Chapter 11 - Climate Change PDF

CHAPTER 11 Climate: How Does Global Climate Change? Copyright © 2023 W. W. Norton & Company, Inc. Chapter 11 Outline 11.1 How Do We Measure Global Climate? 11.2 What Caused Climate Change in the Past? 11.3 How Do Oceans Influence the Climate? 11.4 What’s Happening with Our Climate Now? 11.5 W...

CHAPTER 11 Climate: How Does Global Climate Change? Copyright © 2023 W. W. Norton & Company, Inc. Chapter 11 Outline 11.1 How Do We Measure Global Climate? 11.2 What Caused Climate Change in the Past? 11.3 How Do Oceans Influence the Climate? 11.4 What’s Happening with Our Climate Now? 11.5 What Are Some Effects of Climate Change? 11.6 What about the Future? 11.7 What Can I Do? Chapter Objectives: This chapter will help you describe how Earth’s climate is warmed by a greenhouse effect. explain how scientists estimate historical changes in Earth’s climate. recognize that Earth’s climate has changed dramatically in its history, and that the recent temperature of air and water at Earth’s surface has been warming. explain how ocean currents influence Earth’s climate. describe how human activities are driving recent global warming. discuss how climate models attempt to simulate Earth’s climate system to forecast future climate. summarize how global warming can alter precipitation patterns, the frequency and intensity of extreme weather, sea levels, and ocean acidity. identify steps that individuals, businesses, and governments can take to address climate change. 11.1 How Do We Measure Global Climate? Climate describes average weather conditions over a significant period of time for a particular region of Earth. Global climate describes the average weather conditions over a significant period of time for the planet as a whole. Temperature Records (1 of 2) The instrumental period is the current era in which we have access to temperature readings taken directly with instruments such as thermometers. This period began in 1860. Weather satellites use infrared radiation to record temperature in various layers of the atmosphere. Temperature Records (2 of 2) Since the instrumental period, confidence in plotting annual average temperatures has improved. Comparing temperatures to a fixed base period (1901– 2000) shows how much the climate is changing over time. Each dot on the figure shows the global average temperature for a given year and how it compares to the 20th century global average, indicated by the dashed line. Temperature Measurements from the Ocean Along with collecting surface air temperatures (SAT) over land, scientists also collect average marine air temperatures (MAT) and sea- surface water temperatures (SST). Ocean vessels began collecting MAT and SST data in the 1850’s along shipping routes, but today, specially equipped buoys collect MAT data. Since 2000, more than 3,000 Argo floats have measured SST data from the surface to depths of 6,000 feet below the surface Take-Home Message Scientists use many methods to evaluate changes in global temperature over time. Since the mid-19th century, an instrumental record of temperatures has been available from stations, ships, and buoys across the planet. Since the late 1970s, satellites have recorded the temperature in the atmosphere. 11.2 What Caused Climate Change in the Past? Over geologic time, global climate has changed naturally. Fossil evidence indicates that polar regions were forested during the Cretaceous Period. 700-million-year-old glacial sediments near the equator suggest that Earth was completely iced over during the “snowball Earth” period. What has caused these extreme changes? The Greenhouse Effect (1 of 3) Some energy from the sun is trapped at the Earth’s surface, while some of this energy radiates back into space. The greenhouse effect happens in any system where a barrier causes an inflow of energy that outpaces the outflow such that the interior warms. On Earth, the warming effect is due to atmospheric greenhouse gases preventing radiant heat emitted from the surface escaping into space. The Greenhouse Effect (2 of 3) Earth is surrounded by greenhouse gases (GHGs), e.g., carbon dioxide and water vapor. In the atmosphere, these GHGs redirect heat rising from Earth’s surface back down, causing a warming effect. Light colored surfaces on Earth increase albedo, a measure of the reflectivity of a surface. Darker surfaces absorb radiation and heat Earth’s surface; lighter surfaces reflect it back into atmosphere and help cool Earth’s surface. The albedo effect is decreased by melting ice and snow which exposes darker ocean water and sediment, increasing global warming. The Greenhouse Effect (3 of 3) In the figure below, each arrow represents a transfer of energy and the relative size of that transfer. Take-Home Message Earth's climate is warmed by the greenhouse effect, when gases in the atmosphere like water vapor and CO2 reradiate heat toward the surface. When severe changes to the Earth's climate have occurred, it has caused mass extinction events. 11.3 How Do Oceans Influence the Climate? Saltwater covers most of Earth and has a major impact on global climate. The ocean is always moving as a connected flowing mass that transports energy around the globe, affecting areas thousands of miles from shore. Countercurrents and El Niño Countercurrents, or changes in normal ocean currents, can happen and change weather. The El Niño-Southern Oscillation (ENSO) is a countercurrent that significantly weakens or even shifts the direction of trade winds and ocean currents in the southern Pacific. This affects upwelling currents, where cold water is drawn up from deep in the ocean. Take-Home Message Ocean currents play a large role in shaping Earth's climate. The ocean is a system in motion that distributes heat around the planet. The ocean's surface currents are driven by the rotation of the Earth and continental landmasses. Wind-driven surface currents interact with deeper currents below the ocean surface, and are driven by differences in water temperature and salinity. 11.4 What’s Happening with Our Climate Now? Earth’s climate is in a period of global warming. Current climate change is driven primarily by human activities, such as increased industrialization. Increased industrialization has increased greenhouse gases, global temperatures, glacial melting, and resulted in rising sea levels. For example, the population of Isle de Jean Charles, Louisiana is being relocated because the island is sinking due to sea-level rise. AT A GLANCE Indicators of a Warming World The Concentration of Carbon Dioxide in the Atmosphere Is Increasing (1 of 3) Natural processes like photosynthesis and cellular respiration maintain a balance by cycling CO2 between living organisms and the atmosphere. CO2 is also absorbed into and released from the oceans in a natural balance. The natural atmospheric life of CO2 ranges from 50–200 years. Volcanoes can increase the amount of CO2 in the atmosphere faster than these processes can balance it. The Concentration of Carbon Dioxide in the Atmosphere Is Increasing (2 of 3) The chart shows the increasing carbon dioxide concentrations in the atmosphere recorded at Mauna Loa Observatory, Hawaii. The up-and-down pattern in the graph is caused by the seasonal rhythm of photosynthesis in the Northern Hemisphere. CO2 concentrations decrease in the growing season and increase in the fall and winter when most plants shed their leaves or die. The Concentration of Carbon Dioxide in the Atmospheric Is Increasing (3 of 3) Humans emit much more CO2 through fossil fuel combustion and industrial processes. Recent human emissions of 9.2 billion metric tons CO2 have disrupted natural cycles and increased atmospheric concentrations by 0.05% per year since 1958. Current levels of atmospheric CO2 are 420 parts per million—the highest since before modern humans evolved. Concentrations of Other Human-Caused Greenhouse Gases Are Also Increasing (1 of 3) GHGs exist in different concentrations and differ in effect and in resident time in the atmosphere. CO2 is the most significant GHG, but methane traps heat 25 times more effectively than CO2. Methane accumulates as a GHG after being released from coal mines, natural gas leaks, rice farming, livestock production, and landfills. Methane lasts in the atmosphere for around 12 years. Methane concentrations are 250% greater than before the Industrial Revolution. Concentrations of Other Human-Caused Greenhouse Gases Are Also Increasing (2 of 3) Nitrous oxides (N2O) have increased by 20% since the preindustrial era from industrial processes that produce nylon and from fossil fuel combustion. N2O has an atmospheric lifetime of 120 years and traps heat 310 times more effectively than CO2. Halocarbons have no natural source, but are synthesized for use as aerosol spray, refrigerants, solvents, and fire retardants. Resident time in the atmosphere of halocarbons is 15–180 years. Concentrations of Other Human-Caused Greenhouse Gases Are Also Increasing (3 of 3) How Much Do Human-Caused Greenhouse Gas Emissions Affect the Climate? (1 of 2) GHG emissions have increased more than 80% since 1970. The Intergovernmental Panel on Climate Change (IPCC), created in 1988, reports on climate change every five years. The 2022 IPCC’s Sixth Assessment Report declared that “It is unequivocal that human influence has warmed the atmosphere, ocean and land.” In 2013, the carbon dioxide concentration in the atmosphere surpassed 400 parts per million (ppm). Earth has not seen 400 ppm in more than a million years—since before humans evolved. How Much Do Human-Caused Greenhouse Gas Emissions Affect the Climate? (2 of 2) The Earth is responding as scientists predicted it would to increasing GHG concentrations. Over the past 50 years the troposphere has been warming with the stratosphere cooling. If the planet was warming due to increasing solar radiation, the stratosphere would be warming along with the troposphere, but this is not happening. Hindcasting shows computer simulations in support of real-world observations; results over the past 30 years show that humans are driving global warming, especially by releasing carbon dioxide and methane. Take-Home Message Human activities release greenhouse gases like carbon dioxide (CO2) and methane (CH4) are the dominant factor influencing the recent warming of Earth's climate. The atmosphere's CO2 content is more than 40% higher than before industrialization and higher than levels over the past million years. Climate models that include human and natural factors closely match actual warming. Models which leave out human factors do not. 11.5 What Are Some Effects of Climate Change? The average temperature change from the last ice age is a 6°C (11°F) increase. 75% of the largest cities in the US are in low-lying coastal areas and in danger of flooding due to climate change. The Maldives is the lowest-lying country, average elevation of 5 feet above sea level. The Maldives will be uninhabitable or completely submerged by the end of the century. Precipitation and the Water Cycle (1 of 2) Changes in precipitation patterns, frequency and intensity of extreme weather events are effects we are seeing due to climate change. Major cities, such as Dubai, UAE, have suffered from floods from a record 10 inches of rainfall. Extreme heavy precipitation events are those where the total that falls over 2 days is exceeded only once in a 5-year period. Overall, the climate will become more variable and less predictable. Precipitation and the Water Cycle (2 of 2) Droughts are prolonged periods of low precipitation and high evaporation rates that can lead to water shortages. Droughts, due to increased evaporation from warming, will affect agricultural yields and wildfires. Globally, increased heat waves have resulted in increased deaths. The WMO (world metrological organization) reports 136,000 deaths from 2000-2010 due to heat waves compared to 6,000 deaths from 1990-2000. Hurricanes and Severe Weather The National Climate Assessment predicts that an increase in hurricane intensity will continue, especially in the Atlantic Ocean. Warming oceans evaporate more water and increase the amount of energy feeding tropical storm systems that become hurricanes. Severe thunderstorms, tornadoes, and winter storms are also highly influenced by climate change. Sea-Level Rise (1 of 2) Global sea levels have risen over 9 inches since late 19th century. Thermal expansion, the expansion of something as it warms, has contributed to 40% of sea level change since 1980. The prediction is a 1 to 4-foot sea-level rise by 2100. Sea-Level Rise (2 of 2) More than 23% of the human population now lives in coastal areas affected by rising sea levels. Five of 1,000 Solomon Islands in the South Pacific are now submerged. Storm-surge effects are increased within low-lying coastal areas. Ecosystem Effects (1 of 2) Increasing CO2 has resulted in ocean acidification, the ongoing decrease in pH of Earth’s oceans caused by absorption of CO2 from the atmosphere. NOAA has estimated that pH of ocean surface waters has decreased by 0.1 units since the beginning of the Industrial Revolution. This decrease in pH is equal to a 30% increase in acidity and interferes with calcium carbonate shell formations by many marine species, most of which are at the base of the marine food chain. Ecosystem Effects (2 of 2) Global warming is altering the seasonal behavior and geographic range of many species. Scientists are studying phenology, the seasonal timing of biological activities, such as breeding, flowering, and migration of various species. The ranges of many midlatitude species have been moving towards the poles and up to higher elevations, where it is cooler. Take-Home Message Small temperature changes alter global weather patterns. Warming oceans evaporate more readily, increasing the energy of tropical storm systems. Sea level is rising because of warmer oceans and melting glacial ice. Increases in the ocean's CO2 interferes with shell formation, including important plankton. A warming climate alters the range and behaviors of many land species. 11.6 What About the Future? (1 of 2) Scientists are improving global climate models to forecast future climate change effects by applying feedback loops. Positive feedback enhances the original change, and negative feedback counters the original change. Scientists are also studying tipping points in the climate system, where sudden changes can have a rapid and significant effect on global climate. Attempting to balance feedbacks is complicated due to the complexity of natural systems. Some important reinforcing feedback loops are noted below. What About the Future? (2 of 2) Modeling Alternative Scenarios for Future Human Response Climate modelers run simulations for different scenarios of human-caused GHG emissions. Each trajectory makes assumptions about future economic activity, energy sources, population growth, land-use patterns, and other human factors to arrive at estimates for emissions until the year 2100. Even if all GHG emissions ended in the next few decades, scientists see a warmer future Earth because of existing GHG emissions. Take-Home Message Earth's climate includes reinforcing and balancing feedback mechanisms that enhance and counter warming. Climate models attempt to simulate the way complicated feedbacks would interact over various timescales at various places on Earth. Even if humans immediately cut GHG emissions, the delayed effects of recent emissions are predicted to cause several additional decades of warming. 11.7 What Can I Do? Know your carbon footprint: individual changes can make a big difference! Online carbon footprint calculators can approximate how your daily actions contribute to GHG emissions. You can reduce carbon emissions by conserving energy and using alternatives to GHG-emitting sources. Impact of Your Transportation and Home Energy Use Consider living close to where you work and live. Consider the availability of public transit or bike routes. If driving is the only option, drive sustainably and maintain tire pressure and engine tune-ups to increase efficiency. Consider hybrid or electric vehicles that have lower GHG emissions. Turn down thermostats in winter and up in summer. Choose energy-efficient lights, such as LED light bulbs, and energy-efficient appliances. Consider the Whole Impact of What You Consume Choose goods with smaller carbon footprints and lower embodied energy – the energy used to make and transport goods. Chose natural fibers over synthetic fibers, which are made of petroleum products. Consume more vegetables than meat products—meat production requires more embodied energy than other types of food. Make Changes Visible to Others With social media, individuals and small groups can have an impact on large numbers of people, businesses, and government officials. Ex. Greta Thunberg aggressively calling out for action on climate change For most people, though, the solution can be as simple as making others aware of the effect that humans have on climate change. The website Climate Generation (climategen.org) suggests creating and telling your own “Climate Story... a personal story about you and your experience of climate change,” making it known to others, and then reading other accounts. Question 2 Which of the following may result in a positive feedback mechanism that would intensify climate change effects? A. Warmer temperatures result in thermal expansion, leading to sea level rise. B. At higher temperatures, trees increase rates of photosynthesis. C. A large volcano emits huge quantities of sulfate aerosols into the atmosphere. D. An increase in rainfall results in increased plant growth. Question 2: Answer Which of the following may result in a positive feedback mechanism that would intensify climate change effects? A. Warmer temperatures result in thermal expansion, leading to sea level rise. (Correct) B. At higher temperatures, trees increase rates of photosynthesis. C. A large volcano emits huge quantities of sulfate aerosols into the atmosphere. D. An increase in rainfall results in increased plant growth. Question 4 Small island nations such as the Maldives are in the international spotlight because they __________________________________________. A. may be among the first nations to be completely flooded by rising sea levels B. are accepting climate change refugees from other nations C. are the largest emissions producers in their respective areas D. have exceeded the emissions reductions set by the Intergovernmental Panel on Climate Change Question 4: Answer Small island nations such as the Maldives are in the international spotlight because they __________________________________________. A. may be among the first nations to be completely flooded by rising sea levels (Correct) B. are accepting climate change refugees from other nations C. are the largest emissions producers in their respective areas D. have exceeded the emissions reductions set by the Intergovernmental Panel on Climate Change Question 5 The industrial process that contributes the least to carbon emissions is __________________. A. coal B. gas C. oil D. cement Question 5: Answer The industrial process that contributes the least to carbon emissions is __________________. A. coal B. gas C. oil D. cement (Correct) Credits This concludes the Lecture PowerPoint presentation for Environmental Science and Sustainability, Chapter 11, by David Montgomery and Daniel Sherman For more resources, please visit https://digital.wwnorton.com/environsci2 Copyright © 2023 W. W. Norton & Company, Inc.