The Earth is due for an asteroid that would cause agriculture to virtually end and civilization to cease being.
Broad in 91 (author and a senior writer at The New York Times. Won two Pulitzer prizes, was a Pulitzer finalist, won the Emmy for PBS Nova, won a Dupont Award, The New York Times, Asteroids, a Menace to Early Life, Could Still Destroy Earth; There's a 'Doomsday Rock,' But When Will It Strike?, June 18, 1991, http://www.nytimes.com/1991/06/18/science/asteroids-menace-early-life-could-still-destroy-earth-there-s-doomsday-rock-but.html?pagewanted-print&src-pm, znf)
SOMEWHERE in space at this moment, hurtling toward Earth at roughly 16 miles a second, is the doomsday rock. The question of growing interest to scientists and engineers is exactly when it will approach the planet and whether anything can be done to avoid a catastrophic collision, such as nudging the rock off course with a nuclear blast or two. The doomsday rock is an asteroid large enough to severely disrupt life on Earth upon impact, lofting pulverized rock and dust that blocks most sunlight. Agriculture would virtually end, and civilization could wither and die, just as the dinosaurs and many other forms of life are thought by some to have been wiped out by a massive object from outer space 65 million years ago. So far, no astronomer has located the killer asteroid, which by definition would be a mile wide or larger, would have an orbit that crossed Earth's, and would do so at exactly the wrong moment. But, given enough time, it is inevitable that one will appear. And the odds are that the moment could be relatively soon, in celestial terms. Experts, extrapolating from craters observed on the Moon and from a partial survey of Earth-crossing asteroids, calculate that "a big one" slams into the planet once every 300,000 to one million years. More graphically, that means there is between one chance in 6,000 and one chance in 20,000 of a cataclysmic impact in the next 50 years. "Eventually it will hit and be catastrophic," said Dr. Tom Gehrels, a professor of lunar and planetary science at the University of Arizona who heads a team that searches the sky for killer asteroids. "The largest near-Earth one we know of is 10 kilometers in diameter," or about 6.2 miles. "If a thing like that hit, the explosion would be a billion times bigger than Hiroshima. That's a whopper." The field of asteroid detection and avoidance, once pooh-poohed as laughably paranoid, has grown in size and respectability in the last decade. Last year Congress called for a series of detailed studies after a half-mile-wide asteroid crossed the planet's path at an uncomfortably close distance in 1989. "The Earth had been at that point only six hours earlier," a House report noted. "Had it struck the Earth it would have caused a disaster unprecedented in human history. The energy released would have been equivalent to more than 1,000 one-megaton bombs."
Asteroid impact would destroy agriculture by blocking sunlight with dust which prevents photosynthesis and reduces temperatures.
Chapman in 11 (Clark R. Chapman, planetary scientist at the Southwest Research Institute, Astronomy vol. 39 issue 5 May 2011, What will happen when the next asteroid strikes?, http://proxy.foley.gonzaga.edu/login?url=http ://search.ebscohost.com/login.aspx?direct=true&db=a9h&AN=60031700&site=ehost-live) DF
In addition, Earth would undergo significant climate changes as Sun-blocking dust is launched into the atmosphere after impact. As dust circles the globe during the ensuing weeks, perhaps crossing the equator into the opposite hemisphere, temperatures would cool dramatically, threatening an agricultural growing season and hence the world's food supply. With more than a year of warning, the international community could mitigate the worst effects before impact: prepare for unprecedented food shortages, the required medical effort, and the possible collapse of the world's economic infrastructure. Maybe humanity could weather the storm without letting fears of the terrible prognosis exacerbate tensions, which would magnify the unfolding tragedy. With foreknowledge, civilization might survive, depending on whether we can stay resilient as we face such a natural disaster.
Agriculture Disruption ! – Food Shortages
Food shortages can spark conflict – Empirically proven
Thompson 07 (Andrea, writer, livescience.com, “Climate Change can spark war”, November 21st, 2007; Accessed 7/3/11, AH)
History may be bound to repeat itself as Earth’s climate continues to warm, with changing temperatures causing food shortages that lead to wars and population declines, according to a new study that builds on earlier work. The previous study, by David Zhang of the University of Hong Kong, found that swings in temperature were correlated with times of war in Eastern China between 1000 and 1911. Zhang's newer work, detailed in the Nov. 19 online edition of the journal Proceedings of the National Academy of Sciences, broadens its outlook to climate and war records worldwide and also found a correlation between the two. "This current study covers a much larger spatial area and the conclusions from the current research could be considered general principles," Zhang said. The research does not represent direct cause-and-effect, but rather suggests a link between climate and conflict. Because water supplies, growing seasons and land fertility can be affected by changes in climate, they might prompt food shortages that could in turn lead to conflicts, such as local uprisings, government destabilization and invasions from neighboring regions, the researchers speculate. These conflicts and the food shortages that cause them could both contribute to population declines, they add. To see whether changes in climate affected the number of wars fought in the past, the researchers examined the time period between 1400 and 1900, when global average temperatures reached extreme lows around 1450, 1640 and 1820, with slightly warmer periods in between. Using records reflected in tree rings and ice cores, the researchers compared temperature changes to a database of 4,500 wars worldwide that co-author Peter Brecke of Georgia Tech compiled with funding from the U.S. Institute of Peace. The results of the comparison showed a cyclic pattern of turbulent periods when temperatures were low, followed by more tranquil times when temperatures were higher. This correlation doesn't necessarily mean that all-out war is imminent, William Easterling of Pennsylvania State University, who was not affiliated with the work, had said in regards to Zhang's earlier work. However, the changing distribution of resources could certainly increase international tensions, he added. The new study also showed population declines following each war peak. Specifically, during the frigid 17th century, Europe and Asia experienced more wars of great magnitude and population declines than in more temperate times. Projecting into the future To connect temperature changes of less than 1 degree Celsius (1.8 degrees Fahrenheit) to food shortages, the authors used price increases as a measure of decreases in agricultural production and found that when grain prices reached a certain level, wars erupted. Though these historical periods of climate change featured cooler temperatures, current rising global temperatures could still cause ecological stress that damages agricultural production. "Even though temperatures are increasing now, the same resulting conflicts may occur since we still greatly depend on the land as our food source," Brecke said. "The warmer temperatures are probably good for a while, but beyond some level, plants will be stressed," Brecke explained. "With more droughts and a rapidly growing population, it is going to get harder and harder to provide food for everyone, and thus we should not be surprised to see more instances of starvation and probably more cases of hungry people clashing over scarce food and water."