A record-smashing heat wave isn’t just a symptom of climate change—in a way, it’s also contributing to it.

Efforts to moderate extreme weather—blasting air conditioning or cranking up the heat—in 2018 were one of the major factors behind surging global energy demand, particularly in the U.S., the International Energy Agency said in a recent report. And that demand is directly linked to record-level energy-linked carbon dioxide emissions last year, even as countries pledged to substantially cut back their carbon output.

“In a way, global warming is leading to higher demand for fossil fuels,” says Bjarne Schieldrop, chief commodities analyst at Stockholm-based SEB Bank. “Which is kind of uncomfortable.”

In 2018, global energy demand rose by 2.3% from the previous year, the fastest pace of growth this decade and a jump seen across every source of energy, from coal to renewables, the Paris-based agency said in its annual Global Energy and CO2 Status Report.

Image: IEA

That gain was driven by a basket of factors, mainly robust economic growth, with rising demand in China, the U.S., and India accounting for nearly 70% of the jump. But energy-reliant efforts to heat and cool homes and buildings amid increasingly extreme temperatures contributed to nearly a fifth of the gains in global energy demand, according to the IEA.

While extreme weather events were seen worldwide last year—Europe sweated through a record-breaking summer heat wave, months after a cold snap brought blizzards to the Mediterranean—the impact on demand was the most extreme in the U.S., according to the IEA.

“The U.S. saw both,” says Timothy Goodson, an energy analyst at the IEA and one of the authors of the report. “[A] hotter than average summer, and a colder than average winter.”

In the U.S., a year of memorable weather was responsible for about half of a more than 10% jump in domestic gas demand, the agency said. That increase was the largest jump in gas demand since the early 1950s—equivalent to adding the entire annual gas consumption of the United Kingdom in just a single year.

Higher energy demand across the globe came amid rollbacks in energy efficiency and as growth in renewable energy sources failed to keep pace. Plus, Asia in particular saw increased coal demand. Even as its place in the energy mix has fallen, coal is still responsible for a third of global CO2 emissions linked to energy, according to the IEA.

The result? Higher emissions. Global energy-related CO2 emissions rose by 1.7% to 33.1 Gigatons (GT) last year, a record high.

More momentum behind renewable energy would “decouple” the link between energy demand and CO2 output, says Goodson.

Renewables have grown: output was up a sharp 4% in 2018, the IEA said, largely split three ways between solar energy, wind power and hydro. Those energy sources met one-quarter of 2018’s global demand growth for energy, but the pace is still simply not fast enough to offset the huge upticks in demand, including humans’ indoor heating and cooling needs amid a shifting climate.

The result is a “reinforcing feedback loop,” says Schieldrop; the only way out is a push towards more affordable and widely-available renewable energy.

“The way to salvation is when something is cheaper and better,” he says.