Evidencing, informing and applying satellite-based information on sea surface temperature change for climate
Submitting InstitutionUniversity of Leicester
Unit of AssessmentPhysics
Summary Impact TypeEnvironmental
Research Subject Area(s)
Earth Sciences: Atmospheric Sciences, Physical Geography and Environmental Geoscience
Summary of the impact
Climate change is one of the most critical challenges facing modern
society and there is a paramount requirement for government policy
informed by science, and scientifically credible public information.
Observations of sea surface temperatures, and their corroboration, are a
focus for governments — climate change mitigation is economically
important in a warming world. This UoA has provided the science leadership
for a major satellite programme, the ATSRs, specifically designed to
provide high-quality sea temperature data. Results from our research
reduce uncertainties on global temperature change with unexpectedly wide
benefits also to operational oceanography and weather forecasting. Public
visibility through the Science Museum is also high.
Earth Observation Science (EOS) began at Leicester in 1993 with the
appointment to an externally-funded Chair of David Llewellyn-Jones and has
now expanded into a research group ~30 strong led by Professor John
Remedios, based in the Space Research Centre of the Department of Physics
From the beginning, a flagship of the EOS research has been the
scientific leadership from Leicester of the Along-Track Scanning
Radiometers (ATSRs), a series of satellite instruments flying on European
platforms (ERS-1; ERS-2 and Envisat). These UK-funded, thermal infra-red
sensors of novel design were instigated explicitly to achieve the accuracy
in sea surface temperatures (SSTs) necessary to investigate climate change
in recent decades; Leicester research has been central to the effort to
demonstrate performance and evidence the ATSR observations of SSTs.
Llewellyn-Jones has been the Principal Investigator of the ATSRs
throughout their lifetimes and led this multi-institutional project from
the development and use of novel research instruments to climate policy
relevant operational systems. The instruments and science programmes for
the first two instruments (ATSR-1; ATSR-2) were funded by SERC and NERC,
and later instruments by impact-orientated agencies (see impact section).
Remedios has been the Science Manager for the ATSRs since 2003 and Dr.
Gary Corlett has been the Leicester ATSR Validation Scientist since 2004.
Detailed scientific research at Leicester has focussed on sea surface
temperature data with its accuracy, trends and time series as a prime
driver of our work [1-6]. A major key step forward came in 2004
when Sean Lawrence together with Llewellyn-Jones published a paper 
showing that time tendencies (or trends) in sea surface temperature data
could be observed very well in the ATSR data, even over short timescales,
and also in other satellite data sets .
The next steps were to establish the true quality of the ATSR sea surface
temperature data and to improve the data retrieval skill to maximise the
data quality. Within the Unit, extensive research (see  and references
therein; [4, 5]) was required involving leadership of international,
collaborative teams of scientists analysing standard ocean sensor systems
and dedicated ship cruise data to validate the data. The state-of-the-art
Leicester results of this investigation are detailed in papers showing
that current ATSR data are accurate to better than 0.3 K per pixel with
low bias of less than 0.05 K [4, 5 and references in 3] and
0.015 K on a monthly global mean .
The culmination of the Leicester ATSR research has been to produce
climate records demonstrating that ATSR data are highly suitable for
climate research, which independently corroborate (for the first time) the
in situ record which has been historically used to document surface
temperature change, and which confirm the low uncertainty and low bias in
climate temperature records [3, 6]. These findings are evidenced in
Chapter 2 and Figure 2.17 of the Intergovernmental Panel on Climate Change
(IPCC) 5th Assessment Report see impact below) in which three
co-authored Leicester papers on SSTs are referenced, including 
References to the research
Leicester authors are shown in bold.
1. Lawrence, S. P., D. T. Llewellyn-Jones, and S. J. Smith
(2004), The measurement of climate change using data from the Advanced
Very High Resolution and Along Track Scanning Radiometers, J. Geophys.
Res., 109, C8, C08017, doi: 10.1029/2003JC002104.
2. Good, S.A., G.K. Corlett, J.J. Remedios, E.J. Noyes, and D.T.
Llewellyn-Jones (2007), The global trend in sea surface temperature
from 20 years of Advanced Very High Resolution Radiometer data, Journal of
Climate, 20, no. 7, 1255-1264, doi: http://dx.doi.org/10.1175/JCLI4049.1
3. Veal, K., G.K. Corlett, D.J. Ghent. D. Llewellyn-Jones and J.J.
Remedios (2013), A time series of mean global skin SST anomaly using
data from ATSR-2 and AATSR, Remote Sensing of Environment, 135, 64-76,
2013; doi: 10.1016/j.rse.2013.03.028.
4. Noyes, E. J., P. Minnett, J. J. Remedios, G. K. Corlett,
S. A. Good, and D. T. Llewellyn-Jones (2006), The Accuracy of the
AATSR Sea Surface Temperatures in the Caribbean, Remote Sensing of
Environment, 101, 38-51, 10.1016/j.rse.2005.11.011.
5. Embury, O, C.J. Merchant and G.K. Corlett (2012), A
reprocessing for climate of sea surface temperature from the along-track
scanning radiometers: Initial validation, accounting for skin and diurnal
variability effects, Remote Sensing of Environment, 116, 62-78, doi:,
6. Merchant, C.J., O. Embury, N.A. Rayner, D.I. Berry, G. Corlett,
K. Lean, K. Veal, E.C. Kent, D. Llewellyn-Jones, J.J.
Remedios and R. Saunders (2012), A twenty year independent record of
sea surface temperature for climate from Along Track Scanning Radiometers,
J. Geophys. Res., 117, C12013, doi: 10.1029/2012JC008161, [Editor's
Details of the impact
The impact agenda has been a part of the ATSR story since the inception
of the programme as its objective was to deliver climate science relevant
to policy. However a major step occurred in the 1990s when Llewellyn-Jones
was able to use evidence from ATSR-1 to show that the ATSR sea surface
temperature (SST) data were capable of forming a climate SST data set and
hence an important public utility for government. As a result, the
predecessor departments to the Department of Energy and Climate Change
(DECC) agreed to fund the third AATSR instrument for climate science and
policy support, bringing a series of research instruments together to form
a system for obtaining surface temperature data with climate quality as
advocated by Leicester [a].
DECC is now the lead Department for Government policies on both
international and domestic climate change mitigation, and a strong science
evidence base is crucial for developing these policies. DECC fully
recognises the importance of sea surface temperature as one of the
essential climate variables (ECVs), and that the most accurate climate
time series for SSTs are those that have been derived from the ATSR
instrument series as described in the Leicester research section. Results
from Leicester on the quality validation, interpretation and subsequent
application of these high quality ATSR SST records, on their
interpretation and on corroboration of the historical in situ record have
made an important contribution to the scientific evidence that informs the
development of government policy with respect to reductions of greenhouse
gas emissions and the UK's own requirements to reduce greenhouse gas
emissions by 80% by 2050 [a,b].The ATSR data have also contributed
to the UK government's commitment to climate monitoring obligations under
the United Nations Framework Convention on Climate Change's (UNFCCC)
Internationally, in terms of climate impact, the datasets and their
comparisons to in situ time series of global mean SST are cited for the
first time in the Intergovernmental Panel on Climate Change (IPCC) 5th
Assessment Report [a,d]. Hence the ATSR observations of temperature
change are part of the evidence chain open to international government
scrutiny and important at a time of apparent hiatus in surface temperature
The AATSR has also had an increasing and unexpected impact on operational
oceanography both during its lifetime [e] and on successor sensors
[f] respectively, due particularly to the work carried out by
Corlett in assessing the accuracy of ATSR data and implementing
operational functionalities for data quality. Reference [e]
describes how the Group for High Resolution SST (GHRSST), by providing
access to AATSR data, has enabled operational services using AATSR data.
These successes have been used to define the requirements for operational
ocean services as part of the European Commission GMES/Copernicus service
(the Earth Observation equivalent of Galileo for navigation) resulting in
an EC-funded Sea and Land Surface Temperature instrument (SLSTR or ATSR-4)
on the Sentinel-3 satellite. This instrument is deliberately ATSR-like in
technique, accuracy and precision [f]. Llewellyn-Jones and Remedios
have vigorously used Leicester results, and those of the international
ATSR community, to support the views of operational users as to the
importance and utility of ATSR-type data for the future.
The impact on operational oceanography was so strong that an unexpected
benefit of AATSR has been its use within a sea surface temperature
analysis system which is used to drive the forecast models for weather
forecasting at the Met Office and the European Centre for Medium Range
Weather Forecasting [g]. This is because of the AATSR data's great
utility for correcting the biases of other sea surface temperature
observations which feed into the analysis and then the weather forecasts [h],
as demonstrated by Corlett's work at Leicester
Finally, Leicester ATSR science has specifically contributed to public
information on climate science. Llewellyn-Jones at Leicester worked very
closely with exhibition staff, on behalf of DECC, to arrange the AATSR
engineering model as one of the centrepieces of the "Atmosphere — exploring climate science" gallery in the Science Museum in South
Kensington, opened in December 2010 by HRH The Prince of Wales. The model
hangs from the roof of this special exhibit and is thus visible to the
huge numbers of visitors per year (>1.5 million; 737,000 in the first
year compared to 400,000 target). Accompanying interactive display
material is based on interviews with Llewellyn-Jones, because of his PI
role, and includes a video presentation by Llewellyn-Jones explaining the
science and the provision of credible observational evidence on surface
temperature change. [i]
Sources to corroborate the impact
a) Letter from the Dept. for Energy and Climate Change evidencing the
contribution of AATSR and Leicester research to government policy.
b) Policy statement on "Taking international action to mitigate climate
change; Responsible ministers The Rt Hon Gregory Barker MP and The Rt Hon
Edward Davey MP". Located on gov.uk Inside Government. https://www.gov.uk/government/policies/taking-international-action-to-mitigate-climate-change/supporting-pages/scientific-evidence-to-help-us-understand-climate-change
c) UNFCC reports from UK government (The UK's Fifth National
Communication under the United Nations Framework Convention On Climate
Change; UK Report on national activities with respect to the GCOS
d) Intergovernmental Panel on Climate Change (IPCC) 5th
Assessment Report: Report of Working Group I, September 2013. The report
is available at http://www.ipcc.ch/report/ar5/wg1/.
Chapter 2 is the appropriate chapter.
e) Robinson, I, J-F. Piolle, P. LeBorgne, D. Poulter, C. Donlon, and O.
Arino (2012), Widening the application of AATSR SST data to Operational
Tasks through the Medspiration Service, Remote Sensing of Environment,
116. 126-139, doi: 10.1016/j.rse.2010.12.019.
f) The Copernicus/GMES operational programme of the European Commission:
Strategic Implementation Plan for the GMES Fast Track Marine Core Service;
g) Donlon, C.J., M. Martin, J. Stark, J. Roberts-Jones, E. Fiedler and W.
Wimmer, The Operational Sea Surface Temperature and Sea Ice Analysis
(OSTIA) (2012), Remote Sensing of Environment, 116, 140-158,
h) Letter from Met Office Weather Services plus ATSR is referenced in the
following report http://www.metoffice.gov.uk/media/pdf/h/e/FRTR561.pdf
i) Letter from the Science Museum and linked web-site stories.
1.aspx; exhibition at http://www.sciencemuseum.org.uk/climatechanging/atmospheregallery.aspx.