evidence: But scientists often use a different measure, known as "equilibrium climate sensitivity". This is defined as the global mean warming caused by a doubling of pre-industrial carbon dioxide (CO₂) levels in the atmosphere. [...] As highly reflective ice melts on land or sea, the underlying surface is exposed and less sunlight reflected back into space. This increases the amount of warming for a given amount of greenhouse gases. It’s what scientists refer to as a positive feedback loop. [...] But we feel these high equilibrium simulations still have value. While we are not arguing they are correct, they force us to consider the what-if situation of very high climate sensitivity, where a doubling of CO₂ would result in warming of 5°C or higher. We know the impact on our environment would be devastating.