18th century trade ship observations contribute to new £3.7m global climate project07 May 2019
Weather observations made on board trade ships that sailed between Europe and Asia 200 years ago will help scientists improve estimates of how global climate has changed over the industrial era.
The £3.7m GloSAT project, involving the University of Reading, is backed by £3.2m from the Natural Environmental Research Council (NERC). It will use air temperature records from marine voyages such as the fleet of the English East India Company between 1789–1834 along trade routes from Europe to India and Southeast Asia. It will also incorporate observations from land stations before 1850 that have not yet been used in global datasets.
The project will generate new estimates of global surface air temperature, helping policymakers better assess measures intended to limit increases in the Earth’s surface temperature to well below 2˚C, in-line with the landmark Paris Agreement. It will also shed more light on the causes of natural climate variations.
GloSAT has also teamed-up with the citizen science project, Ed Hawkins, Professor of Climate Science at the University of Reading, said: “Retrieving temperature records from merchant ships and weather stations from more than 200 years ago offers a unique glimpse into the past. This will help us to make sense of today’s climate and use data on historical weather events like storms to forecast those yet to come., to extend the observations available for analysis and evaluation of our temperature records.
“A better understanding of how the Earth’s climate has changed over time is vital if we are serious about keeping global temperature rise to below 2C. This project is another example of how looking back helps us look forward and can guide our action to avoid the dangerous implications of exceeding the Paris Agreement target.”
GloSAT will be led by the National Oceanography Centre (NOC), in collaboration with scientists from the Met Office Hadley Centre and from the Universities of Reading, East Anglia, Edinburgh, York, and Southampton. GloSAT will run for four years from October 2019 with total resources of £3.7m, of which are providing £3.2m.
Current observational estimates of temperature change are a blend of sea-surface temperature over the ocean, and air temperature above land and ice. This mixture of air and water temperatures can be complex to interpret and introduces some inconsistencies, especially when comparing observed temperature changes with those predicted by climate models.
GloSAT will improve the consistency by constructing a new observational record using air temperature over the ocean instead of sea-surface temperature.
Using ship's observations of air temperature has a huge advantage because air temperature was measured on ships for decades before sea-surface temperature, meaning scientists can extend the data record back further in time.
A major part of GloSAT is to analyse these additional land and marine observations, which are not currently used in global surface temperature records, so scientists can more confidently estimate temperature change over more than two centuries.
This longer record will give a better understanding of natural climate variability generated internally within the climate system, as well as that due to external factors, such as increasing greenhouse gas concentrations, volcanic eruptions and solar changes.
Dr Elizabeth Kent from the National Oceanography Centre said: "GloSAT brings together the generation and analysis of new climate temperature records in a single project across ocean, land and ice for the past two centuries. This broad scope ensures we can produce the most globally-consistent temperature estimates possible, and that analysis can properly account for the uncertainties that will inevitably remain."
Image caption - The East Indiaman Asia. Credit: National Maritime Museum, Greenwich, London