The Global Energy Assessment: Toward a Sustainable Energy Future

Options Magazine, Summer 2012: 

A comprehensive, integrated analysis of how to transform energy systems to meet the world’s multiple energy challenges—namely, providing affordable, safe, secure, and environmentally sound energy for all



Since before the Industrial Revolution, societies have relied on increasing supplies of energy to meet their need for goods and services (see figure “World Primary Energy Use”). Major changes in current trends are required if future energy systems are to be affordable, safe, secure, and environmentally sound. There is an urgent need for a sustained and comprehensive strategy to help resolve the following challenges:

  • Providing affordable energy services for the well-being of the 7 billion people today and the 9 billion people projected in 2050
  • Improving living conditions and enhancing economic opportunities, particularly for the 3 billion people who cook with solid fuels today and the 1.4 billion people without access to electricity
  • Increasing energy security for all nations, regions, and communities
  • Reducing global energy system greenhouse gas emissions to limit global warming to less than 2°C above pre-industrial levels
  • Reducing indoor and outdoor air pollution from fuel combustion and its impacts on human health
  • Reducing the adverse effects and ancillary risks associated with some energy systems to safe and acceptable levels

Major transformations in energy systems are required to meet these challenges and to increase prosperity.

The Global Energy Assessment (GEA) assessed a broad range of resources, technologies, and policy options, and identified a number of “pathways” through which energy systems could be transformed to simultaneously address all of the above challenges. The key findings are presented on the following pages.

World Primary Energy Use: The figure shows the explosive growth of global primary energy with two clear development phases, the first characterized by a shift from reliance on traditional energy sources to coal and subsequently to oil and gas. Hydropower, biomass, and nuclear energy during the past decades have a combined share of almost 22%. New renewables such as solar and wind are hardly discernible in the figure. Biomass refers to traditional biomass until the most recent decades, when modern biomass became more prevalent and now accounts for one-quarter of biomass energy. Source: Grubler A et al. (2012). Chapter 1—Energy Primer. In: Global Energy Assessment—Toward a Sustainable Future, IIASA, Vienna, Austria and Cambridge University Press, Cambridge, UK and New York, NY, USA.

Energy systems can be transformed to support a sustainable future

The GEA analysis demonstrates that a sustainable future requires a transformation from today’s energy systems to those with: (i) radical improvements in energy efficiency, especially in end use, and (ii) greater shares of renewable energies and advanced energy systems with carbon capture and storage (CCS) for both fossil fuels and biomass. The analysis ascertained that there are many ways to transform energy systems and many energy portfolio options. Large, early, and sustained investments, combined with supporting policies, are needed to implement and finance change. Many of the investment resources can be found through forward-thinking domestic and local policies and institutional mechanisms that can also support their effective delivery. Some investments are already being made in these options, and should be strengthened and widely applied through new and innovative mechanisms to create a major energy system transformation by 2050. 

An effective transformation requires immediate action

Long infrastructure lifetimes mean that it takes decades to change energy systems. Thus immediate action is needed to avoid lock-in of invested capital into energy systems and associated infrastructure that are not compatible with sustainability goals. For example, by 2050 almost three-quarters of the world population is projected to live in cities. The provision of services and livelihood opportunities to growing urban populations in the years to come presents a major opportunity for transforming energy systems and avoiding lock-in to energy supply and demand patterns that are counterproductive to sustainability goals.

Energy efficiency is an immediate and effective option

Efficiency improvement is proving to be the most cost-effective, near-term option with multiple benefits, such as reducing adverse environmental and health impacts, alleviating poverty, enhancing energy security and flexibility in selecting energy supply options, and creating employment and economic opportunities. Research shows that required improvements in energy efficiency particularly in end use can be achieved quickly. For example:

  • Retrofitting buildings can reduce heating and cooling energy requirements by 50–90%.
  • New buildings can be designed and built to very high energy performance levels, often using close to zero energy for heating and cooling.
  • Electrically powered transportation reduces final energy use by more than a factor of three, as compared to gasoline-powered vehicles.
  • A greater integration between spatial planning and travel that emphasizes shorter destinations and enhances opportunities for flexible and diverse choices of travel consolidating a system of collective, motorized, and non-motorized travel options offers major opportunities.
  • Through a combination of increased energy efficiency and increased use of renewable energy in the industry supply mix, it is possible to produce the increased industrial output needed in 2030 (95% increase over 2005) while maintaining the 2005 level of GHG emissions.

A portfolio of strong, carefully targeted policies is needed to promote energy efficient technologies and address, inter alia, direct and indirect costs, benefits, and any rebound effects.

Read the full article

Further information: The full Global Energy Assessment (GEA) report is published by Cambridge University Press (CUP) ( and is available online at The Web site includes an interactive scenario database that documents the GEA pathways. The text and figures in this article are reproduced with the permission of CUP.

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Last edited: 10 April 2013


Nebojsa Nakicenovic

IIASA Deputy Director General/Deputy Chief Executive Officer


Senior Research Scholar

Transitions To New Technologies

Senior Research Scholar


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Luis Gomez Echeverri

Senior Research Scholar

Transitions To New Technologies

T +43(0) 2236 807 611


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