The head of the United Nations called Monday for scientists to serve up "cold, hard facts" to push governments into making policies that curb climate change before a key global warming threshold is passed.

His comments came as experts and officials from around the world gathered for a week-long meeting in the Swiss Alpine town of Interlaken to finalize the last of seven reports issued by the global body's panel of top scientists since the Paris climate accord was forged in 2015.

In a video address to delegates, U.N. Secretary-General Antonio Guterres said that the latest report by the Intergovernmental Panel on Climate Change "could not come at a more pivotal time."

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"Our world is at a crossroads — and our planet is in the crosshairs," he said. "We are nearing the point of no return; of overshooting the internationally agreed limit of 2.7 Fahrenheit of global warming."

That threshold, agreed in Paris almost eight years ago and measured against average temperatures during pre-industrial times, has become the yardstick for climate scientists who warn of the dangers of an ever hotter planet.

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Guterres cited recent IPCC reports showing that while some impacts of global warming are already unavoidable, "it is possible to limit global warming to 1.5 degrees with rapid and deep emissions reductions across all sectors of the global economy." Some scientists disagree, noting that the rate at which greenhouse gas is being pumped into the atmosphere makes this limit almost impossible to keep to.

The U.N. chief said the final installment in the IPCC's sixth reporting cycle — known as the synthesis report because it brings together insights from six previous papers — should provide governments with "solid, frank, detailed scientific guidance to make the right decisions for people and planet" when they gather for the annual world climate conference in Dubai at the end of the year.

Guterres stressed that speeding up the phase-out of fossil fuels is "tough but essential."

"Show the urgent need to end global heating with cold, hard facts," he told delegates.