Transcript Slide 1

Abrupt Climate Change
Ernie Agee
6 April 2005
 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!)
 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"!