Addressing climate change will require substantial new investment in low-carbon energy and energy efficiency - but no more than what is currently spent on today's fossil-dominated energy system, according to new research from IIASA and partners.

To limit climate change to 2 Celsius, low-carbon energy options will need additional investments of about US $800 billion a year globally from now to mid-century, according to a new study published in the journal Climate Change Economics. But much of that capital could come from shifting subsidies and investments away from fossil fuels and associated technologies. Worldwide, fossil subsidies currently amount to around $500 billion per year.

"We know that if we want to avoid the worst impacts of climate change, we need to drastically transform our energy system," says IIASA researcher David McCollum, who led the study. "This is a comprehensive analysis to show how much investment capital is needed to successfully make that transition."

The study, part of a larger EU research project examining the implications and implementation needs of climate policies consistent with the internationally agreed 2 C target, compared the results from six separate global energy-economic models, each with regional- and country-level detail. The authors examined future scenarios for energy investment based on a variety of factors, including technology progress, efficiency potential, economics, regional socio-economic development, and climate policy.

Investments in clean energy currently total around $200 to 250 billion per year, and reference scenarios show that with climate policies currently on the books, this is likely to grow to around $400 billion. However, the amount needed to limit climate change to the 2 target amounts to around $1200 billion, the study shows.

The energy investments needed to address climate change continue to be an area of large uncertainty. By comparing the results from multiple models, the scientists were able to better define the costs of addressing climate change.

"Many countries say that they're on board with the a target of 2 Celsius global mean temperature stabilization by 2100; some have even made commitments to reduce their greenhouse gas emissions. But until now, it hasn't been very clear how to get to that point, at least from an investment point of view. It's high time we think about how much capital is needed for new power plants, biofuel refineries, efficient vehicles, and other technologies-and where those dollars need to flow-so that we get the emissions reductions we want," says McCollum.

IIASA Energy Program Director Keywan Riahi, another study co-author and project leader, says, "Given that energy-supply technologies and infrastructure are characterized by long lifetimes of 30 to 60 years or more, there's a considerable amount of technological inertia in the system that could impede a rapid transformation. That's why the energy investment decisions of the next several years are so important: because they will shape the direction of the energy transition path for many years to come."

The study shows that the greatest investments will be needed in rapidly developing countries, namely in Asia, Latin America, and Sub-Saharan Africa.

"Energy investment in these countries is poised to increase substantially anyway. But if we're serious about addressing climate change, we must find ways to direct more investment to these key regions. Clever policy designs, including carbon pricing mechanisms, can help." says Massimo Tavoni, researcher at the Fondazione Eni Enrico Mattei, a climate research center in Italy, and overall coordinator of the LIMITS project, of which the new study is a part.

The researchers note that their analysis of future investment costs does not attempt to quantify the potentially major fuel savings from switching from fossil fuels to renewable sources, such as wind and solar energy. As shown in the IIASA-led Global Energy Assessment, such savings could offset a considerable share of increased investment on a global scale.

This study provided an important input into the Intergovernmental Panel on Climate Change Fifth Assessment Report, Working Group III, Chapter 16 on Cross-cutting Investment and Finance Issues.