Chapter 8: Climate and Climate Change

Transcription

1 Chapter 8: Climate and Climate Change p. 1 of 15 Chapter 8: Climate and Climate Change I. Climate Classification A. Intro 1. basic goal of the geographic study of climate: understand its distribution over Earth 2. challenges: climate involves continuous variation and can change over time B. Early Classification Schemes 1. ancient Greek system 3 climate zones a. Temperate Zone of the midlatitudes 38 o N) b. Torrid Zone of the tropics to the south c. Frigid zone to the north C. The Köppen Climate Classification System 1. Köppen German climatologist and botanist 2. first version basis for classification: a. average annual and average monthly values of temperature and precipitation b. 4 of 5 major climatic groups defined primarily by temperature characteristics c. B group defined on basis of moisture d. subdivided each group according to various temperature and precipitation relationships 4. modified Köppen System (Tables 8-1 and 8-2, Fig 8-3) a. Köppen s 5 major climatic groups (A through E) b. subdivided into total of 14 individual climate types c. 6 th group: H highland climates D. Köppen Letter Code System 1. first letter designates the major climate group (A-E, H) 2. second letter describes precipitation patterns 3. third letter (if any) describes temperature patterns E. Climographs 1. graphic representation of monthly temperature and precipitation for specific weather station 2. line graph for monthly temperature 3. bar graph for monthly precipitation II. World Distribution of Major Climatic Types A. Tropical Humid Climates (Zone A) (Table 8-3, Fig 8-5) 1. general characteristics a. almost all land area within the tropics b. climates of perpetual warmth; winterless climates c. prevalence of moisture 1) much of A zone is among wettest in the world 2) onshore winds and thermal convection associated with the ITCZ are common and provide mechanism for uplift

2 Chapter 8: Climate and Climate Change p. 2 of 15 d. 3 subtypes classified on basis of annual rainfall 1) tropical wet: abundant rainfall every month 2) tropical savanna: low-sun dry season and prominent but not extraordinary high-sun wet season 3) tropical monsoon: dry season and distinct very rainy high-sun wet season 2. Tropical Wet Climate (Af) a. geographic location 1) astride the equator to 5 o 10 o poleward on each side 2) on east coasts may extend as far as 25 o N/S 3) largest areas: upper Amazon basin, northern Congo basin, and islands of the East Indies 1) monotonous, seasonless climate 2) every month has average temperature close to 80 o F 3) average daily temperature range exceeds the average annual temperature range a) smallest annual temperature range of any climate type b) Night is the winter of the tropics 4) high humidity high sensible temperature 5) yearly rainfall ( inches) exceeded only by Am climates a) rain can be expected every day b) convective storms yield heavy rain for a short time c. principal climatic control is latitude considerable thermal convection 1) trade wind convergence of ITCZ 2) onshore winds along trade-wind (east-facing) coasts 3) lack of wind except along coastlines 3. Tropical Savanna Climate (Aw) a. geographic location 1) most extensive of A climates 2) lies north and south of Af climates 3) Africa, South America, and southern Asia 1) clear cut seasonal alternation of wet and dry periods 2) between unstable, converging air on equatorial side and stable, anticyclonic air on poleward side 3) winds and pressure shift latitudinally with sun significant weather contrasts a) in low sun/winter season subtropical high pressure dominates clear skies b) in high sun/summer season ITCZ dominates wet tropical weather 4) typical annual precipitation: inches 5) annual temperature range: 5 o 15 o F 4. Tropical Monsoonal Climate (Am)

3 Chapter 8: Climate and Climate Change p. 3 of 15 a. geographic location 1) most extensive: windward/west facing coasts of SE Asia (India, Myanmar, Thailand) 2) western Africa, northeastern South America, the Philippines, northeast Australia, East Indies 1) receive enormous rainfall during high sun season/ summer monsoon a) 30 inches of rain in each of 2 or 3 months b) annual total: inches c) Cherrapunji, India (annual average = 425 ) - world record: 1,042 in 1 year 2) low sun season/ winter monsoon: offshore winds dominate little precipitation B. Dry Climates (Zone B) (Table 8-4, Fig 8-12) 1. general characteristics a. cover 30% of world s land area (more than any other climate zone) 1) largest expanses in subtropical latitudes a) subsidence from subtropical high pressure cells suppresses upward vertical motion of air b) cool ocean currents increase atmospheric stability 3) in the midlatitudes found in areas cut off from moisture sources a) far from water bodies b) in rainshadow of mountain ranges c) central Eurasia b. depends not only on precipitation but also on temperature 1) balance between precipitation and evapotranspiration 2) hot regions can receive more precipitation than cool regions and yet be classified as dry c. two categories (generally): 1) desert: extremely arid 2) steppe: semi-arid d. further classified based on temperature 1) subtropical = hot 2) midlatitude = cold: 2. Subtropical Desert Climate (BWh) a. geographical location 1) band near the subtropical highs in both Northern and Southern Hemispheres 2) extends to western coasts on all continents; not to eastern coasts 3) enormous expanse in North Africa (Sahara) and southwest Asia (Arabian Desert) a) year-round anticyclonic conditions b) remoteness from any moisture source 4) 50% of Australia, much in rainshadow of east coast mountains 5) Atacama Desert of South America

4 Chapter 8: Climate and Climate Change p. 4 of 15 a) longest and driest desert in the world b) double rainshadow (1) Andes Mountains (2) Peru/Humboldt: world s coldest current c) Arica, Chile: world record least annual average precipitation (0.03 /year) and longest rainless spell (14 years, 4 months) of desert climates (BWh) 1) lack of moisture a) scarce: annual totals 2-8 inches b) unreliable: the less the average annual precipitation, the greater its variability thus concept of average yearly rainfall in a BWh location is misleading c) intense: rain that does fall comes as intense convective showers, localized and of short duration brief flooding 2) temperature a) result of vertical sun rays and lack of cloudiness b) moderate annual temperature range: 15 o - 25 o F c) clear skies and low water vapor content permits rapid nocturnal cooling which results in astounding daily temperature range: 50 o F in spring and fall d) Dallol, Ethiopia: highest average daily maximum temperature (106 o F) and highest annual average temperature (94 o F) e) El Azizia, Libya: highest recorded temperature (136 o F) f) In-Salah, Algeria: greatest 1 day temperature range (100 o F) 3) windy days 4) western coasts in subtropical deserts a) cold offshore currents b) advective cooling: frequent fog c) extremely low precipitation 3. Subtropical Steppe Climate (BSh) a. surrounds the BWh except on western sides b. extremes are more muted than desert climate c. meager precipitation has seasonal concentration 4. Midlatitude Desert Climate (BWk) a. geographical location in deep interiors of continents 1) conditions a) far removed geographically from moisture source b) mountain ranges block oceanic influence 2) significant regions: a) central Eurasia b) western North America c) southern South America 1) precipitation a) meager and erratic b) differences with BWh:

5 Chapter 8: Climate and Climate Change p. 5 of 15 (1) bulk of precipitation comes in summer (2) although most showery, some protracted drizzle 2) temperature differences with BWh a) severely cold winters average cold month temperature is normally below freezing b) average annual temperatures much lower c) greater annual temperature range: up to 54 o F 5. Midlatitude Steppe Climate (BSk) a. transitional between desert and humid climates b. differences with BWk 1) more precipitation 2) less temperature extremes c. extensive steppe climate in western North America d. only in the interior southwest of the US is climate arid enough to be classified as desert C. Mild Midlatitude Climates (Zone C) (Table 8-5, Fig 8-20) 1. general characteristics a. marked seasonal contrasts 1) differences in temperature more prominent than in precipitation 2) clearly summer and winter (v. wet and dry in tropics) 3) summers long and hot 4) winters short and relatively mild b. occasional frost means no year round growing season c. precipitation is highly variable in terms of total amount and seasonal distribution d. 3 categories 1) primary basis: precipitation seasonality 2) secondary: summer temperature 2. Mediterranean Climate (Csa, Csb) a. geographical location 1) western sides of continents centered at latitudes 35 o N and S 2) mostly small regions restricted to coastal areas either by interior mountains or by limited landmasses 3) regions: a) borderlands of Mediterranean Sea (only extensive area) b) central and southern California c) central Chile d) southern tip of Africa e) southwestern corners of Australia 1) modest precipitation falls in winter; summers virtually rainless (marine west coast climate only other one with winter precipitation concentration) 2) mild winter temperatures 3) abundant clear skies and sunshine, especially in summer c. Csa: hot summers w/monthly average temperature 75 o F - 85 o F

6 Chapter 8: Climate and Climate Change p. 6 of 15 d. Csb 1) coastal areas 2) milder summers and winters 3) frequent coastal advection fog e. climate explanation 1) dry, stable, subsiding air from subtropical high dominates in summer 2) westerlies dominate in winter 3. Humid Subtropical Climate (Cfa, Cwa) a. geographical location 1) eastern side of continents at same latitude as Mediterranean climates but more extensive both latitudinally and longitudinally 2) extends from 15 o N/S to 40 o N/S 3) greatest east-west extent: North America, Asia, South America b. differences with mediterranean climates: 1) summers are warm to hot a) higher humidity higher sensible temperatures b) little nighttime relief 2) summer precipitation maximum a) result of onshore flow and frequent convection b) annual precipitation: ) winter temperatures mild on average but cold waves a) minimum winter temperatures: 10 o to 20 o F colder than Mediterranean climates killing frosts b) agricultural adjustments: (1) northern limit citrus production in eastern US (Florida-Cfa): 29 o N (2) northern limit citrus production in western US (California-Cs): 38 o N 4. Marine West Coast Climate (Cfb, Cfc) a. geographical location 1) western side of continents 2) latitudinal range: 40 o 60 o N/S 3) windward location westerlies at this latitude 4) regions: a) extensive in western and central Europe b) northwestern US: limited interiorward by mountain ranges 1) persistent onshore air movement extraordinarily temperate climate considering the latitude 2) lack of extreme temperatures 3) consistently high humidity 4) high cloudiness, many days w/precipitation c. temperature 1) moderated most of the time by oceanic influence 2) frosts are relatively infrequent 3) abnormally long growing season for this latitude

7 Chapter 8: Climate and Climate Change p. 7 of 15 4) 1 month longer growing season in Seattle than Atlanta (which is 14 o farther south!) d. precipitation 1) among the wettest climates of the midlatitudes, although total amount of precipitation in not remarkable except in upland areas 2) average annual precipitation: ; higher on exposed mountain slopes 3) snow uncommon in lowlands, but higher, west facing slopes receive some of heaviest snowfalls in the world 4) precipitation frequency marks these climates a) rainfall probability and reliability are high b) intensity is low: drizzly frontal precipitation c) Seattle receives 43% of possible sunshine v. Los Angeles 70% D. Severe Midlatitude Climates (Zone D) (Table 8-6, Fig 8-27) 1. characteristics a. occur in northern hemisphere only 1) latitudinal range: 40 o 70 o N 2) limited land mass in southern hemisphere b. continentality: remoteness from oceans 1) dominates D climates 2) extremely large annual temperature ranges c. 4 seasons d. moderate precipitation 1) exceeds potential evapotranspiration 2) summer precipitation maximum e. 2 types based on temperature 1) humid continental: long, warm summers 2) subarctic: short summers, very cold winters 2. Humid Continental Climate (Dfa, Dfb, Dwa, Dwb) a. geographic location 1) North America and Asia: 35 o 55 o N 2) Europe: 35 o 60 o N 1) westerly winds dominate migratory pressure systems great weather variability and dramatic changes 2) warm summers: average mid 70s o F 3) winters: 1-5 months average below freezing 4) precipitation: inches a) decreases from coast to interior b) decreases from south to north 3. Subarctic Climate (Dfc, Dfd, Dwc, Dwd) a. geographic location 1) 50 o 70 o N 2) 2 vast uninterrupted expanses: a) from western Alaska across Canada b) Eurasia, from Scandinavia to easternmost Siberia

8 Chapter 8: Climate and Climate Change p. 8 of 15 3) boreal refers to Canadian climatic type 4) taiga refers to Eurasian climatic type 1) winter: long, dark, bitterly cold a) 6-7 months average temperature < freezing b) world s coldest temperature records (other than ice caps) (1) Siberia: - 90 o F (2) Alaska: - 82 o F 2) long summer days warm 3) largest annual temperature ranges in the world a) > 80 o F b) world record absolute annual temperature variation: Verkhoyansk, Siberia 188 o F (-90 o to +98 o F) c) world record greatest average annual temperature range: 112 o F Yakutsk, Siberia (Dfd climate) 4) meager precipitation a) annual averages 5 20 b) low evaporation and frozen soil much of year moisture adequate to support forests c) light snowfall but stays on ground Oct-May E. Polar Climate (Zone E) (Table 8-7, Fig 8-32) 1. characteristics a. enduring cold; too little insolation for any significant warming b. all months average temperature 50 o F c. extraordinarily dry but evaporation so low that qualifies as nonarid d. 2 subcategories distinguished by summer temperature 1) tundra: at least 1 month with average temperature > freezing 2) ice cap: all months average temperature < freezing 2. Tundra Climate (ET) a. tundra 1) low, ground hugging vegetation of high latitude and high altitude 2) climate of high latitude regions b. geographic location 1) equatorward limit (boundary between D and E climate) = 50 o F isotherm average temperature of warmest month = treeline 2) poleward limit: 32 o F isotherm for warmest month = extreme limit for any plant cover 3) more than any other climate type, tundra climate delimited by plant communities c. characteristics 1) winter not as severe as subarctic climate farther south because less continental 2) fairly large annual temperature range: >54 o F 3) small daily temperature range a) sun above horizon for most of summer

9 Chapter 8: Climate and Climate Change p. 9 of 15 b) sun below horizon for most of winter 4) annual precipitation < 10 a) air too cold to hold much moisture b) anticyclonic conditions restrict uplift 3. People and the Environment: Signs of Climate Change in the Arctic a. temperatures in the Arctic 1) average temperatures in the Arctic have been increasing at twice the rate of lower latitudes over the past 50 years 2) winter temperatures are ~ 5 o F higher today than 50 years ago in Alaska and Western Canada b. sea ice 1) since 1979 winter maximum sea ice has decreased about 386,000 mi 2 2) decline in perennial sea ice (summer sea ice) is even greater: 2007 was 39% lower than average c. feedback loop 1) cover of sea ice diminishes less reflectance and more absorption by darker ocean surface higher ocean temperatures greater ice pack melting 2) possibility summer Arctic sea ice cover could disappear by end of century d. Greenland Ice Sheet 1) increasing summer surface melting and melt pond formation 2) darker melt pond surface decreased albedo increasing solar radiation absorption even greater melting 3) warmer conditions increased precipitation increased liquid water on ice surface lowered albedo increased melting e. sea level rise 1) global sea level has risen 2mm/year over last few decades as result of melting glaciers and thermal expansion of sea water 2) projected sea level rise of inches by ) increased freshwater entering sea from melting glaciers could reduce salinity and potentially alter deep ocean circulation f. habitat loss 1) conversion from tundra to shrub in parts of Arctic 2) polar bears at risk 4. Ice Cap Climate (EF) a. most severe climate b. Greenland (except for coastal fringe) and Antarctica c. permanent cover of ice and snow 1) high altitude and high latitude 2) vegetation cannot grow d. strong katabatic winds e. polar deserts: precipitation < 5 F. Highland Climate (Zone H) (Fig 8-35) 1. complex local variation in very limited horizontal distances

10 Chapter 8: Climate and Climate Change p. 10 of 15 III. IV. 2. latitude less important than altitude and exposure 3. critical climatic controls in highlands: a. relative elevation b. angle of exposure to sun and wind 4. altitude variations influence all 4 elements of weather and climate: a. temperature and atmospheric pressure decreases rapidly with increased elevation b. wind is brisk, abrupt and variable c. orographic lifting heavier precipitation 5. pattern of vertical zonation in mountainous areas a. several hundred feet increase in elevation equivalent to several hundred miles poleward b. vertical zonation particularly prominent in tropical highlands; tropical vertical zonation: (Fig 8-37) 1) Tierra caliente - hot 2) Tierra templada - temperate 3) Tierra fria - cold 4) Tierra helada - frozen 6. exposure has profound influence on climate a. windward face receives more moisture than leeward face b. south and west facing slopes are warmer and drier than adjacent north and east facing slopes in the northern hemisphere 7. changeability a. thin, dry air very large daily temperature range 1) day: rapid influx of radiation 2) night: rapid loss of radiant energy b. upslope wind and convection rapid cloud development and abrupt storminess The Global Pattern Idealized A. predictable pattern of location based on latitude, position on a continent, and the general atmospheric and oceanic circulation patterns (Fig 8-39) B. general model of climate distribution on a hypothetical continent (Fig. 8-40) 1. zones A, C, D, E a. defined by temperature b. boundaries strongly latitudinal because determined by insolation 2. zone B a. defined by moisture condition b. distribution cuts across those of thermally defined zones Global Climate Change A. Trends (Fig. 8-41) 1. clear global cooling trend over last 70 million years 2. significant temperature fluctuation over last 150,000 years; temperature has remained warm and fairly steady since a sharp increase 10,000 years ago 3. clear warming trend over last 150 years

11 Chapter 8: Climate and Climate Change p. 11 of these temperature changes were not necessarily uniform around the world B. Determining Climates of the Past 1. paleoclimatology: a. study of past climates and causes of past climate change b. proxy measures of climate used to reconstruct past conditions: 1) tree rings 2) ice cores 3) oceanic sediments 4) coral reefs 5) relic soils 6) pollen 2. Dendrochronolgy a. study of past events and past climates through analysis of tree rings b. tree rings: 1) one ring/year 2) wider rings during years with favorable conditions: mild temperatures and/or ample precipitation c. extend tree ring chronology by matching ring patterns of live trees with dead trees 3. Oxygen Isotope Analysis of Oceanic Sediment a. ratio of 18 O/ 16 O in calcium carbonate in ocean sediment indicates glacial v. interglacial period b. high ratio indicates glacial, low ratio indicates interglacial 4. Coral Reefs a. ratio of 18 O/ 16 O in coral provides information about the climate at the time reef was forming b. relative height of coral reefs, which only develop in shallow water help determine fluctuations in sea level 5. Ice Cores a. 18 O/ 16 O ratio serves as thermometer for climate when snow fell b. provide record of past global temperature and atmospheric composition back 800,000 years c. air bubbles trapped in glaciers show close relationship between past greenhouse gas concentration and temperature: higher concentration of greenhouse gases (especially CO 2 and methane) present during warmer interglacial periods 6. Pollen Analysis a. pollen used for radiocarbon dating of organic material of past 50,000 years b. type of prevalent plant community reflects climate at that time 7. Focus: Paleoclimatology at Dome C, Antarctica a. ice core record 3 km deep provides 800,000 years of data b. present concentration of CO 2 is 27 times greater than at any time in last 800,000 years

12 Chapter 8: Climate and Climate Change p. 12 of 15 c. changes in temperature closely correlated with changes in CO 2 concentration: higher concentration of CO 2 correlates with higher temperatures C. Causes of Long-Term Climate Change 1. Atmospheric Aerosols a. large quantities of particulates ejected into atmosphere can block incoming solar radiation and lower temperatures b. volcanoes: 1991 Mount Pinatubo eruption lowered global temperatures by 0.9 o F for the next year c. asteroid impacts: impact of 10 km wide asteroid, in combination with massive flood basalt eruption, 65 million years ago contributed to dinosaur extinction d. anthropogenic aerosols 1) sulfates from burning fossil fuels scatter incoming solar radiation and have a cooling effect 2) black carbon emissions from burning diesel and biofuels absorb radiation and lead to warming 2. Fluctuations in Solar Output a. some speculation about correlation between sunspot activity and Earth s temperatures and precipitation 3. Variations in Earth-Sun Relations a. eccentricity: Earth s elliptical orbit 1) shape of Earth s orbit varies in a 100,000 year cycle 2) currently difference in distance between Earth and sun at aphelion and perihelion is about 3%, but it has varied from 1% - 11% b. obliquity: inclination of Earth s axis 1) varies between 22.1 o and 24.5 o in a 41,000 year cycle 2) greater seasonal contrast between low and high latitudes when angle is greater c. precession: Earth s axis wobbles and points in different directions 1) a 25,000 year cycle 2) alters the timing of the seasons in relation to Earth s position in its orbit around the sun d. Milankovitch cycles 1) combination of cycles involving Earth s obliquity, eccentricity and precession 2) responsible for an approximately 100,000 year cycle of insolation variation 3) believed to be partially responsible for periods of major glaciations and deglaciation 4. Greenhouse Gases Concentration a. past fluctuations in global temperatures have been accompanied by fluctuations in greenhouse gas concentration b. warmer periods in past are associated with higher concentrations

13 Chapter 8: Climate and Climate Change p. 13 of 15 c. evidence that leads most atmospheric scientists think the increase in atmospheric CO 2 since the early 20 th century is the main cause of contemporary global warming: 1) increase in CO 2 correlates well with fossil fuel use since the industrial revolution 2) decreasing relative level of 14 C in the atmosphere since the industrial revolution is result of release of CO 2 from dead sources of carbon, such as coal and petroleum 5. Feedback Mechanisms a. positive feedback mechanisms: 1) warmer temperatures reduced ice cover reduced albedo increased absorption by surface higher temperatures reduced ice cover 2) warmer temperatures increased evaporation increased atmospheric water vapor increased cloud cover a) increased reflection cooling b) increased absorption of terrestrial radiation warming b. effect of clouds remains one of the greatest complications when modeling future climate change 6. The Roles of the Oceans a. concerns include impacts of increasing absorption of CO 2 by oceans, disturbance of methane hydrates, and changes in ocean circulation patterns D. Climate Models 1. GCMs a. general circulation models b. mathematical model of Earth s climate system 2. anticipate how climate will change in the future given various scenarios of greenhouse gas increase in the atmosphere E. Evidence of Current Global Warming 1. IPCC (Intergovernmental Panel on Climate Change): most authoritative international body providing info on climate change 2. major conclusions of IPCC Climate Change 2007 Report: a. warming of the climate system is unequivocal b. observed changes in global climate over last century cannot be explained through natural causes alone c. 90% probability that most of the observed increase in global average temperatures since mid 20 th century is due to increase in anthropogenic greenhouse gas concentration 3. some specific findings: a. increased global average temperature of 1.33 o F between 1906 and 2005 b. global sea level rose 6.7 during the 20 th century; the rate between 1993 and 2003 increased to 0.12 /year c. since 1978 the average summer sea ice in the Arctic has been decreasing at a rate of 7.4% per decade

14 Chapter 8: Climate and Climate Change p. 14 of 15 d. the current concentrations of CO 2 and methane in the atmosphere are higher than at any time in the past 800,000 years 1) CO 2 increased concentration: 280 ppm (pre-industrial) 390 ppm (2009) 2) methane increased concentration: 715 ppb (pre-industrial) 1780 ppb (2009) F. Consequences of Global Warming 1. projections of IPCC are best estimates based on various scenarios 2. major projections include the following: a. projected global temperature increase by 2099 will be between 3.3 o F and 7.2 o F b. projected sea level rise by 2099 will range between 7.1 and 23.2 (more recent studies predict increases from 27 to 39 inches) c. warming will be greatest over land and in the high northern latitudes d. precipitation will likely increase in high latitudes and decrease in most subtropical areas over land e. other projections: more intense tropical cyclones and other weather events; expanded range of tropical diseases; increased wildfire risk; and, extinction of or shifted distribution of species f. global temperatures are projected to continue to increase and sea levels rise even if the concentrations of greenhouse gases are stabilized immediately G. Addressing Global Warming 1. the vast majority of scientists accept the conclusions of the IPCC; disagreement remains in the arena of politics, economics, and public policy 2. The Kyoto Protocol a international agreement to cut greenhouse gas emissions by 5% below 1990 levels by 2012 b. 185 countries have ratified the Kyoto Protocol; the US has not 3. Newly Industrialized Countries a. major issue: should developing countries be asked to cut back emissions as much as rich countries? b. the U.S., with only 5% of the world s population, emits 19% of the world s total CO 2 c. China is currently the leader in CO 2 21% 1) but it has 4 times the US population 2) US far exceeds it on a per capita basis 4. Mitigating and Adapting a NOAA report: temperature increases, sea level rises and rainfall changes are essentially irreversible for several centuries after CO 2 emissions are stabilized b. consequences of global climate change may not be shared equally around the world -- many of the populations most vulnerable are found in the poorest parts of the world

15 Chapter 8: Climate and Climate Change p. 15 of 15 H. People and the Environment: Strategies for Reducing Greenhouse Gas Emissions 1. Conservation a. burn less fossil fuel b. electrical power generation and transportation are responsible for 40% of worldwide greenhouse emissions 2. Cap-and-Trade versus Carbon Tax a. market incentives to address concerns over short-term costs b. cap-and-trade (a financial carrot ): places limits (a cap ) on carbon emissions from industries but allows one emitter to sell or trade its excess carbon allotments to another emitter c. carbon tax (a financial stick ): penalizes industries that emit more than an established emissions cap 3. No Regrets Opportunities a. practices that reduce greenhouse gas emissions while having a net cost savings for society and therefore need not be postponed b. cost of implementing is offset by cost savings through direct or indirect benefits to individuals or society (ex. energy efficient lighting; healthcare cost savings as air pollution is reduced) 4. The Clean Energy Economy a. enormous financial benefits possible for companies and countries that invest in clean energy technology