2018 was Earth's 4th-warmest year on record, coming in behind 2016, the planet's warmest recorded year, as well as 2015 and 2017, according to information released by NOAA, NASA and the U.K. Met Office.
Why it matters: The yearly rankings don't tell the whole story of long-term climate change, since natural variability can still push or pull an individual year up or down the rankings. However, the overall picture is growing starker with each passing year. Nine of the 10 warmest years on record since reliable data began in 1880 have occurred since 2005. At the same time, greenhouse gases from the burning of fossil fuels — as well as deforestation and intensive agriculture — have skyrocketed to levels not seen in more than 800,000 years.