Climate change scenario

Climate change scenario

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This article is about climate change
Climate change
Climate change is a significant and lasting change in the statistical distribution of weather patterns over periods ranging from decades to millions of years. It may be a change in average weather conditions or the distribution of events around that average...

A scenario is a synoptical collage of an event or series of actions and events. In the Commedia dell'arte it was an outline of entrances, exits, and action describing the plot of a play that was literally pinned to the back of the scenery...

. Socioeconomic scenarios are used by analysts to make projections of future greenhouse gas
Greenhouse gas
A greenhouse gas is a gas in an atmosphere that absorbs and emits radiation within the thermal infrared range. This process is the fundamental cause of the greenhouse effect. The primary greenhouse gases in the Earth's atmosphere are water vapor, carbon dioxide, methane, nitrous oxide, and ozone...

 (GHG) emissions and to assess future vulnerability to climate change (Carter et al., 2001:151). Producing scenarios requires estimates of future population levels, economic activity, the structure of governance, social values, and patterns of technological change. Economic and energy modelling (such as via the World3
The World3 model was a computer simulation of interactions between population, industrial growth, food production and limits in the ecosystems of the Earth. It was originally produced and used by a Club of Rome study that produced the model and the book The Limits to Growth...

 or the POLES
Prospective Outlook on Long-term Energy Systems
Prospective Outlook on Long-term Energy Systems is a world simulation model for the energy sector that runs on the Vensim software...

 models) can be used to analyse and quantify the effects of such drivers.

Global futures scenarios

These scenarios can be thought of as stories of possible futures. They allow the description of factors that are difficult to quantify, such as governance, social structures, and institutions. Morita et al. (2001:137-142) assessed the literature
Scientific literature
Scientific literature comprises scientific publications that report original empirical and theoretical work in the natural and social sciences, and within a scientific field is often abbreviated as the literature. Academic publishing is the process of placing the results of one's research into the...

 on global futures scenarios. They found considerable variety among scenarios, ranging from variants of sustainable development, to the collapse of social, economic, and environmental systems. In the majority of studies, the following relationships were found:
  • Rising GHGs: This was associated with scenarios having a growing, post-industrial economy with globalization
    Globalization refers to the increasingly global relationships of culture, people and economic activity. Most often, it refers to economics: the global distribution of the production of goods and services, through reduction of barriers to international trade such as tariffs, export fees, and import...

    , mostly with low government intervention and generally high levels of competition. Income equality declined within nations, but there was no clear pattern in social equity or international income equality.
  • Falling GHGs: In some of these scenarios, GDP rose. Other scenarios showed economic activity limited at an ecologically
    Ecology is the scientific study of the relations that living organisms have with respect to each other and their natural environment. Variables of interest to ecologists include the composition, distribution, amount , number, and changing states of organisms within and among ecosystems...

     sustainable level. Scenarios with falling emissions had a high level of government intervention in the economy. The majority of scenarios showed increased social equity and income equality within and among nations.

Morita et al. (2001) noted that these relationships were not proof of causation.

No strong patterns were found in the relationship between economic activity and GHG emissions. Economic growth was found to be compatible with increasing or decreasing GHG emissions. In the latter case, emissions growth is mediated by increased energy efficiency, shifts to non-fossil energy sources, and/or shifts to a post-industrial (service-based) economy.

Factors affecting emissions growth

  • Development trends: In producing scenarios, an important consideration is how social and economic development will progress in developing countries (Fisher et al., 2007:176). If, for example, developing countries were to follow a development pathway similar to the current industrialized countries, it could lead to a very large increase in emissions.
  • GHG emissions and economic growth: Emissions do not only depend on the growth rate of the economy. Other factors are listed below:
    • Structural changes in the production system.
    • Technological patterns in sectors such as energy.
    • Geographical distribution of human settlements and urban structures. This affects, for example, transportation requirements.
    • Consumption patterns: e.g., housing patterns, leisure activities, etc.
    • Trade patterns: the degree of protectionism
      Protectionism is the economic policy of restraining trade between states through methods such as tariffs on imported goods, restrictive quotas, and a variety of other government regulations designed to allow "fair competition" between imports and goods and services produced domestically.This...

       and the creation of regional trading blocks
      Trade bloc
      A trade bloc is a type of intergovernmental agreement, often part of a regional intergovernmental organization, where regional barriers to trade, are reduced or eliminated among the participating states.-Description:...

       can affect availability to technology.

Baseline scenarios

A baseline scenario is used as a reference for comparison against an alternative scenario, e.g., a mitigation scenario (IPCC, 2007c:810). Fisher et al. (2007:178-194) assessed the baseline scenarios literature. They found that baseline CO2 emission projections covered a large range. Factors affecting these emission projections are described below:
  • Population projections: All other factors being equal, lower population projections result in lower emissions projections.
  • Economic development: Economic activity is a dominant driver of energy demand and thus of GHG emissions.
  • Energy use: Future changes in energy systems are a fundamental determinant of future GHG emissions.
    • Energy intensity: This is the total primary energy supply (TPES) per unit of GDP (Rogner et al., 2007:107). In all of the baseline scenarios Fisher et al. (2007) assessed, energy intensity was projected to improve significantly over the 21st century. The uncertainty range in projected energy intensity was large.
    • Carbon intensity: This is the CO2 emissions per unit of TPES. Compared with other scenarios, Fisher et al. (2007) found that the carbon intensity was more constant in scenarios where no climate policy had been assumed. The uncertainty range in projected carbon intensity was large. At the high end of the range, some scenarios contained the projection that energy technologies without CO2 emissions would become competitive without climate policy. These projections were based on the assumption of increasing fossil fuel prices and rapid technological progress in carbon-free technologies. Scenarios with a low improvement in carbon intensity coincided with scenarios that had a large fossil fuel base, less resistance to coal consumption, or lower technology development rates for fossil-free technologies.
  • Land-use change: Land-use
    Land use
    Land use is the human use of land. Land use involves the management and modification of natural environment or wilderness into built environment such as fields, pastures, and settlements. It has also been defined as "the arrangements, activities and inputs people undertake in a certain land cover...

     change plays an important role in climate change, impacting on emissions, sequestration and albedo
    Albedo , or reflection coefficient, is the diffuse reflectivity or reflecting power of a surface. It is defined as the ratio of reflected radiation from the surface to incident radiation upon it...

    . One of the dominant drivers in land-use change is food demand. Population and economic growth are the most significant drivers of food demand.