* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Global change problems
Climate sensitivity wikipedia , lookup
General circulation model wikipedia , lookup
Climate engineering wikipedia , lookup
Effects of global warming on human health wikipedia , lookup
Climate change mitigation wikipedia , lookup
Climate change and poverty wikipedia , lookup
Global warming controversy wikipedia , lookup
Snowball Earth wikipedia , lookup
Climate-friendly gardening wikipedia , lookup
Scientific opinion on climate change wikipedia , lookup
Low-carbon economy wikipedia , lookup
Surveys of scientists' views on climate change wikipedia , lookup
Climate change, industry and society wikipedia , lookup
Fred Singer wikipedia , lookup
Global warming hiatus wikipedia , lookup
Climate change in the United States wikipedia , lookup
Instrumental temperature record wikipedia , lookup
Attribution of recent climate change wikipedia , lookup
Public opinion on global warming wikipedia , lookup
Years of Living Dangerously wikipedia , lookup
Mitigation of global warming in Australia wikipedia , lookup
Physical impacts of climate change wikipedia , lookup
Global warming wikipedia , lookup
Politics of global warming wikipedia , lookup
Business action on climate change wikipedia , lookup
IPCC Fourth Assessment Report wikipedia , lookup
Ch 4. The three modern global change problems. 1 Earth has been changing and will continue to do so. It is changing faster today than it ever has. The major reason is human activity. 1. Ozone depletion; Ozone hole in South 2. 3. Pole deforestation; Greenhouse gases and global warming 2 Vertical Structure of the Atmosphere 4 distinct layers determined by the change of temperature with height 3 Zonally averaged, annual mean total column ozone in Dobson Units (DU; 1 DU = 2.69 × 1016 O3/cm2) from ground-based measurements combining Brewer, Dobson, and filter spectrometer data WOUDC (red), OME/SCIAMACHY/GOME-2 GSG (green) and merged satellite BUV/TOMS/SBUV/OMI MOD V8 (blue) for (a) Non-Polar Global (60°S to 60°N), (b) NH (30°N to 60°N), (c) Tropics (25°S to 25°N), (d) SH (30°S to 60°S) and (e) March NH Polar (60°N to 90°N) and October SH Polar. (Adapted from Weber et al., 2012; see also for abbreviations.) ENSC425/625UNBC 4 Global lower stratospheric departure of temperature from average since 1979, as measured by satellites. The large spikes in 1982 and 1991 are due to the eruptions of El Chicon and Mt. Pinatubo, respectively. These volcanos ejected huge quantities of sulphuric acid dust into the stratosphere. This dust absorbed large quantities of solar radiation, heating the stratosphere. 5 • Ozone depletion describes two distinct, but related observations: (1) a slow, steady decline of about 4% per decade in the total volume of ozone in Earth's stratosphere (ozone layer) since the late 1970s, (2) a much larger, but seasonal, decrease in stratospheric ozone over Earth's polar regions during the same period. 6 Image of the largest Antarctic ozone hole ever recorded (September 2006). 7 Ozone over Antarctic during Oct. 8 It shows a sharp drop beginning in the early 1970s. The graph to the left shows longterm ozone levels over Arosa, Switzerland. Although ozone levels rise and fall in natural cycles, the average level remained constant from 1926 until 1973. Beginning in 1973, however, and continuing through 2001, ozone levels have dropped at a rate of 2.3 percent / decade. 9 10 11 Why does a ozone hole form over Antarctica? • Firstly, strong winds blowing around the continent form, this is known as the "polar vortex" - this isolates the air over Antarctica from the rest of the world. Secondly, clouds form called Polar Stratospheric Clouds. Clouds turn out to have the effect of concentrating the pollutants that break down the ozone, so speeding the process up. 12 Why does a ozone hole form over Antarctica? The ozone hole is caused by the effect of pollutants in the atmosphere destroying stratospheric ozone. 13 Too much ultra-violet light can result in: • • • • Skin cancer Eye damage such as cataracts Immune system damage Reduction in phytoplankton in the oceans that forms the basis of all marine food chains including those in Antarctica. • Damage to the DNA in various life-forms. So far this has been as observed in Antarctic ice-fish that lack pigments to shield them from the ultraviolet light (they've never needed them before) • Probably other things too that we don't know about at the moment. 14 Deforestation Deforestation is the permanent removal of forest cover from an area, and the conversion of this previously forested land to other uses. 15 Deforestation affects Carbon balance Hydrological cycle Radiative energy balance Biodiversity 16 Statistics It has been estimated that about half of the earth's mature tropical forests — between 7.5 million and 8 million km2 of the original 15 million to 16 million km2 , have now been cleared since 1947. North America and Europe – already done 85% of old growth forests in US destroyed by settlers – most replanted Parts of Pacific NW and Alaska – deforesting now as fast as Brazil Canada: One case of deforestation in Canada is happening in Ontario's boreal forests, near Thunder Bay, where 28.9% of a 19,000 km² of forest area had been lost in the last 5 years and is threatening woodland caribou. This is happening mostly to supply pulp for the facial tissue industry. In Canada, less than 8% of the boreal forest is protected from development and more than 50% has been allocated to logging companies for cutting. 17 Tropics Rainforests 50 years ago covered 14% of the world's land surface and have been reduced to 6%, and that all tropical forests will be gone by the year 2090 Brazil – slash and burn; Amazon – 200% increase in deforested area from 1979 - 1988 Some scientists have predicted that unless significant measures (such as seeking out and protecting old growth forests that have not been disturbed) are taken on a worldwide basis, by 2030 there will only be ten percent remaining. 18 The reasons Disappearing at a rate of tens of thousands of square miles per year Land clearing in developing countries for farming and ranching (e.g., Brazil) Wood as a fuel (e.g., 90% of Africans use wood as primary fuel) Ballooning populations in developing countries 19 20 The effects Lowered oxygen production levels Increased CO2 Changed climate (radiation, temperature) and hydrologic cycle Landslides Loss of fauna associated with the forests Current extinction rate of 50,000 species per year Rate reflects fact that most fauna and flora in tropics are disappearing Loss of soil value for farming (formation of laterites) ; increased soil erosion (i.e., global erosion rate of 25.4 billion tons of top soil per year) 21 Dust Storm in Beijing, China on March 20, 2002. It lasted 52 hours. 22 Effects Cycle (vicious circle): deforestation soil erosion and loss of wood materials lowered productivity of soil and loss of wood source increased human needs enhanced deforestation e.g., 40-50 million trees removed in Haiti each year – correlates with 7x increase in food aid over last 20 years 23 Global warming 24 25 The balance of evidence suggests that there is a discernible human influence on global climate Intergovernmental Panel on Climate Change (United Nations), Second Assessment Report, 1996 26 There is new and stronger evidence that most of the warming observed over the last 50 years is attributable to human activity' Intergovernmental Panel on Climate Change (United Nations), Third Assessment Report, 2001 27 `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’ Intergovernmental Panel on Climate Change (United Nations), Fourth Assessment Report, 2007 28 Human influence has been detected in warming of the atmosphere and the ocean, in changes in the global water cycle, in reductions in snow and ice, in global mean sea level rise, and in changes in some climate extremes. This evidence for human influence has grown since AR4. It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century. Intergovernmental Panel on Climate Change (United Nations), Fifth Assessment Report, 2013 29 Discovery of the Greenhouse Effect Joseph Fourier (1827) Recognized that gases in the atmosphere might trap the heat received from the Sun. John Tyndall (1859) Careful laboratory experiments demonstrated that several gases could trap infrared radiation. The most important was simple water vapor. Also effective was carbon dioxide, although in the atmosphere the gas is only a few parts in ten thousand. Svante Arrhenius (1896) Performed numerical calculations that suggested that doubling the amount of carbon dioxide in the atmosphere could raise global mean surface temperatures by 5-6°C. Guy Callender (1939) Argued that rising levels of carbon dioxide were responsible for measurable increases in Earth surface temperatures. Estimated that doubling the amount of CO2 in the atmosphere could raise global mean surface temperatures by 2°C. 30 31 32 33 GREENHOUSE EFFECT? Glass allows visible radiation to pass through the glass which absorbs thermal radiation and re-emits some of it back into the greenhouse --- like a radiation blanket. 34 Radiation is emitted out to space by these gases from level somewhere near the top of the atmos. – typically from between 5 and 10km high. Here, temperature is much colder -30 – 50C or so colder than at the surface. => emitting less radiation to space. So: absorb radiation emitted from the earth surface but then to emit much less radiation out to space. 35 The enhanced greenhouse effect F = T4 = 5.67 x 10-8 W/m2/K4 average levels from which thermal radiation leaving the atmosphere originates 36 Component of the radiation (in watts per square meter) which on average enter and leave the earth’s atmos. and make up the radiation budget for the atmosphere. 37 38 39 40 41 Planetary energy balance • Earth is at steady state: Energy emitted by Earth = Energy absorbed • E emitted = (area of Earth) Te4 = 4 Re2 Te4 ..(1) (Te= Earth’s effective rad. temp., Re= Earth’s radius) • E absorbed = E intercepted - E reflected • Solar E intercepted = S Re2 (solar flux S) • Solar E reflected = AS Re2 (albedo A) • E absorbed = (1-A) S Re2 • (1) => 4 Re2 Te4 = (1-A) S Re2 42 Magnitude of greenhouse effect • Te4 = (1-A) S/4 • Te = [(1-A) S/(4 )]1/4 (i.e. fourth root) • Te = 255K = -18°C, very cold! • Observ. mean surf. temp. Ts = 288K = 15°C • Earth’s atm. acts as greenhouse, trapping outgoing rad. • Ts - Te = Tg, the greenhouse effect • Tg = 33°C 43 Greenhouse effect of a 1-layer atm. •Energy balance at Earth’s surface: Ts4 = (1-A)S/4 + Te4 ..(1) •Energy balance for atm.: Ts4 = 2 Te4 .. (2) S/4 Te AS/4 Te4 Atm. (1-A)S/4 Ts Ts4 Te4 Earth 44 Subst. (2) into (1): Te4 = (1-A)S/4 ..(3) (same eq. as in last lec.) Divide (2) by ; take 4th root: Ts = 21/4 Te = 1.19 Te For Te = 255K, Ts = 303K. (Observ. Ts = 288K) Tg = Ts - Te = 48K, 15K higher than actual value. • Overestimation: atm. is not perfectly absorbing all IR rad. from Earth’s surface. 45 • Weather forecasting also uses atm. GCMs. Assimilate observ. data into model. Advance model into future => forecasts. • Simpler: 1-D (vertical direction) radiativeconvective model (RCM): Doubling atm. CO2 => +1.2°C in ave.sfc.T • Need to incorporate climate feedbacks: • water vapour feedback • snow & ice albedo feedback • IR flux/Temp. feedback • cloud feedback 46 Water vapour feedback • If Ts incr., more evap. => more water vapour => more greenhouse gas => Ts incr. • If Ts decr., water vap. condenses out => less greenhouse gas => Ts decr. • Feedback factor f = 2. • From RCM: T0 = 1.2°C (without feedback) => Teq = f T0 = 2.4°C. Ts (+) Atm. H2O Greenhouse effect 47 Snow & ice albedo feedback • If Ts incr. => less snow & ice => decr. planetary albedo => Ts incr. snow & ice cover Ts (+) planetary albedo 48 IR flux/Temp. feedback • So far only +ve feedbacks => unstable. • Neg. feedback: If Ts incr. => more IR rad. from Earth’s sfc. => decr. Ts Ts (-) Outgoing IR flux •But this feedback loop can be overwhelmed if Ts is high & lots of water vap. around => water vap. blocks outgoing IR => runaway greenhouse (e.g. Venus) 49 Climatic effects of clouds • Without clouds, Earths’ albedo drops from 0.3 to 0.1. By reflecting solar rad., clouds cool Earth. • But clouds absorb IR radiation from Earth’s surface (greenhouse effect) => warms Earth. • Cirrus clouds: ice crystals let solar rad. thru, but absorbs IR rad. from Earth’s sfc. => warm Earth • Low level clouds (e.g. stratus): reflects solar rad. & absorbs IR => net cooling of Earth 50 • IR rad. from clouds at T4 • High clouds has much lower T than low clouds => high clouds radiate much less to space than low clouds. => high clouds much stronger greenhouse effect. 51 Uncertainties in cloud feedback • Incr. Ts => more evap. => more clouds • But clouds occur when air is ascending, not when air is descending. If area of ascending/descending air stays const. => area of cloud cover const. • High clouds or low clouds? High clouds warm while low clouds cool the Earth. • GCM’s resolution too coarse to resolve clouds => need to “parameterize” (ie. approx.) clouds. • GCM => incr. Ts => more cirrus clouds => warming => positive feedback. => Teq = 2 -5°C for CO2 doubling 52 Greenhouse Gases Water Vapor: Carbon Dioxide (CO2) CH4 methane, N2O = nitrous oxide... NATURAL GREENHOUSE EFFECT Evaporation = > water vapor Common name: marsh gas that can be seen bubbling up from marsh area where organic material is decomposing. plant and animal respiration, the decay of organic materials. 54 ENHANCED GREENHOUSE EFFECT The increase in carbon dioxide (CO2) has contributed about 72% of the enhanced greenhouse effect to date, methane (CH4) about 21% and nitrous oxide (N2O) about 7%. 55 • Water Vapor: source: evaporation from Earth’s surface location: the lowest 5 km of the atmosphere residence time: 10 days variation range: 0.1% - 4% roles in atmosphere: source of moisture for cloud; absorber of energy emitted by Earth’s surface: greenhouse gas. 56 Water Vapor • Naturally occurring greenhouse gas, generally unaffected by humans. Importance: The Clausius-Clapeyron relationship (shown below) suggests that warmer air can hold more water vapor. As the planet warms due to the greenhouse effect, more water vapor will change global climate conditions. By solving for water vapor (e), we can see that temperature (T) increases the amount of water vapor. Increased stratospheric H2O vapour causes the troposphere to warm and the stratosphere to cool and also causes increased rates of stratospheric O3 loss. Water vapour anomalies in the lower stratosphere (~16 to 19 km) from satellite sensors and in situ measurements normalized to 2000–2011. (a) Monthly mean water vapour anomalies at 83 hPa for 60°S to 60°N (blue) determined from HALOE and MLS satellite sensors. (b) Approximately monthly balloon-borne measurements of stratospheric water vapour from Boulder, Colorado at 40°N (green dots; green curve is 15-point running mean) averaged over 16 to 18 km and monthly means as in (a), but averaged over 30°N to 50°N (black) ENSC425/625UNBC 58 • Carbon Dioxide (CO2) source: plant and animal respiration, the decay of organic materials, and natural and anthropogenic (human-produced). Current concentration: 380ppm (parts per million, i.e., 0.038%); a global increase in recent decades. The increase in carbon dioxide (CO2) has contributed about 72% of the enhanced greenhouse effect to date, methane (CH4) about 21% and nitrous oxide (N2O) about 7%. 59 • Carbon is exchanged between the biosphere, lithosphere, hydrosphere, and atmosphere of the Earth. • Four reservoirs of CO2: atmosphere, ocean, biosphere and sediments. • Carbon cycle modeling. Models of the carbon cycle can be incorporated into global climate models, so that the interactive response of the oceans and biosphere on future CO2 levels can be modeled. Such models typically show that there is a positive feedback between temperature and CO2. 60 The “Carbon Cycle” There is a natural process by which carbon dioxide is cycled through the Earth's ecosystems and atmosphere. The blue arrows represent the natural processes by which living organisms emit and absorb carbon throughout their life and death (e.g. Respiration, photosynthesis, decomposition) The red arrows represent the “anthropogenic flux” which is a scientific term for the human effect on the carbon cycle, including industrialization and fossil fuel burning. "GtC" stands for GigaTons of Carbon • The land and ocean are large reservoirs to stock carbon than atmos. For example, the release of just 2% of the carbon stored in the oceans would double the amount of atmos. CO2. • At the time scales which we concern, CO2 is not destroyed but redistributed among the various carbon reservoirs. E.g., about 50% of an increase in atmos. CO2 will be removed within 30 years, a further 30% within a few centuries, and the remaining 20% may remain in the atmos. for many thousands of years. 62 63 The Human Footprint • 5% of the world's population resides in the United States, creating ¼ of the total greenhouse gas emissions. • For most people, their car is the main source of emissions. 22Lbs of CO2 is produced from every gallon of gas. Do the math: • Number of miles traveled by car each year _10000_ , divide by average miles per gallon = 15__ gallons of gas, multiplied by 22 lbs CO2/gallon of gas = _14667_ pounds of CO2 • The 1997 Kyoto protocol called for all people to limit their carbon emissions to 5.4 tons, or about 11,000 lbs, per year. • Some scientists believe that in order to reverse the damage caused by greenhouse gas emissions, we would need to reduce our individual emissions down to 5,000 lbs per year. Solving the Carbon Dilemma: What are some things that you can do to reduce your carbon emissions? Energy-efficient, energy-conserving electronics, lightbulbs, hardware and other devices are available for almost anything. You can expect that energy-efficient products are meant to last longer and will save you money. Reduce your dependency on cars! Greenhouse gases • Greenhouse gases (CH4 = methane, N2O = nitrous oxide): trap outgoing radiation from Earth’s surface • Coal burning Sulfur dioxide (SO2) acid rain. • SO2 Sulfate aerosol, reflects sunlight => cooling. • 1940-1970 cooling may be due to coal burning. • Coal burning incr. CO2 (long-term warming) and incr. sulfate aerosol (short-term cooling) [aerosol washed out by precip.] 66 CO22 (ppm) (ppm) CO 1000 1000 O (ppb) (ppb) NN22O 2000 2000 CH44 (ppb) (ppb) CH 67 From IPCC Report Atmospheric CO2 concentrations-past 1000 years. From “The earth system” 68 Anthropogenic greenhouse warming Atm. CO2: • Keeling started measuring atm.CO2 in 1958 on Mauna Loa, Hawaii • Seasonal cycle (forests absorb CO2 in summer & release CO2 in winter) + rising trend From “The earth system” 69 From “Global Warming” 70 * The most important of the aerosols from anthropogenic forcing are sulphate particles. * Cooling effect; * Life time: 5 days. So their effect is mainly confined to regions near the sources of the particles. From “Global Warming” 71 Red: removing sulphate aerosols in 2000; Blue: maintaining sulphate aerosols at the 2000 level. From “Global Warming” 72 • Some facts of global changes: (1) Global warming: Global mean surface temperatures have increased 0.5-1.0 F since the late 19th century; The 20th century's 10 warmest years all occurred in the last 15 years of the century. Of these, 1998 was the warmest year on record. The snow cover in the Northern Hemisphere and floating ice in the Arctic Ocean have decreased, sea level has risen 4-8 inches over the past century. 73 74 • Multiple independent indicators of a changing global climate. Each line represents an independently derived estimate of change in the climate element. In each panel all data sets have been normalized to a common period of record. A full detailing of which source data sets go into which panel is given in the Supplementary Material 2.SM.5. ENSC425/625UNBC 75 • Independent analyses of many components of the climate system that would be expected to change in a warming world exhibit trends consistent with warming (arrow direction denotes the sign of the change), since 1970s. ENSC425/625UNBC 76 Figure SPM.2 LOSU: assessed level of scientific understanding From IPCC report 77 78 The three serious problems The three modern global change problems discussed in this chapter-- global warming, ozone depletion, or loss of biodiversity 79 The ozone depletion is the serious problem because: • It causes the most immediate damage to our planet and its inhabitants • It can cause skin cancer • It occurs faster than global warming, because global temperatures only rise 1 degree in 100 years so this is an insignificant amount compared to the decline in the total amount of ozone 80 • Low-level ozone damages plants, reducing their capacity to take up carbon dioxide and accelerating global warming. The study suggests that projected increases of ozone concentration from industrial sources will markedly reduce plant productivity. This indirect effect could contribute significantly to global warming. (Nature, 16, August 2007, by S. Sitch, P. M. Cox, W. J. Collins & C. Huntingford) 81 The loss of biodiversity is the serious problem because: • There is potential for recovery for the other problems: the ozone layer could recover within a few generations and greenhouse gas concentrations should return to “normal” within a few million years. • The recovery rate for species following extinction is tens of millions of years. • Once a species is gone, it is gone for good. • It could cause an imbalance in the Earth’s ecosystem and economy. • Deforestation also contributes to global warming. 82 Global warming is the serious problem because: • It affects the greatest number of people • Migration of marine animals could result • Rising sea level could result • Cold climate species might die • Ozone depletion and deforestation are both confined to particular areas whereas global warming is truly global 83