Long before human beings existed as a species, the Earth’s temperature fluctuated. Ice ages cooled the planet, then the ice melted and it became warmer and tropical near the equator. Without any action on our part.

This means that there are factors other than CO2 that cause warm and cold periods on Earth!

If you look at the global average temperature compared to the CO2 in the atmosphere over the course of millions of years, you discover that there is no clear connection.

In these periods of Earth’s history, other factors played important roles. Examples include changes in solar activity, cosmic radiation, shifts in the earth’s axis, etc.

So, does this mean it is possible that carbon dioxide is not the cause of the climate change that has been detected for  the last 150 years? No! It is similar to the idea that the only possible explanation for your fever is the flu, in reality the fever could be caused by malaria, strep throat or a range of other sicknesses. Things will always change and the Earth will keep turning.  

The term β€œman-made climate change” means that the global average temperature has been increasing since the beginning of industrialization, i.e. for about 150 years. Therefore, this surge in carbon dioxide must be something that has been relevant during those 150 years. The causes of climate change in the past are not relevant in this case.

And although the proportion of CO2 in the Earth’s atmosphere is relatively low, 0.0004712 percent, but small changes have a massive impact. As the saying goes, a single drop can make the whole barrel overflow. That is exactly what is currently happening with the climate.

Through the use of fossil fuels, oil, natural gas and coal, and the deforestation of forests, the carbon dioxide concentration has increased by almost 50 percent (http://dpaq.de/Dbr1t).

The average global temperature has risen in parallel with the carbon dioxide content of the atmosphere. The greenhouse effect, which is caused by an over-abundance of carbon dioxide, is the only possible cause because solar activity has not developed in parallel. Additionally, science has also ruled out other possible causes.

In conclusion, even if there have been other causes for climate change in the history of the Earth, there is only one possible cause for rising global temperature of the last 150 years, the increase in carbon dioxide emitted by humans in the atmosphere.

Read more from the Max Planck Society here.