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The climate reanalysis data challenge

10 April 2015

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Looking at how weather patterns have changed over the decades can help us gain insights into climate change. This requires observations going as far back as possible, but finding such data is a challenge. At the same time, advances in science, for example using state-of-the-art reanalysis, mean that more information can be extracted from past data than when the observations were made.

In 2014, working with partners across Europe, ECMWF produced its first atmospheric reanalysis of the entire 20th Century, ERA-20C. Reanalysis combines the latest science with as many observations as possible to reconstruct the past climate. Its results are important for validating climate models, improving reference climate datasets for numerical weather prediction, and providing a baseline to place today's weather events into the climate context.

Recovering older observations from meteorological organisations, satellite agencies, universities and libraries was a key part of the EU-funded ERA-CLIM project that produced ERA-20C. ERA-CLIM2 continues the work to improve access to climate data, with an emphasis on extending the usable satellite climate data records. "People don't realise that some of the old satellite data from the 1970s, which have been residing on magnetic tapes, actually contain valuable information on climate change for some essential climate variables," says Dr Roger Saunders from the UK Met Office. Reanalysis data will contribute to the Climate Data Store at the heart of the new Copernicus services.

Over the last 50 years, satellite agencies have gathered enormous volumes of data about our environment. Each mission pushed the limits of data transmission, processing, and archiving capacity. The speed and capacity of archiving media at the time - top-of-the-range then - pale in comparison with the capabilities of today's hand-held smartphones. The difficulty of accessing historical satellite data has hampered their use until recently.

Source: European Centre for Medium-Range Weather Forecasts (ECMWF)

Image credit: NASA - Nimbus III launch in 1969

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