• “Climate sensitivity” is a metric for describing how sensitive the Earth’s temperature is to doubling of atmospheric CO2
• “Transient climate sensitivity” – the change over years to decades – does not include “slow feedbacks”) – estimated to be between 1.5°C and 4.5°C, with a likely value of about 3
• “Earth system climate sensitivity” – the change over decades to centuries to millennia– includes “slow feedbacks”) – may have a value of between 4°C and 6°C
• When trying to predict how much the Earth will warm in the decades and centuries ahead, “climate sensitivity” is the only metric that really matters.
Source: Bruce Parker