Achievements in ArCS theme 5: Study on Arctic climate predictability

Scientific achievements of ArCS Theme 5 (AT5), whose goal is to assess the predictability of Arctic-related climate variations, are reviewed. AT5 clarified some important roles played by the responses of the Arctic stratosphere and land surface to the Arctic sea ice variations in the predictability of the Arctic climate and its remote influence to lower latitudes. AT5 demonstrated that some climatic phenomena occurring in the tropics and even in the southern hemisphere remotely influence the Arctic climate, wherein the influence from the tropics is found to lead to higher predictability of the Arctic climate while that from the southern hemisphere is a limiting factor for the predictability. AT5 also investigated how long the Arctic sea ice is predictable using a state-of-the-art climate model.