Extreme weather and climate conditions, including Arctic "heatwaves", are continuing this year, after 2016 topped the global temperature charts and saw shrinking sea ice and surging sea levels.
The World Meteorological Organisation (WMO) warned Tuesday that the drastic shifts seen in the global climate system that resulted in a range of alarming records last year appear to be continuing unabated.
"We are now in truly, unchartered territory," David Carlson, head of the World Climate Research Programme, said in a release from the WMO.
He said that even without a strong El Nino - a phenomenon that brings generally warmer temperatures every four to five years - 2017 was "seeing other remarkable changes across the planet that are challenging our understanding of the climate system."
The warning came as the WMO published on Tuesday its annual report on the state of the global climate, confirming previously released figures showing that 2016 was the warmest year on record.
Last year, global average temperatures were about 1.1 degree Celsius (1.98 Fahrenheit) above the pre-industrial period, and about 0.06 degrees Celsius above the previous record set in 2015, the WMO said.
Globally, average sea surface temperatures were also the highest on record last year; sea levels continued to rise; and Arctic sea ice levels were far below average, it found, warning that greenhouse gas emissions were the main driver behind the warming trend.
"With levels of carbon dioxide in the atmosphere consistently breaking new records, the influence of human activities on the climate system has become more and more evident," WMO chief Petteri Taalas said in the statement.
The UN agency said that increasingly powerful computers and the availability of long-term climate data had made it possible to "demonstrate clearly the existence of links between man-made climate change and many cases of high-impact extreme events, in particular heatwaves." .
Even more alarming than the 2016 figures is perhaps the fact that the trends all appear to be continuing.
The WMO noted that at least three times so far this winter, "the Arctic has witnessed the Polar equivalent of a heatwave, with powerful Atlantic storms driving an influx of warm, moist air."
"This meant that at the height of the Arctic winter and the sea ice refreezing period, there were days which were actually close to the melting point," the statement said, adding that Antarctic sea ice had also been at "a record low".
The agency pointed to research showing that changes in the Arctic and melting sea ice were leading to a shift in wider oceanic and atmospheric circulation patterns.
This in turn, is affecting weather elsewhere in the world, since it impacts the waves in the jet stream - a fast-moving band of air that helps regulate temperature.
This has led some areas, like the United States and Canada, to experience unusually balmy temperatures, while others, including the Arabian peninsula and North Africa, have experienced an unusually cold first few months this year.
The WMO also pointed to newly released studies indicating that ocean heat content may have increased even more than reported.
"Provisional data also indicates that there has been no easing in the rate of increase in atmospheric carbon dioxide concentrations," it said