Briefing: Global surface temperature records: an update

Abstract

In the past 3 years, global surface temperatures have spiked considerably. In early 2016 it is possible that they briefly exceeded 1·5 K above ‘pre-industrial’ levels. This spike was the result of a combination of the underlying trend and internal climate system variability. Up until about 2015, there was much discussion of a potential ‘hiatus’ feature in the recent records and the implications thereof for the understanding of climate and the verity of projections. The general message across a broad range of literature is that some combination of internal climate system variability and external forcing effects principally from volcanoes and the sun was responsible for some part of this. However, there has also been renewed interest in analyses of historical records, from which several new and revised data products have arisen. These have served to highlight the roles of both modern marine data biases and spatial coverage. Accounting for these reduces the magnitude of the apparent muted warming in the early twenty-first century. Global mean temperatures have increased on multidecadal timescales, and only invoking human influences can explain these rises adequately. Natural variability can mask or exacerbate the underlying trend for periods of up to a decade or so.