Chapter 3 Global Warming What is global warming

Chapter 3: Global Warming What is global warming? Can anything be done about it? Is there really cause for alarm? How can we assess the information from the popular press?

Greenhouse Effect This is a naturally occurring process: Energy from the sun heats up the earth's surface The earth is constantly losing energy by emitting Infrared radiation (IR) Greenhouse gases trap this energy and keep the Earth warm

The Earth’s Energy Balance Greenhouse effect Our atmospheric gases trap and return a major portion of the heat radiating from the Earth. It is a natural, necessary process. 3. 1

The Sun's energy Composed of IR, visible, UV, … Only a small portion is directed at the Earth About half of this is reflected or absorbed by the upper atmosphere Most of the rest is absorbed by the Earth and turned into thermal energy

Thermal Energy Thermal energy is a measure of how fast atoms and molecules vibrate As an object heats up, the atoms move more quickly All matter emits IR energy: Warmer objects emit more IR energy As IR is emitted, the object cools (conservation of energy)

Some gases in the atmosphere able to absorb and re-emit this IR energy. These gases trap ~80% of the energy given off by the Earth. This is the same effect as glass in a greenhouse or in your car in the summer Without these “greenhouse gases”, the Earth would be 25 °C cooler (-10 °C average versus the actual 15 °C average)

Some of the greenhouse gases are: H 2 O vapor CO 2 CH 4 N O 2 CFCs

According to data taken at Mauna Loa, Hawaii since 1958, CO 2 levels are on the rise. 3. 2

Enhanced Greenhouse Effect When more than 80% of the IR emitted from the Earth is trapped Due to increased greenhouse gases in the upper troposphere This increase in greenhouse gases is due to human activities (anthropogenic) Results in global warming

Anthropogenic sources of greenhouse gases include: Industry Transportation Mining Agriculture Energy (coal power plants) Livestock

Global Warming Due to the Enhanced Greenhouse Effect An average increase in the temperature over the entire surface of the earth Determined by looking at years of data Year to year average temps. may go up or down, but the trend is increasing

History of average temperatures Only recently (last ~hundred years) is accurate data directly available For previous years (up to 400, 000 yrs ago), ice core samples from the poles is used • Average temperatures determined from: – Trapped CO 2 concentrations – Hydrogen isotopes – Microscopic plants and animals • Some species are very sensitive to small temperature changes

Microscopic air bubbles in ice core samples from glaciers can be used to determine changes in greenhouse gas concentrations over time. 3. 2

Comparing ice core data from Antarctica and Mauna Loa observations, the concentration of carbon dioxide appears to be increasing over time. 3. 2

The Vostok ice core shows data going back 400, 000 years, while other ice cores go back even further (the inset shows data from the figure above). The current concentration of atmospheric carbon dioxide is 100 ppm higher than any time in the last million years. 3. 2

Average global surface temperatures have increased since 1880. The red bars indicate average temperatures for the year while the black error bars show the range for each year. The blue line is the 5 -year moving average. 3. 2

Global temperatures for 2006 (in o. C) relative to the 1951– 1980 average. The most dramatic changes have been observed in the higher latitudes (dark red areas). 3. 2

The concentration of carbon dioxide (blue) and the global temperature (red) are well correlated over the past 400, 000 years as derived from ice core data. 3. 2

Why are only some gases greenhouse gases? All molecules can emit infrared light as they release thermal energy But only certain molecules are able to vibrate at the proper frequency to absorb IR light (similar to ozone absorbing UV light) These molecules then re-emit this IR Some of this energy is lost in space Most is trapped and redirected to the Earth

Molecular geometry and absorption of IR radiation Molecular vibrations in CO 2. Each spring represents a C=O bond. (a) = no net change in dipole – no IR absorption. (b, c, d) = see a net change in dipole (charge distribution), so these account for IR absorption. 3. 4

The infrared spectrum for CO 2 As IR radiation is absorbed, the amount of radiation that makes it through the sample is reduced. 3. 4

Molecular response to different types of radiation 3. 4

The Carbon Cycle The natural movement of carbon in the environment • Most carbon transported as CO 2 • All living organisms are part of this cycle – Carbon from many dead organisms is absorbed back into cycle via decay/decomposition – Some carbon may be removed from the cycle if isolated: • entombed, fossilized, petrified, . .

The carbon cycle 3. 5

CO 2 released from the Earth by respiration: mainly animals, but plants also release some CO 2 natural burning volcanoes man-made activities energy combustion cement production accounts for 10% released

CO 2 emission sources by end use: 3. 5

CO 2 absorbed by earth by: plant respiration absorb more than they release this is reduced by deforestation plants use CO 2 and store energy from the sun as saccharide molecules (sugars) Animals absorb some of this carbon as food

Gases, including CO 2, can dissolve in water, though at low concentrations. The oceans: release some CO due to animal 2 respiration absorb much more CO than released 2 Most due to plant respiration Some CO 2 is trapped in pools at the ocean floor due to very high pressures

Mass of Elements and Compounds The mass of carbon is tracked through the carbon cycle Chemical reactions care about the number of atoms/molecules, not mass We cannot count the number of atoms in a reaction (atoms too small: too many atoms) We can measure mass and convert to numbers

Atomic mass – Actual mass of an atom slightly different than mass # due to electrons and nuclear binding energy Average atomic mass Most elements in nature are composed of multiple isotopes The decimal value on the periodic table gives the weighted average of these isotopes in amu (atomic mass units)

If the atomic mass of an isotope is known, then any mass of that isotope can be converted to a number of atoms If the average mass of an element is known, then the number of atoms can also be calculated If the mass of a molecule is known, the we can also calculate the number of molecules in a sample from the mass

The Mole The key to converting between mass and numbers is the mole 'Mole' is just a number 1 mole (mol) = 6. 022 E 23 (Avogadro's #) We can have a mole of anything: atoms molecules grains of sand. .

To convert between moles and numbers: Use the conversion factor: 1 mole = 6. 022 E 23 For example:

One mole of protons (or neutrons) has a mass of one gram (exactly one mole of C-12 atoms has a mass of exactly 12 grams) The decimal value on the PT (the average atomic mass) may also be used to convert mass to moles This value gives the mass, in grams, of one mole of the element

For example, to find the moles of hydrogen atoms in 1. 01 grams: or for 12. 5 grams of hydrogen atoms:

Or to find the mass of 2. 5 moles of helium: or for 2. 5 moles of lead: Note these two examples have the same number of atoms, but different masses

Keep these relationships in mind: grams use molar mass moles use Avogadro’s number molecules Remember – the critical link between moles and grams of a substance is the molar mass. IT’S SIMPLE – THINK IN TERMS OF PARTICLES! 3. 7

Formula Mass The average mass of a compound Calculated by adding up the atomic masses of all of the atoms in one formula For CO 2: 1 carbon atom + 2 oxygen atoms formula mass = 12. 01 + 2(16. 00) = 44. 01 amu also: 1 mole CO 2 = 44. 01 g CO 2

So, to find the mass of 1. 5 moles of CO 2: or to find the moles of 85. 0 grams of CO 2:

Greenhouse Gases (GG) Atmospheric lifetime How long, on average, that a particular gas molecule stays in the atmosphere Ranges from tens to hundreds of years So lowering production of a GG now may take a century to see any effects Global Warming Potential (GWP) Relative effectiveness of how well a molecule absorbs IR GWP for carbon dioxide = 1

Significance of a GG on Global Warming Mainly depends on three factors: Concentration of the gas Atmospheric lifetime of the gas GWP of the gas CO is considered the most significant 2 gas Relatively low GWP, but very high conc. CFCs, for example, are not as significant Larger GWP, but very low conc.

Global Warming Potential (GWP) represents the relative contribution of a molecule of an atmospheric gas to global warming. 3. 8

Greenhouse Gases CO 2 – From combustion, deforestation (less trees to absorb CO 2), cement production CH 4 (methane) – From anaerobic bacteria (live without molecular oxygen) marshes, wetlands, rice paddies, livestock N 2 O – From fertilizers, industry, combustion

CFCs – from air conditioners, aerosols, foams H 2 O (water) – Also a product of combustion Water has a large GWP and is present in the atmosphere in high concentrations The environment usually controls water vapor easily via evaporation and precipitation (rain) But a warmer climate can increase water vapor levels, which will further warm the Earth's surface

Reverse Global Warming? Aerosols – Particulates suspended in the air May be solid or liquid Can block sunlight from reaching the Earth Can cause global cooling In the past, large volcanic eruptions have resulted in significant global cooling for a year or more Resulted loss of crops, famine, climate changes

Carbon Footprint Often used to show CO 2 production a person is responsible for over one year May be direct or indirect Combustion – car use, gas furnace, . . . Reduced vegetation (deforestation) Carbon needed for activities or goods – Cement, energy, food. . .

Carbon Footprint. Also used to show the carbon dioxide formed for a specific activity or product: e. g. air conditioner use, paper. . .

Models can also be used to predict future global temperatures. Black line = data for the 20 th century Other lines = projected 21 st century temperatures based on different socioeconomic assumptions 3. 9

Some results of 1°C Global Warming Change in weather patterns Some small areas could see cooling But average temperatures increase Sea ice disappears Sea level rise – due to water expanding as it warms up More extreme weather Loss of plant and animal species Lose some fresh water sources

Loss of Polar Ice Cap 1979 2003 NASA Study: The Arctic warming study, appearing in the November 1, 2003, issue of the American Meteorological Society's Journal of Climate, showed that compared to the 1980 s, most of the Arctic warmed significantly over the last decade, with the biggest temperature increases occurring over North America. Perennial, or yearround, sea ice in the Arctic is declining at a rate of nine percent per decade. 3. 10

Some ways to reduce anthropogenic GG Reduce energy use All energy production has a carbon footprint More efficient cars (higher mpg) Coal power plants – largest footprint Limit fertilizers Production and use creates GG Reduce food waste Food production produces GG Organic decomposition produces GG

Cap and Trade Government limits GG emissions Each company has a maximum amount of allowed emissions. If a company produces less than the maximum, it can trade or sell this unused allowance to less efficient companies This gives a financial incentive to companies to invest in and develop new technologies

A Cap-and-Trade System can be used to limit CO 2 emissions. 3. 11

Capture and sequestration Proposed method to reduce carbon footprint for coal power plants Capture CO 2 from exhaust and bury to take this GG out of the environment Not simple to isolate the CO 2 Underground storage may eventually leak Prototypes for this process are being investigated

One potential method for mitigation is CO 2 sequestration. 3. 11

Climate Adaptation How well/quickly can the environment adjust to compensate for the enhanced greenhouse effect? Warmer climates may increase plant growth (land aquatic), which would result in increased CO 2 absorption The environment has adapted in the past to extremely large changes in GG levels, but this has also resulted in large scale extinctions of many plants and animals

Amplification of Greenhouse Effect: Global Warming What we know: 1. CO 2 contributes to an elevated global temperature. 2. The concentration of CO 2 in the atmosphere has been increasing over the past century. 3. The increase of atmospheric CO 2 is a consequence of human activity. 4. Average global temperature has increased over the past century. 3. 2

What might be true: 1. CO 2 and other gases generated by human activity are responsible for the temperature increase. 2. The average global temperature will continue to rise as emissions of anthropogenic greenhouse gases increase. 3. 9

Radiative Forcings are factors that affect the balance of Earth’s incoming and outgoing radiation. 3. 9

Intergovernmental Panel on Climate Change (IPCC) Recognizing the problem of potential global climate change, the World Meteorological Organization (WMO) and the United Nations Environment Programme (UNEP) established the Intergovernmental Panel on Climate Change (IPCC) in 1988. It is open to all members of the UN and WMO. In 2007, the IPCC stated in a report that scientific evidence for global warming was unequivocal and that human activity is the main cause. 3. 10

Conclusions from the 2007 IPCC Report 3. 10

Kyoto Protocol – 1997 Conference • Intergovernmental Panel on Climate Change (IPCC) certified the scientific basis of the greenhouse effect. • Kyoto Protocol established goals to stabilize and reduce atmospheric greenhouse gases. • Emission targets set to reduce emissions of six greenhouse gases from 1990 levels. (CO 2, CH 4, NO, HFCs, PFCs, and SF 6) • Trading of emission credits allowed. 3. 11