An annual report that is sometimes called the planet's "physical" finds that 2015 was the warmest year since at least the mid to late 19th century. The year also marked several other milestones, from a record carbon concentration to an unusual number of tropical storms.
The 26th report, State of the Climate in 2015, released online today by the American Meteorological Society (AMS), was compiled by hundreds of scientists from 62 countries and was peer reviewed.
“Last year’s record heat resulted from the combined influence of long-term global warming and one of the strongest El Niño events the globe has experienced since at least 1950," NOAA’s National Centers for Environmental Information says in a statement.
"The report found that most indicators of climate change continued to reflect trends consistent with a warming planet. Several markers such as land and ocean temperatures, sea levels and greenhouse gases broke records set just one year prior,” the statement said.
Here's a look at the report by the numbers:
1. In 2015, the Earth was 1°C warmer than in preindustrial times.
Aided by a strong El Niño, global surface temperatures hit record highs for the second consecutive year, passing the previous record set in 2014 by more than 0.1°C (0.2°F). This exceeded the average for the preindustrial era by more than 1°C (1.8°F) for the first time. This warmth was seen across all inhabited continents.
2. Sea-surface temperatures hit record levels.
The global average sea-surface temperature also passed the previous record, which was also set in 2014. The biggest warming was seen in the northeast Pacific, while the North Atlantic was colder than average.
3. Carbon dioxide concentration surpassed milestone.
Hawaii's Mauna Loa observatory recorded its first annual mean carbon dioxide concentration at greater than 400 parts per million, which has long been seen as an important symbolic threshold. Mauna Loa represents the site of the world's longest observations of carbon dioxide and was chosen because the high-altitude site is less likely to be influenced by local fluctuations.
The new average at Mauna Loa was 3.1 parts per million more than in 2014, representing the largest annual increase observed in the 58-year record.
The 2015 global average carbon dioxide concentration, as measured at multiple sites, was 399.4 parts per million, an increase of 2.2 parts per million over 2014.
4. Global sea level has reached the highest on record.
Often seen as a critical result from warming, global average sea level rose to a new high in 2015, about 70 millimeters (about 2¾ inches) higher than the 1993 average, which marks the start of accurate measurements via satellites. Over the past two decades, sea level has risen an average of 3.3 millimeters (about 0.15 inch) per year, with the highest increase in the western Pacific and Indian Oceans.
5. Many parts of the world experienced extreme weather.
Greater than average rainy seasons led to catastrophic flooding in many parts of the world in 2015. At the same time, places suffering from severe drought rose from 8 percent in 2014 to 14 percent in 2015. There were 101 tropical cyclones in 2015, well above the 1981–2010 average of 82 storms. In particular, the eastern/central Pacific had 26 named storms, the most since 1992. The North Atlantic hurricane season was quieter than normal, as often happens during El Niño years.