Before the global economic crisis hit in 2008, concerns about climate change and the security of energy supplies drove a big investment of financial and political capital in the development of alternative energy resources.
The threat of global warming, combined with record high oil prices, convinced policy makers in the industrial world that dependence on fossil fuels was economically and geopolitically unsustainable.
Europe, the United States and China earmarked billions of dollars for low-carbon technologies like clean coal, wind and even nuclear power.
But the credit crunch and recession reined in the gallop toward a low-carbon future. Now, as countries reassess the likely depth and duration of the economic chill, many are rethinking their energy policies.
In cases like Spain, they are backtracking from the past decade's robust support for low-carbon technologies that require huge front-loaded investments and public aid programs to encourage production and to compete with cheaper but dirtier fossil fuels.
Growth in renewables and nuclear power will surely continue, especially in China, but the double-digit growth rate in renewable capacity is likely to slow sharply in Europe and the United States. Carbon capture and sequestration, or C.C.S., technology that until recently was considered a silver bullet to reduce global warming has, meanwhile, fallen off the radar screen altogether.
The need for major new investments to reduce reliance on fossil fuels has brought uncertainty to the whole electricity sector, said Antony Froggatt, senior energy research fellow at Chatham House in London. "Whether it's renewable or nuclear or both, it means higher costs," Mr. Froggatt said. "If you add the fear of another recession, that means even more uncertainty."
Forecasts from multiple sources, including the United Nations, nuclear industry executives, the U.S. Energy Information Administration and the International Energy Agency all point to a rise of at least 75 percent in nuclear power development by 2030. But in the short term, at least, the Fukushima catastrophe has stalled the sector.