The first results of The Last
Millennium Climate Reanalysis, a research project partly funded by CPO’s Climate Monitoring Program, were recently accepted for publication in the Journal of Geophysical Research: Atmospheres.
The paper details the framework of the multi-year, multi-institution
project, which aimed to produce state-of-the-art reconstructions of the climate
for the past millennium using an offline data assimilation approach.
The project’s results show broad
agreement with previous reconstructions of Northern-Hemisphere-mean 2m air
temperature, with millennial-scale cooling, a multi-centennial warm period
around 1000 CE, and a cold period coincident with the Little Ice Age (ca.
1450-1800 CE). Verification against gridded instrumental datasets during
1880–2000 CE reveals greatest skill in the tropics and lowest skill over
Northern Hemisphere land areas. Also, verification against independent proxy
records indicates substantial improvement relative to the model (prior) data
without proxy assimilation.
The
offline data assimilation approach used in this project provides a
reconstruction of the global mean surface temperature. This approach also
reconstructed the spatial distribution and uncertainty in the temperature field
and potentially many other fields. Such a record can be used to better
diagnose low-frequency climate variability and the statistics of extreme
events. Moreover, such a dataset can provide hindcast information against which
to measure the skill of models used in decadal climate predictions.
Access the paper: http://dx.doi.org/10.1002/2016JD024751