Climate Control and Ozone Depletion Chapter 19
19-1 How Might the Earth’s Temperature and Climate Change in the Future? • Concept 19-1 The overwhelming scientific consensus is that the earth’s atmosphere is warming rapidly, mostly because of human activities, and that this will lead to significant climate change during this century.
Global Warming and Global Cooling Are Not New • Over the past 4.7 billion years the climate has been altered by: • Volcanic emissions • Changes in solar input • Movement of the continents • Impacts by meteors
Estimated Changes in the Average Global Temperature of the Atmosphere • Over the past 900,000 years, the troposphere has experienced prolonged periods of global cooling and global warming. • Since the end of the last ice age a little more than 10,000 yrs ago, the temperature has been relatively stable.
Estimated Changes in the Average Global Temperature of the Atmosphere • For the past 1,000 years temperatures have remained fairly stable but began to rise during the last century. • This increase coincides with the beginning of the industrial revolution, large scale deforestation, and the widespread use of fossil fuels.
Estimated Changes in the Average Global Temperature of the Atmosphere • A record of CO2 measurements taken at the top of Mauna Loa volcano in Hawaii since 1958. • Commonly known as the “Keeling Curve” after Charles David Keeling who supervised the measurements
How Do We Estimate Past Temperature Changes? • Scientists can estimate the changes in Earth’s past by analyzing: • Direct temperature measurements since 1861 • Tree rings • Pollen from the bottom of deep lakes/bogs • Bat dung deposited in caves over 1000’s of yrs. • Ocean floor sediments • Radioiostopes in rocks and fossils • Past glaciation formations • Air bubbles in ancient glaciers…
Science: Ice Cores Are Extracted by Drilling Deep Holes in Ancient Glaciers • Scientists analyze the gas isotopes found in tiny air bubbles trapped in ice cores to learn about past: • troposphere composition • temperature trends • greenhouse gas concentrations • solar activity • snowfall amounts • forest fire activity
Our Climate, Lives, and Economies Depend on the Natural Greenhouse Effect • Three major factors shape the earth’s climate: • Thesun • The Oceans: store CO2 and heat, evaporate and receive water, move stored heat to other parts of the world • The Greenhouse effectthat warms the earth’s lower troposphere and surface because of the presence of greenhouse gases
Our Climate, Lives, and Economies Depend on the Natural Greenhouse Effect • The Earth’s average temp is 57º F (14º C) • Without the natural greenhouse effect the average temp. would be -2º F (-19º C)
Our Climate, Lives, and Economies Depend on the Natural Greenhouse Effect • The major atmospheric greenhouse gases are: • Water Vapor (H2O): the most abundant greenhouse gas, warmer air holds more water vapor (positive feedback) • Carbon Dioxide (CO2): enters the atmosphere through the burning of fossil fuels, solid waste, trees and wood products, etc. It is removed from the atmosphere or “sequestered” when it is absorbed by plants as part of the carbon cycle. • Methane(CH4): emitted during the production and transport of fossil fuels, from livestock and other agricultural practices, and by the decay of organic waste in municipal solid waste landfills. • Nitrous Oxide (N2O): emitted during agricultural and industrial activities and during combustion of fossil fuels and solid waste.
Human Activities Emit Large Quantities of Greenhouses Gases • Since the Industrial Revolution (1860-2004) • Average concentrations of CO2, CH4, and N2O emissions are much higher • Mostly due to: burning of fossil fuels, agriculture, and deforestation
Human Activities Emit Large Quantities of Greenhouses Gases • Countries with the largest CO2 emissions • United States (25%) • China (5%) • European Union (27 countries)
The Atmosphere Is Warming Mostly Because of Human Activities • In 1988, the UN established the Intergovernmental Panel on Climate Change (IPCC). • It includes more than 2,500 climate scientists in more than 130 countries. • It’s 2007 report indicated a 90–99% likelihood that the lower atmosphere is warming AND that human activity is responsible for most of the recent warming. • Evidence that supports the major conclusions of the IPCC: • The 20th century was the hottest in the past 1000 yrs. • 1906–2005: Ave. tropospheric temp increased about 0.74˚C • 1970–2005: Annual greenhouse emissions up 70% • Past 50 years: Arctic temp rising almost twice as fast as the rest of the earth
The Atmosphere Is Warming Mostly Because of Human Activities • Evidence that supports the major conclusions of the IPCC: • Glaciers and floating ice sheets are melting and shrinking at increasing rates • Prolonged droughts: increasing • During the last century, sea level rose by 10-20 cm, mostly due to runoff from melting and land-based ice and the expansion of ocean water as temperatures rise. • Warmer temps. in Alaska, Russia, and the Arctic are melting permafrost releasing more CH4 into the troposphere. • The range and distribution of plants and animals is shifting towards the poles. • In the mid-latitudes, spring is coming earlier and fall is coming later.
The Atmosphere Is Warming Mostly Because of Human Activities May 30, 1868 May 30, 2005
Feedback Loops: Positive and Negative • Some factors can amplify (positive feedback) and some can dampen (negative feedback) projected global warming:
Is a Hotter Sun the Culprit? • Is a hotter sun the culprit? No. • Since 1975, the troposphere has warmed while the stratosphere has cooled. • A hotter sun would cause the entire atmos. to warm
Can the Oceans Save Us? • The oceans can absorb large amounts of CO2 • 25-30% of man-made CO2 is absorbed by the ocean • Some is converted into carbonate salts that sink to bottom • Some is used by marine plants • Problems: • The warmer water is, the less CO2 it can hold • As the oceans warm, more CO2 will have to stay in the atmosphere and warm the planet even more • Positive feedback loop • CO2 levels increase ocean acidity • Also decreases CO2 solubility in ocean water • Effect on coral reefs – dissolves the calcium carbonate
There Is Uncertainty about the Effects of Cloud Cover on Global Warming • Warmer temperatures create more clouds that could shade and cool the troposphere, but water vapor is also a greenhouse gas. • Warmer temperatures create more clouds • Thick, light-colored low altitude clouds: decrease surface temperature • Thin, cirrus clouds at high altitudes: increase surface temperature • Effect of jet contrails on climate temperature?
Outdoor Air Pollution Can Temporarily Slow Global Warming • Aerosol and particulate pollutants produced by human activities can cool the atmosphere through a process called global dimming. The high amounts of pollutants can actually help to shade the planet. • Ironically, global warming will accelerate as particulate and SO2 pollution is reduced. • Creates a cooling effect that may have partially masked the effects of global warming • This is why we have seen a slightly lower global temp. increase than some climate models predicted.
What Is the Scientific Consensus about Future Temperature Change? • Mathematical models used for predictions • They represent simplified models of major processes that interact to determine the average temperature and greenhouse gas content of the troposphere. • Most models show: • Global warming will continue to occur at a rapid rate • Human factors are the major cause of temperature rise since 1950 • Human activities will play an ever increasing role in the warming trend during the next century
CO2 removal by plants and soil organisms Greenhouse gases Cooling from increase Heat and CO2 removal CO2 emissions from land cleaning, fires, and decay Warming from decrease Aerosols Heat and CO2 emissions Long-term storage Simplified Model of Some Major Processes That Interact to Determine Climate Troposphere Ice and snow cover Shallow ocean Land and soil biotoa Natural and human emissions Deep ocean
Core Case Study: Studying a Volcano to Understand Climate Change • NASA scientists correctly predicted that the 1991 eruption of Mount Pinatubo in the Philippines would cool the average temperature of the earth by 0.5o C over a 15 month period and then return to normal by 1995. • Particulates and SO2 were the main reasons for the temp. decrease. • The success convinced scientists and policy makers that climate model projections should be taken seriously.
Comparison of Measured Temperature from 1860–2007 and Projected Changes
19-2 What Are Some Possible Effects of a Warmer Atmosphere? • Concept 19-2 The projected rapid change in the atmosphere's temperature during this century is very likely to increase drought and flooding, shift areas where food can be grown, raise sea levels, result in intense heat waves, and cause the premature extinction of many species.
19-2 What Are Some Possible Effects of a Warmer Atmosphere? • Important distinction: • Global Warming vs. Climate Change • Global warming = the temperature of the troposphere increasing as a result of an increase in the natural greenhouse effect • Climate change = a broader term referring to any changes in the Earth’s climate as a result of a warmer troposphere
19-2 What Are Some Possible Effects of a Warmer Atmosphere? • Remember: we are not talking about local weather, we are talking about global climate. • A rapid increase in the temperature of the troposphere during this century would give us little time to deal with its harmful effects. • Many scientists fear a “tipping point” after which rapid/severe climate changes cannot be prevented. • Plant/animal distribution and ocean/atmosphere circulations are based on the current global climate. • What if the climate changes??
Severe Drought Is Increasing: The Browning of the Earth • Drought accelerates global warming, leads to more droughts • Severe lack of water • Growth of trees and other plants will slow • Less CO2 taken out of atmosphere • Also, more forest and grass fires will add CO2 to the atmosphere • Groundwater, lakes, and rivers will be depleted because of lack of precip., increased evaporation, and increased need to agricultural irrigation.
Ice and Snow Are Melting • Why will global warming be worse in the polar regions? • Because the ice was reflecting 90% of the sunlight back into space…when it melts it is replaced by water which absorbs 90% of the sunlight. • Positive feedback loop
Ice and Snow Are Melting • The world’s sea ice sheets and land-based glaciers are slowly melting. • The loss of ice is happening much faster than scientists thought possible. • Why should we care if snow and ice are melting? • Arctic ice regulates the temperature and precipitation of regions to the south (North America, Europe) • Mountain glaciers play a vital role in the water cycle and the availability of fresh water for hundreds of millions of people. • Drinking • Agriculture
Ice and Snow Are Melting 2004 1948
Sea Levels Are Rising • Average sea level has been slowly rising and the rate is increasing • 2/3 of the rise is the from the thermal expansion of warm water • The remaining 1/3 of the rise is from the melting of land-based ice • Floating ice is already in the water (buoyancy)
Sea Levels Are Rising • Projected irreversible effect • Degradation and loss of 1/3 of coastal estuaries, wetlands, and coral reefs • Disruption of coastal fisheries • Flooding of • Low-lying barrier islands and coastal areas • Agricultural lowlands and deltas • Contamination of freshwater aquifers (groundwater) • Submergence of low-lying islands in the Pacific and Indian Oceans and the Caribbean
Sea Levels Are Rising Areas of Florida to flood if average sea level rises by one meter • 13% of the world’s urban population lives near sea level • Many cities would be devastated by even relatively small increases in sea level
Permafrost Is Likely to Melt: Another Dangerous Scenario • As arctic temperature increases, permafrost melts and the organic matter in soils and lake bottoms decomposes, releasing CH4 • Effect on global warming • Warmer air can release methane gas stored in bogs, wetlands, and tundra soils and accelerate global warming.
Ocean Currents Are Changing but the Threat Is Unknown • Ocean currents act like large conveyor belts redistributing heat all over the planet. • Global warming can change ocean currents by increasing the temp. of the water, adding large amounts of freshwater from melting ice, and increasing salinity by increasing evaporation. • The temp. of water greatly effects the temp. of the air above it. • Many areas have warmer climates despite their higher latitudes; that will change if the ocean currents change
Extreme Weather Will Increase in Some Areas • By altering ocean currents and air circulation, global warming can both excessive warming or cooling. • This will lead to prolonged heat waves and droughts in some areas and prolonged heavy rains and increased flooding in other areas. • Hurricanes and typhoons feed off the warm ocean waters. If these waters are warmer, that means more energy for the storms and stronger storms.
Global Warming Is a Major Threat to Biodiversity • Habitat loss and ecosystem changes will cause many species to seek new habitats or face extinction. • Specialist species that cannot evolve or migrate fast enough are the most vulnerable. • An estimated 30% of land plants/animals could go extinct with only a 2ºC temp. increase
Global Warming Is a Major Threat to Biodiversity Changes in Average Ocean Temperatures, Relative to Coral Bleaching Threshold • Most susceptible ecosystems: • Coral reefs, polar seas, coastal wetlands, alpine and arctic tundra Exploding Populations of Mountain Pine Beetles in British Columbia, Canada
Climate Change Will Shift Areas Where Crops Can Be Grown • Regions of farming may shift • Decrease in tropical and subtropical areas • Increase in northern latitudes • However, it will be less productive; soil not as fertile • Loss of productivity could be offset by a longer growing season • Genetically engineered crops developed to be more tolerant to drought and temperature extremes
Climate Change Will Threaten the Health of Many People • Global warming will increase human deaths from: • Heat stroke • Increased flooding • Malnutrition and starvation from disruption of food supply • Spread of tropical diseases to temperate regions • More insects, microbes, toxic molds, and fungi • Increase in some forms of air pollution, more O3 • Decreased amount of vital natural capital • Increased number of environmental refugees • Increased poverty
19-3 What Can We Do to Slow Climate Change? • Concept 19-3A To slow the rate of global warming and climate change, we can increase energy efficiency, sharply reduce greenhouse gas emissions, rely more on renewable energy resources, and slow population growth. • Concept 19-3B Governments can subsidize energy efficiency and renewable energy use, tax greenhouse gas emissions, set up cap-and-trade emission reduction systems, and help to slow population growth.
Climate change is such a difficult problem to deal with because: The problem is global The effects will last a long time It is a long-term political issue The harmful and beneficial impacts of climate change are not spread evenly Many actions that might reduce the threat are controversial because they can impact economies and lifestyles Dealing with Climate Change Is Difficult
Mitigation – the act of decreasing or reducing something Taking actions aimed at reducing the extent of global warming by reducing the production of greenhouse gases or their emission into the atmosphere We can improve energy efficiency, rely more on carbon-free renewable energy resources, and find ways to keep much of the CO2 we produce out of the troposphere. Adaptation – change along with the changing climate We recognize that some warming is unavoidable and devise strategies to reduce its harmful effects, or live with the outcome. What Are Our Options?