Abrupt Climate ChangeAbrupt Climate Change

Ernie AgeeErnie Agee

6 April 20056 April 2005

Abrupt Climate ChangeAbrupt Climate Change (ACC) (ACC)Periodic and extreme shifts in the climate system in one decade or less Periodic and extreme shifts in the climate system in one decade or less (during the past 100,000 years of climate record).(during the past 100,000 years of climate record).

ACC could happen today, resulting in far-reaching impacts for human ACC could happen today, resulting in far-reaching impacts for human society and ecosystems - including energy consumption and water society and ecosystems - including energy consumption and water supply demands.supply demands.

Key Research Areas for Understanding ACCKey Research Areas for Understanding ACCa) ocean circulation, b) sea-ice/land-ice behavior, c) hydrologic cycle, a) ocean circulation, b) sea-ice/land-ice behavior, c) hydrologic cycle, d) dynamical modes of atmosphere/nonlinear (chaotic) effects, e) d) dynamical modes of atmosphere/nonlinear (chaotic) effects, e) climate models that reorganize the thermohaline circulation (THC) climate models that reorganize the thermohaline circulation (THC) employing high resolution ocean components.employing high resolution ocean components.

ChronicChronic 'vs.' 'vs.' (Acute) Abrupt Climate Change(Acute) Abrupt Climate ChangeChronic - Milankovitch, Volcanoes, Solar, GHG etc.Chronic - Milankovitch, Volcanoes, Solar, GHG etc.Acute - Volcanoes, GHG, etc.Acute - Volcanoes, GHG, etc.

Examples of Chronic: Wisconsin Glacier (Milankovitch); Little Ice Ages Examples of Chronic: Wisconsin Glacier (Milankovitch); Little Ice Ages (Solar); 20th Century Warming (Volcanoes; GHG)(Solar); 20th Century Warming (Volcanoes; GHG)

Examples of Acute: Year Without a Summer (Tambora - 1815/1816); Examples of Acute: Year Without a Summer (Tambora - 1815/1816); "Glacial" Winter in Eastern 2/3 N. America in 76/77 (dynamical mode/14 "Glacial" Winter in Eastern 2/3 N. America in 76/77 (dynamical mode/14 day westward propagating wave); Dec '89; 2004 Florida Hurricane day westward propagating wave); Dec '89; 2004 Florida Hurricane Season (?) (Dustbowl Era remains unexplained!)Season (?) (Dustbowl Era remains unexplained!)

It is very normal to have abnormal weather; and climate is the It is very normal to have abnormal weather; and climate is the statistical ensemble of weather events.statistical ensemble of weather events.

ACC crosses the threshold of "normal" variation; and generally ACC crosses the threshold of "normal" variation; and generally requires a trigger mechanism such as, a) a perturbation in a chaotic requires a trigger mechanism such as, a) a perturbation in a chaotic dynamical system, b) reorganization of the THC, c) volcano, d) solardynamical system, b) reorganization of the THC, c) volcano, d) solar

External forcing mechanisms can damp out chaotic behaviors over External forcing mechanisms can damp out chaotic behaviors over time; chronic changes can produce ACC (e.g., freshwater balance time; chronic changes can produce ACC (e.g., freshwater balance of the N. Atlantic due to CO2 warming).of the N. Atlantic due to CO2 warming).

Climate models may fail to anticipate ACC.Climate models may fail to anticipate ACC.

Solar variability cannot be ignored. Although thermal forcing by Solar variability cannot be ignored. Although thermal forcing by GHG to Solar is 4 to 1, there are no precise models that predict the 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-solar luminosity and its variability (i.e., the Solar Parameter); 11-year cycle, 22-year cycle; Gleissberg Cycle; Quiet Periods; Plages year cycle, 22-year cycle; Gleissberg Cycle; Quiet Periods; Plages 'vs.' Sunspots; Solar Max Mission Satellite).'vs.' Sunspots; Solar Max Mission Satellite).

Climate Model Prediction "must" pass all tests posed by available Climate Model Prediction "must" pass all tests posed by available data sets; and climate change predictions "must stand the test of data sets; and climate change predictions "must stand the test of time." There is no room for "Heliogeophysical Enthusiasts"!time." There is no room for "Heliogeophysical Enthusiasts"!