Weather extremes in 2018 included wildfires in California and Greece, drought in South Africa and floods in Kerala, India.
The past five years have been the hottest in human history. While the East Coast received record precipitation during 2018, the majority of the Midwest and West regions saw a dry year.
Moreover, 2015 was the first year when global annual average surface temperatures reached 1C above pre-industrial levels, and the following three years have all remained close to this level.
"2018 is yet again an extremely warm year on top of a long-term global warming trend", said NASA's Goddard Institute for Space Studies (GISS) director, Gavin Schmidt. According to figures released by specialists running the world's leading temperature datasets confirmed previous estimates that 2018 was the fourth hottest year on record.
NOAA and NASA contribute data to the WMO.
"That is not saying the Paris Agreement is done for. but it's a worrying sign", he added. The United Nations defines the 1.5C Paris temperature target as a 30-year average, not a freak blip in a single year.
Most importantly, ice sheet loss from Arctic and Antarctic glaciers lead to sea level rise, which threatens coastal communities around the globe, particularly in developing regions of the world.
Scientists found that the Arctic has experienced the most warming, contributing to global sea level rise. That puts us more than two-thirds of the way to the warming limit of 1.5 degrees Celsius that was set in the Paris climate agreement.
Patrick Verkooijen, head of the Global Center on Adaptation in the Netherlands, said that the WMO report showed "climate change is not a distant phenomenon but is here right now".
He called for more, greener investments, ranging from defences against rising seas to drought-resistant crops.