This, he said, shows that "the overall long-term warming as a result of greenhouse gas increases is now far larger than the year-to-year variability in global average temperatures caused by naturally occurring climate drivers."
La Nina refers to the large-scale cooling of surface temperatures in the central and eastern equatorial Pacific Ocean, with widespread impacts on weather around the world.
The phenomenon, which typically has the opposite impacts as the warming El Nino phenomenon, usually occurs every two to seven years, but has now hit twice since 2020.
WMO reached its conclusions by consolidating six leading international datasets, including the European Union's Copernicus climate monitor (C3S) and the US National Oceanic and Atmospheric Administration (NOAA), which announced similar findings last week.
The datasets showed that the average global temperature in 2021 was around 1.11 degrees Celsius above the pre-industrial levels measured between 1850 and 1900.
Last year also marked the seventh consecutive year that global temperatures were more than 1C above pre-industrial levels, the datasets showed.
"The global average temperature in 2021 is already approaching the lower limit of temperature increase the Paris Agreement seeks to avert," the WMO warned.
The 2015 Paris Agreement saw countries agree to cap global warming at "well below" 2C above pre-industrial levels, and 1.5C if possible.
The WMO stressed that the unbroken warm streak over the past seven years was part of a longer-term trend towards higher global temperatures.
"Since the 1980s, each decade has been warmer than the previous one," it said.
"This is expected to continue."
The datasets varied slightly in their assessment of where 2021 ranked among the seven warmest years, with C3S ranking it fifth, NOAA ranking it sixth, and others saying it was seventh.
"The small differences among these datasets indicates the margin of error for calculating the average global temperature," the WMO said.
But while 2021 was among the coolest of the top-seven hottest years, it was still marked by a range of record temperatures and extreme weather events linked to global warming.
Taalas pointed to the "record-shattering temperature of nearly 50C in Canada, comparable to the values reported in the hot Saharan Desert of Algeria, exceptional rainfall, and deadly flooding in Asia and Europe as well as drought in parts of Africa and South America."
"Climate change impacts and weather-related hazards had life-changing and devastating impacts on communities on every single continent."