2018 was the fourth warmest year in the global surface temperature record, according to year end updates from NASA, NOAA and the UK MetOffice, albeit somewhat cooler than the 2016 peak. This continues a string of record or near-record annual temperatures, with the top four occurring in the past four years.
As in my previous updates (see here and here), I’ll provide some additional context, highlighting the issue of coverage bias and ongoing Arctic warming. Series that use statistical methods to account for areas with few or no observations, especially in the Arctic, continue to diverge markedly from those with little or no interpolation. Recent observations also show the emergence of a seasonal pattern in Arctic warming, an important aspect of coverage bias that has been less explored thus far. In addition, the last decade or so has seen the emergence of ship-buoy SST bias, first identified in a key 2015 paper from NOAA and confirmed in our 2016 paper.