Report of Global Warming Nian Hongen School of Chemical Engineering and Bioengineering
Higher temperatures threaten dangerous consequences: drought, disease, floods, lost ecosystems. And from sweltering heat to rising seas, global warming's effects have already begun. But solutions are in sight. We know where most heat-trapping gases come from: power plants and vehicles. And we know how to curb their emissions: modern technologies and stronger laws.
Global average air temperature near Earth's surface rose 0.74 ± 0.18 °Celsius in the last century, most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations "An increasing body of observations gives a collective picture of a warming world and other changes in the climate system." Intergovernmental Panel on Climate Change (IPCC), 2001 This map illustrates the local consequences of global warming
Fig.1 Global mean surface temperatures 1850 to 2006 This image shows the instrumental record of global average temperatures as compiled by the Climatic Research Unit of the University of East Anglia and the Hadley Centre of the UK Meteorological Office .. "Uncertainty estimates in regional and global observed temperature changes: a new dataset from 1850". J. Geophysical Research 111 : D12106 . DOI : 10.1029/2005JD006548 . Following the common practice of the IPCC , the zero on
Fig.2 Mean surface temperature anomalies during the period 1995 to 2004 with respect to the average temperatures from 1940 to 1980 This figure shows the difference in instrumentally determined surface temperatures between the period January 1995 through December 2004 and "normal" temperatures at the same locations, defined to be the average over the interval January 1940 to December 1980 . The average increase on this graph is 0.42 °C, and the widespread temperature increases are considered to be an aspect of global warming
Deforestation water conflicts Sea-level rise increased
Causes Of all environmental effects of fossil fuel usage, global warming, including its concomitant climate change, is the most perplexing, potentially most threatening, and arguably most intractable. It is caused by the ever-increasing accumulation in the atmosphere of CO2 and other gases, largely due to emissions of these gases from anthropogenic activities, and reaches levels that exceed those that existed for centuries before the beginning of the industrial revolution. Called greenhouse gases, these substances augment the greenhouse effect of the earth’s atmosphere, which provides a warmer climate at the earth’s surface than would exist in an atmosphere-free earth.
Two millennia of mean surface temperatures according to different reconstructions, each smoothed on a decadal scale. The unsmoothed, annual value for 2004 is also plotted for reference. This figure shows the variations in concentration of carbon dioxide in the atmosphere during the last 400 thousand years. Throughout most of the record, the largest changes can be related to glacial/interglacial cycles within the current ice age . Although the glacial cycles are most directly caused by changes in the Earth 's orbit , these changes also influence the carbon cycle , which in turn feeds back into the glacial system. Since the Industrial Revolution , circa 1800 , the burning of fossil fuels has caused a dramatic increase of CO2 in the atmosphere, reaching levels unprecedented in the last 400 thousand years. This increase has been implicated as a primary cause of global warming .
INTRODUCTION Greenhouse effects Greenhouse gas emissions Solar and terrestrial radiation Sun-earth-space radiative equilibrium Modeling global warming Feedback effects Results of global warming modeling Observed trend of global warming Other effects of global warming Carbon dioxide emission and the carbon cycle Methane Nitrous oxide Chlorofluorocarbons Ozone GHG control
What is the greenhouse effect? The greenhouse gases the surface of the Earth would be as cold as the surface of the Moon, about -18°C. In fact the average surface Temperature of the Earth is about 15°C. The greenhouse effect is the rise in temperature that the Earth experiences because certain gases in the atmosphere trap energy from the sun. Without these gases, heat would escape back into space and Earth’s average temperature would be colder. Because of how they warm our world, these gases are referred to as greenhouse gases.
A schematic representation of the exchanges of energy between outer space , the Earth's atmosphere , and the Earth surface. The ability of the atmosphere to capture and recycle energy emitted by the Earth surface is the defining characteristic of the greenhouse effect. This figure is a simplified, schematic representation of the flows of energy between space , the atmosphere , and the Earth's surface, and shows how these flows combine to trap heat near the surface and create the greenhouse effect . Energy exchanges are expressed in watts per square meter (W/m2)
Solar and terrestrial radiation Solar radiation • emr emitted from sun which passes through the atmosphere and is reflected in varying degrees by Earth's surface and atmosphere • detectable only during daylight • Sun's visible surface (photosphere) has tempera- ture - 6000K energy radiated from gamma to radio waves 99% of sun's radiation fall between 0.2 – 5.6um; 80% - 0.4 - 1.5um • about 50% of solar radiation passes through the atmosphere and absorbed in varying degrees by surface
Terrestrial radiation • energy emitted from the Earth and atmosphere • detectable both day and night • Earth's ambient temperature - 300K • Earth radiates 160,000 times less than the sun • essentially all energy is radiated at thermal infrared • wavelengths between 4-25um maximum emission occurs at 9.7um
Sun-earth-space radiative equilibrium Earth spectrum as observed from the Nimbus-7satellite. Major absorption Bands by greenhouse gases are indicated The sun-earth-space radiative equilibrium is depicted in these figures. The numbers on arrows are average annual radiation received from the sun or emitted from the earth, in watts per square meter.
Sun-earth-space radiative equilibrium. Of the incoming global annual solar radiation, About 30% is reflected into space; the rest Reaches the earth’s surface or is scattered by clouds, aerosols, and atmospheric Molecules. Of the outgoing terrestrial Thermal radiation, about 17% goes directly Into space; the rest emerges after Redistribution by clouds, aerosols, and Greenhouse gases.
Reflected Solar Radiation (W/m2) 425 0 Emitted Heat Radiation (W/m2) 85 350 The top map shows solar radiation reflected from the Earth by clouds, ice, and bright surfaces like desert. Dark, absorbing areas are dark gray, while bright, highly reflective areas are various shades of light gray. The bottom map shows heat radiated from the Earth. More energy is emitted by warmer surfaces, so tropical regions are radiating strongly except where there are high, cold clouds. The areas emitting the least energy are represented by darker shades of gray, while lighter shades of gray represent areas where more heat escapes.
The above chart shows the current scientific understanding of radiative forcing (how different phenomena affect the Earth’s energy balance). Postive numbers represent forcing that will warm the Earth, negative numbers are cooling effects. The height of each bar represents the uncertainty, and the black line is a central estimate. The effects of mineral dust and the indirect effect of tropospheric aerosols are so uncertain That there is no central estimate. Scientists and policy makers who are skeptical of climate change emphasize the cooling effects, and propose feedback mechanisms that help stabilize Earth’s climate. (Graph Adapted from Climate Change 2001, The Scientific Basis)
Greenhouse gas emissions This figure shows the relative fraction of man-made greenhouse gases coming from each of eight categories of sources, (as estimated by the Emission Database for Global Atmospheric Research version 3.2, fast track 2000 project) . These values are intended to provide a snapshot of global annual green- House gas emissions in the year 2000. The top panel shows the sum over all man-made greenhouse gases, weighted by their global warming potential over the next 100 years. This consists of 72% carbon dioxide , 18% methane , 9% nitrous oxide and 1% other gases. Lower panels show the comparable information for each of these three primary greenhouse gases, with the same coloring of sectors as used in the top chart. Segments with less than 1% fraction are not labeled.
Scientists study past trends to predict future changes. The graph above shows the increasing concentration of the three most significant greenhouse gases—methane, carbon dioxide, and nitrous oxide. Since 1850 the concentration of methane has increased 125%, carbon dioxide 30%, and nitrous oxide 15%—and the rate of increase is accelerating. The additional methane in the atmosphere has increased the energy trapped by the atmosphere (called radiative forcing) by 0.48 watts per meter squared, carbon dioxide 1.46 watts per meter squared, and nitrous oxide 0.15 watts per meter squared. (Graph based on data from the Goddard Institute for Space Studies)
Carbon Dioxide concentration in the atmosphere has been increasing since measurements began in 1958. Simultaneously, global temperatures have been rising. The graphs above compare Carbon Dioxide concentration to temperature anomaly (the difference between annual temperatures and a long-term average temperature). Note the decrease of Carbon Dioxide during each Northern Hemisphere summer, which is caused by plant respiration.
Sea-level rise is one of the most widely discussed effects of global warming. The graph above shows real-world tidal gauge measurements (solid line) compared with a model of global average sea level (dashed line), and model calculations at the locations of the real-world gauges (dotted line). Models can both help predict future change (so scientists can estimate the effects of global warming) and evaluate the accuracy of instrumental measurements. (Graph adapted from Cabanes, C. et. al., Sea Level Rise During Past 40 Years Determined from Satellite and in Situ Observations, Science, October 26, 2001, Vol 294, pp. 840-842.)
Associated Climate Changes <ul><li>Global sea-level has increased 1-2 mm/yr </li></ul><ul><li>Duration of ice cover of rivers and lakes decreased by 2 weeks in North. Hemisphere </li></ul><ul><li>Arctic ice has thinned substantially, decreased in extent by 10-15% </li></ul><ul><li>Reduced permafrost in polar, sub-polar, mountainous regions </li></ul><ul><li>Growing season lengthened by 1-4 days in North. Hemisphere </li></ul><ul><li>Retreat of continental glaciers on all continents </li></ul><ul><li>Poleward shift of animal and plant ranges </li></ul><ul><li>Snow cover decreased by 10% </li></ul><ul><li>Earlier flowering dates </li></ul><ul><li>Coral reef bleaching </li></ul>Source: Intergovernmental Panel on Climate Change, 2001 Report
<ul><li>Energy & Carbon Dioxide As an individual, you have little control on how your energy is produced. However, you can control the way in which you use that energy. Using less energy means less needs to be produced. Hence less carbon dioxide is released into the atmosphere. </li></ul><ul><li>Saving Energy </li></ul><ul><li>Recycling </li></ul><ul><li>Leaving the Car at Home </li></ul>What can we do to prevent global warming?
How can renewable energy reduce global warming? Renewable energy is energy created by sources that are not used up or depleted. Most forms of renewable energy do not produce carbon dioxide and other harmful gases. Using more renewable energy sources would reduce carbon dioxide emissions and minimise global warming. Hydroelectric Power Hydroelectric power (HEP) uses the force of moving water to create electricity. However, HEP stations often require large dams , which disrupt ecosystems and displace people. HEP is the most widely used renewable source, providing 20% of the world's energy.
Solar Power The Sun provides the main source of energy for all living things. Solar energy is free and will never run out. We can use solar panels to turn the Sun’s energy into useful energy.
Wind Power Wind turbines harness the movement of air to produce energy. They are often found grouped together in wind farms.
Biomass This is the term used to describe plant materials and animal waste, which can be burnt for energy.
Problems <ul><li>1. What do the higher temperatures threaten dangerous consequences? </li></ul><ul><li>2. What causes the global warming? </li></ul><ul><li>3. What is the greenhouse effect? </li></ul><ul><li>4. How can renewable energy reduce global warming? </li></ul><ul><li>5. What are the benefits of wind power? </li></ul>
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