Temperature has moved with carbon dioxide level for 800,000 years.
The temperature of the Earth’s atmosphere has moved with the carbon dioxide (CO2 ) level in the atmosphere for at least 800,000 years before 1950.
The blue line shows the carbon dioxide level in the atmosphere over the 800,000 years before 1950. This level or concentration is measured in parts per million (ppm). The graph does not show the recent rapid rise in CO2 levels, since 1950, to over 400 ppm.
The red line shows the Antarctic temperature over this same period.
When you look at the two graphs you can see 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. It is evidence that temperature and carbon dioxide level tend to move together.
The most recent ice age ended about 20,000 years ago. This is on the far right of the above graphs, where both the temperatures and CO2 levels are low. During this ice age, an ice sheet up to three kilometres deep covered about half of North America.
You can see that over these 800,000 years, there are about ten temperature peaks. During those short temperature peaks, the Earth experienced a climate similar to the current climate. Apart from this, that is for most of the time, the Earth has been in ice-ages, very cold.
Scientists went 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 measure the CO2 levels in these trapped air-bubbles and determine how CO2 levels moved over this vast stretch of time. From this, they also identify the atmospheric temperatures.
Some people may think that CO2 levels, like 300 parts per million, are so small that they cannot be influential. However, the above evidence contradicts this. The graphs show that changes to these levels of CO2 do pack a big punch. Just like a small pinch of salt can have a big influence on the tasyte of a meal.
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” and the “level of carbon dioxide in the atmosphere” tend to move together. So we can predict that the vast amounts of carbon dioxide released by burning fossil fuels during our industrial age will lead to an increase global temperatures: global warming.
Modified November 2018