Temperature Trends in the Lower Atmosphere:
Steps for Understanding and Reconciling Differences

Notes:

1. Description of Topic, Audience, and Intended Use

Independently produced data sets that describe the four-dimensional temperature structure from the surface through the lower stratosphere provide different temperature trends. These differences are seen in varying degrees in comparisons of separate in situ (surface and weather balloon) data sets, in comparisons of separate space-based data sets, and in comparisons of individual data sets drawn from the different observational platforms and different trend analysis teams.

This CCSP synthesis product will address the accuracy and consistency of these temperature records and outline steps necessary to reconcile differences between individual data sets. Understanding exactly how and why there are differences in temperature trends reported by several analysis teams using differing observation systems and analysis methods represents a necessary step in reducing the uncertainties that underlie current efforts focused on the detection and quantification of surface and tropospheric temperature trends. Consequently, this synthesis product promises to be of significant value to decisionmakers, and to the expert scientific and stakeholder communities. For example, we expect this assessment to be a major contributor to the IPCC (2007) Climate Assessment. In addition, we expect the information generated will be used by the Global Climate Observing System Atmospheric Observation Panel to help identify effective ways to reduce observational uncertainty.

2. List of Questions or Objectives to be Addressed; Description of How These Questions / Objectives were Developed

Recent efforts to address the uncertainties regarding the temperature structure of the lower atmosphere (i.e., from the surface through the lower stratosphere) have included release of a report under the auspices of the National Research Council (NRC) entitled: "Reconciling Observations of Global Temperature Change" (National Academy Press, 2000) and the Third Assessment Report of the Intergovernmental Panel on Climate Change (Cambridge University Press, 2001, pp 101-123). Although these documents provided a great deal of useful information, the complexities of the issue coupled with shortcomings of the available observing systems prevent resolution of a number of fundamental questions.

The set of questions presented below has been framed by the lead agency with the benefit of consultation from members of the Climate Change Science Program Office, the NOAA Science Advisory Board Climate Monitoring Working Group, and participants at a workshop on Reconciling Vertical Temperature Trends that was held at NOAA's National Climatic Data Center (NCDC) on October 27-29, 2003, and attended by 55 scientific experts from academia, the U.S. government, the private sector, and several scientific experts from other countries. The questions were designed to provide a jargon-free expression of the fundamental uncertainties and differences between and within the individual components of the observational and modeling constellations. The responses to the questions are expected to be written at a level similar to international and national assessments (e.g., Intergovernmental Panel on Climate Change (IPCC), and the WMO Global Ozone Research and Monitoring Project).

These questions are:

3. Lead and Supporting Agencies, including Contact Information for Responsible Individuals

NOAA is the lead agency for this synthesis product. Agency contact information is presented in the following table:

4. Required Expertise of Potential Authors

A list of lead author nominees has been identified based on past records of interest and accomplishment in framing the core issues related to changes, trends, and uncertainties in the lower atmospheric temperature records, advancing relevant scientific arguments, and contributing to increased understanding of the behavior of respective components of the end-to-end system that provides the required data sets. Past contributions to relevant scientific assessments, success in peer-reviewed proposal funding competitions, and publications records in refereed journals are among the measures used in the selection process. A list of lead author nominees selected on the basis of these criteria, including question and chapter convening lead author assignments, is presented in Appendix A. Abbreviated curriculum vitae information for the nominees is also included.

5. Proposed Plans for Framing, Drafting, Reviewing, and Producing / Disseminating the Product

The lead NOAA focal point will be the Synthesis Product Chief Editor. The assistant NOAA focal points will serve as Associate Editors.

The workshop conducted at NCDC on October 27-29, 2003, was designed to address a broad range of issues related to vertical temperatures trends, and it provided a scientific foundation for the development of this CCSP synthesis product. The workshop presentations and results of work breakout groups are posted on the Web. The workshop assessed the current state of knowledge on this topic, identified near-term and long-term steps to address existing uncertainties, and provided a framework for a synthesis product structured around the six questions listed above.

There was a strong expression of willingness from the workshop participants to assist with the drafting and delivery of the scientific/technical section of this assessment product. The core of a scientific author team presented in Appendix A has been drawn from the workshop participants. This core group has been supplemented with a number of individuals who have made major contributions to our present understanding of the issues related to vertical temperature change.

Under the leadership of a convening lead author for each of the six questions, this group of lead authors and contributors will be charged with the preparation of the scientific/technical analysis section of the synthesis report. They will draw upon published, peer-reviewed scientific literature in the drafting process, complemented, if necessary and if approved by the CCSP Principals, with information that has not yet been published in the peer reviewed literature, such as new model results or extensions of data sets.

The synthesis product will also include a non-technical summary. This summary will be authored by a team consisting of a convening lead author assisted by the convening lead authors from each of the six questions. The summary will assess what we know now compared to what we knew at the time of IPCC 2001 and address the question: "Do our attempts to reconcile these changes increase or decrease our confidence in explaining and quantifying the human impact on past and future global climate change"? The synthesis product will identify disparate views that have significant scientific or technical support, and will provide confidence levels for key findings, as appropriate.

NOAA, the lead agency for this product, plans to present the document to an expert committee of the National Research Council for scientific review. Upon receipt of NRC review, the deliverable will be revised and undergo final pre-publication review and clearance as required in the CCSP guidelines for preparation of synthesis and assessment reports. In addition to the above-listed review procedures, the synthesis product lead authors will be encouraged to publish their findings in the scientific literature.

6. Proposed Approach for Evaluation and Communication of Uncertainty and Confidence Levels, where Applicable

When presenting results addressing uncertainties and confidence levels in our statements regarding the temperature trends, we note that increased understanding of the complexities of the vertical temperature variability can lead to increased uncertainties regarding long-term behavior patterns. When conducting diagnostic studies and preparing results for presentation, it will be necessary to use several indicators of change, not just linear trends, which are often viewed as excessively sensitive to the selection of time interval end points. Just as independent data sets must be used for comparisons of results, the basic evaluation process must maintain appropriate degrees of separation; for example, data set developers should not be evaluators of data reliability in their products.

The communication of our uncertainties will be quantitative in many instances but, from discussion during the recent workshop, it is clear that expert assessment of uncertainty will be required, as pure mathematical statistical estimates of uncertainty do not reflect the full range of uncertainty. Our intent is to follow the protocol developed in the IPCC (2001) assessment and any updates provided by IPCC.

7. Relationship to Other National or International Assessment Processes

This CCSP synthesis product is being coordinated internationally with a U.K. Met Office workshop on understanding vertical profiles of temperature trends that is planned for September 2004 in Exeter, England. Tentative plans include presentations in Exeter by the lead authors to provide an interim look at progress on addressing each of the key questions. Planning is also ongoing in coordination with a newly constituted Global Climate Observing System (GCOS)/Atmospheric Observations Panel for Climate (AOPC) Working Group on Reconciling Vertical Temperature Trends. All synthesis product reports are expected to provide input to the IPCC Fourth Assessment Report.

8. Proposed Timeline to Complete the Various Phases of Work

The planned completion date for Phase 1 -- which will result in the submission of the synthesis product, including both the Scientific/Technical Section and the Non-Technical Summary, for review by the CCSP Principals -- is December 2004. Phase 2 -- the NRC review of the Synthesis Product, the final clearance through the National Science and Technology Council process, and the production and distribution of the completed Synthesis Product -- is targeted for completion in November 2005. Specific milestones follow.

PHASE 1

PHASE 2

References

Folland, C.K., et al., 2001: Observed climate variability and change. In: Climate Change 2001: The Scientific Basis. Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change (Houghton, J.T., Y. Ding, D.J. Griggs, M. Noguer, P.J. van der Linden, X. Dai, K. Maskell, and C.A. Johnson, eds.) Cambridge University Press, U.K.

National Research Council, Board on Atmospheric Sciences and Climate, Commission on Geosciences, Environment and Resources, 2000: Reconciling Observations of Global Temperature Change. Nat. Acad. Press, Washington D.C., 85 pp.

Scientific Assessment of Ozone Depletion: 1998, WMO Global Ozone Research and Monitoring Project, Report #44, WMO Geneva, 1999.

APPENDIX A - List of Synthesis Report Chapter Questions and Author Nominees

Question #1- Why do temperatures vary vertically (from the surface to the stratosphere) and what do we understand about why they might vary and change over time?

Convening Lead Author: V. Ramaswamy (NOAA/GFDL)

V. Ramaswamy is a Senior Scientist at the NOAA Geophysical Fluid Dynamics Laboratory, Princeton, NJ. He is the Chair of the Stratospheric Temperature Trends Assessment (a project of the WCRP Stratospheric Processes and Their Role in Climate (SPARC) Project (1993-present). Dr. Ramaswamy has been a Lead Author on the WMO State-of-art Stratospheric Ozone Assessment (1992,1994,1998, 2002) and a Lead Author the United Nations-Intergovernmental Panel on Climate Change (1992,1994,1995, 2001). He has an extensive publication list and has received numerous awards including the Department of Commerce Gold Medal Award in 2002 for "world-renowned scientific contributions to the recently concluded state of the art assessment of the science of global change", and the World Meteorological Organization Norbert Gerbier MUMM Award - 2003 for the paper "Stratospheric Temperature Trends: Observations and Model Simulations" by V. Ramaswamy et al., published in Reviews of Geophysics, 39, 71-122, 2001. Other relevant publications include:

Lead Author: Jim Hurrell (NCAR)

Jim Hurrell is a senior scientist and deputy director of the Climate and Global Dynamics Division of the National Center for Atmospheric Research. His research has centered on empirical and modeling studies and diagnostic analyses to better understand climate, climate variability and climate change. He has authored or co-authored more than 60 peer-reviewed journal articles and book chapters, as well as dozens of other planning documents and workshop papers. His peer-reviewed publications include numerous articles on understanding and reconciling differences in surface versus tropospheric temperature trends, and in part for that work he received the Clarence Leroy Meisinger Award from the American Meteorological Society in 2001. Currently, Jim is extensively involved in the World Climate Research Programme on Climate Variability and Predictability (CLIVAR), and he serves as co-chair of Scientific Steering Committee of U.S. CLIVAR. Jim has also been involved in the assessment activities of the Intergovernmental Panel on Climate Change, and he has served on several National Research Council panels. Publications of particular relevance include the following:

Lead Author: Jerry Meehl (NCAR)

Gerald Meehl is a Senior Scientist at the National Center for Atmospheric Research. He is a member of the CLIVAR/WCRP Working Group on Coupled Models (WGCM) and is chairman of the Coupled Model Intercomparison Project, as well as chairman of the WGCM Climate Simulation Panel and co-chairman of the Community Climate System Model Climate Change Working Group. He has been prominent in the Intergovernmental Panel on Climate Change (IPCC) Scientific Assessment activities. Dr. Meehl was a convening lead author of Chapter 9 in "Climate Change 2001: The Scientific Basis," produced as a contribution of Working Group 1 to the Third Assessment Report of the IPCC. He has written or co-authored several refereed articles on the topic of tropospheric and surface temperatures and has a long history of written publications in this area including:

Question #2 - What kinds of atmospheric temperature variations can the current observing systems detect and what are their strengths and limitations, both spatially and temporally?

Convening Lead Author: John Christy (University of Alabama/Huntsville)

John R. Christy is Professor of Atmospheric Science at the University of Alabama in Huntsville, Alabama State Climatologist and Director of the UAH Earth System Science Center. He is/was a member of several National Research Council panels dealing with climate and space based observations and is currently on the NRC Committee on Environmental Satellite Data Utilization. He was selected as a Lead Author of the IPCC 2001 WG 1 (chapter on observations) and as a member of the panel which wrote the AGU Official Statement on Climate Change adopted in 2003. He has written several articles on surface, tropospheric and stratospheric temperatures, including basic construction methodology of conventional and spaced-based data sets, tests for their precision, and analysis of the climate products. His most recent paper "What may we conclude about tropospheric temperature trends?" will appear soon in Geophysical Research Letters. Other relevant publications include:

Lead Author: Dian Seidel (NOAA Air Resources Laboratory)

Dian J. Seidel is a Research Meteorologist at NOAA's Air Resources Laboratory in Silver Spring, Maryland. She has contributed to IPCC Scientific Assessments, WMO/UNEP Scientific Assessments of the Ozone Layer, and scientific assessments by the WMO program on Stratospheric Processes and their Role in Climate. She is a former member of the NRC Climate Research Committee and has contributed to several NRC reports, including "Reconciling Observations of Global Temperature Change" in 2000. She is a Fellow of the AMS and currently chairs its Committee on Climate Variability and Change. Her research on observed climate variations and change has focused on upper-air observations, particularly from radiosondes, and on data quality issues, and is reported in articles in peer-reviewed journals. Relevant publications include:

Lead Author: Steve Sherwood (Yale University)

Steve Sherwood is an Assistant Professor at Yale University. He has published refereed articles on diverse topics relevant to the lower atmosphere temperature trend problem. These topics include moist instability and the physics of vertical (convective) and horizontal (baroclinic) heat transport within the tropical troposphere and tropopause region; the optimal estimation of small climate signals within imperfect datasets; and some performance characteristics of the VIZ and Vaisala radiosonde instruments. He was a contributing author to the 2000 SPARC report on upper troposphere/lower stratosphere water vapor. Relevant publications include:

Question #3 - What do observations indicate about the changes of temperature in the atmosphere and at the surface since the advent of measuring temperatures vertically?

Convening Lead Author: John Lanzante (NOAA/GFDL)

John Lanzante is a research meteorologist at NOAA's Geophysical Fluid Dynamics Laboratory. He is a member of the working group charged by the Climate Change Science Program to produce a report defining science requirements for the next U.S. Reanalysis. In this regard, he has taken the lead in developing a plan for the temporal homogenization of data to be used as Reanalysis input. He recently led a project that produced a temporally homogenized radiosonde temperature dataset which is gaining wide use by climate-change scientists. In a spin-off project, these data are being used and updated to produce upper-air temperature climate monitoring products for NOAA. Some of his past and current work also involves the use of radiosonde data in comparison with/evaluation of satellite data as well as output from climate models. He has been a lead or co-author on a number of refereed papers during the last 5-10 years relevant to the study of atmospheric trends. Relevant publications include:

Lead Author: Frank Wentz (Remote Sensing Systems (RSS))

Frank Wentz is the Director of Remote Sensing Systems, a research company specializing in climate monitoring via satellites. Over the last 25 years, he has been one of NASA's leading principal investigators in the field of microwave remote sensing. Under his direction, Remote Sensing Systems is providing the climate community with research-quality climate datasets, including tropospheric temperature, sea-surface temperature and wind, and atmospheric moisture (water vapor, cloud water and rain). He has served on the National Research Council's Earth Studies Board and on the NRC Panel on Reconciling Temperature Observations. He has a long list of publications on remote sensing and its application to climate monitoring, including recent papers on tropospheric temperature and sea surface temperature including:

Lead Author: Kostya Vinnikov (University of Maryland)

Dr. Konstantin Vinnikov is a Senior Research Scientist in the Department of Meteorology, University of Maryland. He emigrated from Russia in 1991 and is a US citizen. Dr. Vinnikov was the lead and contributing author of several Intergovernmental Panel on Climate Change (IPCC) reports. Dr. Vinnikov is an expert in empirical analysis of observed data on contemporary climate change. He was the first to detect a century-scale (0.5K/100 yr) global warming trend in surface air temperature data (Budyko and Vinnikov, 1976). This was at the time when other climatologists believed in the "observed" global cooling and in the approaching of a new "Little Ice Age." Now, almost three decades later, and after having been confirmed by many other research groups, the surface global warming trend is an accepted fact. Most recently, he developed new statistical techniques to analyze diurnal and seasonal cycles and trends in climatic records with arbitrary observation times (Vinnikov et al., 2004) and in multi-satellite overlapping observations. He applied these techniques to tropospheric temperature observations and found that the satellite-observed tropospheric air temperature trend agrees well with surface observations (Vinnikov and Grody, 2003). Relevant Publications include:

Question #4 - What is our understanding of the contribution made by observational or methodological uncertainties to the previously reported vertical differences in temperature trends?

Convening Lead Author: Carl Mears (Remote Sensing Systems)

Carl Mears is a Senior Scientist at Remote Sensing Systems. Over the past 5 years, Dr. Mears has led a comprehensive independent analysis of the atmospheric sounding data from MSU channels 2,3, and 4, the results of which was recently published in the Journal of Climate. This work was inspired by the significance of the MSU data set in climate change research, and the possibility of systematic errors in it. Dr. Mears has also made numerous contributions to the calibration and validation of geophysical retrievals from several other earth sensing satellites, including SSM/I, TMI, and QuikScat. In addition to this climate-related remote sensing work, Dr. Mears also has extensive past experience in microwave hardware design and lab-based calibration activities. Relevant publications include:

Lead Author: Chris Forest (MIT)

Dr. Chris E. Forest is a Research Scientist at the Massachusetts Institute of Technology in the Joint Program on the Science and Policy of Global Change. He is a member of the American Meteorological Society and the American Geophysical Union and focuses his research on merging issues of climate change detection and uncertainties in future climate prediction. He has written several refereed articles on the topic of using tropospheric and surface temperature diagnostics to estimate uncertainty in future climate change and has a long history of publications in this area. His most relevant articles on this issue are:

Lead Author: Roy Spencer (U. Alabama-Huntsville)

Roy W. Spencer is a Principal Research Scientist at The University of Alabama in Huntsville where he directs a research program on the use of satellite passive microwave measurements to monitor weather and climate variables. He is co-developer of the original method for monitoring global deep-layer temperatures from satellite microwave radiometers, and is the U.S. Science Team Leader for the Advanced Microwave Scanning Radiometer - EOS flying on NASA's Aqua spacecraft. He has authored numerous papers on the global monitoring of temperature, precipitation, and water vapor including:

Question #5 - How well can the observed (vertical temperature profile) changes be reconciled with our understanding of the causes of these temperature changes?

Convening Lead Author: Ben Santer (Lawrence Livermore National Laboratory)

Ben Santer is a Physicist at Lawrence Livermore National Laboratory, where he works in the Program for Climate Model Diagnosis and Intercomparison. He was a member of the National Research Council panel on "Reconciling Observations of Temperature Change", and was the Convening Lead Author of Chapter 8 ("Detection of Climate Change, and Attribution of Causes") of the 1995 Second Assessment Report of the Intergovernmental Panel on Climate Change. He currently serves as a member of the Scientific Steering Committee for the NCAR Community Climate System Model, the Climate Modeling Advisory Panel of the Goddard Institute for Space Studies, and the Science Review Group of the Hadley Centre for Climate Prediction and Research. He has written a number of peer-reviewed articles that deal with comparisons of modeled and observed atmospheric temperature trends including:

Lead Author: Joyce Penner (U. Michigan)

Joyce Penner is a Professor at the University of Michigan. She is a member of the National Research Council Committee on Metrics for Global Change Research and has been prominent in the Intergovernmental Panel on Climate Change (IPCC) Scientific Assessment activities. Prof. Penner was a convening lead author of "Climate Change 2001: The Scientific Basis," produced as a contribution of Working Group 1 to the Third Assessment Report of the IPCC. She has written several refereed articles on the topic of aerosols and their climate effects and has also worked on publications (with B. Santer, lead) in the area of comparing temperature trends with data.

Lead Author: Peter Thorne (U.K. Met Office/Hadley Centre)

Peter Thorne is a research scientist within the Hadley Centre at the Met Office. In 2001 he completed his PhD "Advancing climate change detection and attribution studies in the free atmosphere", available on-line from the Climatic Research Unit at the University of East Anglia. Results from these analyses have since been published in GRL and Clim. Dyn. Since 2001 Peter has been working in the climate variability group at the Hadley Centre. Work there has focused on generation of a new globally gridded (although incomplete) radiosonde dataset using neighbour comparisons, and understanding the physical causes of reported vertical temperature structure changes. A number of papers describing this work are in preparation. Relevant publications include:

Question #6 - What measures can be taken to better reconcile observed changes with present understanding?

Convening Lead Author: Roger Pielke Sr. (Colorado State University)

Roger A. Pielke Sr. is a Professor in the Department of Atmospheric Science at Colorado State University. He is a member of the National Research Council's Committee on Radiative Forcing Effects on Climate, and is the immediate Past-President of the American Association of State Climatologists. In 2004 he was elected as a Fellow in the American Geophysical Union. He has published articles on global and regional tropospheric and surface temperature variability and trends, including several papers on the role of land use change and vegetation dynamics in influencing these variations. He is a co-author of a book published by Cambridge University Press with William R. Cotton on Human Impacts on Weather and Climate, with a second edition to be completed this year.

Lead Author: David Parker (U.K. Met Office)

David Parker manages a small group involved in research into observed climate variability at the Met Office's Hadley Centre. A particular focus is tropospheric temperature and humidity as observed by radiosondes and from satellites and comparisons with surface temperature and humidity. In 1999-2000 Mr Parker was a member of the National Research Council's Panel on Reconciling Temperature Observations, and is the author of one of the leading radiosonde temperature data sets. David has written many papers in the peer-reviewed literature on climate variability and climate observations. He has also contributed to the recent WMO Global Climate System Review and to the 2nd GCOS Report on the Adequacy of the Global Climate Observing System for the UN Framework Convention on Climate Change. Mr Parker was a Lead Author of the Supplementary and Second Assessments of the Intergovernmental Panel on Climate Change and a contributing author to the First and Third Assessments. Relevant publications include:

Lead Author: Dick Reynolds (NOAA/NCDC)

Dr. Richard W. Reynolds is a Research Oceanographer at the National Climatic Data Center (NCDC), which is part of the US National Oceanic and Atmospheric Administration's (NOAA) National Environmental Satellite Data and Information Service. In 1980 Dr. Reynolds began his career at NOAA as the lead scientist responsible for the development, implementation and operational production of sea surface temperature (SST) analyses and associated products and has continued working in this area for the past 18 years. He has been active in improving the accuracy of the SST analyses by optimizing the advantages of in situ and satellite data. He has recently led the development of an improved historical sea surface temperature analysis which has been produced from 1880 to present. He has also been involved in the evaluation of the sea surface temperature observing system. In this project, the situ sea surface temperature network was evaluated to determine the minimum number of in situ observations needed to correct any potential satellite bias. This procedure is now operationally produced and is resulting in optimization of US buoy deployment strategies. Dr. Reynolds is also the principal investigator in the US efforts to improve the collection and archiving of surface marine data for the International Comprehensive Ocean-Atmosphere Data Set (I-COADS).

Summary Chapter Question: "Do our attempts to reconcile these changes increase or decrease our confidence in explaining and quantifying the human impact on past and future global climate change"?

Convening Lead Author: Tom M.L. Wigley

Tom Wigley, a senior scientist at the National Center for Atmospheric Research, is one of the world's experts on climate change. He is a U.S. citizen, born and educated in Australia where he trained as a meteorologist with the Commonwealth Bureau of Meteorology. His Ph.D. is in Theoretical Physics. He has published widely in the field of climatology and related sciences. He is the author of more than 200 refereed journal articles and book chapters and is one of the most highly cited scientists in the field. He is a Fellow of the American Meteorological Society (AMS) and of the American Association for the Advancement of Science (AAAS). His main current interests include projections of future climate and sea-level change, carbon-cycle modeling, and the interpretation of past climate changes (including the detection of anthropogenic influences). He has contributed as an author to all Intergovernmental Panel on Climate Change assessments, and developed the MAGICC coupled gas-cycle/climate model that has been used to produce the primary temperature and sea level projections given in these assessments. He also authored `The Science of Climate Change: Global and U.S. Perspectives' published by the Pew Center on Global Climate Change. Wigley is the former Director of the Climatic Research Unit, University of East Anglia, Norwich, U.K. Relevant publications include: