Chapter 1 EAR 203
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This 4 page Class Notes was uploaded by Hannah Slifstein on Tuesday January 19, 2016. The Class Notes belongs to EAR 203 at Syracuse University taught by G. Hoke in Spring 2016. Since its upload, it has received 15 views.
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Date Created: 01/19/16
THE EARTH SYSTEM: CHAPTER 1 GLOBAL CHANGE I. Introduction i. The speed at which Earth changes has continued to increase ii. Humans have been the agents of the Earth’s change ex) deforestation, and pollution in cities iii. The global climate has increased because of the addition of greenhouse gases in the atmosphere iv. Humans have also damaged the ozone layer thus being the cause of the ozone hole over Antarctica b. Three Major Themes i. In order to understand how the environment is going to change, we must understand how the environment changed before humans ii. We get evidence of past climates from cores drilled into sediments in the ocean floor iii. The evidence gathered by this proves that we are in a short interglacial period (period of warmth) iv. However, without human influence, the Earth would likely slip into the next Ice Age v. An example of a forcing is the variation in the amount of sunlight received in each hemisphere during the course of a year ”The Earth System” Third Edition by Lee R. Kump, James F. Kasting and Robert G. Crane II. Global Change on Short Time Scales i. Three major global environmental changes that are occurring today: global warming, ozone depletion, and tropical deforestation b. Evidence of Global Warming i. Involves many parts of the Earth System ii. There are natural and anthropogenic (human induced) influences iii. It is an increase in the Earth’s surface temperature iv. Not all scientists agree that global warming has begun v. In 2007 the Intergovernmental Panel on Climate Change (IPCC) released a report saying that the Earth’s average temperature has increased resulting in melting of snow and ice, and rising the global sea level vi. Al Gore and the IPCC jointly received the Nobel Peace Prize in 2007 for promoting the understanding of global warming c. Measurements of Atmospheric CO : The Keeling Curve 2 i. Atmospheric CO co2 entration measured at the top of Mauna Loa, a 4300-m-high volcano in Hawaii over the last 50 years has periodically increased ii. The measurements began in 1958 by Dr. Charles David Keeling of the Scripps Institute of Oceanography iii. Because of Keeling’s data it is indisputable that the long term trend in atmospheric CO i2 real rather than artifact d. Other Greenhouse Gases i. Methane (CH ) 4nd nitrous oxide (N O) 2ave also been increasing as a result of primarily human agriculture ii. CFCs are also called freons iii. The evidence for an increase in anthropogenic greenhouse gases is unequivocal: Humans are indeed modifying the composition of Earth’s atmosphere e. LosObserved Changes in Surface Temperature i. At a number of stations around the world, scientists have made accurate atmospheric temperature measurements that date back to more than a century ii. Ocean-crossing ships have also routinely measures sea-surface temperatures iii. Problems do exist with these historical temperature data iv. Sea-surface temperature measurements are also subject to systematic errors v. Prior to the mid-1900s, water temperatures were determined by the “bucket method” vi. Since then, water temperatures have generally been measured with flow-through devices located on the ship’s hull vii. A second problem with the temperature data is that the coverage in time and space is much better in some parts of the world than in others viii. The warming trend seemed to slow, or stop entirely, between about 1940 and 1970 ix. By 1970 some climatologists were concerned that Earth might be entering a new glacial period x. One possible explanation for the 1940 to 1970 cooling trend is that it was caused by increased reflection of sunlight by sulfate aerosol particles f. Changes in the Cyrosphere i. The temperatures in the North Pole have been increasing more rapidly than the rest of the globe ii. Could potentially cause the melting of the Greenland ice sheet which can cause a rise in sea level (approx 6 meters or 20 feet) g. Possible Consequences of Global Warming i. A change in temperature might cause other changes as well ii. Sea level has risen at least 10 cm in the past century iii. The intensity of tropical hurricanes can increase over time h. Evidence of Ozone Depletion i. Stratospheric ozone us important to living organisms because it absorbs many of the Sun’s harmful UV rays ii. 1985 marked the discovery of the ozone hole above Antarctica iii. Every year since 1976 in October ozone levels in the South Pole have fallen iv. The ozone column depth is the total amount of ozone per unit area above a certain location v. By 1974, scientists had confirmed that chlorine is capable of destroying stratospheric ozone vi. The definitive evidence was provided in 1987, when a NASA research plane i. Deforestation and Loss of Biodiversity i. Humans are the cause of loss of trees and increased amount of extinct species ii. Loss of tropical rainforests with a loss rate of 1.8% a year j. Which Changes Should Concern Us the Most? i. Ozone depletion and global warming are the highest concerns ii. The time scale for global warming recovery could be much longer than 50 years iii. However, it would take longer to restore global biodiversity iv. It could take tens of millions of years to restore an extinct species III. Global Change on Long Time Scales i. Eons, the broadest level of time, are subdivided into eras; eras are broken down into periods, which are further split into epochs b. Glacial-Interglacial Cycles: The Ice-Core Temperature Record from Vostok and Dome C i. A set of ice cores drilled between the mid-1980s and the early 1990s at Vostok, Antarctica has provided a lot of information about the Pleistocene glacations ii. A new core drilled in 2003 at Dome C, about 560 km from Vostok, has provided an even longer and more detailed record iii. The reason that both the Vostok and Dome C records extend so far back in time is that snow accumulates very slowly at these sites iv. Vostok results showed that the atmospheric CO and CH 2 4 concentrations had varied in concert with surface temperature v. Atmospheric CO lev2ls affect climate and that climate, in turn, affects atmospheric CO le2els c. Mass Extinction: Iridium and the K-T Boundary at Gubbio i. In 1980 Luis and Walter Alvarez, and their colleagues, published a paper about a clay layer they had studied in rocks from the mountains near Gubbio, Italy ii. Walter Alvarez went to Gubbio in an effort to determine how long it had taken for the clay layer to be deposited iii. Luis Alvarez reasoned that he could calculate the time required to form the clay layer by measuring the abundance of the element iridium (Ir) iv. Reasoned that he could use the measured Ir abundance in the Gubbio clay layer as a kind of “cosmic clock” to determine the time needed for the clay to have been deposited v. Their experiment failed however it gave information they needed vi. The Ir abundance in the clay layer was up to 10 ppb by mass- more than 100 times higher than what the group expected to find vii. It was much too large to have been supplied by debris from asteroids or comets viii. The Alvarez team reasoned that the iridium must have come instead from the impact of some large, extraterrestrial object, such as an asteroid or a comet d. Changes in Solar Luminosity i. The Sun produces its energy through nuclear fusion ii. 4 hydrogen nuclei ( H) fuse to form one helium nucleus ( He) 4 iii. The Sun’s luminosity should gradually increase as it depletes its hydrogen fuel e. The Gaia Hypothesis i. Earth is a self regulating system in which the biota plays an integral role ii. Organisms do play an important role in the overall functioning of the Earth System
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