Geology Final (ch. 10)
What is albedo? What substances have high albedo and why? How does albedo influence climate change? What are some examples of positive feedback and negative feedback regarding climate change? (what does positive & negative feedback mean?)
Glaciers, being white in color, typically help reduce global warming levels by reflecting sunlight back into outer space = albedo. positive feedback cycle: Glacial ice (and white clouds) has a high albedo. As the Earth warms, glaciers retreat, and so their albedo potential decreases, and the Earth warms up slightly more quickly than if the glacier had been fully present. The more glaciers retreat, the lower the albedo, the more quickly the Earth warms up Negative feedback: It is possible that as temperatures rise, large-scale storms will become more frequent, and the increased cloud- coverage would potentially offset the albedo lost by retreating glacial activity, and help slow down the rate of global warming. the warming induces changes that encourage the opposite (in this case, cooling). ex) There are also arguments as to how CO2 dissolving in the oceans will affect CO2 levels. A positive feedback cycle would find CO2 being dissolved from the oceans as they warm: as it travels into the air, CO2 traps more heat, furthering warming the waters. Or, in a negative feedback cycle, the melting glacial ice helps somehow reduce CO2 levels in the water.
What is a greenhouse gas? What is the most abundant greenhouse gas?
Greenhouse gases trap infrared rays and promote the warming of the atmosphere. The actual percentage of CO2 in the atmosphere is very small! Dry air (removed of water vapor) contains: - 78% nitrogen - 21% oxygen - 0.1% argon - and just 0.04% carbon dioxide
What influences the temperature of the Earth?
Greenhouse gases. The presence of gases in our atmosphere insulate the Earth like a blanket, trapping the longwave radiation emanating out from the Earth's surface. Greenhouse gases trap infrared rays and promote the warming of the atmosphere.
Who was Ralph Keeling and what was his contribution to the study of climate change? Why are there fluctuations in the curve over the course of a single year?
Modern CO2 levels were first measured in 1958, by Ralph Keeling, of Scripps Institution of Oceanography, in California, and its levels then were 310 ppm (or 0.031%). Current atmospheric CO2 levels are at 410 ppm (0.041%)
What is the greenhouse effect?
Part of the reason is due to the presence of gases in our atmosphere that insulate the Earth like a blanket, trapping the longwave radiation emanating out from the Earth's surface. This is called the greenhouse effect and is a natural phenomenon that has been occurring for millions of years on Earth (and other planets); and without this effect, the Earth would effectively be, on average, ~40°C cooler.
What is permafrost and why is it of concern with regard to global warming?
Permafrost: permanently frozen ground, seen in northern latitudes above 60°, underlying about 20% of the land area in the world. Changes in permafrost affects the distribution of surface water and groundwater.
Approximately by how much have CO2 levels risen since the Industrial Revolution (mid-1800s)? Approximately by how much has global surface temperature risen since the Industrial Revolution?
Since the onset of the Industrial Revolution in the late-1700s, CO2 levels have steadily been rising in our atmosphere, upwards of 40%, and its levels continue to rise. Since the mid-1800s, the Earth's surface temperature has risen ~ 0.85°C (1.5°F). This may not sound like very much, but as we shall see that small rise in temperature is having a dramatic impact around the world.
How does wind influence upwelling along a coast, and what is its effect on local ecosystems? How does El Nino disrupt this system along the western shore of South America?
The Gulf Stream is part of this larger belt, whereby warm surface water is transported east and north to Greenland, where it cools from contact with cold Canadian air. As the water cools, it increases in density and sinks to the bottom (a process called (called downwelling), then flows south and east to the Pacific, where it warms up again and upwelling occurs. The heat released to the atmosphere from the Gulf Stream helps keep Northern Europe at least 10°F warmer than it would be if this thermohaline circulation pattern was not present. Abrupt historical changes in climate are sometimes attributed to disruptions in currents such as the Gulf Stream El Niño: There is a thermal gradient with ocean water depth: surface ocean water is, on average, 15°C (60°F), as it is warmed by the sun, but with increasing depth, ocean water becomes colder. As winds blow offshore, the warm surface water is pushed away from the coast, and the deeper, cooler waters upwells (rises up) toward the ocean surface. This water is nutrient-rich, and in many regions of the world where upwelling occurs (e.g. the west coasts of North and South America), diverse, aquatic ecosystems grow and thrive. El Niño refers to a periodic halt in this upwelling, where the fertile cold waters no longer rise up along the western South American coasts.
How does rising CO2 affect ocean acidity levels? What implications does this have for limestone reefs (recall what concentrated acids do to limestone) and photosynthetic marine microorganisms?
The oceans are capable of absorbing excess CO2 and thus help slow the rate of global warming. But as CO2 levels build up in the oceans, the oceans become more acidic. The equation is as follows: CO2 + water (H2O) carbonic acid (H2CO3) hydrogen ions (H+) + bicarbonate (HCO3-). Increased acidity levels weakens or outright dissolves the limestone shells of marine invertebrates such as coral and phytoplankton, species that forms the base for entire ecosystems. phytoplankton, microscopic photosynthetic marine algae that form the base of many ecological food webs.
How do the oceans play a role in climate change and global warming? (i.e., how are they effective as reservoirs and for what materials / states of matter?)
The oceans store and transport a tremendous amount of heat around the globe. Much of the heat currently absorbed by the Earth is stored in its oceans. The increased heat supplies energy to spawn hurricanes of greater intensity.
How far back do glacial ice-core records date?
The oldest ice-core records come from the Antarctic and date back 800,000 years. Those from Greenland date back 160,000 years. The records from both, when compared, show similar results: warming trends, cooling trends, and correlations between historic CO2 and methane (CH4) levels and global temperature. Modern CO2 levels are unprecedented in the history of modern humans.
How are O^18 / O^16 levels used as a proxy for measuring ancient climates? Why are they found in ice cores, and how do their levels change with global warming and cooling trends?
The relative abundances of O18 / O16 found in sea water, in fossil shells, and in bubbles in glacial ice are used to make predictions of past global temperatures. Briefly, because O16 is lighter than O18 (because O18 has 2 additional neutrons), O16 will evaporate from an equatorial sea more readily than O18. Conversely, O18 will precipitate out more readily than O16 when returning as rain or snow back to the Earth. As air moves from the Equator to the poles (from warm to cold), O18 preferentially precipitates out first (as rain), leaving the residual air moving toward the pole more concentrated in O16. That O16 is finally deposited as rain or snow over the poles, and gets incorporated into glacial ice. Because O18 tends to not make it up to the poles as readily, glacial ice is more enriched in O16 than O18. To summarize, the O18 / O16 ratio would be larger during ice ages because ocean water would be enriched in O18 and O16 would be trapped in ice caps. Microorganisms making their shells during this period would have higher concentrations of O18 in them.
What is thermohaline circulation? What does the phrase "ocean conveyor" refer to and how does it influence regional temperatures?
Thermohaline Circulation ("thermo" = heat, "haline" = salt; the roles of temperature and salinity in moving water around the globe Ocean conveyor belt: global circulation of ocean waters contributes to the change.
How do greenhouse gases contribute to global warming?
These gases trap heat and warm the lower atmosphere, similar to the effect of the trapping of solar heat by a greenhouse.