U.S. Report on Climate Change Finds ‘Substantial Human Impact’

May 4, 2006

A large majority of meteorologists, scientists and other researchers now agree that global climate change is a reality backed up by well-documented findings of higher temperatures in the world’s oceans and atmosphere. However, questions as to what extent human activity is responsible for the rise are still a subject of vigorous – and sometimes acrimonious – debate.

A new study issued by the U.S. Climate Change Science Program (CCSP) may help settle the issue. The report, “Temperature Trends in the Lower Atmosphere: Steps for Understanding and Reconciling Differences,” the first of first of 21 “Synthesis and Assessment S&A Products” scheduled to be released, is aimed at improving “our understanding of climate change and human influences on temperature trends”.

The announcment of the report, also referred to as S&A Product 1.1, said it “tackles some of the long-standing difficulties that have impeded understanding of changes in atmospheric temperatures and the basic causes of these changes.” An initial finding states: “There is no longer a discrepancy in the rate of global average temperature increase for the surface compared with higher levels in the atmosphere. This discrepancy had previously been used to challenge the validity of climate models used to detect and attribute the causes of observed climate change. This is an important revision to and update of the conclusions of earlier reports from the U.S. National Research Council and the Intergovernmental Panel on Climate Change.”

“This synthesis and assessment report exposes the remaining differences among different observing systems and data sets related to recent changes in tropospheric and stratospheric temperature,” stated Chief Editor Dr. Thomas Karl, director of the National Oceanic and Atmospheric Administration’s (NOAA’s) National Climatic Data Center. “Discrepancies between the data sets and the models have been reduced and our understanding of observed climate changes and their causes have increased. The evidence continues to support a substantial human impact on global temperature increases. This should constitute a valuable source of information to policymakers.”

“S&A Product 1.1 corrects errors that have been identified in the satellite data and other temperature observations,” the bulletin continued.” It then stressed that the improved analysis should “have increased confidence in the understanding of observed climatic changes and their causes.” Most importantly the bulletin comes up with the meteorological equivalent of a “smoking gun.” It states, “that research to detect climate change and attribute its causes using patterns of observed temperature change in space and time shows clear evidence of human influences on the climate system due to changes in greenhouse gases, aerosols, and stratospheric ozone. Also, the observed patterns of change over the past 50 years cannot be explained by natural processes alone, nor by the effects of short-lived atmospheric constituents such as aerosols and tropospheric ozone alone.”

Continuing, the report says: “The previously reported discrepancy between surface and atmospheric temperature trends is no longer apparent on a global scale. These trends are consistent with climate model simulations.”

The model report points to one yet unresolved issue – “related to the rates of warming in the tropics. Here, models and theory predict an amplification of surface warming higher in the atmosphere. However, this greater warming aloft is not evident in three of the five observational data sets used in the report. Whether this is a result of uncertainties in the observed data, flaws in climate models, or a combination of these is not yet known. Using the evidence available, the author team favors the first explanation.”

Resolving this issue would be of major importance for the insurance industry, as tropical latitudes are the main areas in which tropical cyclones – hurricanes and typhoons – form and go on to wreak havoc.

“The publication of S&A Product 1.1 signals a tremendous accomplishment, not simply because of its scientific content, but also because of the breadth in scope of contributing authors’ backgrounds and the meticulous research they undertook,” noted Dr. James Mahoney, recently retired CCSP director. “The findings reflect years of effort in tackling difficult and complex issues that have hampered our understanding of global climate. It is the first of several significant products that are illustrative of the outstanding research that will result from the CCSP.”

The bulletin also provided some background on the work the CCSP is engaged in. Following a 2002 meeting attended by senior officials in the Bush administration, it adopted “five overarching scientific goals that guide all climate research conducted by the federal government. The 21 S&A Products further refine these goals and address key topics that are necessary to resolve in order to make well informed decisions. The S&A Products are designed to inform public debate, policy and operational decisions, as well as defining and setting the future direction and priorities of the program.”

For further information and future reports in the series consult the official NOAA Website at www.noaa.gov; or the CCSP Website at: www.climatescience.gov.

The NOAA is an agency of the U.S. Department of Commerce, “dedicated to enhancing economic security and national safety through the prediction and research of weather and climate-related events and providing environmental stewardship of the nation’s coastal and marine resources. Through the emerging Global Earth Observation System of Systems (GEOSS), NOAA is working with its federal partners, 61 countries and the European Commission to develop a global network that is as integrated as the planet it observes, predicts and protects.”

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