United Nations Secretary-General Ban Ki-moon warned on Wednesday that extreme weather events are becoming "the new normal" and bold climate action is needed to "face the future now."

"Only by responding decisively to the climate challenge can we avoid the worst impacts of climate change and lay the foundations of a world of peace, prosperity and opportunity for all," the UN chief said in a message to mark the World Meteorological Day.

The window of opportunity for limiting global temperature rise to well below two degrees Celsius – the threshold set under the Paris Agreement adopted last December – is narrow and rapidly shrinking, Mr. Ban warned, noting that the effects of a warming planet will be felt by all, including rising sea levels, and extreme weather events, which are becoming "the new normal."

On 22 April, world leaders will gather in New York to sign the Paris Agreement. "But, even before the agreement comes into force, every country, every business and every citizen has a role to play in combating climate change and building a sustainable future for this and future generations," he said.

Petteri Taalas, Secretary-General of the World Meteorological Organization (WMO), said in his message that the Earth is already one degree Celsius hotter than at the start of the twentieth century, indicative of this year's theme of the World Meteorological Day: "Hotter, drier, wetter: face the future."

"Climate change is affecting our natural and human environment. Our emissions of greenhouse gases continue to rise, and the temperature of the lower atmosphere and the ocean is increasing, he said, adding: "The international community has unanimously recognized the need for bold action."

Citing the Paris Agreement to "hold the increase in the global average temperature to well below two degree Celsius above pre-industrial levels and pursue efforts to limit the temperature increase to 1.5 degrees," he stressed that WMO and the national meteorological and hydrological services are playing an essential role in building climate-resilient societies.

Health risks related to heat can be reduced through multi-hazard early warning systems that provide timely alerts to decision-makers, health services and the general public, he said, also underscoring the need to improve access to scientific knowledge and share best practices for coping with drought.

The WMO community will continue to support countries in pursuing sustainable development and tackling climate change by providing the best possible science and operational services for weather, climate, hydrology, oceans and the environment.

According to the "WMO Statement on the Status of the Climate in 2015", the year made history, with shattered temperature records, intense heatwaves, exceptional rainfall, devastating drought and unusual tropical cyclone activity.

"Our planet is sending a powerful message to world leaders to sign and implement the Paris Agreement on climate change and cut greenhouse gases now before we pass the point of no return," Mr. Taalas said earlier this week in a press release, emphasizing that the worst-case scenarios can be averted by taking urgent and far-reaching measures to cut carbon dioxide emissions.