The report also noted that surges in sea temperatures known as "marine heatwaves" which devastate underwater life had become more common.
The report said the concentration of CO2 in the atmosphere hit a record level of 407.8 parts per million in 2018 and continued to rise in 2019. Opening the climate summit on Monday, United Nations Secretary-General Antonio Guterres had warned that 400 parts per million had once been considered an "unthinkable" tipping point.
A drumbeat of dire reports from climate science in the past year has fuelled environmental activism, prompted some companies to commit to slashing emissions and raised concerns among investors about the stability of asset prices.
Nevertheless, delegates in Madrid are facing an uphill battle to persuade major emitters to embrace the kind of radical change needed to shift the Earth's climate system onto a more habitable trajectory.
