According to IPCC, the quantity of carbon dioxide in the air had been steady through the long history until modern times, and the concentration of carbon dioxide is proportional to the temperature.
(the quantity of carbon dioxide in the air; had been; steady; T:until modern times) (the concentration of carbon dioxide; is; proportional to the temperature)
the quantity of carbon dioxide in the air the concentration of carbon dioxide
had been is
steady T:until modern times
proportional to the temperature