 |
Global Warming: The Physical Science BasisSpeaker: Kevin Trenberth The Intergovernmental Panel on Climate Change (IPCC) is a scientific body tasked to evaluate the risk of climate change caused by human activity. It was established to provide the decision-makers and others interested in climate change with an objective source of information about climate change. The major conclusion of the recently released IPCC Fourth Assessment Report was that “the warming of the climate system is unequivocal” and is “very likely” caused by human activities. This talk will review the evidence behind these important conclusions. A key point is that an increasing number of many independent observations give a consistent picture of a warming world. For instance, there has been a widespread reduction in frosts; there have been more warm extremes; and decreases are occurring in snow cover, Arctic ice extent and thickness, and mountain glacier mass and extent. Increases in atmospheric water vapor content and resulting heavier precipitation events, increased drought, and increasing atmospheric temperatures above the surface are other signals of a warming world. Climate models are extremely useful tools for understanding and determining the changes in forcing that are driving the observed changes. Simulations performed with state-of-the-art models have now convincingly shown that the warming of recent decades is beyond the range of natural variability: only those simulations that include human-induced increased concentrations of greenhouse gases and sulfate aerosols in the atmosphere are able to capture it. Moreover, this attribution of the recent climate change has direct implications for the future. Because of the very long lifetime of carbon dioxide in the atmosphere and the slow equilibration of the oceans, there is a substantial future commitment to further global climate change even if concentrations of greenhouse gases in the atmosphere remain at current levels. |
|||
For more information or questions about Measuring Up, contact Kristen Alipit, 303-497-1661 |
||||
|
|