Historical Ocean Surface Temperatures: Adjustment, Characterisation and Evaluation (HOSTACE)

Lead Research Organisation: National Oceanography Centre
Department Name: Science and Technology

Abstract

The surface temperature of the land and sea is the main measure of "global warming". Measurements of sea surface temperature (SST) have been made for more than 200 years, first on sailing ships, now on a mixture of ships and buoys (drifting and moored). Technology has changed dramatically over this period, raising serious questions about whether technology changes over time give a misleading impression of how the temperature has changed - and therefore how climate has changed.

People first measured the temperature of a seawater sample hauled up in a wooden bucket. Buckets are now made of insulating rubber. Most direct SST measurements are now sent via satellites from drifting buoys. Many other measurement methods have also been used. Different methods don't yield precisely the same SST values, and because global warming is a gradual change, these subtle discrepancies (or "biases") could distort our picture about the timing and magnitude of global warming. So, we must be sure that we understand how the different methods used to measure SST have affected the observations.

These biases in SST have been a known problem for years, so why do we believe we can solve it? One reason is that recently many more observations have been retrieved from historical sources. Many ships' logbooks containing weather observations have been digitised. This has nearly doubled the number of observations before World War 2. Another reason is new, stable observations of SST from sensors on satellites orbiting Earth. Most satellite sensors give a detailed picture of patterns in SST and are tuned to drifting buoy SSTs to give reasonable accuracy. But compared to the subtle trends of global warming, they are not stable enough from year to year and across large distances. New high-quality SST measurements from a reworking of the SST measurements of a particular series of sensors are accurate and stable enough. Even better, they do not rely on ship or buoy SST observations, so we can use them as an independent point of reference.

A major challenge is that the biases in SST made on ships are different for different measurement methods and we don't always know what methods were used. But we do know how we expect the biases for each method to vary with factors like the amount of heating by the Sun and wind speed. We will use these variations of the biases for each ship or buoy to assign measurement methods to observations (or, where it is not clear cut, the likelihood that the method is one or another type). E.g., we might be 80% confident that a particular ship used a canvas bucket to sample the water, but allow a 20% chance that a wooden bucket was used. We can then adjust for the expected biases according to method, and indicate how uncertain our adjustment may be.

The next step will be to combine the scattered observations into maps of monthly average SST over the whole ocean. We must also calculate our degree of uncertainty in these monthly maps. There are few observations in the 19thC, so a global SST map requires sophisticated gap-filling methods. The final step is to compare our maps of SST with those produced by other scientists. Normally when such comparisons are made it is hard to understand the source of differences between the datasets. Was it due to different input data? Or different bias adjustments? Or the way the gaps were filled? Collaborating with other dataset producers, we will separate these different effects. For example, we will all use identical inputs, and isolate the effects of different gap-filling methods. This will also test our the uncertainty estimates - if important factors affecting the SST biases have been missed, then estimates of uncertainty may be too small to explain the differences between the SST maps produced by different groups.

Such problems can mislead us in interpreting climate changes. We will use the new SST history to reassess explanations of phases of climate warming during in the 20th C.

Planned Impact

There is intense public interest in climate change and the level of certainty we have in those changes. Our research will provide new clarity in the understanding of biases and uncertainty that exist in historical observations of sea surface temperature (SST). All the results of our research will be made available to the public, including estimates of bias and uncertainty for every observation in the archive. We will make our results available through partnership with the International Comprehensive Ocean-Atmosphere Data Set (ICOADS) Value-Added Database project (IVAD). This will ensure that our results are integrated with the original data archives. Such transparency will help to build confidence in the bias adjustments we apply and hence in the climate change signals seen in the adjusted SST observations. Anyone will be able to download the adjustments and explore their characteristics of our bias adjustments themselves. Further public engagement is through our partnership with the oldWeather citizen science digitisation activity and through material specifically developed for use in secondary schools.

One important outcome from the proposed work will be a comparison of SST datasets from different providers, including ourselves, the National Climate Data Center and Lamont Doherty Earth Observatory in the US and the Met Office in the UK. The comparison will be designed to tease out the causes of the differences seen between the datasets and also to provide some verification of the uncertainty estimates. Such comparisons have been shown to be important in reconciling and understanding climate datasets, for example different datasets of upper-air temperatures are now much better understood following such comparisons. To make the information derived from the dataset comparison more relevant to users of SST datasets we will, with our project partners, produce advice on the strengths and weaknesses of the datasets for different applications. Direct users of our research outside the academic community will include fisheries research, and planning for commercial and military marine operations.

Better estimates of SST and its uncertainty will feed through to better climate predictions. One of our aims is to improve the regional accuracy of historical SST. Improved regional prediction of climate change will have wide societal and economic impact. Benefits will be felt by policy makers who will have improved information for decision making, by everyone affected by climate change and mitigation policies, by engineers designing structures resilient to a changing environment and many others. Our main point of engagement with policy makers themselves is through the UK Department of Energy and Climate Change (DECC) and we will also continue to contribute directly to the Marine Climate Change Impacts Partnership (MCCIP) Annual Reports which transfer high quality evidence on marine climate change impacts to the UK and devolved governments, their agencies and industry.

The early-career researchers and PhD studentships engaged by this project will gain skills in analysis techniques that will be widely applicable beyond the immediate area of their research. Such skills will include statistical and physical analysis, the quantification of uncertainty in observations and analyses, the management of large datasets and the dissemination of complex information.

Publications

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Kent E (2017) A Call for New Approaches to Quantifying Biases in Observations of Sea Surface Temperature in Bulletin of the American Meteorological Society

 
Description Global Surface Air Temperature (GloSAT), NERC Large Grant
Amount £3,314,772 (GBP)
Funding ID NE/S015647/1 
Organisation Natural Environment Research Council 
Sector Public
Country United Kingdom
Start 10/2019 
End 09/2023
 
Title International Comprehensive Ocean-Atmosphere Data Set, Release 3.0 
Description The International Comprehensive Ocean-Atmosphere Data Set (ICOADS) is a global ocean marine meteorological and surface ocean dataset. It is formed by merging many national and international data sources that contain measurements and visual observations from ships (merchant, navy, research), moored and drifting buoys, coastal stations, and other marine and near-surface ocean platforms. Each marine report contains individual observations of meteorological and oceanographic variables, such as sea surface and air temperatures, wind, pressure, humidity, and cloudiness. The coverage is global and sampling density varies depending on date and geographic position relative to shipping routes and ocean observing systems. The latest Release 3.0 (R3.0) of ICOADS covers 1662-2014, and is coupled with improved "preliminary" monthly data and product extensions past 2014. R3.0 includes changes designed to enable more effective exchange of information describing data quality between ICOADS, reanalysis centers, data set developers, scientists and the public. These user-driven innovations include the assignment of a unique identifier (UID) to each marine report, to enable tracing of observations, linking with reports and improved data sharing. Other revisions and extensions of the International Maritime Meteorological Archive (IMMA) common data format incorporate new near-surface oceanographic data elements and cloud parameters. Many new input data and metadata sources have been assembled, and updates and improvements to existing data sources, or removal of erroneous data, made. 
Type Of Material Database/Collection of data 
Year Produced 2016 
Provided To Others? Yes  
Impact Development of new gridded sea surface temperature long-term datasets: Boyin Huang, Peter W. Thorne, Viva F. Banzon, Tim Boyer, Gennady Chepurin, Jay H. Lawrimore, Matthew J. Menne, Thomas M. Smith, Russell S. Vose, Huai-Min Zhang, Extended Reconstructed Sea Surface Temperature, Version 5 (ERSSTv5): Upgrades, Validations, and Intercomparisons, Journal of Climate, 2017, 30, 20, 8179 
URL http://onlinelibrary.wiley.com/doi/10.1002/joc.4775/abstract
 
Description Collaboration with researchers at Colorado State University, leading to publication in Bulletin of the American Meteorological Society 
Organisation Colorado State University
Department Department of Atmospheric Science
Country United States 
Sector Academic/University 
PI Contribution Collaborative research leading to publication in Bulletin of the American Meteorological Society
Collaborator Contribution Collaborative research leading to publication in Bulletin of the American Meteorological Society
Impact Davis, L. B. B., D. W. J. Thompson, J. J. Kennedy and E. C. Kent, 2019: The importance of unresolved biases in 20th century sea-surface temperature observations, Bull. Amer. Meteor. Soc, 100, 621-629, doi: 10.1175/BAMS-D-18-0104.1.
Start Year 2017
 
Description Collaboration with researchers at Harvard University, leading to publication in Nature 
Organisation Harvard University
Department Department of Earth and Planetary Sciences
Country United States 
Sector Academic/University 
PI Contribution Collaborative research into biases in sea surface temperature measurements.
Collaborator Contribution Collaborative research into biases in sea surface temperature measurements.
Impact Chan D., E. C. Kent, D. I. Berry and P. Huybers, 2019: Correcting datasets leads to more homogeneous early 20th century sea surface warming, Nature, 571, 393-397, doi: 10.1038/s41586-019-1349-2.
Start Year 2018
 
Description SST bias collaboration 
Organisation Columbia University
Department Lamont Doherty Earth Observatory
Country United States 
Sector Academic/University 
PI Contribution Co-convened workshop of SST bias experts at the Met Office in 2015, led high-profile publication in Bulletin of the American Meteorological Society "A Call for New Approaches to Quantifying Biases in Observations of Sea Surface Temperature".
Collaborator Contribution Co-convened workshop of SST bias experts at the Met Office in 2015, contributed to high-profile publication in Bulletin of the American Meteorological Society "A Call for New Approaches to Quantifying Biases in Observations of Sea Surface Temperature".
Impact Kent, E.C., J.J. Kennedy, T.M. Smith, S. Hirahara, B. Huang, A. Kaplan, D.E. Parker, C.P. Atkinson, D.I. Berry, G. Carella, Y. Fukuda, M. Ishii, P.D. Jones, F. Lindgren, C.J. Merchant, S. Morak-Bozzo, N.A. Rayner, V. Venema, S. Yasui, and H. Zhang, 2017: A Call for New Approaches to Quantifying Biases in Observations of Sea Surface Temperature. Bull. Amer. Meteor. Soc., 98, 1601-1616, https://doi.org/10.1175/BAMS-D-15-00251.1
Start Year 2015
 
Description SST bias collaboration 
Organisation Japan Meteorological Agency
Department Global Environment and Marine Department
Country Japan 
Sector Public 
PI Contribution Co-convened workshop of SST bias experts at the Met Office in 2015, led high-profile publication in Bulletin of the American Meteorological Society "A Call for New Approaches to Quantifying Biases in Observations of Sea Surface Temperature".
Collaborator Contribution Co-convened workshop of SST bias experts at the Met Office in 2015, contributed to high-profile publication in Bulletin of the American Meteorological Society "A Call for New Approaches to Quantifying Biases in Observations of Sea Surface Temperature".
Impact Kent, E.C., J.J. Kennedy, T.M. Smith, S. Hirahara, B. Huang, A. Kaplan, D.E. Parker, C.P. Atkinson, D.I. Berry, G. Carella, Y. Fukuda, M. Ishii, P.D. Jones, F. Lindgren, C.J. Merchant, S. Morak-Bozzo, N.A. Rayner, V. Venema, S. Yasui, and H. Zhang, 2017: A Call for New Approaches to Quantifying Biases in Observations of Sea Surface Temperature. Bull. Amer. Meteor. Soc., 98, 1601-1616, https://doi.org/10.1175/BAMS-D-15-00251.1
Start Year 2015
 
Description SST bias collaboration 
Organisation Japan Meteorological Agency
Country Japan 
Sector Public 
PI Contribution Co-convened workshop of SST bias experts at the Met Office in 2015, led high-profile publication in Bulletin of the American Meteorological Society "A Call for New Approaches to Quantifying Biases in Observations of Sea Surface Temperature".
Collaborator Contribution Co-convened workshop of SST bias experts at the Met Office in 2015, contributed to high-profile publication in Bulletin of the American Meteorological Society "A Call for New Approaches to Quantifying Biases in Observations of Sea Surface Temperature".
Impact Kent, E.C., J.J. Kennedy, T.M. Smith, S. Hirahara, B. Huang, A. Kaplan, D.E. Parker, C.P. Atkinson, D.I. Berry, G. Carella, Y. Fukuda, M. Ishii, P.D. Jones, F. Lindgren, C.J. Merchant, S. Morak-Bozzo, N.A. Rayner, V. Venema, S. Yasui, and H. Zhang, 2017: A Call for New Approaches to Quantifying Biases in Observations of Sea Surface Temperature. Bull. Amer. Meteor. Soc., 98, 1601-1616, https://doi.org/10.1175/BAMS-D-15-00251.1
Start Year 2015
 
Description SST bias collaboration 
Organisation Japan Meteorological Agency
Country Japan 
Sector Public 
PI Contribution Co-convened workshop of SST bias experts at the Met Office in 2015, led high-profile publication in Bulletin of the American Meteorological Society "A Call for New Approaches to Quantifying Biases in Observations of Sea Surface Temperature".
Collaborator Contribution Co-convened workshop of SST bias experts at the Met Office in 2015, contributed to high-profile publication in Bulletin of the American Meteorological Society "A Call for New Approaches to Quantifying Biases in Observations of Sea Surface Temperature".
Impact Kent, E.C., J.J. Kennedy, T.M. Smith, S. Hirahara, B. Huang, A. Kaplan, D.E. Parker, C.P. Atkinson, D.I. Berry, G. Carella, Y. Fukuda, M. Ishii, P.D. Jones, F. Lindgren, C.J. Merchant, S. Morak-Bozzo, N.A. Rayner, V. Venema, S. Yasui, and H. Zhang, 2017: A Call for New Approaches to Quantifying Biases in Observations of Sea Surface Temperature. Bull. Amer. Meteor. Soc., 98, 1601-1616, https://doi.org/10.1175/BAMS-D-15-00251.1
Start Year 2015
 
Description SST bias collaboration 
Organisation Meteorological Office UK
Country United Kingdom 
Sector Academic/University 
PI Contribution Co-convened workshop of SST bias experts at the Met Office in 2015, led high-profile publication in Bulletin of the American Meteorological Society "A Call for New Approaches to Quantifying Biases in Observations of Sea Surface Temperature".
Collaborator Contribution Co-convened workshop of SST bias experts at the Met Office in 2015, contributed to high-profile publication in Bulletin of the American Meteorological Society "A Call for New Approaches to Quantifying Biases in Observations of Sea Surface Temperature".
Impact Kent, E.C., J.J. Kennedy, T.M. Smith, S. Hirahara, B. Huang, A. Kaplan, D.E. Parker, C.P. Atkinson, D.I. Berry, G. Carella, Y. Fukuda, M. Ishii, P.D. Jones, F. Lindgren, C.J. Merchant, S. Morak-Bozzo, N.A. Rayner, V. Venema, S. Yasui, and H. Zhang, 2017: A Call for New Approaches to Quantifying Biases in Observations of Sea Surface Temperature. Bull. Amer. Meteor. Soc., 98, 1601-1616, https://doi.org/10.1175/BAMS-D-15-00251.1
Start Year 2015
 
Description SST bias collaboration 
Organisation National Oceanic And Atmospheric Administration
Country United States 
Sector Public 
PI Contribution Co-convened workshop of SST bias experts at the Met Office in 2015, led high-profile publication in Bulletin of the American Meteorological Society "A Call for New Approaches to Quantifying Biases in Observations of Sea Surface Temperature".
Collaborator Contribution Co-convened workshop of SST bias experts at the Met Office in 2015, contributed to high-profile publication in Bulletin of the American Meteorological Society "A Call for New Approaches to Quantifying Biases in Observations of Sea Surface Temperature".
Impact Kent, E.C., J.J. Kennedy, T.M. Smith, S. Hirahara, B. Huang, A. Kaplan, D.E. Parker, C.P. Atkinson, D.I. Berry, G. Carella, Y. Fukuda, M. Ishii, P.D. Jones, F. Lindgren, C.J. Merchant, S. Morak-Bozzo, N.A. Rayner, V. Venema, S. Yasui, and H. Zhang, 2017: A Call for New Approaches to Quantifying Biases in Observations of Sea Surface Temperature. Bull. Amer. Meteor. Soc., 98, 1601-1616, https://doi.org/10.1175/BAMS-D-15-00251.1
Start Year 2015
 
Description SST bias collaboration 
Organisation University of Bonn
Country Germany 
Sector Academic/University 
PI Contribution Co-convened workshop of SST bias experts at the Met Office in 2015, led high-profile publication in Bulletin of the American Meteorological Society "A Call for New Approaches to Quantifying Biases in Observations of Sea Surface Temperature".
Collaborator Contribution Co-convened workshop of SST bias experts at the Met Office in 2015, contributed to high-profile publication in Bulletin of the American Meteorological Society "A Call for New Approaches to Quantifying Biases in Observations of Sea Surface Temperature".
Impact Kent, E.C., J.J. Kennedy, T.M. Smith, S. Hirahara, B. Huang, A. Kaplan, D.E. Parker, C.P. Atkinson, D.I. Berry, G. Carella, Y. Fukuda, M. Ishii, P.D. Jones, F. Lindgren, C.J. Merchant, S. Morak-Bozzo, N.A. Rayner, V. Venema, S. Yasui, and H. Zhang, 2017: A Call for New Approaches to Quantifying Biases in Observations of Sea Surface Temperature. Bull. Amer. Meteor. Soc., 98, 1601-1616, https://doi.org/10.1175/BAMS-D-15-00251.1
Start Year 2015
 
Description SST bias collaboration 
Organisation University of East Anglia
Department Climate Research Unit
Country United Kingdom 
Sector Academic/University 
PI Contribution Co-convened workshop of SST bias experts at the Met Office in 2015, led high-profile publication in Bulletin of the American Meteorological Society "A Call for New Approaches to Quantifying Biases in Observations of Sea Surface Temperature".
Collaborator Contribution Co-convened workshop of SST bias experts at the Met Office in 2015, contributed to high-profile publication in Bulletin of the American Meteorological Society "A Call for New Approaches to Quantifying Biases in Observations of Sea Surface Temperature".
Impact Kent, E.C., J.J. Kennedy, T.M. Smith, S. Hirahara, B. Huang, A. Kaplan, D.E. Parker, C.P. Atkinson, D.I. Berry, G. Carella, Y. Fukuda, M. Ishii, P.D. Jones, F. Lindgren, C.J. Merchant, S. Morak-Bozzo, N.A. Rayner, V. Venema, S. Yasui, and H. Zhang, 2017: A Call for New Approaches to Quantifying Biases in Observations of Sea Surface Temperature. Bull. Amer. Meteor. Soc., 98, 1601-1616, https://doi.org/10.1175/BAMS-D-15-00251.1
Start Year 2015
 
Description SST bias collaboration 
Organisation University of Edinburgh
Country United Kingdom 
Sector Academic/University 
PI Contribution Co-convened workshop of SST bias experts at the Met Office in 2015, led high-profile publication in Bulletin of the American Meteorological Society "A Call for New Approaches to Quantifying Biases in Observations of Sea Surface Temperature".
Collaborator Contribution Co-convened workshop of SST bias experts at the Met Office in 2015, contributed to high-profile publication in Bulletin of the American Meteorological Society "A Call for New Approaches to Quantifying Biases in Observations of Sea Surface Temperature".
Impact Kent, E.C., J.J. Kennedy, T.M. Smith, S. Hirahara, B. Huang, A. Kaplan, D.E. Parker, C.P. Atkinson, D.I. Berry, G. Carella, Y. Fukuda, M. Ishii, P.D. Jones, F. Lindgren, C.J. Merchant, S. Morak-Bozzo, N.A. Rayner, V. Venema, S. Yasui, and H. Zhang, 2017: A Call for New Approaches to Quantifying Biases in Observations of Sea Surface Temperature. Bull. Amer. Meteor. Soc., 98, 1601-1616, https://doi.org/10.1175/BAMS-D-15-00251.1
Start Year 2015
 
Description Contribution to BBC documentary "Climate Change by Numbers" 
Form Of Engagement Activity A broadcast e.g. TV/radio/film/podcast (other than news/press)
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Discussions with BBC researcher regarding the use of buckets to sample water for sea surface temperature measurements. Loan of replica historical buckets for use in program and digital thermometer. Resulting program broadcast as 75 minute documentary on BBC4.
Year(s) Of Engagement Activity 2015
URL http://www.bbc.co.uk/programmes/p02jsdrk
 
Description Contribution to piece on US National Public Radio 
Form Of Engagement Activity A broadcast e.g. TV/radio/film/podcast (other than news/press)
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Public/other audiences
Results and Impact Research published with colleagues at Harvard University was featured in a piece including interviews with US colleagues on National Public Radio.
Year(s) Of Engagement Activity 2019
URL https://www.wbur.org/npr/750778010/how-much-hotter-are-the-oceans-the-answer-begins-with-a-bucket
 
Description Filmed piece for BBC on historical SST measurements 
Form Of Engagement Activity A broadcast e.g. TV/radio/film/podcast (other than news/press)
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Media (as a channel to the public)
Results and Impact Filmed piece on boat RV Callista, formed part of an item on historical climate observations broadcast on BBC breakfast (7 March 2019) and BBC News Channel, estimated reach 99 million people.
Year(s) Of Engagement Activity 2019
URL https://www.youtube.com/watch?v=x_iWTFv-qeM
 
Description London Ocean Forum 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Postgraduate students
Results and Impact Presentation and panel discussion at London Ocean Group "London Ocean Forum" meeting 17th June 2019. Presentation entitled "Understanding the global marine surface temperature record". Outcome was raised awareness of attending undergraduate and postgraduate students and researchers into recent progress in research into the production of surface temperature marine climate data records.
Year(s) Of Engagement Activity 2019
URL https://mecheng.ucl.ac.uk/londonoceangroup/
 
Description University of East Anglia Atmosphere Ocean and Climate Seminars 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Postgraduate students
Results and Impact Invited presentation in regular seminar series "New estimates of sea surface temperature biases from 1850". Outreach to researchers normally working with land climate record, discussion followed.
Year(s) Of Engagement Activity 2019
URL https://www.uea.ac.uk/environmental-sciences/news-and-events/atmosphere-ocean-and-climate-seminars/a...