Holocene = Anthropocene? The HYDE database for integrated global change research over the past 12,000 years

More and more studies of global (climate) change are focusing on the past. Hundreds and thousands of years of land use, driven by population growth have left their trace/mark on the Earth's surface. We are only at the beginning to understand the complex relationship of human induced disturbances of the global environment, and the consequences for future climate. It is therefore essential that we get a clear picture/understanding of past relationships between population growth, land use and climate. In order to facilitate climate modelers to examine these relationships, the HYDE database has been updated and extended. The update of HYDE described here (Klein Goldewijk et al. 2006; Klein Goldewijk et al. 2007) includes several improvements compared to its predecessor: (i) the HYDE 2 version used a Boolean approach with a 30 minute degree resolution, while HYDE 3 uses fractional land use on a 5 minute resolution; (ii) more and better sub-national (population) data (Klein Goldewijk, 2005) to improve the historical (urban and rural) population maps as a basis for allocation of land cover; (iii) implementation of different allocation algorithms with time-dependent weighting maps for cropland and grassland; (iv) the period covered has now been extended from the emergence of agriculture (10,000 B.C) to present time (2,000 A.D.), with different time intervals. Examples of (future) use of the database is to help test the 'Ruddiman hypothesis', who proposed a theory that mankind already altered the global atmosphere much earlier than the start of the Industrial Revolution in the early 18th century (Ruddiman, 2003), which put forward the research question whether we detect a pre- Industrial Revolution anthropogenic signal, and how strong is that signal? References Klein Goldewijk, K. A.F. Bouwman and G. van Drecht, 2007. Mapping current global cropland and grassland distributions on a 5 by 5 minute resolution, Journal of Land Use Science, Vol 2(3): 167-190. Klein Goldewijk, K. and G. van Drecht, 2006. HYDE 3: Current and historical population and land cover. MNP (2006) (Edited by A.F. Bouwman, T. Kram and K. Klein Goldewijk), Integrated modelling of global environmental change. An overview of IMAGE 2.4. Netherlands Environmental Assessment Agency (MNP), Bilthoven, The Netherlands Klein Goldewijk, K. 2005. Three centuries of global population growth: A spatial referenced population density database for 1700 - 2000, Population and Environment, 26 (5): 343-367. Ruddiman, WF, 2003. The anthropogenic greenhouse era bagan thousands of years ago, Climatic Change, 61(3), 261-293.