Separating Natural from Human Factors in Climate Change

The Earth's temperature is a response to various factors.

These are called climate forcings.

They are - changes in the gases in the air; changes in the Earth's orbit and rotation (which alters the amount of energy reaching the surface from the Sun); plate movements; ocean currents - and some other things.

Various research groups have investigated the possibility that the current warming could be caused by natural factors.

This kind of research is called an attribution study. 

These studies show that the natural factors cannot be driving the current warming.

The warming trend fits what would be expected to be caused by combining the natural factors with the effects of human activity.

Attribution studies include 

"Global temperature evolution 1979–2010" - Foster & Rahmstorf, 2011

and

"A probabilistic quantification of the anthropogenic component of twentieth century global warming" - Wigley & Santer, 2012.
"Detecting Greenhouse-Gas-Induced Climate Change with an Optimal Fingerprint Method." - Hegerl et al, 1996

The rise in CO2 concentration plotted against global temperature rise:

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