Experts now say that an increase of 0.0001 mole fraction CO2 caused all warming over the past century.
Alarmist John Cook says that simply isn’t true.
Before 1940, the increase in temperature is believed to have been caused mainly by two factors:
- Increasing solar activity; and
- Low volcanic activity (as eruptions can have a cooling effect by blocking out the sun)
I’m inclined to go with the original claim that humans at NASA and NOAA are responsible for almost all of the perceived warming. They tamper with the data to create fake graphs and fake news.