The climate data for 2018 is now mostly in, though the ongoing shutdown of the US government has caused some datasets to be delayed. In this article, Carbon Brief explains why last year proved to be so remarkable across the oceans, atmosphere, cryosphere and surface temperature of the planet. A number of records for the Earth’s climate were set in 2018: It was the warmest year on record for ocean heat content, which increased markedly between 2017 and 2018. It was the fourth warmest year on record for surface temperature. It was the sixth warmest year in the lower troposphere – the lower part of the atmosphere. Greenhouse gas concentrations reached record levels for CO2, methane, and nitrous oxide. Sea ice was well below the long-term average at both poles for most of the year. The summer Arctic sea ice minimum was the sixth lowest since records began in […]