Donald Trump has cancelled NASA’s greenhouse gas monitoring system, prompting concern it will hinder efforts to bring down global emissions.
The space agency’s Carbon Monitoring System (CMS) has until now used satellite and aircraft instruments to monitor carbon dioxide and methane levels remotely - spending $10m (£7.35m) each year.
But the White House has now scrapped the funding as part of its wider attack on climate science.
The moves jeopardises plans to verify levels of emissions in the US.
"If you cannot measure emissions reductions, you cannot be confident that countries are adhering to the [Paris climate] agreement," Kelly Sims Gallagher, director of Tufts University's Centre for International Environment and Resource Policy, told Science Magazine.
Stephen Hagen, a senior scientist at Applied GeoSolutions in New Hampshire, said scrapping the system was “disappointing”.
“[This] means we're going to be less capable of tracking changes in carbon," he added.
The CMS has been an obvious target for Mr Trump as it is associated with climate treaties.
In June last year Mr Trump began the withdrawal process from the Paris accord.
The agreement was signed under former President Barack Obama's administration in December 2015 by nearly 200 countries to curb global carbon emissions and contain global warming to 2C.
Mr Trump has called climate change a "hoax" in the past - one perpetrated by the Chinese.
"The concept of global warming was created by and for the Chinese in order to make US manufacturing non-competitive," he tweeted in 2012.
The president said when announcing the US withdrawal from the Paris agreement that the deal put American workers - particularly in the coal industry - at an "economic disadvantage".
