The International Energy Agency is out with its latest medium-term outlook for global renewables. And once again, projections for installation and energy production have been revised upward. 

According to the IEA's analysis, renewable electricity will surpass output from natural gas and double generation from nuclear by 2016, becoming the second-most important source of electricity behind coal.

Those projections for generation are 90 terawatt-hours higher than last year's medium-term renewable energy market report. The IEA now says that renewable electricity will make up one quarter of gross power generation in 2018, with non-hydro renewables accounting for 8 percent by that date.

Although the IEA has always been outspoken about the need to deploy more low-carbon technologies and address climate change, the organization has been known for its conservative analysis about the future growth of renewables.

For example, in 2003, it projected that non-hydro renewables would only represent 4 percent of global generation by 2030 under an aggressive policy scenario. But the industry hit that threshold in 2011 -- nearly twenty years early.

Eric Martinot, research director at the Institute for Sustainable Energy Policies, wrote in his recent Renewables Global Futures report about how the IEA and other international organizations have consistently underplayed the growth trajectory for renewables.

"Given the dynamic nature of this growth over the past decade, many past projections of renewable energy have already fallen short. For example, the International Energy Agency (IEA) in 2000 projected 34 gigawatts (GW) of wind power globally by 2010, while the actual level reached was 200 GW. The World Bank in 1996 projected 9 GW of wind power and 0.5 GW of solar PV in China by 2020, while the actual levels reached in 2011, nine years early, were 62 GW of wind power and 3 GW of solar PV. The history of energy scenarios is full of similar projections for renewable energy that proved too low by a factor of 10, or were achieved a decade earlier than expected," wrote Martinot.

Chris Nelder also wrote about this in his analysis of why conventional wisdom about clean energy costs and growth are often years behind reality.

The IEA now says that renewable electricity is on track to reach levels that could theoretically help the world stabilize recent global temperature increases. But the continued reliance on coal, the lack of progress with renewable fuels and glaring inefficiencies in the built environment are all preventing a global reduction in carbon emissions.

"Progress is not fast enough," concluded IEA Executive Director Maria van der Hoeven recently. "Glaring market failures are preventing adoption of clean energy solutions; considerable energy efficiency potential remains untapped; policies must better address the energy system as a whole; and energy-related research, development and demonstration all need to accelerate."