However, estimates of the planetary climate sensitivity to increasing atmospheric CO2 and other radiative forcings are not solely based on the change
in the mean global temperature over the past 100 years.
Separate research published by the Met Office today shows emissions of CO2 will need to be reduced close to zero by the end of this century if a rise
in the mean global temperature beyond 2C is to be avoided.
For each of the three parameters, calculate the increase or
decrease in mean global temperature for an increase of 5 % of the initial value of that parameter with the other two parameters held at their initial values.
A decade ago Calder showed that the variations around the trend correlate to
variations in mean global temperature (MGT)-- he called this his «CO2 thermometer» — and others have since found the same.
Climate science indicates that to have even a chance of avoiding a catastrophic increase
in mean global temperature, the worldwide economy must be largely decarbonized by 2050.
Most attention in the debate over climate change has been based on the assumption of a gradual increase
in mean global temperatures, equilibrating to a new higher level some decades after concentrations of greenhouse gases have stabilized, with effects that will then play out for centuries.