UN chief Antonio Guterres said climate-related devastation was striking the planet on a weekly basis and warned on Sunday that urgent action must be taken to avoid a catastrophe.
"We are here because the world is facing a grave climate emergency," Guterres told a two-day Abu Dhabi Climate Meeting to prepare for a Climate Action Summit in New York in September.
"Climate disruption is happening now... It is progressing even faster than the world's top scientists have predicted," the UN secretary general said.
"It is outpacing our efforts to address it. Climate change is running faster than we are," he said.
"Every week brings new climate-related devastation... floods, drought, heatwaves, wildfires and super storms," Guterres said.
He warned the situation would only deteriorate unless "we act now with ambition and urgency", but some of the world's decision-makers still did not realise the dangers.
The UN chief held out hope in the Paris Agreement to cut harmful emissions and reduce global warming.
"But we know that even if the promises of Paris are fully met, we still face at least a three-degree temperature rise by the end of the century -- a catastrophe for life as we know it," Guterres said.
He was convening the Climate Action Summit because many countries were not even keeping pace with their promises under the Paris Agreement.
Under the Paris Agreement, the world is required to keep temperature rise under 2 degrees Celsius by the end of the century.
A landmark report last year by the Intergovernmental Panel on Climate Change (IPCC) said a safer cap of a 1.5 degree rise would see nations rapidly slash planet-warming greenhouse gas emissions via a sharp drawdown of fossil fuel use.
But some high-polluting nations, led by Saudi Arabia, have questioned the IPCC's findings, leading to angry exchanges at closed-door talks in Bonn.
It is thought that $300 billion will be needed annually by 2030 to help nations deal with climate-related disasters.
IPCC warned in October that warming was on track towards a catastrophic 3C or 4C rise, and that avoiding global chaos would require a major transformation.
"The Climate Action Summit is an opportunity for political, business and civil society leaders to set an example," Guterres said.