How do the modern trends in temperature, carbon dioxide and methane compare to their historical natural counterparts? Are the modern rates of change with respect to temperature, carbon dioxide and methane comparable to their historical counterparts or are there significant differences? What is driving the modern trends in carbon dioxide, methane and temperature, relative to their historical counterparts? Is 2005 one of the warmest years on record? If so, can any of the warming witnessed in 2005 be a result of an El Nino condition? Do these modern trends in temperature, carbon dioxide and methane have implications now and into the future?
Dr. Anthony Socci, Senior Science Fellow, American Meteorological Society
Dr. Dominique Raynaud, Research Director at CNRS (French National Center for Scientific Research), SaintMartind’Hères Cedex, France
Raynaud PowerPoint HTML Version
Dr. Thomas R. Karl, Director of the National Oceanic and Atmospheric Administration’s National Climatic Data Center, U. S. Department of Commerce, Asheville, NC
Karl PowerPoint HTML Version
Carbon Dioxide and Methane: the Lesson of the Past
There is a high correlation between greenhouse gases such as methane and carbon dioxide and climate change during the last 650,000 years.
Carbon dioxide and methane contributed significantly to the glacialinterglacial (coolingwarming) variability of climate.
The relationship between temperature and greenhouse gases does not change even when the periodicity and style of orbital forcing of climate changes, at least within the last 650,000 years or more.
Carbon dioxide and methane concentrations today are without precedent over nearly the last million years.
Carbon dioxide changes are proportional to temperature changes and therefore, the historical record of CO2 provides information on how the climate system reacts when atmospheric carbon dioxide concentrations increase or decrease.
During the past, at the scale of glacialinterglacial cycles, CO2 increases have been activated by orbital forcing of the climate system but have thereafter, played a major role in strongly amplifying, together with the collapse of the northern ice sheets, the amplitude of the climate warming. The temperature response of these past CO2 changes appears to remain the same over time, whatever the conditions of the climate change are. It therefore, gives the research community more confidence in the CO2temperatue proportionality observed during the past, when making projections of future global warming.
The historic record of interglacials (naturallyoccurring warm periods) informs us about what our climate system was, and would have been, without human perturbation.
The record of carbon dioxide provides a validation of climate models over a wide range of climate situations.
From an historical climate standpoint, we are living in an exceptional time.
It appears that the main natural forcing of climate, at the millennial scale, will not vary much in the future; anthropogenic forcing resulting from the buildup of greenhouse gases may have a stronger influence in the long run.
Global SurfaceAir Temperatures of 2005:
Record or Near Record Highs?
Global surface temperatures are regularly compiled by three separate institutions and continually being assessed and improved. Depending on the analysis, whether by NOAA, NASA, or the UK Meteorological Office temperatures during 2005 either broke the previously established record set during the ElNiño year of 1998 or were very close to those levels. This is noteworthy, considering the lack of an ElNiño event that temporarily produces an upward spike in global surfaceair temperatures, and reflects a significant (in a statistical sense) warming trend. Observed warming since the mid 1970s is three times the rate of the overall rise of temperature during the 20 th Century (0.18°C/decade versus 0.06°C/decade).
The observations used to calculate global temperatures are derived from various observing systems including land surface air temperatures measurements from weather and climate observing stations around the world, sea surface measurements from ships and buoys and various sensors on satellites. The differences in 2005 temperatures among the various institutions are largely due to differing methodologies used to address areas of the globe with sparse observations e.g., the poles. Data have been assessed, adjusted, and corrected to remove the effects of nonclimatic factors in the observational record. These include:
- Changes in instrumentation and observing systems with time;
- Moves in observing location;
- Changes in observing practice.
Urbanization effects have also been assessed and accounted for in the global averages. All of these factors introduce uncertainty to the results derived from the analysis. This is why we cannot say whether or not 2005 was warmer than 1998. We can however, be confident that 2005 was one of the warmest years in the instrumental record and global temperatures over the last several decades are rising at a rate appreciably (three times) higher than observed during the 20 th Century. Increases in atmospheric concentrations of greenhouse gases have been identified as the dominant cause of this recent rise.
Dr. Dominique Raynaud is presently Research Director at CNRS (the French National Center for Scientific Research) and works at the Laboratory of Glaciology and Environmental Geophysics (LGGE) in SaintMartind’Hères, Cedex, France. He is also the coordinator of the European EPICAMIS project, a project aimed at drilling deep ice cores in Antarctica, and to contribute to the understanding of past climate and, therefore, present and future climate, through marine and ice core studies.
He is a lead author for the 4 th assessment report of the Intergovernmental Panel on Climate Change. He is the former director of LGGE and is a member of Academia Europeae. He participated in several Antarctic (Vostok, South Pole, Adélie Land) and Greenland glaciological field expeditions. Dr. Raynaud has several honours for his scientific work, including the CNRS silver medal, the grand prize of the French Academy of Science and the Gold medal of the Belgica, Belgian Academy of Science). He has also participated in a number of international scientific committees (e.g., SCAR, IGBP/PAGES).
His main interest and expertise lie in the fields of Paleoclimatology, Glaciology, Greenhouse Gases and Polar Regions. He has published 110 scientific papers in peer reviewed international journals.
Dr. Raynaud was born on June 14th, 1942, and received his PhD in Physical Sciences from Grenoble University.
Dr. Thomas R. Karl is the Director of NOAA’s National Climatic Data Center, United States Department of Commerce, located in Asheville, NC. He also serves as Program Manager for NOAA’s Climate Observations and Analysis Program, and Director of NOAA’s Climate Change Data and Detection Applied Research Center. Dr. Karl is a fellow of the American Meteorological Society and the American Geophysical Union, and a National Associate of the National Research Council. In 2002, he was elected to serve on the Council of the American Meteorological Society. Dr. Karl is author of many climatic atlases and technical reports, and has well over 100 published articles in various peerreviewed scientific journals. He is a past editor of Journal of Climate and is currently an Associate Editor of the journal Climatic Change.
Dr. Karl was born and raised in Evergreen Park, Illinois. He received his B.S. degree in Meteorology from Northern Illinois University, DeKalb, Illinois in 1973, his Masters Degree from the University of Wisconsin, Madison in 1974, and was awarded an honorary Doctorate of Humane Letters from North Carolina State University in 2002.
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