History Database of the Global Environment - HYDE

There are also other reasons for using grid-scale information. First, policy makers are interested in regional/national policies to address climate change. Secondly, grid-scale information makes model caluclations more testable against observations as compared to more aggregated models.

Nevertheless, it is infeasable to perform grid-based calculations for economic models, because of the difficulty in specifying economic/demographic factors on a country scale for the entire world over the long horizon of the model. Therefore, the world has been divided into 19 world regions, according to economic and geographic similarity. This classification also takes into account the regional aggregations used by the IPCC, OECD, FAO, UN and IEA.

It should be noted, however, that IMAGE has the additional requirement that countries within a region be adjacent or nearby because of the model's approach to global land cover simulation. An important initiative for the update the previous version of HYDE (Klein Goldewijk, 2001) was the publication of a new population density data base, the Gridded World Population v.3 (Balk et al, 2005), which is now used as a starting point for historical gridded population calculations.

Because population data are important in many calculations, it resulted in modified land cover estimates, as well as estimates for GDP, value added, private consumption. Furthermore, numerous new data have been incorporated in many tables. Besides the testing of IMAGE, HYDE has already been used for integrated environmental assessents such as the Global Environmental Outlook (GEO) of the United Nations Enviromental Programme (UNEP, 1997), technical background reports for GEO (RIVM/UNEP, 1997), the TARGETS project (Rotmans and De Vries, 1997), the Dutch National Environmental Outlook (RIVM, 1997) and the Mappae Mundi project (Goudsblom and De Vries, 2002).

Also, HYDE has contributed to other research e.g. in the field of historical atmospheric trace gas inventories (e.g. Kroeze et al, 1999; den Elzen et al, 1999; van Aardenne et al, 2001; Pitman et al, 2000; Pielke et al, 2003 ), biological diversity (e.g. Gaston et al, 2003), and climate reconstructions (e.g. Matthews et al, 2003; Brovkin et al, 2004). Furthermore, this effort very much fits within the Land-Use and Land-Cover Change LUCC project, (activity 3; database development), part of the the International Human Dimensions Project (IHDP), and the PAGES (Human Interactions in Past Environmental Changes) - focus 3: Human Impacts on Terrestrial Ecosystems (HITE) initiative.

PAGES is the International Geosphere-Biosphere Programme (IGBP) core project charged with providing a quantitative understanding of the Earth's past climate and environment. Please note that this data base is far from complete. Work is continuous in progress to update and extent the data series where possible.

[Summary provided by MNP]