Earth has experienced a climate similar to the current climate. Most of the time, the Earth has experienced very long periods of intense cold.
The graphs show that, for the last 800,000 years, when level of CO2 has been high, the temperature has been high. Also, when the level of CO2 has been low, the temperature has been low. This is evidence that temperature is closely related to the level of carbon dioxide in the atmosphere.
Levels of CO2 like 300 parts per million may seem insignificant, but the graph shows that these seemingly small levels of CO2 pack a big punch.
John Tyndall identified the basic science behind this long ago, in 1863. When you increase the concentration of carbon dioxide in the atmosphere, this decreases the heat escaping from our planet into outer space and this tends to increase temperatures on our planet.
“Global temperature” is closely related to the “level of carbon dioxide in the atmosphere”.
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