ERA-CLIM

The ERA-CLIM project set out to develop observational datasets suitable for global climate reanalysis, with a focus on the past 100 years. These include atmospheric, terrestrial and oceanic observations from a variety of sources, global reanalyses of the observations, and various uncertainty indicators needed for climate applications.

In-situ data rescue efforts conducted within the project have led to a large improvement of the digital instrumental record for the early 20th century. The number of pre-1957 weather observations from kites and early radiosondes available for climate reanalysis has more than doubled as a result of these efforts.

ERA-CLIM has provided initial impetus for an important international activity in satellite data rescue by investigating the availability of data records from preoperational satellites and their potential use in future climate reanalyses. This has led to a first comprehensive survey of early satellite data for reanalysis, including priorities for data rescue and information about next steps.

Several satellite data records important for climate reanalysis have been reprocessed during the project. These activities have helped develop and solidify a comprehensive programme for reprocessing of satellite data holdings at the Organisation for the Exploitation of Meteorological Satellites (EUMST).

The UK Met Office Hadley Centre (UKMET) has developed improved global gridded estimates of the evolution of sea-surface temperature and sea-ice concentration during the 20th century, together with meaningful information about uncertainties in these estimates (HadISST.2). In addition, important new data collections containing high-quality sub-surface and surface ocean observations have been developed (EN4, HadIOD).

Using many of the observational data sets developed in ERA-CLIM, a set of climate model integrations (ERA-20CM) and several pilot reanalyses for the 20th century (ERA-20C, ERA-20CL) have been produced at ECMWF. A first test reanalysis for the period 1939-1949 has been conducted using newly recovered upper-air observations from the project.

Several project activities have contributed to the estimation and reduction of uncertainties, in climate observations as well as gridded products derived from them. A permanent Observation Feedback Archive facility has been developed by the project to allow users easy access to the input observations used in climate reanalyses, and to information about uncertainties associated with the observations.  

A follow-up project (ERA-CLIM2, Grant Agreement No. 607029) continued to strengthen data rescue, data reprocessing, and climate reanalysis. ERA-CLIM2 introduced an added focus on development of consistent reanalyses of the coupled Earth system, including atmosphere, ocean, land and carbon. The combined results of the two successive ERA-CLIM projects provided key resources and capabilities needed to implement Copernicus Climate Change Services.