Scientific Information

SCENGEN is a software tool that enables the user to exploit results from both simple and global climate model experiments, combined with observed global and regional climatologies, to construct a range of geographically- explicit future climate change scenarios for the world. The scientific rationale for the approach adopted in SCENGEN has been developed over a number of years by the Climatic Research Unit, working with colleagues around the world. The software framework allows the user to explore the consequences for future climate of adopting different assumptions about climate system parameters and emissions scenarios. The software also allows the user to select and apply the results from a range of diffrent General Circulation Model (GCM) experiments. The effects of sulphate aerosols on future climate are included in the software, and the user may explore these effects at both the global-mean and regional (spatial pattern) scales.

The 'driver' for SCENGEN is the global-mean temperature anomaly produced by the linked software program MAGICC. MAGICC was used to produce the global-mean temperature and sea-level rise projections given in the IPCC Working Group I Second Assessment Report (IPCC, 1996). The present softwre therefore gives results entiely consistent with the SAR. The concept used by SCENGEN can be summarised as follows:

  1. Define one or more future global greenhouse gas and regional sulphur dioxide emissions scenarios from 1990 to 2100 or later.
  2. Convert these emissions scenarios into future global warming (greenhouse gases) and regional warming/cooling (sulphate aerosols) estimates.

    These first two stages are accomplished by MAGICC.

  3. Define geographic patterns of global climate change from GCM greenhouse gas only experiments, standardised to 1degC of global warming.
  4. Select a future time interval and one or more GCM change patterns.
  5. Scale the standardised greenhouse gas GCM change pattern(s) by the appropriate global warming increment from MAGICC and then view.
  6. Add this climate change scenario to a 1961-90 baseline climatology.

    Steps 3 to 5 will define a global or regional climate change scenario forced by greenhouse gas emissions only. Step 6 will create an actual future climatology for this scenario by using a 1961-90 climatology to define current regional climate patterns upon which the future climate change is superimposed.

  7. Define geographical standardised patterns of regional climate change from GCM sulphate aerosol experiments.
  8. Scale the regional aerosol GCM change patterns by the appropriate regional cooling increments from MAGICC for the same time interval chosen in Step 4.
  9. Add this aerosol-based climate change scenario to the greenhouse gas-based climate change scenario constructed by Step 5.
  10. Add this combined aerosol and greenhouse gas climate change scenario to a 1961-90 baseline climatology.

    Steps 7 to 9 will create a global or regional climate change scenario using both greenhouse gas and aerosol forced patterns of climate change, with Step 10 creating a future actual climatology for this scenario.

The scenarios created by SCENGEN are dependent upon a number of assumptions for which no parameter settings can be included. The three main assumptions are:

References

IPCC (1996) Climate change 1995: the science of climate change (eds.) Houghton,J.T., Meiro Filho,L.G., Callendar,B.A., Harris,N., Kattenburg,A. and Maskell,K. Cambridge University Press, Cambridge, UK, 572pp.

SCENGEN scientific developers, Mike Hulme, Tom Wigley and Olga Brown, January 2000