Iran was one of the biggest culprits behind a spike in carbon emissions in 2015, right behind China and India, while California and U.S. emissions were falling, according to a new study released on Thursday.

The study, produced by the consulting firm Beacon Economics for the innovation group Next 10, tracks California's decadelong implementation of its climate change law, AB 32, signed by former Republican Gov. Arnold Schwarzenegger.

The new greenhouse gas inventory details how the Golden State ranks when compared to 50 countries by using the most recent data compiled by the California Air Resources Board, the Environmental Protection Agency, and other government entities.

"When looking at the global level, California was still the 18th-largest polluter in terms of carbon dioxide emissions from fossil fuel activities among the top 50 global polluters in 2015," the study said in its executive summary.

At the same time, however, carbon dioxide emissions from fossil fuels rose 15 percent, driven by China, India, and Iran, which led countries in greenhouse gas emissions that year, the study said.

It was the same year that nearly 200 countries signed onto the Paris climate change accord, which President Trump decided to later exit in 2017.

California’s emissions reduction over the decade amounted to 0.08 percent of the total 2015 global emissions, factoring in the rise in emissions from China, India, and Iran.

Global emissions rose by 4.2 billion metric tons of carbon dioxide for a total of 32.7 billion metric tons of CO2 equivalent emissions due to the surge from the trifecta of China, India, and Iran.

The increases were led by China, which accounted for 74 percent of the increase, followed by India, 17 percent, and Iran, 5 percent.

The top-50 country ranking was just part of the study.

Next 10, the group that published the study, was founded by the venture capitalist F. Noel Perry to track how California performs on emissions, given its landmark climate law and resulting carbon dioxide regulations. Next 10 tracks California's ability to attract investments in advanced technologies to meet the law's requirements.

"Significantly, California beats all but China and the U.S. as a whole, when it comes to clean technology investment," the report said. "In 2017, California attracted the third largest inflow of global clean technology venture capital funding ($1.42 billion)."

The study is being released by the group ahead of Democratic Gov. Jerry Brown's Global Climate Action Summit that begins on Sept. 12. The summit will feature international representatives to discuss how to move forward on the Paris climate deal after Trump decided to withdraw from it.

"The data reveal a virtuous cycle of policy, investment, technology innovation, emissions reduction and economic growth," the study claims. "But while California is a world leader when it comes to emissions reductions and economic growth, the state represents a fraction of the world’s total emissions and population. Global collaboration is critical to continued progress worldwide, and California has much to be leveraged by other governments."