In March 1958 the US Weather Bureau agreed to set up continuous CO2 monitoring on Mauna Loa, under the direction of Charles Keeling. The result was the famous Keeling curve, a saw-toothed climate graph of inexorably rising CO2 concentrations.

It is a famous climate change graph and the graph tells us that the concentration of carbon dioxide in the atmosphere is 389 PPM today and still rising every year. An increase in concentration of over 38 % since 1850.

David Attenborough shows a different climate graph, depicting the warming of our planet from 1850 through the year 2000. Until the 70's the climate models tells us the variability in temperature is likely natural. But after 1970 the natural variations in the sun's output, volcanoes going of etc cannot explain the warming that has occurred in the climate change graph.

Adding the greenhouse gasses that humans have released into the atmosphere to the model makes the graphs fit together even after the 70's. This is by no means a proof that humans really are causing the warming, but it does seem likely.