Global temperatures hit a record on Monday, underscoring the dangers of ever-increasing greenhouse gas emissions generated from burning fossil fuels.

The average worldwide temperature was 17 degrees Celsius, just above the previous record of 16.9C reached in August 2016, according to data from the National Centers for Environmental Prediction. The new high underscores the extremity of 2023’s summer in the northern hemisphere, and brings into focus the slow pace of global progress on curbing emissions.

"This is not a milestone we should be celebrating, it's a death sentence for people and ecosystems,” said Friederike Otto, a senior lecturer at the Grantham Institute for Climate Change and the Environment. "Worryingly, it won't be the hottest day for a long time.” The El Nino weather phenomenon is set to push global temperatures higher, she said.

The heat this summer has already put millions of people around the world at risk. China is experiencing a scorching new heat wave less than two weeks after temperatures broke records in Beijing. Extreme heat in India last month has been linked to deaths in some of its poorest regions. Last week saw a dangerous heat dome cover Texas and northern Mexico, while the U.K. baked in its hottest June on record.

El Nino conditions have developed in the tropical Pacific for the first time in seven years and will trigger a surge in temperatures, according to the World Meteorological Organization. "The onset of El Nino will greatly increase the likelihood of breaking temperature records,” WMO Secretary-General Petteri Taalas said in a Tuesday statement.

It’s likely the world will exceed 1.5C of warming "in the near term,” with efforts on climate action still insufficient, the Intergovernmental Panel on Climate Change said in March in a report summarizing five years of its own research. Global greenhouse gas emissions need to be cut to 60% below 2019 levels by 2035, according to the report, and climate-related risks are rising with every increment of warming.

"Our world needs climate action on all fronts — everything, everywhere, all at once,” U.N. Secretary General Antonio Guterres said in a statement at the time. Guterres has urged nations to rapidly accelerate plans to phase out the use of fossil fuels.