2004�N3��30���X�V (�u������)>15:00 - 16:30 at ���R�Ȋw 3 ���� 5 �K�Z�~�i�[�� (508) "Modelling Local and Global Climate Sensitivity over a Broad Range of Climate Perturbations" >17:00 - 18:30 at ���R�Ȋw 3 ���� 609���� ���`���̈�ɂ����钴�Ꮏ�ʓV�̒T���Ƃ��̌��x�� �F�l �ȉ��̓����ōu������s���܂��B�����E�@���E�w�������킸 �����̕��X�̂��Q�������҂����Ă���܂��B ---------------------------------------------------- �����@�F 2004 �N 3 �� 31 �� 15:00-16:30 �ꏊ�@�F���R�Ȋw 3 ���� 5 �K�Z�~�i�[�� (508) ---------------------------------------------------- "Modelling Local and Global Climate Sensitivity over a Broad Range of Climate Perturbations" Kevin Hamilton International Pacific Research Center University of Hawaii Honolulu, Hawaii The changes top the radiative balance at the top of the atmosphere in a climate change experiment can be conveniently divided into the perturbation forcing component and the atmospheric response. Climate sensitivity is then defined as the ratio of surface temperature response divided by the forcing. Both local and global-mean values of the sensitivity may be defined. To first order, the sensitivity is rather independent of the details of the forcing. So, for example sensitivity of the surface temperature is similar whether the perturbation forcing is from an increase in atmospheric carbon dioxide, or a change in the solar constant. While the climate sensitivity for any model is thus a robust quantity, the sensitivity values are known to vary greatly among different models. The recent IPCC report summarizes results from a large number of state-of-the-art coupled ocean-atmosphere models and finds that the equilibrium global-mean surface warming in response to a doubling of carbon dioxide levels varies from less than 2C to more than 5C. This talk will summarize work diagnosing the detailed climate feedback mechanisms that determine the sensitivity of one model - the NCAR Climate System Model. Long integrations of the model under control conditions and then with the solar constant increased by 2.5%, 10%, 15%, 25%, 35% and 45% were conducted. This allowed feedback mechanisms to be evaluated for both modest climate perturbations and very strong ones. It will be shown that at sufficiently large climate perturbation the climate response is unstable and a "runaway climate" is simulated.