The U.S. Department of Defense is the largest institutional consumer of fossil fuels in the world, new research shows, creating more planet-warming greenhouse gas emissions than industrialized countries such as Portugal or Sweden.
The Pentagon, which oversees the U.S. military, released around 1.2 billion metric tons of greenhouse gases between 2001 and 2017, according to research by Brown University. The study, published Wednesday, is the first of its kind to compile such comprehensive data.
The Pentagon's emissions were "in any one year… greater than many smaller countries total greenhouse gas emissions," researchers of the study said.
The findings showed that if the Pentagon was listed as a country, its emissions would make it the world's 55th largest contributor of greenhouse gases.
The Pentagon was not immediately available to comment when contacted by CNBC on Thursday.
"Although the Pentagon has, in recent years, increasingly emphasized what it calls energy security — energy resilience and conservation — it is still a significant consumer of fossil fuel energy," Neta Crawford, the study's author and a political scientist at Boston University, said in a statement.
"Indeed, the DOD (Department of Defense) is the world's largest institutional user of petroleum and correspondingly, the single largest producer of greenhouse gases (GHG) in the world," Crawford said.
Using and moving troops and weapons accounted for approximately 70% of the DOD's energy consumption, largely due to the burning of jet and diesel fuel, the study said.
In 2017, the study estimated the Pentagon had released about 59 million metric tons of carbon dioxide and other greenhouse gases.
That dwarfed annual emissions by Portugal and Sweden, according to the Global Carbon Atlas. The international research project ranks Portugal and Sweden as 57th and 65th respectively for its carbon dioxide emissions.
"The U.S. military has begun greenhouse gas emissions reductions, but there is room for much steeper cuts," Crawford said.
China is the world's largest emitter of carbon dioxide, the main gas responsible for climate change, followed by America.
The world's top climate scientists say countries all over the world must take "unprecedented" and immediate action to prevent the catastrophic impact of an escalating climate crisis.
Late last year, the United Nations' World Meteorological Organization said global temperatures are on track to rise between 3 and 5 degrees Celsius this century, far exceeding a global target of limiting the increase to 2 degrees Celsius or less.
President Donald Trump, who questions climate science and downplays its impacts, has withdrawn the U.S. from the global framework for reducing emissions.