March 18th 2011
|THE SHIFT IN STATE OF THE ATMOSPHERE|
|Speaker: Dr. Andrew Glikson|
|Time: 1.00 - 2.00pm|
|Location: Building C4A Room 318|
|Audience: Academics and Students|
Abstract: Long term gradual and protracted shifts in the state of the atmosphere/ocean/cryosphere system through the Cainozoic (65-0 Ma) include the decline of global temperatures through the Eocene (50-34 Ma), warm periods in the late Oligocene (21 Ma), mid-Miocene (~16 Ma) and mid-Pliocene (3 Ma), followed by a descent to Pleistocene (<1.8 Ma) glacial-interglacial cycles. These changes have been perturbed by abrupt climate shifts associated with methane eruption at ~55 Ma (CO2 increase at 0.4 ppm/year), a major asteroid cluster at ~35 Ma, abrupt cooling and formation of the Antarctic ice sheet at ~34 Ma, volcanic eruptions (cf. Toba, 71 Kyr) and glacial terminations (410, 320, 230, 140, 14-10 Kyr). Rates of change in atmospheric GHG forcings and temperatures varied from minutes for asteroid impacts, to days and weeks for volcanic eruptions, to decades and centuries for terminations of intra-glacial 1470 years-long O-D cycles, to centures to a few millenia for major glacial terminations. Glacial terminations involved rises of atmospheric CO2 on the scale of ~100 ppm and global temperatures ~4-5C. Anthropogenic climate change associated with emission of >320 GtC since 1750, as well as land clearing, progressing at ~2 ppm CO2/year, constitutes a rapid shift in the state of the atmosphere/ocean/cryosphere system tracking toward conditions which existed in the mid-Pliocene (~3 Ma, ~400 ppm CO2, +3-4C; +25+/-12 meters sea level rise). However, the very high rate of increase in GHG forcing, unknown in the history of Earth (excepting major asteroid, volcanic and methane release events), triggering rapid ice melt feedback processes, is shifting the atmosphere/ocean system into uncharted territory.
Bio: Dr. Andrew Glikson is an Earth scientist at the Australian National University. He conducted geological surveys in central and western Australia, investigated early crust evolution in several continents, the role of asteroids as triggers of major crustal events, extreme climate events and mass extinction of species, and the effects of climate on evolution of pre-historic humans.