At a time when the world is struggling to fight climate change, US President Donald Trump's administration has quietly killed a NASA system to monitor the flow of greenhouse gas, the media reported.

The White House has mounted a broad attack on climate science, repeatedly proposing cuts to NASA's earth science budget, including NASA's Carbon Monitoring System (CMS), the Science Magazine reported this week.

It has now scrapped the funding for the US space agency's CMS which has until now used satellite and aircraft instruments to monitor carbon dioxide and methane levels remotely — spending $10m each year, the Independent reported on Thursday.

Canceling the CMS "is a grave mistake", Kelly Sims Gallagher, director of Tufts University's Centre for International Environment and Resource Policy, told the Science Magazine.

"If you cannot measure emissions reductions, you cannot be confident that countries are adhering to the (Paris climate) agreement," Gallagher added.

Other scientists also expressed their concerns about the impact the killing oc CMS would have on fighting climate change.

Scrapping the system was "disappointing", said Stephen Hagen, a senior scientist at Applied GeoSolutions in New Hampshire.

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"(This) means we're going to be less capable of tracking changes in carbon," he added.

But the NASA system has been an obvious target for Trump who had begun the withdrawal process from the Paris accord.

The accord was signed in December 2015 by nearly 200 countries to curb global carbon emissions and contain global warming to 2 degrees Celsius. (IANS)