On the connection between tropical circulation, convective mixing, and climate sensitivity

Abstract

The connection between the large‐scale tropical circulation of the atmosphere, convective mixing, and climate sensitivity is explored in a wide range of climates through a perturbed‐parameter ensemble of a comprehensive Earth System Model. Four parameters related to the representation of atmospheric moist convection are found to dominate the response of the model. Their values govern the strength of the tropical circulation, the surface temperature, atmospheric humidity, and the strength of the tropical overturning circulation, largely through their influence on the atmospheric stability. The same convective parameters, albeit in different combinations, also have a strong influence on the equilibrium climate sensitivity of the model, which ranges from a little over 3 °C to more than 10 °C. The importance of the most poorly represented processes in determining important aspects of the behaviour of the model argues for the need to move beyond statistical approaches to estimating climate sensitivity and to focus on the development of a better understanding and representation of convective mixing, particularly in the Tropics.