The downward shift in global energy intensity has quickened its pace in recent years. But that still may not be enough to limit Earth’s temperature increase to 2 degrees Celsius, according to a new report from the International Energy Agency.

The IEA has turned its focus to energy efficiency as the cornerstone of sustainable energy policy in the face climate change. “We call energy efficiency the first fuel,” said Brian Motherway, head of energy efficiency for IEA. “Some countries have sun, some have oil, some have wind, but all countries have energy-efficiency resources.”

Investment in energy efficiency topped more than $220 billion in 2015, but that figure needs to be much larger. Last year the gains in energy efficiency, as measured by the drop in energy intensity, were three times what they were in 2013. Energy intensity is measured as the energy consumption per unit of gross domestic product.

From 2003 to 2013, each year saw an approximate 0.6 percent drop in global energy intensity. That decline jumped to 1.8 percent in 2015. However, IEA estimates that figure needs to rise to about 2.6 percent annually to meet Paris climate goals by 2030. For all of the gains, especially in recent years, 70 percent of the world’s energy use takes place outside of any efficiency requirements.

“We need to improve [energy efficiency] by 50 percent, and we need to do so immediately,” said Motherway.

As with most global metrics, the focus is largely on China. China improved its energy intensity by 30 percent in the past 15 years, a savings equal to China’s entire fleet of renewable energy generation.

In the previous decade, China’s energy intensity improved at a rate of about 3 percent per year, but that figure jumped to 5.6 percent in 2015, a pace that will have to be maintained for the next 15 years in order for China’s greenhouse gas emissions to meet the climate goals set out in Paris.

The focus on China is important, as that country was responsible for approximately half of global energy demand growth from 2000 to 2015, according to IEA. The advances in efficiency across China are due to the national energy-intensity targets first set in 2006 in the country’s eleventh five-year plan.

The most recent five-year plan has only strengthened those goals, with a target for energy intensity to be 44 percent below 2005 targets by 2020. Most of the savings are expected to come from the continued shift from heavy industry to a service-based economy.

Although gains in China will have the biggest impact on global energy efficiency and total final consumption (TFC) of fuels, all countries could strengthen efficiency standards, and some emerging economies in particular.

In Brazil, India, Mexico and Indonesia, only a fraction of total energy consumption is covered by efficiency standards. But there has still been significant progress since 2000, according to the IEA, when India and Brazil had no energy efficiency regulations. By contrast, now 17 percent of India’s total energy consumption is covered by regulations.

Lighting has already been a big winner, with more regulations than any other end use. But headroom is everywhere, particularly for road transportation, cooking, industrial processes and agriculture, according to the IEA.

“If all cars were subject to decent standards, it would be nearly 4 million barrels [of oil] a day saved,” said Motherway. “Energy efficiency has a lot more to give than what’s currently being asked of it.”