Donald Trump's run for the US presidency gained an unwanted kind of endorsement, as several of the world's top scientists congregated to pen an open letter warning Americans against voting for the Republican presidential candidate.

The likes of renowned physicist Stephen Hawking and prolific astrophysicist Neil deGrasse Tyson have supported the pact written by 375 members of the US National Academy of Sciences, which basically says that a vote for Trump is a vote against the environment.

The top scientists, among them being 30 Nobel Prize winners, warned that the possibility of the US pulling out of the Paris Climate Agreement is as good as guaranteed under a Trump presidency, by way of his statements condemning climate change as just a "hoax."

Such a possibility, referred to as "Parexit" by the letter, "would send a clear signal to the rest of the world: 'The United States does not care about the global problem of human-caused climate change. You are on your own."

The US, along with China - two of the world's largest greenhouse gas emitters, ratified the agreement just this month. It's a symbolic move that commits the world's largest economy to more sustainable means of production that cuts down on carbon emissions, the Huffington Post has reported.

The letter, which actually doesn't mention Trump by name, calls on Americans to use the upcoming presidential elections to push for agendas supporting environmental sustainability. It recognizes that the US "must be a major player in developing innovative solutions to the problem of...greenhouse gases."

"During the Presidential primary campaign, claims were made that the Earth is not warming, or that warming is due to purely natural causes outside of human control. Such claims are inconsistent with reality," the letter elaborated in a subtle dig against Trump.

Tyson, while not being a signatory to the open letter, endorsed it via Mashable, saying, "For lawmakers to not heed the advice of esteemed scientists on matters of science, in this the 21st century, signals the beginning of the end of an informed democracy."