If you accept that, after calibration, KISS does a reasonable job of explaining climate change over the pat few decades then you can also use KISS to model what will happen in the future.
Scenarios for the future production of CO2 by humans are controlled in KISS by three parameters:
1. The rate of increase of global carbon dioxide production. Between 2000 and 2010 world output grew by 8800 Gt/year so the present growth rate is 880 Gt/year/year and this is the default value for the future but, if you wish, you can change this to see the effect of more rapid (or slower) change.
2. The year when CO2 production peaks. Production is assumed to continue growing steadily until this specified year.
3. The speed with which production falls after the peak year. This is given as a half-life, i.e. the time for production to fall by half.
Given the CO2 production scenario produced by these parameters, KISS predicts the future growth of CO2 in the atmosphere and the resulting future climate change. It is believed that climate change of more than 2 ºC will be dangerous (taking us to a global average of 16 ºC).
The key question is: “when do we have to start bringing CO2 production down to avoid dangerous climate change?”