Supplementary code for ‘Greenhouse Warming and Changes in the Seasonal Cycle of Temperature: Model Versus Observations’ (Mann and Park 1996)

Thomson [1995] argues that an enhanced green-house effect may be altering the seasonal cycle in temperature. We compare trends in the amplitude and phase of the seasonal cycle in observational temperature data in the northern hemisphere with the response of two general circulation models to increased CO2 concentrations. Sizeable amplitude decreases are observed in both models and observations. Significant phase delays (ie, later seasonal transitions) are found in the simulations, opposite to the phase advances isolated in the observations. The retreat of winter sea ice in high-latitude regions appears to explain the models' response to CO2 increase. Much of the variability in the observational data is not predicted by the models.

汤姆森（Thomson，1995）指出，增强温室效应（enhanced greenhouse effect）可能会改变气温的季节循环。我们将北半球观测气温数据中季节循环的振幅与相位变化趋势，与两类通用环流模型（General Circulation Models）在二氧化碳（CO₂）浓度升高情景下的响应结果进行对比。两类模型与观测数据均出现了显著的振幅衰减现象。模拟结果显示存在显著的相位延迟（即季节转换时刻延后），这与观测中得到的相位提前结果截然相反。高纬度地区冬季海冰的消退，似乎能够解释模型对二氧化碳浓度升高的响应机制。观测数据中的多数变异性特征并未被模型所预测。