Chapter 19 - Climate Change and Ozone Depletion

Greenhouse Effect

is the process in which greenhouse gases prevent the radiation of heat into space by trapping it in the troposphere.  More greenhouse gases in the atmosphere create higher temperatures near the Earth. 

The atmosphere allows

ultraviolet rays to strike the Earth, heating it up.  The Earth then radiates infrared rays (heat) back outward. 

albedo

The ability of the earth’s surface to reflect light

Major Greenhouse Gases

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* water vapor (H2O) - naturally occurring
* carbon dioxide (CO2) - burning of __________ fuels
* nitrous oxide (N2O) - burning of fossil fuels, fertilizers
* __________ (CH4) - burning of fossil fuels, wetlands, livestock
* chloroflourocarbons (CFC’s) - aerosols, refrigerants

As a result of the greenhouse effect

the average temperature of the Earth will rise at least 2 degrees C by 2050. This predicted increase in temperature is called global warming.

The effects of this seemingly small increase in temperature could include:

weather change: stronger storms, more flooding in some areas, more droughts in other areas, the best farming areas would move northward and a rise in sea level

Layers of Antarctic ice provide the data for the past 900,000 years

it is found that cycles of heating and cooling have occurred on a global basis.

Each ice age lasts

approximately 100,000 years and is followed by a period of warming that lasts 10,000 to 12,500 years.

The warming period

during the last 10,000 years has been a major factor in the development of agricultre, human civilizations, and population growth.

The past 100 years

have seen a significant increase in global mean temperature caused by a rapid increase in major classes of air pollutants/greenhouse gases.  The primary source of these pollutants is the burning of fossil fuels.  The second leading source is agriculture (slash & burn).

The biggest GHG’s are

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* CO2 – carbon dioxide - not as potent of a GHG, but lots of it.  The good news: half of man-made CO2 would be reabsorbed by plants and the ocean within 30 years if we stopped excess production.
* CH4 – methane - 20 times as potent as CO2 over a 100 year period.   The good news: we can capture CH4 and use it as fuel.
* Particulates (aka soot, aka black carbon) - The good news: it is washed out of the atmosphere by precipitation relatively quickly.

Water vapor

is the gas most responsible for the greenhouse effect, accounting for 60-70%.  It is the most prevalent greenhouse gas by mass and volume.

The amount of water vapor the atmosphere can hold

is almost entirely a function of temperatre.  As temperature rises, this causes more evaporation, and therefore more water vapor.

The Positive Feedback Loop

the emission of excess GHGs leads to warmer temperatures, which leads to more water vapor, which leads to warmer temperatures.

The good news: 

* doing the things that decrease greenhouse gases will help Americans in many ways
* Reduce air pollution, which will reduce negative effects to human health including asthma, lung cancer, bronchitis and emphysema
* Reduce dependence on foreign energy sources
* Reduces environmental effects such as habitat destruction from mining and acid rain.
* Renewable energy sources save money in the long term

The bad news:

it will cost money in the short term and political will for the long term

The Intergovernmental Panel on Climate Change

was established in 1988 to provide decision makers with an objective source of information on climate change.  It was set up by the World Meteorological Organization and the United Nations Environmental Programme and consists of hundreds of scientists from around the world.

The most recent report from the IPCC stated that

“Human interference with the climate system is occurring, and climate change poses risks for human and natural systems” and that during this century, temperatures will rise between __________ and __________ oC and sea levels will rise between 18 and 59 cm.

The Kyoto Treaty

was the first major international agreement on greenhouse gas emissions.  In December of 1997, the treaty was designed and agreed on by the major countries involved in the 1992 U.N. Earth Summit.  This treaty would reduce emissions by 5% from 1990 levels by 2012.

The 15th United Nations Climate Change Conference took place in Copenhagen, Denmark in December 2009. 

The conference ended with an agreement by the 194 countries to “cap temperature rise, reduce emissions, and raise finance to kick start action in the developing world to deal with climate change.”  The emissions targets are meant to keep temperatures from rising more than 2 degrees C.

The 2015 UN Climate Change Conference

known as COP21, was held in Paris, France. This conference was of particular importance because of significant contributions by the two largest carbon emitters – China and USA. In April of 2016, 174 countries signed the agreement and began implementing plans to limit global warming to 1.5o Celcius. This will require a target of zero emissions by sometime between 2030 and 2050. 

Ozone

is a form of oxygen with molecules of three oxygen atoms. It is colorless and has a strong odor.

in the Stratosphere

ozone absorbs the majority of ultraviolet radiation hitting the Earth ☺

in the troposphere

 ozone contributes to air pollution ☹

chlorofluorocarbons

destroy ozone in the stratosphere, and have created a thinning (hole is an incorrect term) in the ozone shield above the south pole

the burning of fossil fuels

increases ozone in the troposphere

Each sunless Antarctic winter,

ice crystals in the air collect CFCs and catalyze the reaction that release Cl atoms and ClO.  Without the sunlight to catalyze ozone destruction, the ClO combine to form Cl2O2, which accumulates in the atmosphere.

When sunlight and spring return

the light breaks up the stored molecules, releasing large numbers of Cl atoms.  This leads to a loss of 40-50% of the ozone in most areas – 100% in some.

CFC’s (chlorofluorocarbons)

a type of halocarbon, were manufactured in the 1930’s as a refrigerant and spray can propellant.

CFC’s were found

to destroy stratospheric ozone in the 1970’s, which lead to The Montreal Protocol (1987).  This international agreement phased out a series of substances, including CFC’s, responsible for ozone depletion.

As a result, stratospheric chlorine levels in polar regions should return

to 1980 levels by 2065.  This is often cited as the largest global environmental success story.