Projections of future Climate Change Lead Authors: Boer, G.J, Stouffer R.J, Dix M, Noda A, Senior C.A, Raper S, Yap K.S Presenter: Rudzani Makhado Module: Climate Change Lecturer: Dr Richard Knight Assignment task: Article Review University of Western Cape Due date: 09 Sep 2005

Table of Contents 1. Introduction 2. Climate Change 3. Projections of Climate Change 4. Conclusion _____________________ Note: Click on the underlined hyperlinked words for further information

Introduction The purpose of this review is to assess and quantify projections of possible future climate change, from the hierarchy of models to provide indicators of global as well as regional patterns of climate change. One type of the configuration in this climate model hierarchy is an Atmospheric General Circulation Model (AGCM), with equations describing the time evolution of temperature, winds, precipitation, water vapour and pressure.Atmospheric General Circulation Model (AGCM), It was until the late 1980s, where a more comprehensive Atmosphere-Ocean Global Climate Models or Atmosphere- Ocean General Circulation Model or simply AOGCMs begun to run with slowly increasing CO 2, and preliminary results of these models appeared in the 1990 IPCC Assessment (IPCC, 1990).

Introduction Cont… Since 1995, sequence of experiments continued, including additional forcings, experimenting other greenhouse gases such as Chlorofluorocarbon (CFCs).

Climate Change Climatic changes may occurs, both naturally (eruption of volcano) and as a consequence of human activity (burning of fossil fuel).naturallyhuman activity Climate models are used to quantify this changes, based on the physical processes governing the climate system. The simulated climate change depends, therefore, on projected changes in emissions, the changes in atmospheric greenhouse gases and particulate (aerosols) concentrations that result, and the manner in which the models respond to these changes.atmospheric greenhouse gasesparticulate (aerosols)

Climate Change Cont… The response of the climate system to a given change in forcing is broadly characterised by its “climate sensitivity”. Since these requires many years to come into equilibrium with a change in forcing, remains a “commitment” to further climate change even if the forcing itself ceases to change.climate sensitivity The availability of multiple simulations from a given model with the same forcing, and of simulations from many model with similar forcing, allows ensemble change and the agreement or disagreement (a measure of reliability) of models results.

Projections of Climate Change - Projections of future climate change can be stimulated from Global Mean Response, Patterns of Future Climate Change, Range of Temperature Response to SRES Emission scenarios, Factors that Contribute to the Response, Changes in Variability and Changes of Extreme Events. 1. Global Mean Response There are number of new AOGCM climate simulations with various forcings that can provide estimates of possible future climate change. Each model’s simulation of a future climate state is treated as a possible outcome for future climate. These simulations falls under three categories:

Projections of Climate Change Cont… The first are integrations with idealised forcing, namely, 1%/yr compound increase of Carbon dioxide (CO 2), which also represents other greenhouse gases like methane. These runs extend at least to the time of effective CO 2 doubling at year 70, and are useful for direct model intercomparison since they use exactly the same forcing and thus are valuable to calibrate model response. A second category of AOGCM climate model simulations uses specified time-evolving future forcing where the simulations start sometime in the 19 th century to the 20 th century. The state is subsequently used to begun simulations of future climate with estimated forcings of greenhouse gases. A third category are AOGCM simulations using as an initial state the end of the 20 th century integrations, and then following the A2 and B2 scenarios. These simulations are assessed to quantify possible future climate change and its consistency at the end of the 21 st century.

Projections of Climate Change Cont.. 2. Patterns of Future Climate Change For the change in annual mean surface air temperature in the various cases, the model experiments show the familiar pattern documented in the Second Assessment Report of the IPCC, with a maximum warming in the high latitudes of the Northern Hemisphere and a minimum in the Southern Ocean (due to ocean heat uptake), evident in the zonal mean for the CMIP2 model and the geographical patterns for all categories of models (Figure 1).

Projections of Climate Change Cont.. Figure 1: Multi-model ensemble of annual mean temperature change. However, difference in models also occurs especially in the regional moderating of warming mainly over industrialised areas.

Projections of Climate Change Cont.. 3. Range of Temperature Response to SRES Emission Scenarios This section investigates the range of future global mean temperature changes resulting from the thirty-five final SRES emissions scenario with complete greenhouse gas emissions.SRES emissions scenario To investigate this, implications of the full range of the final SRES scenarios, a simple climate model is used as a tool to simulate the AOGCM results (Wigley and Raper, 1992). Atmospheric concentrations of greenhouse gases are calculated from the emissions using gas cycle model (Widley 1993). Although, the strength of the climate feedbacks on the carbon cycle are uncertain, the models show that they are in the direction of greater temperature change, giving greater atmospheric CO 2 concentrations.

Projections of Climate Change Cont.. The estimated total historical anthropogenic radiative forcing from 1765 to 1990 followed by forcing resulting from the six illustrated SRES scenarios are both shown in (figure 2: Simple model results) Based on the comparison using the simple climate model, the final scenarios for the three markers A1B, A2 and B2 give temperature changes that are slightly smaller than the draft scenarios (Smith et al., 2001).

Projections of Climate Change Cont.. The change in the scenarios is 1 to 2%. However, in the long- term, the level of emissions of long-lived greenhouse gases such as carbon dioxide and nitrous oxide become the dominant determinant of the resulting global mean temperature changes.

Projections of Climate Change Cont.. 4. Factors that Contribute to the Response Factors that contribute to the climatic models response includes the followings: Climate sensitivity- a basic measure of the response of the climate system to a change in forcing. The role of climate sensitivity and ocean heat uptake. Thermohaline circulation changes, and Time-scale of response.

Projections of Climate Change Cont.. 5. Changes in Variability The capacity of the models to stimulate the large-scale variability of climate (e.g. El Niňo-Southern Oscillation, ENSO) has improved in recent years through the development of ocean-atmosphere models. These changes in variability occurs on different time- scale as outlined below: Intra-seasonal variability (daily precipitation variability, Circulation patterns), Interannual variability-year-to-year variability in climate features (e.g. ENSO, MONSOON) and Decadal and Longer time-scale variability.

Projections of Climate Change Cont.. 6. Changes of Extreme Events Possible future changes in extreme weather and climate event are assessed from global models. These models stimulate changes in temperature, precipitation and convection, Extra- tropical storms, Tropical cyclones and Commentary on changes in extremes of weather and climate to predict climatic changes. Although, these models have improved over-time, still some limitations that affect the stimulations of extreme events in term of special resolution and simulation errors due exists.

Conclusion Climatic models are the viable tools to predict future climatic changes. However, there is a need to improve our understanding of climate changes so as correct some of the errors encountered in climate change models.

References IPCC (1990) Climate Change: The IPCC Scientific Assessment. Contribution of Working Group I to the First Assessment Report of the Intergovernmental Panel on Climate Change. In: Houghton J.T, Jenkins G.J and Ephraums J.J (eds). Cambridge University Press, Cambridge, UK and New York. 365pp Smith S. J, Wigley T.M.L, Nakic´enovic´ N and Raper S.C.B (2001) Climate implications of greenhouse gas emission scenarios. Technological Forecasting and Social Change, 65, Wigley T.M.L and Raper S.C.B (1992) Implications for Climate and Sea level of revised IPCC emission scenarios. Nature, 330, Widley T.M.L (1993) Balancing the Carbon Budget. Implications for Projections of Future Carbon dioxide concentration changes. Tellus, 45B,

Additional Readings For more information on this subject, visit the following sites. Climate Change Prediction Future Projection on Climate Change Global Climate Change Intergovernmental Panel on Climate Change (IPCC) Projections of Climate Change