The "world is in a mess" and the effects of climate change are dangerous and accelerating, according to the UN secretary general.
In a speech on Tuesday at the New York University Stern School of Business, António Guterres said that it was "absolutely essential" that the world implemented the Paris Agreement.
He also sought to draw attention to the links between policy and security, stating that there was a "compelling security case for climate action."
Under the Paris Agreement, reached at the end of 2015, world leaders have committed to making sure global warming stays "well below" 2 degrees Celsius and to "pursue efforts" to limit the temperature rise to 1.5 degrees Celsius.
There are fears that President Donald Trump is set to pull the U.S. out of the deal – it was reported by Axios on Wednesday that he had indeed decided to do so – although Guterres remained forthright in his support for it and called for a united front.
"Yes, not everyone will move at the same pace or with equal vigor," he said. "But if any government doubts the global will and need for this accord, that is reason for all others to unite even stronger and stay the course."
On the issue of security, Guterres sounded a note of caution. "Around the world, military strategists view climate change as a threat to global peace and security," he said. "We are all aware of the political turmoil and societal tensions that have been generated by the mass movement of refugees."
"Imagine how many people are poised to become climate-displaced when their lands become unliveable."
In a question and answer session after his speech, Guterres said that a vacuum could not exist in geostrategic dimensions. "If one country decides to leave a void, I can guarantee someone else will occupy it," he said.
"Today, the economy and the social aspects are linked to the environmental aspects but they're also linked to the security aspects, they are linked to the risks of conflict, and the conflicts are becoming more and more interlinked and linked to the new threat of global terrorism," he said.
"You have seen what has happened in Manchester, just a few days ago, so I mean if you leave a void to others to occupy you might be creating a problem to your own internal security."
Concerns regarding climate change's impact on security are nothing new. Last September, members of the U.S. national security community said that the effects of climate change presented "a strategically significant risk to U.S. national security and international security" and added that inaction was "not a viable option."
The Climate Security Consensus Project – a bipartisan group composed of 26 national security and military leaders – said that its conclusion was based on a range of factors, including: climate change increasing stresses on water, food and energy security both in the U.S. and abroad; and climate change increasing the possibility of state failure, mass migration and intra or international conflict.
During his speech, Guterres said that the "sustainability train" had "left the station."
"Those who fail to bet on the green economy will be living in a grey future," he went on to state.
"On the other hand, those who embrace green technologies will set the gold standard for economic leadership in the 21st century."
Back in the question and answer session, Guterres said, "We believe that it will be important for the U.S. not to leave the Paris Agreement."
"But even if (the) U.S. government decides to leave the Paris Agreement, it's very important for the U.S. societies as a whole – for the cities, the states, the companies, the businesses – to remain engaged with the Paris Agreement."