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Atmosphere ocean coupled General Circulation and Climate Modeling

Climate system feedbacks and hydrological cycle response: Climate modeling studies

The climate of our planet can change because of changes in incoming solar radiation, changes in the atmospheric greenhouse gases (e.g. CO2, CH4, N2O), aerosols and land cover. Understanding the response of the climate system to the changes in these forcing agents is crucial for projecting future climate change. Earlier, it was assumed that all cli- mate change agents are equal they cause the same climate change as that of CO2 if the amount of radiative forcing introduced by them is the same. It was also assumed that the precipitation change per unit warming is the same irrespective of the forcing agents. However, climate modeling studies in the last two decades have shown that this is not al- ways the case. To measure the effectiveness of various forcing agents in causing climate change, relative to CO2, the concept of efficacy was introduced. Efficacy is defined as the ratio of global temperature change due to a particular forcing agent to the temperature change caused by CO2 for the same imposed radiative forcing. Previous climate modeling studies have made estimates for some forcing agents such as solar radiation, CH4 , O3 , and black carbon aerosols. At CAOS, we use idealized cli- mate model simulations to understand the differing efficacy and differing hydrological cycle response to various forcing agents. We use the “fast versus slow response framework to study the climate system adjustment on various timescales.