EESA05 - Environmental Hazards - Lec 9 (near-verbatim).docx

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Department
Environmental Science
Course
EESB18H3
Professor
Mandy Meriano
Semester
Fall

Description
EESA05 Lecture 9: Climate Change PY Date: Nov 13, 2012 Slide 2: Climate Change – Who Cares?  Usually hear apocalyptic stories because of climate change  But it has happened throughout Earth’s history – several periods of cooling & warming (cold and hot houses); difference now is that there’s so many humans on the planet now and we’ve had significant impact on rate of climate change  Models and using historical records – to understand how systems work  Climate models – so many factors and so much uncertainty in so many of the variables – the results/predictions are questioned Slide 3: Areas Threatened by Climate Change  Climate change kills 150,000 ppl  Arctic regions is one of the areas mostly affected (esp with warming trend) – Canada should be concerned with this o Arctic – have permafrost – layer that is frozen throughout the year – can be from 1-2 m thick to 150m thick  Warming trend – permafrost will thaw  There’s layer on top of permafrost = active zone/layer – actually thaws in summer months and re-freezes again; whereas the permafrost doesn’t thaw at all = frozen for 1000s of years  With warming trend and permafrost actually melts  Permafrost provides us with lot of stability in Arctic and sub-Arctic b/c it is hard – can drill into, can put up structures, build airports – everything in Arctic built on permafrost  Permafrost provides stability for ecosystems  In terms of surface water flows and groundwater flows – makes huge difference; if hard, a lot of the run-off during summer will run-off the frozen surface of permafrost ground; if melted permafrost – get more groundwater circulation, more groundwater recharge – behavior of groundwater and surface water therefore changes  Might disappear because if permafrost melts, may just seep into the ground and with them whatever ecosystem they support will also disappear  Permafrost = very important  Arctic and sub-Arctic regions are also impt carbon reservoirs  Lot of organic matter throughout earth’s history now trapped in permafrost – hasn’t been able to decompose; if you heat it up, get accelerated decomposition of organic matter  So far, arctic has been carbon sink but if things dramatically change – get major permafrost melt – then arctic becomes major carbon source  Cali (fire and flood) o An effect of warming – more droughts, drier summers – causes forest fires 1 EESA05 Lecture 9: Climate Change PY Date: Nov 13, 2012 o Warming trend and not enough precipitation – forest fires  Maldives (sea level rise) o Sea level rise due to ice melting – a lot of these islands = vulnerable to any sea level change o Maldives = built sea wall around island to protect - every square meter = $4000 Slide 4: Climate Change – Who Cares?  If the rate of change goes beyond what our ecosystems can handle (carrying capacity of economy or ecosystem) = bad  Upward trend to continue = increase in damage to our economy due to changes in climate (floods, hurricanes)  Graph – see year vs. millions of dollars spent; huge increase in amount of losses ($30B)  Ranking based on dollar value of damage; even with smaller intensity storm – can have greater damage – more of us living on coastlines, urbanization  Reasons: o Growing values o Value concentration in coastal areas o Changing hazard cycles and trends  Ex) natural and man-made climate change Slide 6: Earth’s Present Climate  The most important factor controlling the Earth’s climate is solar NRG o If we didn’t have solar NRG – nothing would be here – cold place  The earth receives solar heating unevenly o Insulation = amount of solar NRG that a surface receives o Not every place receives same insulation amount – differential heating of the planet – very impt in how planet it works/reacts  Near the equator the Sun’s rays impinge at near-vertical angle, making the earth warmer there; temperature doesn’t change much; for the most part – regular, consistent temp patter – the sun’s rays hit that area @ right angle o Not the same everywhere else b/c there’s tilt to Earth’s rotational axis = 22.5 degrees – this tilt angle results in surface of Earth not getting same amount of solar rays in diff regions  Near poles, the Sun’s rays strike at an oblique angle, making Earth cooler in those regions  With this uneven heating of surface – certain areas are warmer than other areas – temperature gradient; heat from warmer areas migrates towards cooler areas – get stability in temperature pattern – transfer of NRG around globe to ensure that equator doesn’t get hotter and hotter and the poles don’t get colder and colder  Diagram: o Equator getting most solar NRG throughout year – get greater heating of surface, air and water 2 EESA05 Lecture 9: Climate Change PY Date: Nov 13, 2012 o Warm air = lighter and rises around equator; as air rises (you can thermodynamically make something hotter or cooler by adding/removing heat from it) but there are other ways of changing temp or gas/air mass  When air rises, it actually starts to cool down – adiabatic cooling because it expands  As it expands – gas mocs moving further and further away from one another – there is adiabatic cooling (=changing temperature of mass of gas by changing its pressure – if reduce its pressure, the gas mocs move further apart – cools down)  It rises and then it cools, as it cools, it starts to descend back towards the earth b/c cooler air mass = more dense – moves back into surface  As it moves back into surface – then adiabatic warming comes into play – gas mocs getting closer and closer – so gas mass gets warmer  So as gas gets warmer and comes down around 30 degrees latitude – N and S – find all the deserts around this region b/c this is where = warm/dry air  As the air rose (which had moisture) – got cooler and the moisture of air mass comes out = precipitation and that’s why around equator – get lush forests – because the hot air that is moist is going up and cooling and moisture comes out and as the air mass moves and then comes back down it is much drier and warmer air mass (in 30 degrees latitude) o Doldrums = horse latitude = 30 degrees latitude  Called doldrums b/c not much wind there (sailors – called it this)  Horse latitude – ships weren’t moving b/c lack of wind; to get rid of weight to move the ships, they threw their horses off  This area = most of the deserts o It is a cycle and then it goes to 60 degrees latitude etc; o Southern hemi exact same as Northern hemi Slide 7: Earth’s Present Climate  Uneven solar heating warms the Earth more near equator, causing the warmer air to rise  Conversely, cool air near the poles tens to sink  The rising and sinking of air causes winds – horiztonal flows of air away from areas where air sinks and toward areas where air rises Slide 8: Earth’s Present Climate  Prevailing winds are persistent winds that ten to blow the same direction most of the time  Winds are affected by the Coriolis effect, which is an observed deflection of wind direction caused by the rotation of the Earth o In Northern hemi – deflection towards right o In southern hemi – deflection towards left  So air mass goes up but coriolis effect will force you over to the right – get deflection in air masses 3 EESA05 Lecture 9: Climate Change PY Date: Nov 13, 2012  Trade winds around equator – change in the strength of trade winds  el nino  Polar cells, walker cells etc; there are circulation cells Slide 9: Earth’s Present Climate  Where air rises (warm moist) consistently, we have areas of high precipitation o Warm, moist air rises  precipitation comes out  cooler, dry air  sinks  gets warmer; happens @ zero and 30 degrees and 30 & 60 degrees in North & South hemi  Conversely, where air sinks persistently, we have areas of low precipitation, b/c as air sinks, it compresses and warms up, making it unlikely for water vapor to condense to rain or snow  Adiabatic warming and cooling Slide 10: Earth’s Present Climate – Animation  What happens in a year  Equinox – equal day and equal night; 2 equinoxes per year (in Spring and Fall) o Tilt in Earth’s rotational axis (22.5 degree) o Sun o Dashed line = plane of ecliptic = Earth’s orbital path around the sun o As Earth moves around the sun o In Northern hemi – our summers – this tilt is kind of more tilted, more sun hitting the Northern hemi  Earth @ June solstice = longest day of year in Northern hemi; opposite in South o Earth for June solstice – closer to the sun – very impt; if it didn’t tilt closer to the sun and during our summers if the tilt was further from sun – things will dramatically change – summers much colder  Tilt of the Earth’s rotational axis is very impt  Going around the sun, then expect autumn equinox  We have winter solstice then o Longest night of year, shortest daylight o Now, northern hemi is @ its furthest away from the sun – nighttime for around 6 mths o Orbit & tilt are impt Slide 11: Earth’s Present Climate  Albedo is a measure of reflectivity o We have a lot of solar radiation coming to surface but some is reflected back – depends on how reflective surface is o Albedo – 0-1 = 0 to 100% o Clouds, ice, vegetation have certain amount of reflectivity o Water is interesting in terms of reflectivity b/c depends on if there are any ripples or waves; water also has very large heat capacity – takes up a lot of solar radiation and not a completely reflective surface  It reduces the amount of NRG that reaches the Earth’s surface 4 EESA05 Lecture 9: Climate Change PY Date: Nov 13, 2012  Albedo is generally caused by clouds or snow and ice cover  Greater cloud or ice cover reflects away more heat  Average reflectivity of whole planet = 30% - so 30% of solar radiation that we receive surface reflects back  NRG balance of the planet – so much of it is reflected back o The solar radiation that reaches us 342 Watts per square meter  measure of NRG o If you reflect 30%  235 Watts per square meter o We actually have a lot more than what we actually get Slide 12: Earth’s Present Climate  Winds drive surface ocean currents, which travel in roughly circular paths in each ocean basin, carrying warm water away from the equator towards the poles o This uneven distribution of heat somehow has to move around the planet – winds are some of the most effective ways of – moving further up to the Arctic o Another way that heat is transferred around the globe is by ocean currents – water takes up so much heat; temperature is a driver of that but so is salinity o Saltier water = more dense than fresh water – will sink; density difference drives ocean currents that transfer the NRG around the globe  In addition to ‘evening out’ heat distribution, ocean circulation also evens out salinity over oceans  In the tropics, evaporation is intense and the ocean is salty, so that warm, salty water flows towards the poles to mix with the less saline waters there (from precipitation and glacier melting)  Ocean water moderates against large changes in temperature so that climates in coastal regions tend to be much more stable and moderate than climates in regions far from the ocean Slide 13: Earth’s Present Climate  Animation shows ocean currents – how they move around the equator  Vortices of water – mvt  Subtropical gyres  Equatorial – going around equator – warmer waters and then have high latitude currents around poles  With wind: o Same as b4 with circulation cells o Trade winds (impt 4 climatic changes – el nino) & westerlies (winds moving from west to east) Slide 14: Earth’s Ancient Climate  Earth’s climate hasn’t always been so pleasant  We didn’t have right proportion of atmospheric gases that we have right now  Earth may have been much like Venus (T = 477 degrees Celsius) 5 EESA05 Lecture 9: Climate Change PY Date: Nov 13, 2012  Earth used to be very hot, inhospitable, didn’t have a proper ozone layer to protect from incoming solar rays/other cosmic things (solar winds, magnetic fields) o Protect ourselves from UV rays, visible light, infrared  what we get from sun o Some of it is reflected back by Earth o Water vapor, CO2, nitrogen oxides, methane, chlorofluorocarbons (we introduced to enviro from fridges, aerosols etc;)  greenhouse gases o CO2 also introduced by us b/c burning fossil fuel o Methane  from cattle, rice paddies o If any changes in permafrost can have both CO2 and methane be put back into atmosphere o Infrared goes back and forth and is trapped in the atmosphere by greenhouse gases o Altogether  warming, cozy enviro for us created  If Earth was just a chunk of rock – avg temp = -18 deg Cel  Earth isn’t like Venus now because its atmospheric composition has changed  Mars and Venus haven’t changed Slide 15: Earth’s Present Climate – Atmospheric Composition Constituent % by volume Nitrogen 78.084 Oxygen 20.946 Argon 0.934 Carbon Dioxide – Greenhouse gases 0.035 Neon 0.00182 Helium 0.000524 Methane – Greenhouse gases 0.00015 Krypton 0.000114 Hydrogen 0.00005 Water vapor = greenhouse gas and it is the highest quantity of greenhouse gas in the atmosphere Greenhouse gas – traps heat (like winter coat- doesn’t produce heat itself, but trap it in – like greenhouse gas); the long?? wave sun radiation – some reflected back right away but some reaches our surface but some of it is trapped  Increasing trend in concentration of CO2  CO2 280ppm @ the beginning of graph; currently @ 375 ppm CO2 o Increase since mid-1900s  lots of fossil fuels burned, industrialization o Continuous growth in CO2 concentration o Is there relationship btn CO2 concentration & temperature? o Yes, there’s correlation  b/c CO2 is greenhouse gas o Human & anthropogenic causes CO2 into atmosphere o Can CO2 be taken up by anything? Yes, just as there are sources of CO2, there are also sinks of CO2 6 EESA05 Lecture 9: Climate Change PY Date: Nov 13, 2012  One of the greatest sinks of CO2 = ocean  takes up a lot; deposits on corals (microorganisms)  Big sink of CO2 is the ocean and the removal of it from the water by microorganisms and creating all the limestone that we have – has a lot of CO2 in it (trapped)  When there is subduction of these carbonate rocks (limestone), some of it does go back into the mantle and CO2 is released into mantle and comes back up thru volcanic activity  Limestone in ocean – not all get subducted; some of it gets uplifted; can find limestones on peaks of mountains b/c of uplift o Groundwater can also hold CO2 and carbonate material; can take in so much  becomes supersaturated (dissolve a lot more material than it normally can; there’s some circumstance that allows this to happen – temp/pressure)  When enviro changes, carbonates comes out Slide 16: Earth’s Present Climate – Greenhouse Effect  Earth’s History in terms of climate change  Graph: o Diff geologic periods o Today = Holocene (last 10,000) o Pleistocene = last 2 million years o Versus temperature o In the past 600 million years – back and forth – warming and cooling o Present – there’s some warming but we are actually in a cooling stage – more than 20% of planet’s surface is covered by ice; whenever you have 30%+ ice coverage = ice house o In the global climate trend – we’re in a cooling period o What does this mean? o About 11 000 million yrs ago – had supercontinent – Rodinia – first supercontinent we had – had one ocean – and then Rodinia broke up and the one ocean changed too; continents scattered and then merged again 500 million yrs ago to 200mya – Pangaea  So distribution of continents around the Earth also has an effect on the cooling & warming trends  Most recently in Pleistocene – had serious glaciations and deglaciations – period where you go for glaciation but you get some kind of warming – some melt – interglacial barrier o Laurentide ice covering N.America o Within most recent Earth history – had several glaciations o Glaciers are like frozen rivers – they are strong, pulled up by gravity, pick up whatever’s in their way and put it somewhere else – learn about these deposits o Glaciers are also found in high altitudes even if in warmer area Slide 18: Removing CO2 from an Atmosphere 7 EESA05 Lecture 9: Climate Change PY Date: Nov 13, 2012  A combo of biological and geological processes have removed CO2 from the atmosphere throughout Earth history  On Earth, most of the CO2 that has been removed from the atmosphere is stored in limestone (carbonate rock)  Some of this limestone is subducted into the mantel, where it is broken down into CO2, which may be released by volcanism, but some is uplifted permanently onto land Slide 19: Climate Change – The Long View  On the longest timescales, climate change has been dominated by the gradual decrease in CO2 content of the atmosphere and tectonic processes  The decline in [email protected] has led to long-term cooling trend  Tectonic processes cause climate change in 2 ways: o Episodic formation of supercontinents o Latitudinal distribution of continents Slide 20: Climate Change – The Long View  More recently, climate has been cooler than at present  Past glaciations are evidence of global climate change  Glaciations have been frequent over the past 2.5 Myr Slide 21: Glaciers and Glaciation  The advance and retreat of glaciers over time provides important evidence of past climate change  Glaciers form at high altitudes (in mountains) and at high ___ (as polar ice sheets)  Glaciers today cover about 10% of the world’s land surface  During the Ice Ages, glaciers covered up to 30$ of the land surface Slide 22: Glaciers and Glaciation  Glaciers grow in high areas where snow accumulates – the zone of accumulation o If no snow adding to ice mass (glacier) then won’t get growth  The ice flows slowly downhill, carrying vast amounts of rock debris  Glaciers lose ice in their lower areas at the zone of ablation, where the rate of melting exceeds the rate of accumulation o Sometimes balance o If increase in zone of accumulation – then it grows o If melting increase – lose ice; the water gets put into ocean – can really change ocean – salinity of water will change – reduce salinity – will interfere with ocean circulation o Annually, 8mm of ocean gets put back into glaciers o But there’s balance o If we were to lose all 20% of the ice that we have right now – sea level increase by 80m – devastate coastal communities 8 EESA05 Lecture 9: Climate Change PY Date: Nov 13, 2012  Glaciers may also lose mass by calving icebergs where the glaciers flow into the ocean Slide 23: Glacier action  Snow falling @ higher altitude area  Snow accumulates, with enough time, compression & pressure (if it doesn’t melt everywhere) – becomes glacier (is blue)  River of ice in valleys of mountains – this river of ice is actually flowing due to gravity  Glacier moves down; as it moves down, picks up things underneath it  Wastage zone = zone of ablation – zone below snow line o As it loses mass, it starts to retread; deposits load that it picked up previously (brown) and there’s glacial run-off (blue)  Deposits called moraine (engrained deposits)  Plucking = when ice moves on the surface and starts breaking up the bed and starts to pluck bits and pieces of the material up and it carries this material o Video:  Deposits  Left over of glacier that was there  Lines = striations as the glacier moves, they scratch surfaces of rocks – evidence that glacier was there and direction of mvt  Melt water deposits  Other deposits – snaking ridges = another glacial deposit – esker d
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