GLOBAL CLIMATE CHANGE. Adapted from MBHS

Transcription

1 GLOBAL CLIMATE CHANGE Adapted from MBHS

2 What is climate change? Climate change is the fastest-developing area of environmental science Climate = an area s long-term atmospheric conditions Temperature, moisture, wind, precipitation, etc. Weather = short-term conditions at localized sites Global climate change = describes trends and variations in Earth s climate Temperature, precipitation, storm frequency Global warming and climate change are not the same

3 Global warming Global warming = an increase in Earth s average temperature Only one aspect of climate change Climate change and global warming refer to current trends Earth s climate has varied naturally through time The current rapid climatic changes are due to humans Fossil fuel combustion and deforestation Understanding climate change requires understanding how our planet s climate works

4 Greenhouse gases warm the lower atmosphere As Earth s surface absorbs solar radiation, the surface increases in temperature and emits infrared radiation Greenhouse gases = atmospheric gases that absorb infrared radiation Water vapor, ozone, carbon dioxide, nitrous oxide, methane, halocarbons (chlorofluorocarbons [CFCs])

5 Introduction to Climate Change Evidence for Climate Change Warmest years since mid-1800s have occurred since 1990 Phenological spring in N. hemisphere now begins 6 days earlier (date the buds of specific plants open) Retreat of glaciers Thinning of polar ice Weather change Sea Level Rise Warming is not due to natural causes Human produced greenhouse gases are most plausible explanation

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7 Climate in the Past Past Record of past 100+ years only Since 1855 global temp. has fluctuated from warming to cooling Has increased 0.6 C Further back Proxies- tree rings, pollen deposits, changes in landscapes, marine sediment, corals, ice sheets Milankovitch cycles Oscillated between ice ages and warm periods

8 Milankovitch cycles influence climate Milankovitch cycles = periodic changes in Earth s rotation and orbit around the sun Alter the way solar radiation is distributed over Earth These cycles modify patterns of atmospheric heating Triggering climate variation For example, periods of cold glaciation and warm interglacial times

9 Direct measurements tell us about the present We document daily fluctuations in weather Precise thermometer measurements over the past 100 years Atmospheric CO 2 concentrations have increased from 315 ppm to 389 ppm Measuring of ocean and atmospheric chemistry began in 1958 Precise records of historical events Droughts, etc.

10 Introduction to Climate Change: Mean Annual Global Temperature John Wiley & Sons, Inc. All rights reserved.

11 Proxy indicators tell us about the past Paleoclimate = climate of the geological past Gives a baseline to compare to today s climate Proxy indicators = indirect evidence that serve as substitutes for direct measurements - Shed light on past climate - Ice caps, ice sheets, and glaciers hold clues to Earth s climate history - Trapped bubbles in ice cores provide a timescale of: - Atmospheric composition, greenhouse gas concentrations, temperature trends - Snowfall, solar activity, and frequency of fires

12 Ice cores from Antarctica Ice cores let us go back in time 800,000 years Reading Earth s history across eight glacial cycles Ice cores can show us the CO2 data and more from the past. Air gets trapped inside bubbles in the ice and preserved!

13 More proxy indicators Cores in sediment beds preserve pollen grains and other plant remnants Tree rings indicate age, precipitation, droughts, and fire history In arid regions, packrats carry seeds and plants to their middens (dens) Plant parts can be preserved for centuries Researchers gather data on past ocean conditions from coral reefs Scientists combine multiple records to get a global perspective

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15 Climate Change Terminology Greenhouse Gas Gas that absorbs infrared radiation Water vapor, ozone, carbon dioxide, nitrous oxide, methane, halocarbons [chlorofluorocarbons (CFCs)] Positive Feedback Change in some condition triggers a response that intensifies the changed condition Infrared Radiation Radiation that has a wavelength that is longer than that of visible light, but shorter than that of radio waves Greenhouse Effect Increase of heat in a system where energy enters (often as light), is absorbed as heat, and released sometime later energy that travels downward, warming the atmosphere and the planet s surface

16 Greenhouse gas concentrations are rising fast The greenhouse effect is a natural phenomenon Greenhouse gases have always been in the atmosphere We are not worried about the natural greenhouse effect Anthropogenic intensification is of concern We have added new gasses (CFCs) and increased concentrations of others Human activities increased atmospheric CO 2 from 280 parts per million (ppm) to 396 ppm in 2013 The highest levels in more than 800,000 years Likely the highest in 20 million years

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18 The fate of solar radiation The atmosphere, land, ice, and water absorb 70% of incoming solar radiation

19 Greenhouse Gases Carbon dioxide Water vapor Methane (CH 4 ) Nitrous oxide (N 2 O) CFCs and other halocarbons Ozone (tropospheric) CFC

20 The Greenhouse Gases Water Vapor (H 2 O) Most common Absorbs more IR radiation but not as persistent Natural contributor to global warming Concentrations have not changed Positive feedback loop Traps energy, heats ocean surface and lower atmosphere As temp rise over land ocean, evaporation will increase and water vapor concentration will rise, causing more warming Carbon Dioxide (CO 2 ) Greatest contributor to GH effect because of abundance Natural- volcanoes Anthropogenic- fossil fuel combustion and deforestation

21 The Greenhouse Gases Methane (CH 4 ) Most potent greenhouse gas Because of its ability to absorb IR and it s abundance Natural- wetlands (largest natural source of methane), termite digestion (second natural source) Anthropogenic- Animal Husbandry (cows), landfills, production/storage/transport of natural gas when methane leaks, rice cultivation (plant decay), biomass burning If it s decaying/decomposing think methane!

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23 The Greenhouse Gases Nitrous Oxide (N 2 O) Natural- denitrification turns nitrates into N 2 O before converting to N 2 Anthropogenic- fossil fuel combustion from cars, from agricultural soils synthetic fertilizers, manure, nitrogen fixing crops Side note: N 2 O contributes to Stratospheric O 3 depletion in addition to CFCs

24 The Greenhouse Gases CFC s (and other halocarbons) No natural causes Long loved Anthropogenic- coolants in refrigerators and air conditioners, pressurized aerosol cans Ozone (O 3 ) Tropospheric Short lived Nox + VOCs + sun

25 Sources of various greenhouse gases: Greenhouse Gas Natural Sources Anthropogenic Carbon Dioxide Methane Nitrous Oxide * Cellular respiration and decay * Natural fires * Volcanoes * Warming oceans * Animal digestion * Methane hydrates * Temperate and tropical soils * Oceans * Combustion of fossil fuels * Land use conversion * Cement production * Combustion of fossil fuels * Rice paddies * Livestock * Landfills * Combustion of fossil fuels * Fertilizer * Industrial processes Chlorinated Fluorocarbons * None * Liquid coolants * Foam production

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27 Greenhouse gas concentrations are increasing 2012 John Wiley & Sons, Inc. All rights reserved.

28 The greenhouse effect is natural Greenhouse gases have always been in the atmosphere We are not worried about the natural greenhouse effect Anthropogenic intensification is of concern Global warming potential = the relative ability of one molecule of a greenhouse gas to contribute to warming Expressed in relation to carbon dioxide (potential = 1)

29 GWP span wide ranges because they can differ in how much IR they absorb and how long they persist Expressed in relation to carbon dioxide (potential = 1) Methane is 25 times more potent than carbon dioxide Nitrous oxide is 298 times more potent than carbon dioxide

30 Greenhouse gas concentrations are rising fast Methane levels have increased 2.5-fold since 1750 Highest level in over 800,000 years Released by tapping into fossil fuel deposits and from livestock, landfills, and crops such as rice Nitrous oxide has increased nearly 20% since 1750 Produced by feedlots, chemical manufacturing plants, auto emissions, and synthetic nitrogen fertilizers

31 Greenhouse gas concentrations are rising fast Tropospheric ozone levels have risen 36% Halocarbon gases (CFCs) are declining Water vapor is the most abundant greenhouse gas Contributes most to the natural greenhouse effect Concentrations have not changed

32 Feedback complicates our predictions Tropospheric warming will transfer more water to the air The effects of increased water vapor are uncertain. Two possible feedback loops could result A positive feedback loop: more water vapor more warming more evaporation more water vapor A negative feedback loop: more water vapor more clouds shade and cool Earth less evaporation Because of the feedback loops, minor modifications of the atmosphere can lead to major effects on climate

33 U.S. emissions of major greenhouse gases

34 Carbon dioxide is not the most potent greenhouse gas BUT It is present in the largest concentrations It exerts six times more impact than methane, nitrous oxide, and halocarbons combined

35 Carbon dioxide Primary concern Most carbon is stored in the upper lithosphere Deposition, partial decay, and compression of organic matter led to formation of coal, oil, and natural gas These deposits remained buried for millions of years Burning fossil fuels transfers CO 2 from lithospheric reservoirs into the atmosphere The main reason atmospheric carbon dioxide concentrations have increased so dramatically

36 What caused levels of CO 2 to increase? Burning fossil fuels transfer CO 2 from lithospheric reservoirs into the atmosphere The main reason atmospheric carbon dioxide concentrations have increased dramatically Deforestation contributes to rising atmospheric CO 2 Forests serve as reservoirs for carbon Removing trees reduces the carbon dioxide absorbed from the atmosphere Human activities increased atmospheric CO 2 from 280 parts per million (ppm) to 389 ppm The highest levels in more than 800,000 years

37 Increased concentration of CO 2 Burning fossil fuels in cars, industry and homes Deforestation Burning of forests 2012 John Wiley & Sons, Inc. All rights reserved.

38 Seasonal Fluctuations of Carbon Dioxide Carbon Dioxide Seasonal fluctuations of photosynthesis and respiration in terrestrial ecosystems The N. Hemisphere has more land area and thus more vegetation, therefore more CO2 is absorbed during the northern summer

39 Fluxes of carbon dioxide

40 Ocean Sinks The ocean is the largest reservoir of CO 2 Ocean absorption = the ocean holds 50 times more carbon than the atmosphere Gas dissolved directly in ocean water Not absording as much CO 2 as emitting Slowing global warming but not preventing it Warmer oceans absorb less CO 2 Rate of absorption is slowing down A positive feedback effect that accelerates warming etguid/155d1e9c-517c-492c-b840-9e0aa2aea353

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43 Pollutants That Cool the Atmosphere Atmospheric Aerosols Aerosols = microscopic droplets and particles Both human and natural sources Tiny particles (or sulfur) that remain in troposphere for weeks or months (can be created by volcanoes) Sulfur-laden layer in the atmosphere reduces the amount of sunlight reaching earth They have either a warming or a cooling effect Soot (black carbon aerosols) causes warming by absorbing solar energy But most tropospheric aerosols cool the atmosphere by reflecting the sun s rays Sulfate aerosols produced by fossil fuel combustion may slow global warming, at least in the short term Volcanic eruptions reduce sunlight reaching Earth s surface and cool the Earth

44 Core Case Study: Studying a Volcano to Understand Climate Change NASA scientist correctly predicted that the 1991 Philippines explosion would cool the average temperature of the earth by 0.5C o over a 15 month period and then return to normal by Figure 20-1

45 Radiative forcing expresses change in energy Radiative forcing = the amount of change in thermal energy that a given factor causes Positive forcing warms the surface Greenhouse Effect Greenhouse Gases (GHGs) Negative forcing cools it ~50% covered by clouds, reflecting 21% solar rad. back into space (known as albedo) Volcanic eruptions (aerosols reflect radiation) Anthropogenic aerosols (smog)

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47 Arctic Albedo Feedback

48 The U.S. Global Change Research Program In 2009, scientists reported and predicted: Temperature increases Worse droughts and flooding Decreased crop yields Water shortages Health problems and diseases Higher sea levels, beach erosion, destroyed wetlands Drought, fire, and pests will change forests More grasslands and deserts, fewer forests Undermined Alaskan buildings and roads

49 Effects of Global Climate Change- Melting Ice and Rising Sea Levels IPCC projects sea-level rise of18-59cm by 2100 Sea level rise caused in 2 ways Thermal Expansion Melting of land ice Melting has positive feedback Increased melting decreases ice, which decreases albedo leading to further warming Permafrost melting can increase methane which is a greenhouse gas 2012 John Wiley & Sons, Inc. All rights reserved.

50 EFFECTS OF GLOBAL WARMING Between 1979 and 2005, average Arctic sea ice dropped 20% (as shown in blue hues above). Figure 20-8

51 Muir Glacier in the Past

52 Muir Glacier Today

53 Rising Sea Levels If seas levels rise by 9-88cm during this century, most of the Maldives islands and their coral reefs will be flooded. Figure 20-11

54 Central Case: Rising seas may flood the Maldives Tourists think the Maldives Islands are a paradise Rising seas due to global climate change could submerge them Erode beaches, cause flooding Damage coral reefs Residents have evacuated the lowest-lying islands Small nations are not the cause of climate change, yet they suffer

55 Case-In-Point Impacts in Fragile Areas Eskimo Inuit live traditional life dictated by freezing climate Climate change is altering their existence Wildlife displaced Reduced snow cover and shorter river ice seasons Thawing of permafrost (right ) 2012 John Wiley & Sons, Inc. All rights reserved.

56 Effects of Global Climate Change- Changing Precipitation Patterns Some areas will get more water, some areas will have greater droughts 2012 John Wiley & Sons, Inc. All rights reserved.

57 Effects of Global Climate Change- Effects on Organisms Zooplankton in parts of California Current have decreased by 80% since 1951 Affecting entire food chain Species have shifted their geographic range Migrating birds are returning to summer homes earlier Ecosystems at greatest risk of species loss (short term): coral reefs, mountain ecosystems, coastal wetlands, tundra, and polar spas 2012 John Wiley & Sons, Inc. All rights reserved.

58 Effects on Organisms - Coral Reefs Coral reefs can be bleached (right) due to increase in water temperature Affects coral symbiotes and makes them more susceptible to diseases 2012 John Wiley & Sons, Inc. All rights reserved.

59 Effect on Organisms - Vegetation 2012 John Wiley & Sons, Inc. All rights reserved.

60 Effect on Organisms - Vegetation 2012 John Wiley & Sons, Inc. All rights reserved.

61 Climate change affects people Societies are feeling the impacts of climate change Agriculture: shortened growing seasons, decreased production, crops more susceptible to droughts Increasing hunger Forestry: increased fires, invasive species Insect and disease outbreaks Health: heat waves and stress can cause death Respiratory ailments, expansion of tropical diseases Disease and sanitation problems from flooding Drowning from storms

62 Effects on Human Health Increased number of heatrelated illnesses and deaths 2012 John Wiley & Sons, Inc. All rights reserved.

63 Effects on Agriculture Difficult to anticipate Productivity will increase in some areas and decrease in others Rise in sea level will inundate flood plains and river valleys (lush farmland) Effect on pests is unknown- warmer weather increases range of mosquitoes that can carry disease Warmer temperatures will decrease soil moisture - requiring more irrigation Location (i.e., elevation and altitude) where certain crops can be grown may have to change

64 International Implications of Climate Change Developed vs. Developing countries Differing self-interests Differing ability to meet the challenges of climate change 2012 John Wiley & Sons, Inc. All rights reserved.

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66 Dealing with Global Climate Change Two ways to manage climate change Mitigation: Limiting greenhouse gas emissions to moderate global climate change Adaptation: Learning to live with environmental changes and societal consequences brought about by global climate change 2012 John Wiley & Sons, Inc. All rights reserved.

67 Relationship Between Mitigation and Adaptation 2012 John Wiley & Sons, Inc. All rights reserved.

68 Dealing with Global Climate Change - Mitigation Locate/invent alternative fuels to fossil fuels Increase efficiency of cars and trucks Carbon Capture and Storage Plant and Maintain trees to naturally sequester carbon 2012 John Wiley & Sons, Inc. All rights reserved.

69 Dealing with Global Climate Change - Adaptation Rising sea levels and coastal populations Move inland Construct dikes and levees Adapt to shifting agricultural zones NYC sewer line John Wiley & Sons, Inc. All rights reserved.

70 International Efforts to Reduce Greenhouse Gas Emission Kyoto Protocol** Provides operational rules on reducing greenhouse gases By 2010, 183 countries had ratified it US has not signed it - it will be difficult to implement without US backing EPA is taking it upon itself to define laws associated with CO 2 reduction in US 2012 John Wiley & Sons, Inc. All rights reserved.

71 The Kyoto Protocol tried to limit emissions This treaty took effect in 2005 After Russia became the 127th nation to ratify it The United States will not ratify the Kyoto Protocol It requires industrialized nations to reduce emissions But it does not require industrializing nations (China and India) to reduce theirs Other countries resent the U.S. because it emits 20% of the world s greenhouse gases but won t take action In 2007, one delegate said, If for some reason you are not willing to lead...please get out of the way.

72 The Copenhagen conference The conference in 2009 tried to design a successor treaty to the Kyoto Protocol Nations hoped the U.S., under President Obama, would participate in a full international agreement Obama would not promise more than Congress had agreed to In a last-minute deal, developed nations will help developing nations pay for mitigation and adaptation Nations that reduce deforestation will be rewarded Nothing is legally binding and no targets are set

73 States and cities are advancing policies The U.S. federal government is not taking action State and local governments are By 2010, 1,000 mayors signed the U.S. Mayors Climate Protection Agreement To meet or beat Kyoto Protocol guidelines California passed the Global Warming Solutions Act - To cut emissions 25% by 2020 Regional Greenhouse Gas Initiative (RGGI) in northeastern states - Set up a cap-and-trade program

74 Market mechanisms address climate change Permit trading programs harness the economic efficiency of the free market to achieve policy goals Businesses have flexibility in how they meet the goals Polluters choose how to cut their emissions They are given financial incentives to reduce them

75 Cap-and-trade emissions trading programs The approach of the Regional Greenhouse Gas Initiative: Each state decides which polluting sources participate Each state sets a cap on total CO 2 emissions it allows Each emissions source gets one permit for each ton they emit, up to the amount of the cap Each state lowers its cap over time States with too few permits must reduce emissions, buy permits from others, or pay for carbon offsets Sources with too many permits may sell them Any source emitting more than permitted will be penalized

76 Cap-and-trade programs already exist Chicago Climate Exchange = the world s first emissions trading program for greenhouse gas reduction 350 corporations, institutions, etc. Voluntary but legally binding trading system aims for a 6% reduction in emissions by 2010 The European Union Emission Trading Scheme The world s largest cap-and-trade program Governments had allocated too many permits Permits only work if government policies limit emissions

77 Carbon taxes are another option Critics say cap-and-trade systems are not effective Carbon tax = governments charge polluters a fee for each unit of greenhouse gases they emit Polluters have a financial incentive to reduce emissions European nations, British Columbia, and Boulder, Colorado have carbon taxes Polluters pass costs on to consumers Fee-and-dividend = funds from the carbon tax (fee) are passed to taxpayers as refunds (dividends)

78 Carbon offsets are popular Carbon offset = a voluntary payment intended to enable another entity to reduce the greenhouse emissions that one is unable to reduce oneself The payments offset one s own emissions Popular among utilities, businesses, universities, governments, and individuals Trying to achieve carbon-neutrality, where no net carbon is emitted Carbon offsets fall short Needs rigorous oversight to make sure that the offset money accomplishes what it is intended for