Presentation on theme: "Natural Hazards, 2e Climate and Climate Change Chapter 11."— Presentation transcript:
Natural Hazards, 2e Climate and Climate Change Chapter 11
Learning Objectives Understand the difference between climate and weather, and how their variability is related to natural hazards Know the basic concepts of atmospheric science such as structure, composition, and dynamics of the atmosphere Understand how climate has changed during the last million years, through glacial and interglacial conditions, and how human activity is altering our current climate
Learning Objectives, cont. Understand the potential causes of climate change Know how climate change is related to natural hazards Know the ways we may mitigate climate change and associated hazards
Climate and Weather Weather refers to atmospheric conditions over short periods of time. Climate refers to characteristic atmospheric conditions over a long period of time. Climate zones Defined using Koeppen System Uses monthly average temperature and precipitation associated with different types of vegetation
Koeppen’s Classification System A-tropical, temp>18 o C (64 o F) year round B-Dry, evaporation > precipitation C- Mild Mid-latitude, 18 o C (64 o F)>coldest month> -3 o C (27 o F) D- Severe Mid-latitude, coldest month< -3 o C (27 o F) E – Polar, temp < -3 o C (27 o F) year round H-Highland, Mountain areas
Atmospheric Conditions Permanent gasses Gasses whose proportions stay constant Ex. Nitrogen Variable gasses Gasses whose proportions vary with time and space Ex. Carbon dioxide
Permanent Gasses Percentages in atmosphere remain essentially constant Nitrogen, oxygen, and argon Compose approx. 99% by volume Relatively unimportant to atmospheric dynamics
Variable Gasses – Carbon Dioxide (CO 2 ) Extremely important, but small in percentage (approx %) Describe in parts per million (ppm) or billion (ppb) Released naturally by volcanic activity, plant and animal respiration, decay of organic material Removed through photosynthesis, chemical weathering in soil, and mixing of air and seawater
Variable Gasses – Carbon Dioxide (CO 2 ), cont. Anthropogenic sources Burning of fossil fuels increases CO 2. Deforestation decreases amount used by trees, increasing ppm in atmosphere. Natural processes that remove CO 2 don’t work as rapidly as amounts are increasing. Levels increase by 2 ppm per year.
Variable Gasses – Water Vapor Created from evaporation at Earth’s surface. Returns to surface through hydrologic cycle. Air temperature is primary control of water vapor content.
Variable Gasses – Ozone O 3 Forms when atomic oxygen (O) collides with oxygen molecule (O 2 ) Mostly found in stratosphere Acts as a shield for ultraviolet light and is essential to life on earth Chlorofluorocarbons (CFCs) partially destroyed ozone shield Increases skin cancer, cataracts, caused local crop failures Can also be found in smog
Variable Gasses – Methane (CH 4 ) Primary constituent of natural gas Occurs naturally from bacterial decay, intestinal tracks of termites, cows, and sheep Anthropogenic sources: coal mines, oil wells, leaking natural gas pipelines, rice cultivation, landfills, and livestock Levels have doubled since 1700 and is a significant contributor to warming
Variable Gasses – Nitrous Oxide (N 2 O) Natural sources include microbiological processes in soil and ocean and wildfires. Anthropogenic sources include fertilizers and burning fossil fuels. Contributes to atmospheric warming.
Variable Gasses – Halocarbons Chemical compounds containing halogen elements bonded with carbon Include CFCs and are almost entirely anthropogenic Used in industrial processes, fire fighting, and as fumigants, refrigerants, and propellants Contribute to warming in troposphere and ozone depletion in stratosphere
Aerosols Microscopic liquid or solid particle that acts as nuclei for water particles to condense to form clouds Associated with air pollution Natural sources: desert dust, wildfires, sea spray, and volcanoes Anthropogenic sources: burning of forests and fossil fuels Effects are complex
Structure of Atmosphere, revisited Defined by changes in air temperature Troposphere is where weather happens Stratosphere dry, cold layer Little weather occurs here Strong winds circulate aerosols Figure 8.7
Atmospheric Circulation Responsible for location of climate zones At equator, warm air rises towards poles As it rises, it cools and loses moisture as rain Dry air descends between 15 o and 30 o North and South Descending air produces high pressure and low rainfall High pressures at North and South Poles Polar deserts
Climate Change Currently, the climate is warming Based on 30 years of warming in atmosphere Also, global increase in sea temp, widespread melting of snow, glaciers, ice sheets, and permafrost, and sea level rise Referred to as global warming 90% probability that humans are responsible Ecosystems capable of adjusting, but changes are too fast for these to take place Studies changes in atmosphere and linkages with lithosphere, cryosphere, hydrosphere, and biosphere
Cryosphere Part of the hydrosphere where most of the water is frozen Includes permafrost, sea ice, ice caps, glaciers, and ice sheets Glaciers Flow from high to low elevations under weight of accumulated ice Have budgets with input and output Periods of continental glaciation called glacial intervals Interglacial intervals occur in between
Glaciations Refer to multiple advances and retreats of glaciers. Rare during the earth’s 4.6 billion year history. Several in the last 1 billion years. We are now living during one of those events that began 2.5 million years ago.
Pleistocene Epoch Multiple ice ages Glaciers covered 30% of Earth (today 10%) Maximum extent 21,000 years ago Global sea level >100 m (330 ft) lower than today Figure 11.3
Causes of Glaciation Mostly unknown Related to position of continents Changes in amount of solar radiation influence advance and retreat Milankovitch cycles Changes in Earth’s orbit around Sun, tilt and wobble of Earth’s axis of rotation Correlate well with minor changes in global temperatures Explain the “Medeival Warming Period” and the “Little Ice Age” They are not the primary cause of glaciation or global temperature changes.
Glacial Hazards Huge, actively flowing masses of ice and debris Hazards include: property damage, injuries, and deaths People can fall into deep crevasses. Can expand to overrun villages, etc. Produce an ice jam to cause flooding. Blocks of ice may fall. Calving produces icebergs in ocean.
The Greenhouse Effect Discovered by Joseph Fourier in 1824: the Sun’s energy passes through, but reradiated heat is absorbed by, Earth’s atmosphere. Fourier also described the planetary balance of heat gain and loss ( the “heat budget”) The greenhouse effect was first reliably experimented on by John Tyndall in the year 1858 and first reported quantitatively by Svante Arrhenius in his 1896 paper. The mathematics were first proposed by Jožef Stefan in 1879, based on experiments by John Tyndall. Thermodynamic formulas describing the effects of greenhouse gas concentrations of the heat balance of Earth were developed by Ludwig Boltzmann, 1884.
The Greenhouse Effect In 1896, Swedish scientist Svante Arrhenius was the first to claim that fossil fuel combustion may eventually result in enhanced global warming. He proposed a relation between atmospheric carbon dioxide concentrations and temperature. He found that the average surface temperature of the earth is about 15 o C because of the infrared absorption capacity of water vapor and carbon dioxide. This is called the natural greenhouse effect.
The Greenhouse Effect Arrhenius suggested a doubling of the CO 2 concentration would lead to a 5 o C temperature rise. He and Thomas Chamberlin calculated that human activities could warm the earth by adding carbon dioxide to the atmosphere. This research was a by-product of research of whether carbon dioxide would explain the causes of the great Ice Ages. This was not actually verified until 1987.
In 1972, eminent atmospheric scientist J.S. Sawyer summarized what was known about the role of carbon dioxide in enhancing the natural greenhouse effect, and made a remarkable prediction of the warming expected at the end of the twentieth century. He concluded that the 25% increase in atmospheric carbon dioxide predicted to occur by 2000 corresponded to an increase of 0.6 °C in world temperature. (Nature 239, 23-26; 1972). In 1988, NASA scientist Jim Hansen gave congressional testimony showing model projections of continued global warming. In spite of being one of the earliest transient climate model experiments, there is an impressive match between the recently observed data and Hansen’s projections. The Greenhouse Effect
Scientific Agreement By the early 1990’s, climatologists generally agreed that humans were making significant contributions to climate change. In 1995, the National Academy of Sciences reported that the research strongly supported anthropogenic warming. By this time, the burden of proof had now shifted to scientists who disagreed with these findings. Since this time, the research has not provided evidence to refute the basic findings. On the contrary, thousands of papers have been published providing further evidence of anthropogenic warming. Since 2007, no scientific body of national or international standing has maintained a dissenting opinion. In a recent University of Illinois at Chicago survey sent to 10,257 Earth Scientists, 97.4% of the climatologists who responded answered "yes" when asked "do you think human activity is a significant contributing factor in changing mean global temperatures?"University of Illinois at Chicago survey
The Greenhouse Effect Earth’s temperature depends on three things: 1. Amount of sunlight received Most is ultraviolet with short wavelength About 2/3 is absorbed to warm the atmosphere 2. Amount of sunlight reflected Mostly reflected as infrared radiation 3. Degree to which the atmosphere retains heat Water vapor, carbon dioxide, methane, nitrous oxides, and halocarbons absorb IR radiation Gasses act as “blanket” to retain heat in troposphere
The Greenhouse Effect, cont. Greenhouse effect is a natural and necessary process. Earth would be 33 o colder without it. All surface water would be frozen. Little life would exist. Natural effect is from water vapor. Absorption by greenhouse gasses (carbon dioxide, methane, nitrous oxide, halocarbons) Enhance the greenhouse effect
Carbon Dioxide and The Greenhouse Effect Carbon dioxide accounts for most of the anthropogenic greenhouse effect. It is the most studied. Figure 11.6
Air Temperature and Carbon Dioxide CO 2 concentrations from air bubbles in glacial ice in Antarctic ice sheet Figure 11.7
Atmospheric Carbon Dioxide Concentrations Since the burning of fossil fuels, CO 2 concentration has increased exponentially. Measurements are from glacial ice and from Mauna Loa in Hawaii. Figure 11.8b
Atmospheric Carbon Dioxide Concentrations, cont. Atmospheric concentrations continue to rise and are likely to continue. Data from Mauna Loa in Hawaii. Figure 11.8a
Global Temperature Change–Last 800,000 Years Low temperatures coincide with major continental glaciations, high temperatures with interglacial periods Figure 11.9a
Global Temperature Change–Last 150,000 Years Last major interglacial period, Eemian, sea level was 4–6 ft higher than today Figure 11.9b
Global Temperature Change–Last 18,000 Years Cold interval, Younger Dryas, occurred 11,500 years ago, followed by warming to Holocene maximum. Recent cooling, called Little Ice Age, 15th – 19th centuries. Figure 11.9c
Global Temperature Change–Last 1000 Years Several warming and cooling trends Warming in 11 – 1300 allowed Vikings into Iceland, Greenland, and North America Figure 11.9d
Global Temperature Change–Last 140 Years 1750, warming trend begins until 1940s to 1998, global temperatures rise. Temperatures in past 30 years are warmest since monitoring began. Figure 11.9e
Why Does Climate Change? Milankovitch Cycles Natural changes in Earth’s Orbit, tilt, and precession Explain some changes, but not the observed large-scale changes Ocean conveyor belt Circulation of ocean water in oceans Can cause fast changes in climate Keeps Northern Europe warmer than without it
Ocean Conveyor Belt – Atlantic Ocean West side, strong warm current flows northward to Arctic. At Greenland, it is cool and salty and sinks to bottom. Cold, dense water flows southward around Africa.
United Nations Intergovernmental Panel on Climate Change UN report found that shutdown of conveyor belt current has occurred historically, but there is no evidence that it will occur again this century. There is sufficient evidence to state: 1. There is widespread evidence of human influence on global climate. 2. Warming is now occurring. 3. Mean surface temperature of Earth will likely increase between and 4 0 C (3 0 and 7 0 F) during this century.
Solar Forcing There is a relationship between changes in solar energy and climate change. Medieval Warm Period (A.D – 1300) corresponds to increased solar radiation. Little Ice Age corresponds to decreased solar radiation. Partially explains climate change, but effect is very small.
Volcanic Forcing Ash from eruptions becomes suspended in the atmosphere, reflects sunlight having a cooling effect. Mount Tambora, 1815 eruption contributed to cooling in North America and Europe. Mount Pinatubo in 1991 counterbalanced global warming during 1991 and 1992.
Anthropogenic Forcing Mathematical models of climate can isolate human causes from solar and volcanic forcing of climate change. Models found that present warming greatly exceeds natural variability. Models agree with climate change predicted from greenhouse gas forcing.
Effects of Climate Change Figure 11.13
Climate Patterns Climate important to agriculture Rainfall patterns, soil moisture, etc. Northern Canada and Eastern Europe may be more productive. Lands closer to equator become more arid. Violent storms may intensify Warmer oceans provide more energy.
Changes in Hydrosphere Increased sea surface temperature Increased precipitation in polar and temperate regions Decreased precipitation in tropical and subtropical regions
Changes in Hydrosphere, cont. Rising sea level Thermal expansion of ocean Melting glaciers Increases coastal erosion Increases vulnerability of structures to waves Flood low-lying Pacific and Indian Ocean islands Flood coastal cities, New York, Boston, Tampa, Washington, D.C.
Changes in Cryosphere Global warming effects occur more rapidly here. Shrinking permafrost. Decreased Arctic Ice cap, ice sheets, and glaciers Affects communities dependent on snowmelt for water supply
Changes in Biosphere Shifts in range of plants and animals Changes in plant and animal habitat Mosquitoes are moving to higher elevations. Northward movement of butterflies in Europe and birds in U.K. Expansion of sub-alpine forests in Cascades. Sea ice melting stresses seabirds, walruses, and polar bears. Warming in Florida Keys bleaching coral reefs. Seawater increasing in acidity, threatening coral animals and algae. These are areas of extreme animal diversity.
Desertification and Drought Climate change increases human induced conversion of land to desert Causes soil and natural vegetation degradation Long-term loses for agriculture and grazing Increase in drought events
Wildfires Wildfire events will increase due to global warming. Both in in frequency and intensity
Minimizing the Effects of Climate Change Focus on reduction of greenhouse gasses Most scientists believe that we have a decade to reduce gas emissions to avoid catastrophe. Reduction of gasses must be done on an individual, community, national, and international level. Carbon sequestration Necessary as we make transition to new energies
International Agreements Montreal Protocol 1987 agreement to limit depletion of ozone layer by CFCs CFCs have declined since 1989 Kyoto Protocol United Nations Framework Convention on climate change Establishes targets to reduce greenhouse gas emissions by 2012 Copenhagen No binding agreement was achieved. The U.S. Congress did not pass new laws in advance, and President Obama attended without any real authority to take meaningful action.
Carbon Sequestration Capture and store carbon dioxide before it enters atmosphere Biological sequestration Planting more trees Oceanic sequestration Injecting CO 2 into oceans Geologic sequestration Power plants capture CO 2 Inject it, under pressure into wells in the earth
Fossil Fuels and Future Threat of Climate Change Two scenarios for global warming in which there is rapid economic growth with population peaking and declining A1–More efficient energy technologies, but still fossil fuel intensive B1 – Clean resource-efficient technologies, economic structures change
Figure 11.18aFigure 11.18b B1 – Clean resource-efficient technologies, economic structures change A1–More efficient energy technologies, but still fossil fuel intensive
End Climate and Climate Change Chapter 11 You are now free to walk about the cabin