Chapter 21- Global Climate Change

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what causes air masses to move from place to place?


what is the difference between weather and climate?

weather refers to the state of the atmosphere at a given time and place; climate is a description of aggregate weather conditions based on observations over many decades; climate is often defined as "average weather"

what are some climate proxies?

(1) seafloor sediments- contain remains of organisms that one lived near sea surface; useful recorders of worldwide climate change
(2) oxygen isotope analysis- based on precise measurement of the ratio bt 2 isotopes of oxygen; O^16 is most common and the heavier O^18: O^18/O^16 ratio in shells of microorganisms- past temperatures
(3) climate change recorded in glacial ice
(4) tree rings- archives of environmental history
(5)fossil pollen, corals, historical data

the climate system

includes atmosphere, hydrosphere, geosphere, biosphere and cryosphere; these interact and involve exchanges of energy and moisture among the spheres- resulting in temperature and precipitation patterns (climate) around the globe

what is the composition of foraminifera shells (or tests)?

foraminifera is a skeleton made of CaCO3 (same as calcite) oxygen isotope rations depend upon water temp; these tiny, single celled organisms are sensitive to even small fluctuations in temperature; seafloor sedimetns containing fossils such as this are useful recorders of climate change

what isotopes form what part of the foraminifera test composition can be used to tell us about past ice sheet volume changes, and ALSO about past changes in ocean water temperature?


what was the purpose of the Ocean Drilling Program?


what heavy isotope changes relative to what light isotope in sea water, as ice sheets get larger during a glacial interval?

heavy isotope increases relative to light isotope at cooler temperatures (O18/O16 goes up).

can you figure out why O18 increases (relative to O16) in the tests of foraminifera during cold intervals, but decreases (relative to O16) during cold intervals in water samples from ice cores?

in ice, O18 increases relative to O16 during warm intervals. IN forarms, O18 decreases relative to O16 during warm intervals. Ice cores go back more than 400,000 years and record oxygen isotopes (T), atmospheric CO2 and methane in trapped air bubbles. The O isotope record form forarms "mirrors" that from glacial ice.

how do we know what the concentration of atmospheric CO2 was during past glacial and interglacial cycles? where do these samples come from?

changes in carbon dioxide and methane are linked to fluctuating temperatures. the cores also include atmospheric fallous such as wind-blown dust, volcanic ash and modern day pollution

how far back can we trace temperature and atmospheric CO2 concentration using ice core data?

> 400,000 years

how are tree rings used to tell us about past climate change?

every year, trees add a layer of new wood under the bark; characteristics of each tree ring such as size and density reflect the environmental conditions (especially climate); the age of the tree can be determined by counting the rings --> ring chronologies are used to reconstruct climate variations within a region for spans of thousands of years prior to human historical records

how far back in time can we trace climate using historical documents?


how do pollen grains tell us about past climate?

by analyzing pollen from accurately dated sediments, it is possible to obtain high-resolution records of vegetational changes in an area because pollen and spores are parts of life cycles of many plants and are easily identifiable

trophospheric ozone

ozone near the earth's surface (the troposphere is the lowest ~12 km of the atmosphere) - and affects us adversely when levels get to high. This is because ozone (O3) is a strong oxidizer. Tropospheric ozone is created from an interaction between sunlight and pollutants such as nitrous and sulfur oxides - in our area, most of these pollutants come from combustion in vehicles burning fossil fuels. But, a certain (regulated) amount is emitted from power plants as well. Ozone alerts (or Ozone action days) in Dallas are days when tropospheric ozone concentrations are higher than acceptable for good health. These are nearly always during the summer months.

stratospheric ozone

forms at ~ 20 - 30 km above Earth's surface, and is a protective layer that helps to filter out UV radiation by absorbing some of its energy. Life on planet Earth needs this because too much UV at Earth's surface (where we all live) can be harmful to cell function.

at what end of the electromagnetic spectrum does one find higher energy wavelengths, and at what end are the lower energy waves?


at higher energy, do waves have a shorter or longer wavelength?

the hotter the radiating body, the shorter the wavelength of maximum raidation

what is albedo?

the fraction of the total radiation that is reflected by a surface; thus the albedo for Earth as a whole is 30 percent

what has a higher albedo, ice or land?


what is the greenhouse effect?

the atmosphere warms the planet and makes Earth livable; the important role it plays in heating earth's surface is called the greenhouse effect: this energy heats the air and increases the rate at which it radiates energy, both out to space and back; think of short-wave UV coming in, long-wave radiation going back up from the surface as heat, these waves are absorbed by greenhouse gases, including CO2, methane, and others). We are most concerned about CO2 because we are adding it to the atmosphere in the greatest amounts, and it accumulates (does not dissipate for hundreds of years)owards Earth;

what are aerosols? how might they influence climate?

tiny, often microscopic, liquid and solid particles that are suspended in the air. Aerosols act directly by reflecting sunlight back to space and indirectly by making clouds "brighter" reflectors

what are other, natural sources of CO2 and aerosols?

plate tectonics, variations in earth's orbit involving shape, obliquity and precession, volcanic activity and changes in sun's output associated with sunspots

how do we know there has been a sharp rise in atmospheric CO2 since the industrial revolution?

30% higher than highest level over at least the last 650,000 years

how do we know that CO2 is coming primarily from fossils?


How do CO2 levels today compare with those of the last 400,000 years?

highest its ever been

how much has the average temperature of the earth increased over the last 100 years? would this increase have been greater or lesser at high latitudes?

1 degree Celsius rise in average temperature; increase greater at high latitudes- but the 10 warmest years have been during the past 15 years!

positive-feedback mechanisms

positive feedbacks are changes that reinforce the initial change
ex: warmer surface temperatures can cause an increase in evaporation, which further increases temperature as the additional water vapor absorbs more radiation emitted by Earth

what are some of the consequences of climate change- which we are already seeing?

hard to predict specific regional changes because increased levels of CO2 but consequences include:
(1) altering the distribution of the world's water resources
(2) a probable rise in sea level
(3) a greater intensity of tropical cyclones
(4) changes in the extent of Arctic sea ice and permafrost

negative-feedback mechanisms

produce results that are the opposite of the initial change and tend to offset it
ex: the negative effect that increased cloud cover has on the amount of solar energy available to hear the atmosphere

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