Question: do you think that the planets climate change is mainly down to humans or do you think that it is naturally warming up?

James Pope answered on 6 Mar 2015:

Hi Owen,

I think that beyond all reasonable doubt that the warming we have seen in the last 100 years (0.85 degrees Celsius) is due to humans and our release of greenhouse gases.

I am certain of this because while our climate has changed naturally throughout geological time, it doesn’t change as fast as we have seen know. There are natural events that affect our climate, such as El Nino (which warms it for a year or two) or large volcanic eruptions (like Mt Pinatubu in 1993) that cool it for a a year or 18 months, the long term warming has continued.

The big questions for climate science are how much warming we see for the greenhouse gases we release (the “Climate Sensitivity” of the Earth) and for that warming, what it means for different countries around the world. This will be really important for humans as the climate will affect how much water countries have, how much food and what type of food they can grow and how easy it will be to live there.