IPCC SRES scenarios - causes of climate change
By S.M. Enzler MSc
Causes of climate change: driving forces and emissions
The IPCC SRES scenarios contain various driving forces of climate change, including population growth and socio-economic development (figure 3). These drivers encompass various future scenarios that might influence greenhouse gas (GHG) sources and sinks, such as the energy system and land use change. The evolution of driving forces underlying climate change is uncertain. This results in a very wide range of possible emissions paths of greenhouse gases.
Figure 3: integrated framework of climate change by IPCC
Population growth is determined by fertility and mortality rates. Global population projections range from 7,1 to 15 billion people by 2100 across the scenarios, depending on the rate and extent of the demographic transition. Figure 4 shows that population growth is strongest in the regional and material scenario (A2) for 1992 results. Regionalization causes more population growth than does globalization.
Economic development is expressed in GNP (Gross National Product). The SRES scenarios span a wide range of future levels of economic activity. The highest overall prediction is for the A1 scenario; an estimated GNP of US$529 trillion (1990 US dollars) in 2100. The lowest overall prediction is for the B2 scenario; an estimated GNP of US$235 trillion in 2100. This means that globalization combined with an emphasis on wealth would generate the highest economic growth. This is mainly because population growth is lower in a global scenario, causing a narrower division of the GNP. The emphasis on wealth rather than on sustainability also increases the GNP. It is estimated that the future income gap between developed and developing countries will be smaller than was initially estimated in the IS92 scenarios.
Figure 4: population growth according to the SRES scenario's of 1992
The impact of future energy use will largely depend on the fuel type. Both global scenarios depict a transition towards more non-fossil fuel sources. In the regional sustainable scenario the transition towards non-fossil fuel sources is much more gradual. The regional wealth scenario marks a stark transition back to fossil fuels. In all scenarios the share of oil and gas declines and more coal will be used for energy generation in the future.
Land use change
There are many different land use types. The main land use types that are considered by the IPCC are forests, arable land and grassland. Land use change is largely related to demands for food by a growing population and changing diets.
Currently there is a lot of deforestation. In most SRES scenarios, the current trend of deforestation is eventually reversed because of slower population growth and increased agricultural productivity. Reversals of deforestation trends are strongest in the globalized scenarios. In the globalized sustainable scenario pasture lands decrease significantly because of increased productivity in livestock management and dietary shifts away from meat.
IPCC scenario presentations à http://www.ipcc.ch/present/graphics.htm
IPCC SRES technical summary à http://www.grida.no/climate/ipcc/emission/015.htm
RIVM, the Netherlands à file:///D:/Data/Temporary%20Internet20Files/Content.IE5/K5W3OJCV/IMAGE_model%5B1%5D.ppt
Summary of the 1996 SRES report à http://www.grida.no/climate/ipcc/emission/014.htm