1. The Importance of Atmospheric Heat and Moisture Advection in Arctic Climate Purpose To determine the importance of large-scale horizontal fluxes of heat and moisture on Arctic cloud feedbacks. Rationale Recent model studies have shown that Arctic and low latitude clouds respond differently to increased CO2, but that the Arctic climate responds very similarly whether only local cloud feedbacks are allowed or whether only remote cloud feedbacks are allowed. Thus, remote cloud changes from outside the Arctic are approximately as important for Arctic climate as local cloud changes within the Arctic. Approach Quantify the contribution of heat and moisture advection to the Arctic atmospheric heat/moisture budgets; i.e, redo the Nakamura and Oort 1988 study with current models and data. Improve model physics for polar processes and continue model simulations of cloud feedbacks.

2. Change in Mean Annual Cloud Amount under Greenhouse Forcing Polar Regions: Cloud amount increases (especially low clouds) Tropics-Mid Latitudes: Fewer low clouds, more high clouds

3. Impact of Cloud Changes on Greenhouse Warming Vavrus, J. Climate (2004) 2CO2: Standard 2 x CO 2 simulation with prognostic cloud changes 2CO2F: 2 x CO 2 simulation with fixed clouds (no cloud changes from control run)

4. +2.6 W m -2 +1.0 W m -2 +0.8 W m -2 +3.6 W m -2 Change in Energy Transport to Arctic 2CO2: Standard 2 x CO 2 simulation with prognostic cloud changes 2CO2F: 2 x CO 2 forcing with fixed clouds globally (no cloud changes) 2CO2FLOW: 2 x CO 2 forcing with clouds fixed in lower latitudes only (60 o S-60 o N) 2CO2FHIGH: 2 x CO 2 forcing with clouds fixed in high latitudes only (60 o -90 o )