How do we know it is human carbon emissions
Reading time: 2 minutesTL;DR
The changing combination of carbon isotopes in the atmosphere are the result of burning fossil fuels.
Also the lowest part of the atmosphere called the troposphere is warming, but the outer part isn’t.
Explanations
Isotopes
There’s 3 different forms of carbon - 12C, 13C and 14C. These are known as isotopes. Burning of fossil fuels results in a combination of 12C and 13C, but not 14C.
In the atmosphere we’re seeing an increase of carbon 12C and 13C, while 14C is decaying.
That’s not to say it’s the only explanation, but it helps understand the contribution of activities like burning wood which would include 14C, and eruptions from volcanoes which are heavy in 13C.
The spheres
No not the U2 show in Las Vegas. The atmosphere has different layers.
The lowest one, the one we live and breathe in is called the troposphere. It’s getting hotter. Next is the stratosphere. Satellites and weather balloons show it is getting colder. That’s one of the reasons we know it’s not the sun. If it was the sun increasing in power we’d see this layer getting warmer as well.
I won’t cover the remainder of the layers, I just wanted to include that with the above explanation of the isotopes.
Sources
How do we know the build-up of carbon dioxide in the atmosphere is caused by humans?