Chapter 20 – The Atmosphere: Climate, Climate Change and Ozone Depletion

27/10/2010 01:11

1) Explain the possible connection between intense hurricanes and the effects of current warming.


Page 509- In the year 2005, a record 27 storms developed in the Atlantic Ocean; 14 of which were hurricanes. Hurricane experts pointed out that in particular, abnormally warm sea-surface temperatures and low wind sheer. They link hurricanes and global warming. There is a trend with the development of category 4-5, the strongest, hurricanes and rising sea and air temperatures. The high sea surface temperatures result in more water vapor in the air, leading to conditions that create a rising column f warm, humid air that can be set spinning by Coriolis force (Earth’s rotation) and lead to hurricane formation. The question is, what is the connection between hurricanes, the atmosphere, oceans, and human activities (Page 509)? 2005 was the hottest year ever recorded since the late 1800’s. Because of the continued increases in anthropogenic greenhouse gases in the atmosphere, observed warming is considered to be the consequence of an “enhanced greenhouse effect.” A recent analysis of Earth’s energy imbalance makes the case for the oceans’ continuing absorption of heat such that over the last decade, the ocean has absorbed essentially all of the heat not yet seen in the atmosphere (Page 522). The upper 3000 meters of the ocean have warmed measurably since 1955, a warming that dwarfs the observed warming of the atmosphere, accounting for 90% of the heat increase of Earth systems in the last several decades (Page 523). As we saw earlier, there is a trend towards more intense tropical hurricanes, which correlate with higher sea surface temperatures (Page 523).  



2) What are the most important aspects of the troposphere? Of the stratosphere?


Troposphere: This layer of the atmosphere basically helps regulate, control and stabilize Earth’s weather and climate and contains all of the planet’s clouds and water vapor. The troposphere is the lowest level of the atmosphere and the gases within this level are responsible for moderating the flow of energy to Earth and are involved with the biogeochemical cycling of many elements and compounds- oxygen, nitrogen, carbon, sulfur and water, to name the most crucial ones. The troposphere tends to get colder with latitude allowing pollutants to reach the top of this layer in a few days.  Pollutants may be changed chemically, and washed back to Earth’s surface by precipitation (Page 510).


Stratosphere: Temperature increase with latitude. Contains Ozone which cause temperatures to increase, and absorbs high energy radiation from the sun. Since there is no weather in this layer, pollutants can remain in the stratosphere for some time (Page510).



3) How does solar radiation create our weather patterns?


It is fair to think of the atmosphere-ocean-land system as an enormous weather engine, fueled by the sun. Solar radiation enters the atmosphere and takes a number of possible courses, see figure 20-3, page 511. Some is reflected by the clouds and the Earth’s surfaces but most is absorbed by the atmosphere, oceans and land which are heated in the process. The land and oceans then radiate some of their heat back upward as infrared energy. Some of the heat that is radiated back is transferred to the atmosphere. Lighter warmer air will then rise creating vertical air currents. This creates a convection of currents. Air must flow in to replace the rising warm air, and the inflow leads to horizontal airflows, or wind. As warm air rises higher and higher it begins to cool and then sinks which creates a cycle similar to a conveyer belt. These major flows of air create regions of high rainfall, deserts and horizontal winds (trade winds). This affects our day to day weather. This is all do to solar heating and rising warm air, heated by the sun. Rising warm air also creates high pressure leaving cold pressure below. Conversely, once the moist high pressure air has cooled by radiating heat to space and losing heat through condensation, rain, the air then flows horizontally toward regions of sinking cool, dry air (Pages 510-511).




4) What has been discovered about global climate trends in the past? What is the contemporary trend showing?

Records indicate that the weather and climate are not constant. Since 1880, weather monitoring systems have demonstrated that there are warming and cooling periods, but in general, the climate has increased 0.8 degrees C. Two warming trends occurred during the 20th century, one from 1919 to 1945 and from 1976 to the present. Proxies such as tree rings, pollen deposits, change in landscapes, marine sediments, corals and ice cores show that between 1100 and 1300 A.D. there was a warming period and between 1400 and 1850 A.D. there was a “Little Ice Age”. This provides evidence that remarkable changes in the Earth’s climate can change within a few decades. In figure 20-5, page 513, the anomaly depicts global surface temperatures increasing from 1975 until present. The warming is conspicuous or obvious (Page 513).


5) What is the conveyer system? How does it work? How does it connect with global warming?

This is the thermohaline circulation pattern that dominates oceanic currents, see figure 20-7, page 515. Thermohaline refers to the effects that temperature and salinity have on the density of sea water. The conveyer system acts as a giant, complex conveyer belt, moving water masses from the surface to deep oceans and back again, according to the density of the mass. A key area is the north Atlantic, where salty water from the Gulf Stream moves northward on the surface and is cooled by Arctic air currents. Cooling increases the density of water, causing it to sink, sometimes to depths of 4,000 meters. This deep water spreads southward through the southern tip of Africa where it is joined by cold Antarctic waters. Together the two streams spread northward towards the Indian and Pacific Ocean’s deep currents. Gradually, the currents slow down and warm, becoming less dense and welling up to the surface, where they are further warmed and begin to move surface waters back again toward the North Atlantic. This is vital for the maintenance of current climatic conditions, (page 515). If global warming persists, polar ice caps will continue to melt, decreasing salinity and density of ocean water and also warming the temperatures in the Arctic region, which could interrupt the conveyor system, which would in turn impact global climate, particularly in the northern latitudes (page 515).


6) What is radiative forcing? Describe some positive and negative forcing agents.

Radiative forcing is the influence a particular factor has on the energy balance of the atmosphere-ocean-land system. Examples include oceans, temperature, snow cover, solar radiation, Earth’s rotation, and atmospheric gases). A factor can be positive, leading to warming, or negative, leading to cooling, as it effects the energy balance. This is not to be confused with good or bad, but instead as adding and taking or decreasing. Positive agents can include GHGs (green house  gases). GHG’s such as water vapor, oxygen and carbon dioxide are natural GHG’s that as radiation and heat trappers to regulate temperature. The constant addition of GHGs via industry, into the Earth’s atmosphere will intensify or strengthen the temperatures by trapping more of the Sun’s radiation (page 516). Negative forcing agents include the planetary albedo effect which also regulates climates and acts as a cooling system. The albedo effect has a lot to do with clouds as they block suns rays and solar radiation, (page 517).


7) Which of the greenhouse gases are the most significant? How do they work?

Carbon Dioxide (CO2), Methane (CH4), Nitrous Oxide (N2O), Water Vapor, Chlorofluorocarbons and halocarbons.     

CO2 is important in regulating the Earth’s temperature and trapping heat. Increasingly present in Earths atmosphere due to burning of fossil fuels. Carbon sinks are places where CO2 mainly thrives and is best apt to remain… such as the atmosphere and the oceans, via phytoplankton, (page 520).

Water Vapor absorbs infrared energy and is the most abundant green house gas. As global temperatures increase, more evaporation will occur creating more vapor, (example of positive feedback). This will accelerate future warming because it helps trap more GHGs (page 520).

Methane is the third most abundant gas, and is a product of microbial fermentative reactions, and its main natural source is wetlands. Methane is also created in the stomachs of agricultural animals such as cows, and is also produced in landfills, coal mines, natural gas production and transmission, rice cultivation and manure. Methane is being introduced/added into the atmosphere faster than it can be broken down. Also traps heat in atmosphere, page 521).

Nitrous oxide have increased 18% in last 200 years. Sources include agriculture and burning of bio-mass, and fossil fuel burning to an extent. N2O is produced in agriculture via anaerobic denitrification processes, which occur wherever nitrogen is highly available in soils. This gas contributes to warming and ozone depletion (page 521).

Ozone’s greatest source is anthropogenic, through the action of sunlight on pollutants. Ozone has increased 36% since 1750. Major sources are automotive traffic and burning forests and agricultural waste (page 521).

CFCs and halocarbons contribute to global warming and ozone destruction. They are used as refrigerants, solvents and fire retardants, and have a much higher capacity to absorb radiation than CO2, (page 521).


8) Describe the data for atmospheric CO2; what are the significant sources and sinks for atmospheric CO2?

Concentrations of CO2 increase as energy demand goes up. Data reveals oscillation of 5-7 ppm, which reflects seasonal changes of photosynthesis and respiration in terrestrial ecosystems in the Northern Hemisphere. When respiration pre-dominates (late fall through spring), CO2 levels rise. They decrease during spring and summer months when photosynthesis again dominates. CO2 levels are 35% higher today tan they were before the Industrial Revolution. Sources include fossil fuel burning and burning of forests. Sinks include the atmosphere, forests and densely vegetated areas and the oceans, (pages 519-520).


9) What evidence do global land and ocean temperatures provide for a warming Earth?

Most of the evidence is demonstrated in the oceans: The upper 3000 meters of the ocean have warmed measurably since 1955, a warming that dwarfs the observed warming of the atmosphere, accounting for 90% of the heat increase of Earth systems in the last several decades. The impact of this stored heat as it eventually comes into equilibrium with the atmosphere, will raise temperatures over land and in the atmosphere. The sea level will rise due to thermal expansion and warmer ocean water. Sea level rose about 15 cm in the 20th century. Polar ice caps, glaciers and ice fields are continuing to melt. Also due to the ocean’s rising temperatures are increased storm activity during the rain and hurricane seasons. Increases in average global temperatures, warmer in hot places and colder in cooler places. Spring come earlier and fall comes later. Heat waves, increased malaria cases, and more forest insect damage. There are also increased droughts and their durations, more forest fires with greater intensity. Increased Arctic/Antarctic temperatures, patterns of rainfall and precipitation are changing, marine fish species populations are shifting northward as sea temperatures have warmed. And increased frequency and intensity of El Nino events are occurring, pages 523-524).


10) What additional climate variables contribute to the picture of human-caused warming? 

This best explained by green house gas forcing and increased industrial activity, and economic development in a wider array of nations, more cars, more travel, and demand for more resources and increased energy consumption. All of the points mentioned in question 9 attest to the results of increased GHGs in the atmosphere. (Check point 6 on page 525).


11) How are models employed in climate change research? Describe several scenarios for 21st century climate change.

Weather forecasting employs powerful computers capable of handling large amounts of atmospheric data and applying appropriate mathematical equations modeling the processes taking place in the atmosphere, oceans, and land. Modeling climate, based on years of records and data compilations, is an essential strategy for exploring the potential future impacts of rising GHGs. Climatologists employ systems that monitor global atmospheric circulation patterns with oceanic circulation, radiation feedback from clouds, and land surface processes to produce atmosphere-ocean general circulation models (AOGSMs) that are capable of simulating long-term climatic conditions. 14 centers around the world are now engaged in exploring climate change by running 23 models coupling the atmosphere, oceans and land. The 4th IPCC Assessment Report, shows how closely models track the observed temperature changes from 1900 to 2004, taking into consideration natural and anthropogenic forcing, (page 525).


12) What are the major IPCC projections for climate changes in the 21st century?

Earlier assessment reports projected global temperature increases from .15 to .29 Celsius per decade, based on less sophisticated models. This compares favorably with the observed values of about 0.2 C per decade occurring since the projections. The IPCC scenarios also demonstrate the crucial importance of energy choices. The great range of GHG emissions and consequent atmospheric concentrations (5 to more than 10 teratons CO2) in the scenarios reflect the range of energy options from a shift to renewable energy (B1) to “business as usual” fossil fuel use. The scenario also depicts the doubling of atmospheric CO2 over pre-industrial levels (page 525-526).


13) Summarize the key findings of the Arctic Climate Impact Assessment.

Arctic temperatures are increasing at nearly twice the rate that they are in the rest of the world. The Arctic is expected gain between 4-7 degrees C in warming this century. Warmer winters and increased precipitation will persist for centuries. The Arctic is hardest hit by the Albedo change. More of the sun’s energy is absorbed in the Arctic than anywhere else. Being that the Arctic plays a huge role in regulating global temperatures, so if the Arctic warms up, the rest of the planet will too. Glaciers will melt and the ocean level will rise. Stored CO2 and methane will be released as more ice, and glaciers melt, adding to atmospheric green house gases and causing more warming.  Arctic vegetation zones will shift, and cause animal populations to migrate to other areas. This will also cause a reduction in numbers of polar bears, seals, and sea birds. Reduced sea cie is very likely to increase marine transport and access to resources. Thawing ground will disrupt transportation, buildings, and other infrastructure.

14) What mitigation steps could be taken to stabilize the greenhouse gas content of the atmosphere?  

Stabilizing green house gas content of the atmosphere at levels and on a time scale that would prevent dangerous anthropogenic interference with the climate system and that are consistent with sustainable development. Moving societies to more sustainable methods of producing and consuming energy. This is also to reduce the dependency of fossil fuels. Framework Convention on Climate Change, Kytoto Protocol, (page 530 and page 531 for examples of mitigating).

15) Trace the political history of the FCCC and the Kyoto Protocol. What is the current status protocol?

FCCC: one of 5 documents signed by heads of state in Rio de Janeiro in 1992. Convention agreed to stabilize green house gas levels in the atmosphere by reducing GHG emissions to 1990 levels by 2000 in all industrialized nations. Five years later, the program showed obvious signs of failure. All developed countries expect those in EU failed to reduce levels and instead increased by 25%.

Kyoto Protocol: third conference to parties involved in FCCC and also major island nations such as Japan held a summit in Kyoto, Japan in December 1997 to craft binding agreement on GHG reduction. In Kyoto, 38 industrial and former Eastern bloc nations agreed to reduce nations of six GHGs to 5% below 1990 levels, to be achieved by 2012. Basically, developing countries said that they should not have to oblige by these reductions and slow their development down because of environmental problems caused by the industrialized nations. So far, the largest industrialized emitter, the USA, has withdrawn from the Kyoto Protocol, (page 532).

16) Describe current US climate change policy, and compare it with that of other developed countries.

Currently, the Bush administration has avoided the Kyoto Protocol for 2 reasons: It exempts the developing countries and thus is unfair, and it would cause serious harm to the US economy. President Bush also cited the “incomplete state of scientific knowledge of the causes of, and solutions to, global climate change.” The US has created a GCCI, Global Climate Change Initiative however. The aim of the initiative is the reduction of 18% in emissions intensity over the next 10 years. However, this emissions intensity really means is the ration of GHG emissions to economic output, the latter measured as GDP. Many critics say, that this measure will not even come close to the Kyoto Protocol goals and in fact, will cause emissions to increase. In contrast, the other developed countries have stuck to the Kyoto Protocol, although to varying degrees of success thus far. (page 532).


17) How is the Ozone Shield formed? What causes its breakdown?

The stratospheric ozone layer protects Earth from harmful UV radiation. Ozone is formed when UV radiation acts on oxygen molecules. The high-energy UV radiation first causes some molecular oxygen (O2) to split apart into free oxygen (O) atoms, and these atoms then combine with molecular oxygen to then form ozone. When ozone absorbs UVB, it is converted back to free oxygen and molecular oxygen: O3+UVBàO+O2       The presence of other chemicals in the stratosphere can upset the normal ozone equilibrium and promote undesirable reactions there. Chlorofluorocarbons (CFCs) are a type of halogenated hydrocarbon. CFCs are non-reactive, nonflammable, non toxic organic molecules in which both chlorine and fluorine atoms have replaced some hydrogen atoms. CFCs have been released in huge amounts into the atmosphere where they mix with atmospheric gases. Scientific research concluded that due to the release of chlorine atoms from CFCs once under the heavy pressure of the stratosphere, the chlorine atoms attack stratospheric ozone molecules and form chlorine monoxide (ClO). Chlorine is continuously regenerated as it reacts with ozone. Chlorine atoms have the capability of remaining in the atmosphere for 40-100 years. Severe ozone layer damage has occurred over Antarctica and to a lesser extent over the Arctic. The Polar Vortex (like a whirlpool) in the stratosphere, confines stratospheric gases within a ring of air circulating the Antarctic, concentrating these contaminants over that location (page 537).


18) How do CFCs affect the concentration of ozone in the stratosphere and contribute to the formation of the ozone hole?

See answer for question 17.


19) Describe the international efforts that are currently in place to protect our ozone shield. What evidence is there that such efforts are effective?

First and foremost there are a number of Ozone Depletion monitoring programs around the world (World Ozone Data Center in Toronto, Canada). The Montreal Protocol: Under the auspices of its environmental program, the United Nations convened a meeting in Montreal, Canada, to address ozone depletion. Member nations reached an agreement. To scale CFC production back 50% by 2000. To date, 184 countries, including the US, have signed the original agreement. One of the amendments required participating nations to have phased out the major chemicals destroying the ozone layer by 2000 in developed countries and by 2010 in developing countries. However, due to rapid growth of the ozone layer hole, all manufacturing, as obliged by reforms in the Montreal Protocol, of CFCs have been stopped since December 31, 2005. Evidence of the slowing of ozone depletion since the halting of CFC production is depicted in figure 20-25. It is clear that this has been a successful move. The US also released the Clean Air Act in 1990 to address the ozone problem. This required US farmers and the entire agricultural industry to ban other chemicals which could harm the ozone layer. The evidence of success is evident the global consensus amongst the worlds political leaders to agree and call for the end of CFC production, (page 539-540).