Twentieth-Century Trends of Arctic Precipitation from Observational Data and a Climate Model Simulation

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Abstract
The ECHAM-4 global climate model, forced by time-dependent ocean boundary conditions and CO2 concentrations, shows a substantial increase of precipitation in the Arctic during a simulation of the twentieth century. Observational data from the Intergovernmental Panel on Climate Change and other sources show a similar increase. The largest increases occur at nearly the same time in the observational data and the model output, implying that the ocean boundary conditions may be the primary driver of the increase. However, attribution to ocean boundary conditions is subject to the caveat that the largest increase of simulated precipitation occurs near the sea-ice margin, which contained essentially no interannual variability in the ECHAM-4 simulation during the first half-century (for which sea-ice data were sparse), after which time the model’s sea-ice extent was prescribed to decrease substantially. Uncertainties in the precipitation data must also be addressed further before the observationally der... Abstract The ECHAM-4 global climate model, forced by time-dependent ocean boundary conditions and CO2 concentrations, shows a substantial increase of precipitation in the Arctic during a simulation of the twentieth century. Observational data from the Intergovernmental Panel on Climate Change and other sources show a similar increase. The largest increases occur at nearly the same time in the observational data and the model output, implying that the ocean boundary conditions may be the primary driver of the increase. However, attribution to ocean boundary conditions is subject to the caveat that the largest increase of simulated precipitation occurs near the sea-ice margin, which contained essentially no interannual variability in the ECHAM-4 simulation during the first half-century (for which sea-ice data were sparse), after which time the model’s sea-ice extent was prescribed to decrease substantially. Uncertainties in the precipitation data must also be addressed further before the observationally der...

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