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Abrupt Climate Change

This article explores the concept of abrupt climate change (ACC) and its potential impacts on human society and ecosystems. It also discusses key research areas related to ACC, such as ocean circulation, ice behavior, the hydrologic cycle, and climate models. The article highlights the difference between chronic and acute ACC and provides examples of each. It emphasizes the importance of external forcing mechanisms and the challenges of accurately predicting solar variability. The article concludes by emphasizing the need for climate models to pass all tests posed by available data sets and stand the test of time.

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Abrupt Climate Change

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  1. Abrupt Climate Change Ernie Agee 6 April 2005

  2. Abrupt Climate Change (ACC) Periodic and extreme shifts in the climate system in one decade or less (during the past 100,000 years of climate record).  ACC could happen today, resulting in far-reaching impacts for human society and ecosystems - including energy consumption and water supply demands.  Key Research Areas for Understanding ACC a) ocean circulation, b) sea-ice/land-ice behavior, c) hydrologic cycle, d) dynamical modes of atmosphere/nonlinear (chaotic) effects, e) climate models that reorganize the thermohaline circulation (THC) employing high resolution ocean components. Chronic 'vs.' (Acute) Abrupt Climate Change Chronic - Milankovitch, Volcanoes, Solar, GHG etc. Acute - Volcanoes, GHG, etc.  Examples of Chronic: Wisconsin Glacier (Milankovitch); Little Ice Ages (Solar); 20th Century Warming (Volcanoes; GHG)  Examples of Acute: Year Without a Summer (Tambora - 1815/1816); "Glacial" Winter in Eastern 2/3 N. America in 76/77 (dynamical mode/14 day westward propagating wave); Dec '89; 2004 Florida Hurricane Season (?) (Dustbowl Era remains unexplained!)

  3. It is very normal to have abnormal weather; and climate is the statistical ensemble of weather events.  ACC crosses the threshold of "normal" variation; and generally requires a trigger mechanism such as, a) a perturbation in a chaotic dynamical system, b) reorganization of the THC, c) volcano, d) solar  External forcing mechanisms can damp out chaotic behaviors over time; chronic changes can produce ACC (e.g., freshwater balance of the N. Atlantic due to CO2 warming).  Climate models may fail to anticipate ACC.  Solar variability cannot be ignored. Although thermal forcing by GHG to Solar is 4 to 1, there are no precise models that predict the solar luminosity and its variability (i.e., the Solar Parameter); 11-year cycle, 22-year cycle; Gleissberg Cycle; Quiet Periods; Plages 'vs.' Sunspots; Solar Max Mission Satellite).  Climate Model Prediction "must" pass all tests posed by available data sets; and climate change predictions "must stand the test of time." There is no room for "Heliogeophysical Enthusiasts"!

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