HR: 13:45h
AN: A23D-01 INVITED     [Abstracts]
TI: Bjerknes Lecture: Anticipating the Big Impacts of Anthropogenic Carbon Dioxide Increases
AU: * Overpeck, J
EM: jto@u.arizona.edu
AF: ISPE, Dept. of Geosciences, Dept. of Atmospheric Sciences, University of Arizona 715 N. Park Ave. 2nd Floor, Tucson, AZ 85721 United States
AB: The reality of human-caused global warming is no longer a subject of much serious scientific debate, but many critical details remain to be worked out in what has come to define a whole generation of geophysical careers. We could be called the "Keeling Generation" - those who came to science in the shadow of Keeling curve of atmospheric carbon dioxide concentrations rising steadily and foreshadowing large potential change for the Earth System. To many, the call to help figure out this change has been a prime career motivation. We owe much to the visionaries such as David Keeling, for they build the foundation on which we build. Three decades after the start of the Keeling curve, we know that atmospheric carbon dioxide levels are now unprecedented in nearly a million years, and that global warmth could be unprecedented to a similar degree - if it is not now, it could be soon. To many in society, this is enough to warrant action, but to many others the response is more of a "so what?" Society has many technological tools at its disposal, and air conditioning is one that many of us (at least in Arizona) have come to depend on. So, why worry about increasing temperatures? Rising temperatures can, and likely will, have many impacts that will cause society to incur costs (both market and non-market). Many of the possible costs will be incurred by current generations, but paid for by future generations. Perhaps the biggest one, in terms of economic costs, cultural impacts and possibly lives, will be global sea level rise. Sea level could rise up to a meter in this century, and in doing so put entire countries underwater. However, these changes will pale compared to the post-2100 sea level rise that 21st century generations could commit future generations to. Paleoclimatic constraints indicate that warmth by the end of this century could be enough to melt large portions of both the Greenland and Antarctic Ice Sheets, with resulting sea level rise of 4-7m, and at rates that could exceed one meter per century. Couple this with likely more intense hurricanes (and storm surges in excess of several meters), and it should be clear to all that impacts could be enormous. "Buy now, pay later" isn't the whole story, however. The western United States is already seeing signs that global warming could create unprecedented challenges in the 21st century. Spring snow pack is retreating steadily, and temperatures are rising just as fast as regional human populations are growing. Couple these changes with drought such as witnessed in the last seven years, and it becomes clear that climate change can have large impacts. We've seen unprecedented wildfire and drought-related forest mortality, but our water infrastructure is doing its job. However, what if the West gets hit with a decades long "megadrought?" We know from the recent drought that important aspects of water infrastructure would buckle. We also know from the paleoclimatic record that such droughts are a regular feature of natural climate variability. Lastly, there is good reason to suspect that global warming will increase the odds of such megadrought. Even without this increase in odds, the recent drought makes it clear that high temperatures and weak snow pack exacerbate the impacts of drought. It is probably time for current generations to learn how to use water more wisely, but also to show that the Keeling curve can trend downward as well as upward.
DE: 1605 Abrupt/rapid climate change (4901, 8408)
DE: 1620 Climate dynamics (0429, 3309)
DE: 1630 Impacts of global change (1225)
DE: 1637 Regional climate change
DE: 1641 Sea level change (1222, 1225, 4556)
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005