Presentation on theme: "Things to Ponder 1.Why are polar bears often used to illustrate climate change? 2.What is the atmosphere? 3.What are the primary layers of the atmosphere?"— Presentation transcript:
Things to Ponder 1.Why are polar bears often used to illustrate climate change? 2.What is the atmosphere? 3.What are the primary layers of the atmosphere?
Chapter 23 The Atmosphere, Climate and Global Warming
Climate Change Central Questions & Key Concepts What is the atmosphere? What is the difference between weather & climate? How does the Earths climate fluctuate? What factors affect climate? What are the possible effects of global warming? What can humans do about potential climate change? Ozone depletion and global warming are two very different things.
The Atmosphere The thin layer of gases that envelops the Earth Chemical reactions Atmospheric circulation produces weather and climates
The Atmosphere by weight thickest layer weather Very little water
Processes That Remove Materials from the Atmosphere Sedimentation: –Particles that are heavier than air settle out as a result of gravity. –Ex: Coal /volcanic particles will settle out over time Rain out: –Precipitation will physically and chemically flush materials from the atmosphere. –Ex: CO 2 + H 2 O H 2 CO 3 carbon dioxide is removed Oxidation: –Where oxygen is chemically combined with other substances. –Ex: atmospheric sulfur dioxide oxidizes to form sulfur trioxide which produces sulfuric acid Photodissociation: –Solar radiation can break down bonds in this chemical process. For example ozone may break down due to this process from O 3 to O 2.
Vocabulary Used to Characterize Air Pressure: –force per unit area Atmospheric pressure: –is the weight of overlying atmosphere per unit area –Question: Does the atmospheric pressure increase as altitude increases or does it decrease? Temperature: –a measure of thermal energy, ie the kinetic energy of the motion of atoms in a substance. –Question: as temperature increases does kinetic energy increase or decrease? Water vapor: –The amount of water vapor present in a particular place depends on several things including air temperature, air pressure and available water vapor (from various processes – remember the water cycle?)
Weather vs. Climate NOT THE SAME THING!! Weather: –Weather is what conditions of the atmosphere are over a short period of time, (hours, days, weeks) Climate: –climate is how the atmosphere "behaves" over relatively long periods of time (seasons, decades) –that behavior includes the representative or characteristic atmospheric conditions for a region on Earth Microclimate –The climate of a very small local area
Short Term Climate Variation In addition to long-term climate change, there are shorter term climate variations. This so-called climate variability can be represented by periodic or intermittent changes related to El Niño, La Niña, volcanic eruptions, or other changes in the Earth system.
El Niño/Southern Oscillation (ENSO) Natural. Occurs every 5-10 years. Last 12-18 months A disruption in the natural weather circulation –The trade winds that usually blow warm surface water towards the western edge of Australia and Indonesia, and nutrient rich cold water (good for fish) towards the west coast of South America weaken or change direction totally. –Causes small changes in ocean temperature that in turn cause very large changes in global weather patterns. Events believed to have been caused by El Nino: –drought conditions in Indonensia, Africa and Australia. Flooding in South America as well as 1993 Mississippi and 1995 California floods, So what is La Niña NormalEl Niño
Major Climatic Change Major climatic changes have occurred during the past 2 million years Appearances and retreats of glaciers During the past 100 years, the mean global annual temperature has increased by.5 degrees Celsius
The Greenhouse Effect Greenhouse Effect –The process of trapping heat in the atmosphere NATURAL! Without it the world would be too cold to support life! –Water vapor (85% of greenhouse warming), water particles (12%) and several other gases warm the Earths atmosphere because they absorb and emit radiation Greenhouse Gasses –Gasses that have a greenhouse effect –Water vapor –Anthropogenic sources: carbon dioxide, methane, nitrous oxide, CFCs (page _____)
The Natural Greenhouse Effect Albedo: known as surface reflectivity of suns radiation
Changes in the Earths Temperature During the Past Million Years The mean average temperature of the Earth has swung up and down by several degrees Celsius over the past million years due to variations in the Earths orbit around the sun. Interglacial periods – Times of relatively ice free periods, whereas times of low temperature reflect glacial events. Global climate can also change in shorter times – ex: continental glaciation ended 12,500 years ago with rapid warming – only lasting a few decades.
20 th Century Rise The first 5 years of the 20 th century were some of the warmest in the 142 years since temperatures have been recorded and in the last 1,000 years according to geologic data (see pages ____________ for how this data is collected). Warming since the mid 70s has been approximately 3X as fast as the previous 100 years The 10 warmest years have all occurred since 1990 and the five warmest since 1997 The warmest year on record was 2005, with 1998 second, and 2002 and 2003 tied for second. (2005 data) In the US 2003 was cooler and wetter than average in the eastern US, warmer and drier in the western part. New Mexico had its warmest year on record. In Europe in 2003 summer heat waves occurred with the warmest seasonal temperatures ever recorded in several countries. 15,000 people died in Paris. Warm conditions with drought contributed to severe wildfires in Australia, the United States and Canada. A year or two of high temperatures is NOT by itself an indication of global warming, however, the persistent trend of increasing temperatures over three decades is compelling evidence that global warming is real.
So what is Global Warming A natural or human induced increase in the average global temperature of the atmosphere near the earths surface 4 factors –Amount of sunlight Earth receives –Amount of sunlight Earth reflects –Retention of heat by atmosphere –Evaporation and condensation of water vapor Negative and Positive feedback cycles affect the atmosphere Increase in emission of greenhouse gasses Solar Forcing, Natural Cycles, Aerosols (global dimming), Volcanic Eruptions, El Nino
Climate models Apparent influence of human activities Could be natural changes Projecting Future Changes in Earths Climate
Evidence for Global Warming http://climate.nasa.gov/evidence/ Sea level rise –Global sea level rose about 17 centimeters (6.7 inches) in the last century. The rate in the last decade, however, is nearly double that of the last century. Global temperature rise –All three major global surface temperature reconstructions show that Earth has warmed since 1880. The 2000s had a solar output decline but still warmed. Warming oceans –The oceans have absorbed much of this increased heat, with the top 700 meters (about 2,300 feet) of ocean showing warming of 0.302 degrees Fahrenheit since 1969. Shrinking ice sheets –The Greenland and Antarctic ice sheets have decreased in mass. Data from NASA's Gravity Recovery and Climate Experiment show Greenland lost 150 to 250 cubic kilometers (36 to 60 cubic miles) of ice per year between 2002 and 2006, while Antarctica lost about 152 cubic kilometers (36 cubic miles) of ice between 2002 and 2005.
Evidence for Global Warming http://climate.nasa.gov/evidence/ Declining Arctic sea ice –Both the extent and thickness of Arctic sea ice has declined rapidly over the last several decades Glacial retreat –Glaciers are retreating almost everywhere around the world - including in the Alps, Himalayas, Andes, Rockies, Alaska and Africa Extreme events –The number of record high temperature events in the United States has been increasing, while the number of record low temperature events has been decreasing, since 1950. The U.S. has also witnessed increasing numbers of intense rainfall events. Ocean acidification –Since the beginning of the Industrial Revolution, the acidity of surface ocean waters has increased by about 30 percent. This increase is the result of humans emitting more carbon dioxide into the atmosphere and hence more being absorbed into the oceans. The amount of carbon dioxide absorbed by the upper layer of the oceans is increasing by about 2 billion tons per year.
Warming stimulates algae growth. –Algae absorbs CO 2. Warming stimulates plant growth. –Plants absorb CO 2. Polar regions receive more precipitation from warmer air carrying more moisture –Increased snow and ice could cause the solar energy to be reflected causing cooling Increases in water evaporation from the ocean and the land could increase clouds. –The clouds reflect the sunlight and cool the surface. Negative Feedback Cycles Associated with the Greenhouse Effect
Increased evaporation –Added water vapor in the air that does not condense will cause additional warming. Melting permafrost at high latitudes –Releases methane, as a by product of decomposition of organic materials in the melted permafrost layer, which would cause additional warming. Releasing old carbon locked in the soil.. Reduction in the amount of snow pack –Replaced by darker vegetation/soil could increase absorption of solar energy further warming the Earths surface. Increased use of air conditioning in warmer climates –Increased use of fossil fuels could increase release of CO 2. Positive Feedback Cycles Associated with the Greenhouse Effect
Old Carbon vs. New Carbon Old carbon can be defined as carbon that is trapped and not currently part of our current carbon cycle. –In fossil fuels – released through burning. –In Arctic Soils – being released as temperatures increase. New carbon is carbon that is part of the current carbon cycle. It has recently entered the soil through vegetation. –Biofuels release CO 2 but it is NEW carbon
Factors Affecting Changes in Earths Average Temperature Changes in solar output Changes in Earths albedo Moderating effect of oceans Clouds and water vapor Air pollution
Climate Change and Human Activities Increased use/burning of fossil fuels –Adds ~ 5.5 gigatons per year to the atmosphere. The carbon combines with oxygen to produce CO 2 Deforestation –Adds ~ 1.6 gigatons per year to the atmosphere. Burning of the trees releases carbon stored in the wood that combines with oxygen to produce CO 2 –Not to mention the fact that the trees are no longer taking IN CO 2 !
Effects of Global Warming Changes in climatic patterns Melting icecaps & glaciers Rise in sea level Coral reef bleaching Changes in biosphere
Solutions: Dealing with the Threat of Climate Change Options: Do nothing Do more research Act now to reduce risks Precautionary Principle
Tree plantation Coal power plant Tanker delivers CO 2 from plant to rig Oil rig Crop field Switchgrass field Spent oil reservoir is used for CO 2 deposit CO 2 is pumped down to reservoir through abandoned oil field Abandoned oil field CO 2 is pumped down from rig for Deep ocean disposal = CO 2 deposit = CO 2 pumping Removing CO 2 From the Atmosphere
Reducing Greenhouse Gas Emissions European Climate Exchange: Carbon Trading –A nation will agree to cap its emissions –Corporations are issued emission permits that allow X amount of emissions. These can be traded. Rio Earth Summit (1992) –Rio de Jeneiro, Brazil: Blueprint for reduction of CO 2 emissions. USA disagreed said it was too costly. Kyoto Treaty (1997) –Legally binding emission limits discussed. –166 nations signed. USA refused to sign, though eventually agreed to cut emissions 7% below 1990 levels. Recommended levels were 60-80%.
Reducing Greenhouse Gas Emissions Continued… G-8 meeting (2008) –New U.N. treaty to be discussed in Copenhagen in 2009. Leaders including USA agreed to consider and adopt reductions of greenhouse gas emission of at least 50%. Facts: –United States has 5% of the worlds population, yet emits 25% of the atmospheric CO 2. –California by ITSELF is 12 th in the world for CO 2 emissions. CA, however, passed legislation in 2006 to reduce emissions by 25% by 2020.
The ozone hole is a completely different phenomenon to global warming! There are links between them. For next time: What are those links?