Prince William did not mince his words on Thursday when he issued a stark warning at the Greentown Labs near Boston.
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The Prince and Princess met with the Chief Executive Officer of the organisation and the President of the Northeast Clean Energy Council, to learn about the history of the labs and how it is contributing to global efforts to address the climate crisis.
WATCH: Princess Kate and Prince William visit Greentown Labs during Boston royal tour
During the visit, the Prince revealed: "For all of us the time is ticking," whilst in conversation with a number of finalists of last year's Earthshot Prize winners as he praised them for their groundbreaking work.
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Speaking about the prize he said: "After last year, this year we've had a lot more interest in the last few weeks."
Prince William and Princess Kate visited Greentown labs on Thursday
William added, "Well done, you guys. It's very good to hear these success stories. I know there is more to do."
Greentown is recognised as the largest climate technology start-up incubator in North America, having supported more than 500 companies since its founding that have collectively created more than 9,000 jobs and raised more than $4 billion.
This year's Earthshot Prize's will be presented on Friday on the third day of their three-day-tour in the US.
The pair enjoyed a basketball game on Wednesday
The revelation came just after HELLO!'s royal editor, Emily Nash, explained how the royal couple will react to Prince Harry and Meghan Markle's new trailer for their upcoming docuseries, which was released ahead of their visit.
Emily explained: "I think that everyone in the Prince and Princess of Wales' team is just very keen to keep the focus on Earthshot. That's the whole reason they're here and this is something they've been building up to for 18 months.
Prince Harry and Meghan Markle's trailer was released on Thursday
"So they're going to be very disappointed that the attention is going elsewhere at the moment and I'm sure that there are going to be concerns about what's to come in this documentary."
"But I expect it to be business as usual. They are just going to get on with it, get their heads down and do the engagements they've committed to today. I wouldn't expect to see any comment."