Emission Scenarios
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Emission scenarios
Emission scenarios are consistent descriptions of how greenhouse gases, the factors behind the emissions and the climatic system will evolve in the future, usually within a timeframe of several decades or even up to a century or two. Scenarios do not necessarily aim to predict the most probable future, and should be thus contrasted with forecasting, but often to explore a large array of possible future emission and possibly mitigation pathways.
Due to the inertia in the climatic system and energy infrastructure, a long timeframe is inherent in the analysis of the issue, and therefore large uncertainties are involved in analyzing what might happen or how a given target might be achieved. This large uncertainty about the distant future inhibits the use of single best-estimate prediction, and gives rise to using instead a set of possible scenarios.
Emission and energy scenario analyses have been carried out for a number of uses. The earliest prominent emission scenario studies, e.g. the IPCC SRES[1], analyzed mostly what might happen if the emissions follow the business-as-usual pathway, i.e. no mitigation action for climate change takes place. More recent analyses in turn have been analyzing the different aspects of climate change mitigation, such as what technologies can be used to achieve a given target, what economic consequences might follow, or how the possible economic burden from mitigation efforts (effort sharing) should be shared.
Purpose of energy and emission scenarios
The purpose and viewpoint of scenarios can be divided into three main categories:
• what-if (predictive)
• what-can-happen (explorative)
• how-to-achieve (normative)
Using this division, scenarios regarding emissions can be used for a number of purposes to address e.g. the questions of
• what happens if nothing is done
• what effects a given policy might have
• with what political and technological measures a given emission target can be achieved
• how policies should be designed to meet a given climatic target, e.g. regarding
o the timing and amount of emission reductions
o the level of tax for emissions with emission taxation
o effort sharing with cap-and-trade
Methods for producing scenarios
Two main categories can be defined [2]:
• qualitative or storyline-based scenarios
• quantitative scenarios
Qualitative scenarios present a coherent storyline of the future, painting the picture for shifts in factors in the background of the issue being analyzed. In this sense, qualitative scenarios are better able to emphasize shifts in variables that are not easily quantifiable, such as lifestyle or behavioral changes. Numeric values for certain variables can be used to consolidate the analysis, but are not necessary.
Quantitative scenarios are most often calculated with mathematical models, which include the numerical relationships between the variables being analyzed. Due to this, the scenario is innately consistent as long as the relationships and input parameters represent reality in a sensible fashion. On the other hand, all the other factors and variables that are not covered by the model are disregarded completely. The shortcomings of each model should be thus always be understood and borne in mind when analyzing the resulting scenarios.
In some cases, a combination of storylines and quantitative scenarios can be used. The storylines can then provide alternative descriptions on how the world generally evolves, especially regarding the variables beyond the scope of the quantitative models being used. The alternative storylines can then be quantified and analyzed in a what-if manner. This approach has been used in e.g. the IPCC SRES scenarios (link to below).
Prominent energy and emission scenarios
IPCC SRES 2000 scenarios
The Intergovernmental Panel on Climate Change (IPCC) developed a set of greenhouse emission scenarios to 2100, reported in the Special Report on Emissions Scenarios [SRES][3], that are generally referred to as SRES-scenarios. Although the scenarios might be slightly outdated, they are still widely used as a reference point in climate policy analyses.
The scenarios were divided into four iteratively developed narrative storylines, labeled as A1, A2, B2 and B2, with divisions on the development of global integration and whether there would be emphasis on either economics or the environment. These storylines formed four scenario families, and within each family scenario analysis was carried out by six modeling teams to represent the uncertainty arising from the modeling approach for the storyline. A total of 40 scenarios were formed, with the work of one modeling group set as a marker scenario for each storyline.
As the scenarios were published already in 2000, they obviously do not follow the historical emissions after 2000. Especially the unanticipated rapid economic and emission growth in Asia is not captured in the models, and the majority of SRES scenarios projected considerably lower emissions than what is suggested by recent estimates on global greenhouse gas emissions. Updated IPCC SRES scenarios are currently being developed. The release of the new scenario report has been planned for 2012.
IEA World Energy Outlook
The international Energy Agency (IEA) publishes its view on the future of the energy system, the World Energy Outlook, on a yearly basis. The scenarios are produced by using the IEA World Energy Model (WEM), a large scale mathematical partial equilibrium model. [4]
Since 2000, the WEO has reported the Reference Scenario, the reference Business-As-Usual case, and the Alternative Policy Scenario, which analyzes the impact of possible additional government actions. Along with providing global projections on energy markets, each report also focuses more on one or a few specialized subjects with more depth, such as the energy market of a certain area, the role of energy in development <ef>The International Energy Agency, "World Energy Outlook 2004;" Paris, France</ref> or investments [5]. The most recent reports of 2008 and 2009 focus respectively on the role of energy in climate policy and energy investment under a post-2012 climate framework.
IEA Energy Technology Perspectives
The IEA Energy Technology Perspectives report has a different focus than the World Energy Outlook. With previous reports published in 2006 and 2008 and one planned for 2010, the reports assess the role and possibilities of new technologies in scenarios closely related to the World Energy Outlook scenarios. The technology scenarios have been calculated with the IEA ETP model [6], using also the WEM model and country specific TIMES and MARKAL models in the 2008 edition[7]. The reports provide a comprehensive coverage on different production, transformation and end-used energy technologies. The possible different pathways are analyzed in an Accelerated Technology (ACT) scenarios, and in the 2008 edition also the BLUE scenario, which analyzes more uncertain, unproven technologies that are still under development.
Shell energy scenarios
Although the Shell energy scenarios might not be as comprehensive and quantitative as the IPCC or IEA scenarios, they have been pioneers in the scenario discipline. The first Shell scenarios were drafted in the early 1970’s, and are released on three intervals.
As the goal of scenario studies is different for a company than for a non-commercial organization, so is the approach from the mathematical modeling of IPCC SRES or IEA scenarios. The Shell Global Scenarios are more qualitative and intend to describe societal forces which would affect the whole worldview as well as market drivers that would determine more directly the field of business.
The Shell scenario publications include two or three scenarios, with very different storylines with regard to e.g. economic integration or consumption patterns. The 2008 scenarios [8], reaching up to 2050, include two scenarios labeled as “Scramble” and “Blueprints”. The scenarios provide very differing views on the future. In the former, immediate pressures drive decision makers for a scramble for energy resources, and energy efficiency and emission reductions are mostly disregarded. The Blueprints scenario, in turn, depicts coalitions taking action mutually on these issues. As a result, efficiency measures emerge more quickly, and market-driven emission management practices spread.
References
- ↑ Intergovernmental Panel on Climate Change, 2000. Special Report on Emissions Scenarios, Cambridge University Press, Cambridge, UK; 2000
- ↑ Börjeson, L., et. al., "Scenario types and techniques: Towards a user’s guide," Futures 38, pp. 723-739; 2006 http://dx.doi.org/10.1016/j.futures.2005.12.002
- ↑ Intergovernmental Panel on Climate Change, 2000. Special Report on Emissions Scenarios, Cambridge University Press, Cambridge, UK; 2000
- ↑ The International Energy Agency, "Energy Technology Perspectives 2008"; Paris, France
- ↑ The International Energy Agency, "World Energy Outlook 2003;" Paris, France
- ↑ The International Energy Agency, "Energy Technology Perspectives 2006;" Paris, France
- ↑ The International Energy Agency, "Energy Technology Perspectives 2008;" Paris, France
- ↑ Shell International BV, 2008. "Shell energy scenarios to 2050," http://www-static.shell.com/static/public/downloads/brochures/corporate_pkg/scenarios/shell_energy_scenarios_2050.pdf