The federal government confirmed 2016 as the planet's warmest year on record, according to a report released Thursday by the National Oceanic and Atmospheric Administration.
The combined influence of long-term global warming and a strong El Niño early in the year led to last year's all-time record heat, NOAA said.
While El Niño is a natural warming of Pacific Ocean water, man-made global warming is caused by greenhouse gases released into the atmosphere from the burning of fossil fuels such as oil, gas and coal.
The amount of carbon dioxide, one of the main greenhouse gases, in the atmosphere climbed to its highest level in 800,000 years, the report found.
The report also noted other signs of a warming planet in 2016:
- Greenhouse gases were the highest on record.
- Sea-surface temperatures were the highest on record.
- Global upper ocean heat content near-record high.
- Global sea level was the highest on record.
- Antarctic had a record low sea ice extent.
Known as the State of the Climate, the annual report is prepared by more than 450 scientists from more than 60 countries around the world and published in conjunction with the American Meteorological Society. It's the most comprehensive annual summary of Earth's climate.