The past five years have been, in total, the hottest on record, with 2018 the fourth-warmest since modern records began. In 2018, Earth’s global surface temperatures were the fourth warmest since 1880, according to space agency Nasa, and the National Oceanic and Atmospheric Administration (NOAA).
Global temperatures last year were 0.83 degrees Celsius warmer than the 1951 to 1980 mean (when you add up all the numbers and divide by the total), and 1.01 degrees Celsius warmer than the 1880 mean. Globally, 2018’s temperatures lie behind those of 2016, 2017, and 2015, but altogether, the past five years are the warmest on record.
According to scientists, the warming is being driven mostly by increased emissions into the atmosphere of carbon dioxide and other greenhouse gases caused by human activities.
Weather patterns affect regional temperatures, so not every place on Earth has had the same amount of warming, but the trend is strongest in the Arctic region, where 2018 saw the continued loss of sea ice. Additionally, mass loss from the Greenland and Antarctic ice sheets continued to contribute to rising sea levels. Increasing temperatures are also contributing to longer fire seasons and some extreme weather events.
Nasa’s analyses add temperature measurements from 6,300 weather stations, ship- and buoy-based observations of sea temperatures, and temperature measurements from Antarctic research stations. These raw measurements are analysed using an algorithm that considers the different spacing of temperature stations around the world and other effects that could change the conclusions. These calculations produce the global average temperature changes from the benchmark period of 1951 to 1980.
Nasa estimates that 2018’s global mean change data has a 95 per cent certainty level.