Abstract
AbstractWe present a new version of the Met Office Hadley Centre/Climatic Research Unit global surface temperature data set, HadCRUT5. HadCRUT5 presents monthly average near‐surface temperature anomalies, relative to the 1961–1990 period, on a regular 5° latitude by 5° longitude grid from 1850 to 2018. HadCRUT5 is a combination of sea‐surface temperature (SST) measurements over the ocean from ships and buoys and near‐surface air temperature measurements from weather stations over the land surface. These data have been sourced from updated compilations and the adjustments applied to mitigate the impact of changes in SST measurement methods have been revised. Two variants of HadCRUT5 have been produced for use in different applications. The first represents temperature anomaly data on a grid for locations where measurement data are available. The second, more spatially complete, variant uses a Gaussian process based statistical method to make better use of the available observations, extending temperature anomaly estimates into regions for which the underlying measurements are informative. Each is provided as a 200‐member ensemble accompanied by additional uncertainty information. The combination of revised input data sets and statistical analysis results in greater warming of the global average over the course of the whole record. In recent years, increased warming results from an improved representation of Arctic warming and a better understanding of evolving biases in SST measurements from ships. These updates result in greater consistency with other independent global surface temperature data sets, despite their different approaches to data set construction, and further increase confidence in our understanding of changes seen.
Highlights
Observational evidence plays an essential role in our understanding of the climate, the causes of the observed changes and distance travelled along predicted future trajectories
The differences between the non-infilled HadCRUT5 and HadCRUT4 primarily arise from updates to the sea-surface temperature (SST) observational bias assessment in HadSST4
The most obvious difference is the relative warming of HadCRUT5 between around 1970 and 604 1980
Summary
Observational evidence plays an essential role in our understanding of the climate, the causes of the observed changes and distance travelled along predicted future trajectories. Global near-surface temperature analyses, based on a combination of air temperature observations over land with sea-surface temperature (SST) observations, are among the longest instrumental records of climate change and variability. They are routinely used in assessments of the state of the climate Blunden & Arndt, 2019) They underpin our understanding of multi decadal to centennial changes and the causes of those changes (e.g. Hartmann et al, 2013) and are a key metric against which climate change policy decisions are made and progress against international agreements is measured (e.g. Allen et al, 2018)
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