Project: IPCC Data Distribution Centre : Second Assessment Report data sets - The Intergovernmental Panel on Climate Change (IPCC) has been established by WMO and UNEP to assess scientific, technical and socio-economic information, relevant for the understanding of climate change, its potential impacts and option for adaption and migration. Projection of future trends for a number of key variables are provided through this section of the DDC (http://ipcc-data.org/sim/gcm_clim/IS92A_SAR/). This information contained in either IS92 emission scenarios (IPCC 1992) or published model studies using data from these scenarios. Six alternative IPCC scenarios (IS92a to f) were published in the 1992 Supplementary Report to the IPCC Assessment. These scenarios embodied a wide array of assumption affecting how future greenhouse gas emissions might evolve in the absence of climate policies beyond those already adoped. Model experiments, also using different forcing scenarios, were calculated at other modeling centres. Leggett, J., W.J. Pepper and R.J. Swart, 1992: Emissio ns Scenarios for IPCC: An Update. In: Climate Change 1992. The Supplementary Report to the IPCC Scientific Assessment [Houghton, J.T., B.A. Callander and S.K. Varney (eds.)], Cambridge University Press, Cambridge, UK, pp. 69-95. _ Model experiments, also using IS92a forcing scenarios, were calculated at other modeling centres: NCAR (National Center for Atmospheric Research, USA) GFDL (Geophysical Fluid Dynamics Laboratory, USA) CCCma (Canadian Centre for Climate Modelling and Analysis, Canada) CSIRO (Commonwealth Scientific and Industrial Research Organisation, Australia) Hadley Centre (Met Office Hadley Centre, UK) CCSR (Atmosphere and Ocean Research Institute, the University of Tokyo, Japan) DKRZ (German Climate Computing Center, Germany) MPI-M (Max Planck Institute for Meteorology, Germany) and more. Summary: Here the greenhouse gas forcing is increased gradually to represent the observed changes in forcing due to all the greenhouse gases from 1860 to 1990. From 1990 to 2100 it uses an increase in concentrations represented by the IS92a emissions scenario with the Copenhagen modifications of industrial gases. This is sometimes referred as "IS95a". Greenhouse gas experiment (GHG) In GHG, the concentrations of the following greenhouse gases are prescribed as a function of time: CO2, CH4, N2O and several industrial gases. From 1860 to 1990, the annual concentrations of these gases are prescribed as observed and, from 1990 onward, according to the IPCC'92 scenario IS92a. For the industrial gases, the IS92a scenario has been updated to be consistent with a Copenhagen-like emission scenario (IPCC'96). All of the time dependent, or 'transient', forcing experiments have been initialised at year 100 of CTL, nominally 1860 in the transient experiments. However, these initial values do not correspond to 'pre-industrial' (1860) but to present-day conditions. This applies not only to SST and other climate variables but also to the concentrations of CO2, CH4 and N2O. In the transient experiments, this initial shift in concentration is taken into account by enhancing the observed/projected concentrations of these gases in an appropriate way (Appendix A). The climatology constructed from this 240-year CTL run serves as a reference for the time-dependent forcing experiments GHG, GSD and GSDIO (EH4OPYC_22670GHG_,EH4OPYC_22697GSD_, EH4OPYC_22723GSDIO_). These data represent monthly averaged surface values of selected variables for the IPCC-Data Distribution Centre. (see also http://www.ipcc-data.org/ )