Climate change scenarios for global impacts studies

We describe a set of global climate change scenarios that have been used in a series of studies investigating the global impacts of climate change on several environmental systems and resources - ecosystems, food security, water resources, malaria and coastal flooding. These scenarios derive from modelling experiments completed by the Hadley Centre over the last four years using successive versions of their coupled ocean-atmosphere global climate model. The scenarios benefit from ensemble simulations (made using HadCM2) and from an un-flux-corrected experiment (made using HadCM3), but consider only the effects of increasing greenhouse gas concentrations. The effects of associated changes in sulphate aerosol concentrations are not considered. The scenarios are presented for three future time periods - 30-year means centred on the 2020s, the 2050s and the 2080s - and are expressed with respect to the mean 1961-1990 climate. A global land observed climatology at 0.5 degrees latitude/longitude resolution is used to describe current climate. Other scenario variables - atmospheric CO2 concentrations, global-mean sea-level rise and non-climatic assumptions relating to population and economy - are also provided. We discuss the limitations of the created scenarios and in particular draw attention to sources of uncertainty that we have not fully sampled. (C) 1999 Elsevier Science Ltd. All rights reserved.