Last year was the undisputed warmest on record, as the planet Earth watched as sea levels rose, oceans became warmer, and sea ice disappeared.

The United Nations World Meteorological Organization (WMO) in Geneva issued its annual State of the Global Climate statement in advance of World Meteorological Day on Thursday. 

"This report confirms that the year 2016 was the warmest on record - a remarkable 1.1 (degrees Celsius) above the pre-industrial period, which is 0.06 (degrees Celsius) above the previous record set in 2015," said WMO Secretary-General Petteri Taalas.  "This increase in global temperature is consistent with other changes occurring in the climate system," he continued.  "Globally averaged sea surface temperatures were also the warmest on record, global sea levels continued to rise, and Arctic sea-ice extent was well below average for most of the year."

Warming may have been boosted by the El Nino weather phenomenon, but the big driver of "long-term climate change caused by greenhouse gas emissions" was human activity.

"Even without a strong El Nino in 2017, we are seeing other remarkable changes across the planet that are challenging the limits of our understanding of the climate system," said David Carlson, director of the World Climate Research Program.  "We are now in truly uncharted territory."