WHAT IS ACRE The          international          Atmospheric          Circulation Reconstructions   over   the   Earth   (ACRE)   initiative   works to   retrieve   our   global   climate   history.   It   harnesses   the work   of   many   professionals   and   volunteers   to   recover historical   terrestrial   and   marine   weather   observations. Project    members    search    out    millions    of    documents, typically     paper-based,     convert     them     to     electronic images   and   then   digitise   the   useful   data   they   contain. The   data   supports   computer-based   4D   weather   recon- structions    (reanalyses)    spanning    the    last    200-250 years.    Climate    applications    and    analyses    of    climate impacts   worldwide   benefit   from   the   work   of   the   ACRE initiative.     All   of   the   historical   surface   weather   data   and the reanalyses are freely available. ACRE achieves its mission by: • linking international meteorological organisations & data rescue infrastructures; • facilitating the recovery, extension, quality control & consolidation of global historical terrestrial & marine instrumental surface data covering the last 250 years; • making these observations available to all international reanalyses; • ensuring that 4D reanalysis products can be tailored/downscaled to flow into various climate applications & production models. • providing access to tools and techniques for analyses and interpretation of historical documentary weather observations.