Offering a "clear sign that an energy transition is underway," renewable energy comprised nearly half of the world's power generation capacity in 2014 and is already the second-largest electricity source on the planet after coal, according to a new report published Tuesday by the International Energy Agency (IEA).

What's more, green power is set to surpass coal in the early 2030s, particularly as oil prices drop and the link between energy demands and economic growth weakens, the IEA's latest World Energy Outlook (pdf) report found.

But a full transition to clean energy can only happen with a concerted global push, IEA said—and humanity has a lot of urgent work to do.

The "plunge in oil prices has set in motion the forces that lead the market to rebalance, via higher demand and lower growth in supply, although the adjustment mechanism in oil markets is rarely a smooth one," the report states. Coal use in China has hit a plateau, which means the "single largest energy demand growth story is near its end." In the U.S., oil demands have fallen by roughly 4 million barrels a day, a level not seen since the 1960s.

Meanwhile, the world's "appetite for electricity" will elevate demand for renewables 70 percent by 2040, IEA found.

As renewables rise, greenhouse gas emissions fall. That means the time to act is now, the agency said.

"The impossible is becoming possible. The global breakthrough of renewable energy has happened much faster than anticipated."

—Emily Rochon, Greenpeace

"It would be a grave mistake to index our attention to energy security to changes in the oil price," said IEA executive director Fatih Birol. "Now is not the time to relax. Quite the opposite: a period of low oil prices is the moment to reinforce our capacity to deal with future energy security threats."

In fact, according to the report, the world is still on course for a 2.7°C global temperature rise, higher than the 2°C threshold to prevent irreparable global warming and extreme weather events. The best bet for curbing runaway climate change is the upcoming United Nations COP21 summit in Paris, the IEA said, where heads of state should commit to full implementation of "unconditional pledges" to reduce carbon emissions.

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"World leaders meeting in Paris must set a clear direction for the accelerated transformation of the global energy sector," Dr. Birol said. "As the largest source of global greenhouse-gas emissions, the energy sector must be at the heart of global action to tackle climate change."

The IEA's findings are supported by a recent Greenpeace analysis (pdf) which found that global coal consumption between January and September 2015 fell by at least 2.3 percent—the largest drop on record, the environmental group said.

"This historic fall was caused by a 'perfect storm' of circumstance: dire fossil fuel economics, rising renewable energy uptake, slowing global energy demand, and China’s crackdown on air pollution," Greenpeace wrote.

Lauri Myllyvirta, the group's coal and energy campaigner, said the trends "show that the so-called global coal boom in the first decade of the 21st century was a mirage."

"Coal is in terminal decline, and those countries investing in coal for export markets are making reckless decisions," Myllyvirta said. "They will be scarring the landscape and damaging the climate with little prospect of a return on their investment."

Emily Rochon, Greenpeace International's global energy strategist, said the clean energy revolution could happen even faster than the IEA estimates. "The impossible is becoming possible," Rochon told the Guardian. "The global breakthrough of renewable energy has happened much faster than anticipated. The IEA is catching up on renewable energy trends, but it is still failing to see the full potential of change."

"We believe that with the right level of policy support, the world can deliver 100% renewable energy for all by 2050," Rochon said.