The pace of climate change has not been slowed down by the global health crisis.
The United Nations made the declaration on Thursday (September 16), adding that the world is still behind in its battle to cut carbon emissions.
Petteri Taalas is Secretary-General of the World Meteorological Organization.
"There has been classically thinking that perhaps in the future something may happen, but it's obvious that we have to start acting already now, if we want to reach the low limit of Paris agreement."
The WMO said lockdowns and other restriction measures only led to a temporary downturn in CO2 emissions last year.
It added there is a rising chance the world will miss a target set in 2015's Paris Agreement, where global powers agreed to reduce global warming to 1.5 degrees celsius above pre-industrial levels.
The WMO also talked about recent freak weather events.
"In western Germany that was very unusual and led also to almost 200 casualties and, because of climate change, these kinds of events that used to happen every hundred years, they may happen nowadays every 20 years and, in the future, even more often. So, the risk of this kind of event is growing because of climate change."
The U.N. said concentrations of major greenhouse gases like CO2, methane and nitrous oxide continued to rise in 2020 and the first half of this year.
The average global temperature for the past five years was among the highest on record.
The U.N. Secretary-General Antonio Guterres said in a statement the results were an "alarming appraisal of just how far off course we are."