Climate Change: A 21st Century Issue

17.1 Earth Is a Greenhouse Planet

  • Earth's temperature allows water to exist in liquid form, essential for life.
  • The Earth's temperature is determined by:
    • Distance from the sun.
    • Energy output of the sun.
    • Presence of carbon dioxide.
  • Greenhouse gases:
    • Transparent to UV and visible light.
    • Absorb infrared radiation.
    • Trap heat, causing the greenhouse effect.
  • Carbon dioxide:
    • A significant greenhouse gas.
    • Without it, Earth's temperature would be around −18∘C-18^{\circ}C (0∘F0^{\circ}F).
    • The current average is closer to 15∘C15^{\circ}C (60∘F60^{\circ}F).

17.2 Geologic Evidence of Climate Change

  • Global warming: Average increase in Earth's temperature.
  • Climate change: Other changes resulting from global warming.
  • Earth's climate has varied significantly over time.
  • Evidence of past continental glaciers indicates significant climate change in the recent geologic past.

17.3 Growth in Knowledge of Global Warming and Climate Change

  • The average temperature of the Earth has been increasing.
  • Correlation between greenhouse gas concentration and global temperatures over the past 160,000 years.
  • Computer models predict further warming with increased greenhouse gases.
  • Evidence of climate change:
    • Steady increase in atmospheric carbon dioxide.
    • Gas bubbles in glaciers reveal pre-industrial revolution carbon dioxide levels.
    • Changes in snow and ice conditions (Satellite photos).
    • Changes in migration behavior of animals.
    • Changes in ocean CO2 content and pH (pH is lower).
    • Longer growing seasons.
    • Glacier retreat and ice sheet thinning.
    • Effects of increased carbon dioxide on photosynthesis.
    • Changes in wind patterns and ocean currents.
    • Effects of particulates from natural and human activities.
    • Sea level rise.
    • Frequency and strength of tropical storms.

17.4 Sources and Impacts of Principal Greenhouse Gases

  • Most important greenhouse gases:
    • Carbon dioxide (CO2).
    • Methane (CH4).
    • Chlorofluorocarbons (CFCs; primarily CCl3F and CCl2F2).
    • Nitrous oxide (N2O).
  • Carbon dioxide (CO2):
    • Most abundant greenhouse gas (65% of global warming).
    • Natural consequence of respiration and fermentation.
    • Waste product of burning fossil fuels.
    • Deforestation reduces carbon dioxide absorption.
  • Carbon dioxide levels:
    • Increased from 317 ppm in 1960 to over 411 ppm in 2019 at Mauna Loa Observatory.
    • Pre-industrial revolution levels were about 280 ppm.
    • A 47% increase over preindustrial concentrations.
  • Methane (CH4):
    • Second most abundant greenhouse gas (17% of global warming).
    • From biological sources and fossil-fuel use.
    • Released by microorganisms in wetlands and rice paddies.
    • Released from the digestive systems of ruminants and termites.
    • Natural gas is primarily methane and oil and coal, contain some methane as well.
    • Preindustrial concentrations were about 700 parts per billion (ppb).
    • Current concentrations are about 1,870 ppb.
  • Nitrous oxide (N2O):
    • Enters the atmosphere through fertilizers and fossil fuels.
    • Soil bacteria convert nitrogen compounds in fertilizers and manure to nitrous oxide.
    • Formed during the burning of fossil fuels.
  • Chlorofluorocarbons (CFCs):
    • Synthetic compounds with no natural sources.
    • Formerly used in refrigerants, cleaning solvents, aerosols, and foam products.
    • Extremely efficient greenhouse gases (15,000 times more efficient than carbon dioxide).
    • Production phased out due to ozone destruction; atmospheric levels are decreasing.
  • Principal Greenhouse Gases:
    • Carbon dioxide (CO2):
      • Pre-1750 Concentration: 280 ppm
      • 2019 Concentration: 411 ppm
      • Contribution to Global Warming: 65%
      • Principal Sources: Burning of fossil fuels, deforestation
    • Methane (CH4):
      • Pre-1750 Concentration: 0.70 ppm
      • 2019 Concentration: 1.87 ppm
      • Contribution to Global Warming: 17%
      • Principal Sources: Produced by bacteria in wetlands, rice fields, and guts of livestock, release from fossil fuel use
    • Chlorofluorocarbons (CFCs):
      • Pre-1750 Concentration: Zero
      • 2019 Concentration: 0.00083 ppm
      • Contribution to Global Warming: 8%
      • Principal Sources: Release from foams, aerosols, refrigerants, and solvents
    • Nitrous oxide (N2O):
      • Pre-1750 Concentration: 0.270 ppm
      • 2019 Concentration: 0.332 ppm
      • Contribution to Global Warming: 6%
      • Principal Sources: Use of fertilizer and manure in agriculture, burning of fossil fuels

17.5 The Current State of Knowledge about Climate Change

  • Intergovernmental Panel on Climate Change (IPCC):
    • Established in 1988 by the UN Environment Programme and the World Meteorological Organization.
    • Assesses the state of knowledge about climate change.
  • IPCC Working Groups:
    • Working Group I: Physical science related to climate change.
    • Working Group II: Impacts of climate change.
    • Working Group III: Mitigation of climate change effects.
  • Fifth Assessment Report (2013) findings:
    • Human activity is clearly influencing climate.
    • Increased greenhouse gas concentrations, particularly carbon dioxide, increase temperature.
    • Clear evidence of increased temperature.
      • The average temperature of the Earth has increased 0.65-1.06°C (1.2 to 1.9°F) since 1880.
      • Amounts of spring snow and ice have decreased in the northern hemisphere. Snow is melting earlier in the year.
      • The number of cold days has decreased and the number of warm days has increased.
      • The Arctic region is warming 2 to 3 times faster than the rest of the world.
      • Permafrost (permanently frozen soil) temperatures have increased 2 to 3oC (3.6 to 5.4oF) and the thickness of the permafrost layer and the area of the world that has a permafrost layer has decreased.
      • There has been a reduction in the area covered by arctic sea ice at the end of the summer season (September).
      • Greenland and Antarctic ice sheets have been losing mass.
      • Glaciers are melting.
      • The arrival of spring is earlier in many parts of the world.
    • Oceans are affected by increased carbon dioxide and temperature.
      • About 28 percent of carbon dioxide emissions end up in the ocean.
      • Increased CO2 dissolved in water has decreased pH by 0.1pH unit. (A 26 percent increase in hydrogen ion concentration.)
      • About 90 percent of the additional energy added to the Earth has been stored in the oceans resulting in an increase of about 0.44°C (0.8°F) in the temperature of the upper 75 meters of the oceans in the last 40 years.
      • Sea level has risen about 19 cm (7.5 in.) between 1901 and 2010.
      • The rate of sea level rise has been increasing and was about 3.2mm/year (0.125 inches/year) from 1993 to 2010. (In 2019, sea level was rising about 3.4 mm/year).

17.6 Consequences of Climate Change

  • A small average temperature increase can significantly alter regional climates.
  • Computer models predict changes to the hydrologic cycle, sea level, human health, organism survival and distribution, and natural resource use.
  • Vulnerability:
    • Poorer nations are more vulnerable.
    • Dependent on climate-sensitive economic activities (e.g., agriculture).
    • Lack economic resources for adaptation.
    • Africa is identified as the most vulnerable continent.
  • IPCC Working Group II's 8 major risks:
    1. Risk of death or harm from coastal flooding.
    2. Risk to health and livelihoods from inland flooding.
    3. Risk of severe weather disrupting infrastructure and public services.
    4. Risk of death and illness due to extreme heat.
    5. Risk of food insecurity due to warming, drought, or flooding.
    6. Risk to agricultural productivity due to a shortage of water for irrigation and drinking.
    7. Risk of loss of marine and coastal ecosystem services.
    8. Risk of loss of terrestrial and freshwater ecosystem services.
  • Climate Change and the Oceans
    • Oceans are intimately interrelated with climate.
    • Equatorial waters are warmer than other parts of oceans.
    • Uneven heating causes wind patterns.
    • Oceans are the ultimate source of water vapor for precipitation.
    • Prevailing winds and water vapor from oceans causes weather patterns that begin over oceans and move over land.
  • Increased ocean temperature
    • About 90% of additional heat from climate change is absorbed by the oceans.
    • In 2019, the average surface temperature of the ocean was about 0.8°C (1.4°F) above the long- term average.
  • The oceans are becoming more acid.
    • About 25% of the carbon dioxide released is absorbed into the oceans.
    • Carbon dioxide dissolved in water creates carbonic acid.
    • There has been about a 0.1 pH unit decrease in ocean pH. (About a 33% increase in acidity).
    • Many marine organisms have difficulty constructing and maintaining the skeletal structures.
  • Disruption of the Hydrologic Cycle
    • The hydrologic cycle (evaporation, precipitation, water flow, groundwater, etc.) is driven by energy.
    • The primary source of energy is the temperature of the Earth, which is determined by the input of energy from the sun and the heat-trapping effect of greenhouse gases.
    • Thus, a change in the Earth’s temperature is expected to change weather and climate.
    • Weather includes short-term activities such as; temperature changes, rain and snow events, winds, clouds, and other factors.
    • Climate is the long-term average of weather patterns.
    • Thus, if climate is changing, we should expect changes in weather patterns also.
    • Higher temperatures result in increased evaporation
      • Some areas to become drier,
      • Drought, less water in lakes and rivers.
      • Some areas will have greater rainfall.
      • Floods, more severe storms, wetter soil.
      • Snowfall patterns are also expected to change with some areas receiving more snow and others less.
  • Recent data suggest that:
    • The amount of spring snow has decreased.
    • Snow is melting earlier in the year.
    • Hurricanes are more powerful.
    • There are more hot days and fewer cold days.
    • Spring is arriving earlier.
  • Rising Sea Level
    • A warmer Earth will result in rising sea levels for two different reasons:
    • When water increases in temperature, it expands and takes up more space.
    • In addition, higher temperatures are causing the melting of glaciers, which adds more water to the oceans.
    • Rising sea level erodes beaches and coastal wetland, inundates low-lying areas, and increases the vulnerability of coastal areas to flooding from storm surges and intense rainfall.
    • By 2100, the IPCC projects sea level to rise by 26 to 98 centimeters (10 to 39 inches).
    • A 50-centimeter (20-inch) sea-level rise will result in substantial loss of coastal land in North America, especially along the southern Atlantic and Gulf coasts, which are subsiding and are particularly vulnerable.
    • Many coastal cities would be significantly affected by an increase in sea level.
    • World-wide about 600 million people live in low-lying coastal areas.
    • The land area of some island nations and countries such as Bangladesh would change dramatically as flooding occurred.
  • Changes to Ecosystems
    • Geographic distribution of organisms will change,
    • Terrestrial plants and animals are shifting their range toward poles.
    • Tundra regions are converting to forests.
    • Ocean organisms (plankton, fish, mammals) are shifting their ranges.
    • Coral reefs are affected because of increase ocean temperature and acidity.
    • Mangrove forests and marshes on shorelines are being affected by sea-level rise and storm surges from more violent weather events.
  • Health Effects
    • The most direct effect of climate change is the impact of hotter temperatures.
    • Extremely hot temperatures increase the number of people who die (of various causes) on a given day.
    • For example, people with heart problems are vulnerable because the cardiovascular system must work harder to keep the body cool during hot weather.
    • Heat exhaustion and respiratory problems increase.
    • Climate change will also make air pollution problems worse.
    • Higher air temperature increases the concentration of ozone at ground level, which leads to injury of lung tissue and increases the incidence of respiratory disease, asthma, and allergies.
    • Because children and the elderly are the most vulnerable, they are likely to suffer disproportionately from both warmer temperatures and poorer air quality.
    • Tropical diseases could migrate to former temperate regions.
    • Several serious diseases appear only in warm areas.
    • As the Earth becomes warmer, some of these tropical diseases may be able to spread to parts of the world where they do not currently occur.
    • Diseases that are spread by mosquitoes and other insects could become more prevalent.
    • Such “vector-borne” diseases include malaria, dengue fever, yellow fever, and encephalitis.
    • Some scientists believe that algal blooms could occur more frequently as temperatures rise.
  • Challenges to Agriculture and the Food Supply
    • Climate strongly affects crop yields.
    • Yields fall in regions where drought and heat stress increase.
    • In regions that receive increased rainfall and warming temperatures yields should increase.
    • However, episodes of severe weather will cause crop damage that will affect yields.
    • A warmer climate will alter the kinds of crops that can be grown in an area and increase irrigation demands.
    • Expansion of the geographic ranges of insect pests could also increase vulnerability and result in greater use of pesticides.
    • Total world agricultural productivity is not likely change much. Regional changes will occur—some will have reduced productivity.
    • Poor regions of the world will suffer decreased productivity.

17.7 Addressing Climate Change

  • Energy Efficiency and Green Energy
    • Improving energy efficiency has the double impact of reducing carbon dioxide release and conserving the shrinking supplies of energy resources.
    • It makes sense to increase energy efficiency even if global warming is not a concern.
    • A tax on the amount of carbon individuals and corporations release into the atmosphere would increase efficiency.
    • This would increase the cost of fuels and stimulate a demand for fuel efficient products because the cost of fuel would rise.
    • It would also stimulate the development of alternative fuels with a lower carbon content and generate funds for research in many aspects of fuel efficiency and alternative fuel technologies.
    • One way to stimulate a move toward greater efficiency would be to place a tax on the amount of carbon individuals and corporations release into the atmosphere.
    • This would increase the cost of fuels and stimulate a demand for fuel efficient products because the cost of fuel would rise.
    • It would also stimulate the development of alternative fuels with a lower carbon content and generate funds for research in many aspects of fuel efficiency and alternative fuel technologies.
    • Increases in energy efficiency and reductions in greenhouse gas emissions are likely to have important related benefits that could offset the costs.
    • Greater energy efficiency would lead to reduced air pollution, which would result in lower health care costs and time lost from work.
    • A study in China determined that there are about 1 million premature deaths per year in China due to air pollution.
    • Greater energy efficiency reduces the need for new powerplants and related infrastructure.
    • Switching to green sources of energy such as wind, solar, and hydroelectric, as well as nuclear power do not release carbon dioxide and lead to reduced carbon dioxide emissions.
  • The Role of Biomass
    • Since carbon is an important component of living things, what happens to biomass has a role to play in determining atmospheric carbon dioxide.
    • Forests consist of many long-lived tree species that can tie up carbon for centuries.
    • Preserving forests slows the rate of increase of atmospheric carbon dioxide.
    • This is particularly true for tropical forests since they are the last remaining major unmodified forested areas in the world and they are very efficient at capturing carbon dioxide.
    • The burning of tropical rainforests to provide farm or grazing land.
    • Adds carbon dioxide to the atmosphere.
    • Reduces the rainforests’ ability to remove carbon dioxide from the atmosphere.
    • A commonly cited estimate is that 10 percent of the additional carbon dioxide entering the atmosphere is due to deforestation.
    • Planting trees has also been supported as a way to reduce atmospheric carbon dioxide.
    • Long-lived plants like trees will tie up carbon for longer periods of time than grasses and other short-lived plants.
    • Critics argue that this approach will provide only a short-term benefit.
    • Eventually, the trees will mature and die, and their decay will release carbon dioxide into the atmosphere at some later time.
  • Technological Approaches
    • The U.S. Department of Energy has concluded that, relying primarily on already proven technology, the United States could reduce its carbon emissions by almost 400 million metric tons.
    • This is enough to stabilize U.S. emissions at 1990 levels.
    • Alternative energy sources like wind, solar, hydroelectric, geothermal, and nuclear power do not release carbon dioxide and can replace current fossil-fuel energy sources.
    • Fossil fuels currently provide nearly 90 percent of the world’s energy.
    • Converting to a greater reliance on nonfossil-fuel energy sources will require a great deal of new construction and technological improvements.
    • Prevent carbon dioxide from being released into the atmosphere.
    • Carbon dioxide can be reacted to produce solid carbonate minerals (limestone is calcium carbonate) that could be stored in landfills.
    • Carbon dioxide can be captured and stored underground.
    • Technological changes come with a cost that will be paid by the consumer.
    • Government policies that stimulate the deployment of these technologies will be needed.
  • International Agreements
    • The Montreal Protocol—Dealing with Chlorofluorocarbons.
      • Established to phase out chlorofluorocarbon production.
      • Required significant technological changes,
      • CFCs in the atmosphere have begun to decline.
      • Changes made to protect the ozone layer have had the side benefit of reducing the release of a potent greenhouse gas.
    • Kyoto Protocol—Dealing with Greenhouse Gases.
      • Established in 1997.
      • Economically developed countries required to limit their greenhouse gas emissions below 1990 levels.
      • Economically developing countries did NOT have requirements.
      • Nearly all of Latin America, Africa, and Asia.
      • Goals to be met by 2012.
      • Most countries of the world ratified the treaty.
      • The United States did not officially ratify the treaty.
      • 2006 China became the largest emitter of greenhouse gases, followed the United States and European Union.
      • The Kyoto Protocol expired in 2012, an agreement was reached to extend the protocol through 2020.
      • New agreement required that ALL countries publish plans for reducing greenhouse gases.
    • The Paris Agreement—Establishing Goals to Cut Greenhouse Gas Emissions
      • A follow-up to the Kyoto Protocol.
      • Meeting in Paris 2015.
      • Goals of the agreement:
      • Prevent human activity from causing a 2°C increase in global temperature this century.
      • strive to keep it below 1.5°C.
      • Mechanism for achieving goals.
      • Each country publish its plans to reduce greenhouse gas emissions.
      • Nationally Determined Contributions (NDCs)
      • Each country pledged to report every 5 years on progress and revise plans.
      • Developed countries pledged to provide funding to help developing countries (Green Climate Fund).
    • The Paris Agreement progress.
      • United States withdrew from Paris Agreement in 2017.
      • Many U.S. states, cities, and companies continued to work toward their climate related goals.
      • The U.S. will likely rejoin the Paris Agreement.
      • European industrialized countries are meeting their NDCs.
      • Funding for Green Climate Fund is not meeting the goal of $100 billion.
    • Madrid Climate Change Meeting.
      • Took place in 2019.
      • Goals.
      • Establish how each countries N D Cs will be measured.
      • Establish carbon credit trading mechanism—Not achieved.
      • Develop plan for compensating developing countries for the damage they incurred because of energy use in developed countries.—No agreement reached.
      • Encourage more aggressive greenhouse gas reductions.
      • Current NDCs do not meet the goal of limiting temperature increase to 2°C.
      • Further action deferred to next meeting.
    • The Kigali Agreement—Dealing with Chlorofluorocarbons and Hydrofluorocarbons.
      • Chlorofluorocarbons and hydrofluorocarbons destroy stratospheric ozone and are greenhouse gases.
      • The Kigali Agreement is an amendment to the Montreal Protocol.
      • Phases out the production of hydrofluorocarbons.

Summary

  • The concept of climate change is not new. Geological studies have demonstrated that climates have change greatly over the Earth’s history.
  • Today’s climate change is different in that it is highly likely that it is being caused by human activities.
  • The primary greenhouse gases are carbon dioxide, nitrous oxide, methane, and chlorofluorocarbons. These gases are strongly linked to an increase in the average temperature of the Earth and, consequently, are leading to major changes in the climate.
  • These include warming of the Earth, particularly near the poles. The warming will result in melting of the permafrost, glaciers, and sea ice; changes in rain and snowfall patterns; shifts in the distribution of plants and animals; more intense heat waves and severe storms; a rise in sea level; and acidification of the oceans.
  • Other likely effects of climate change are health effects in humans, extinction of some plants and animals, flooding of cities, and changes in agricultural productivity.
  • The primary factor involved in climate change appears to be the carbon dioxide released from the burning of fossil fuels. Since fossil fuel use is closely tied to economic development, many developing countries are unwilling to accept limits to their use of fossil fuels.