The temporary decline in global emissions last year driven by COVID-19 restrictions had little to no impact at all on the long-term forecast, the report said.
"At the current rate of increase in greenhouse gas concentrations, we will see a temperature increase by the end of this century far in excess of the Paris Agreement targets of 1.5 to 2 degrees Celsius above preindustrial levels," WMO Secretary-General Petteri Taalas said in a statement. "We are way off track."
Monday's report said the concentration of carbon dioxide in 2020 was 149% of the preindustrial level. That figure for methane was 262% and 123% for nitrous oxide. The preindustrial level is the point at which scientists believe that human activity began to destabilize the climate.
Monday's WMO report noted that the long-lifespan of carbon dioxide means that the present level in the atmosphere would last for decades, even if the world stopped all global-heating emissions today. File Photo by Kevin Dietsch/UPI
The assessment said the burning of coal, oil and gas are the greatest source of heat-trapping carbon dioxide, causing about two-thirds of worldwide heating.
The report also noted the long-lasting effects of carbon dioxide, saying that the present level would last for decades, even if the world instantly stopped all emissions.
"The last time the Earth experienced a comparable concentration of CO2 was 3 to 5 million years ago, when the temperature was 2-3 degrees Celsius warmer and sea level was 10-20 meters higher than now," Taalas said. "But there weren't 7.8 billion people then."
Monday's sobering assessment came about a week before the start of the United Nations COP26 summit, at which leaders hope to set out clear and coordinated climate guidelines to mitigate global warming. Some scientists have said the summit may be the last best chance for the international community to effectively impact the direction of climate change.
"We need to transform our commitment into action that will have an impact of the gases that drive climate change," Taalas said. "We need to revisit our industrial, energy and transport systems and whole way of life.
"The needed changes are economically affordable and technically possible. There is no time to lose."