Textbook Notes (363,062)
Canada (158,169)
Geography (105)
GG231 (31)
Rob Milne (27)
Chapter 12

Chapter 12 - Climate Change/ Drought, Heatwaves, Famine

8 Pages
Unlock Document

Wilfrid Laurier University
Rob Milne

Chapter 12 and 9 – Climate Change & Drought and Famine  Arctic threatened by climate change o Aboriginal peoples of N. Canada have witnessed marked warming of climate, decrease in Arctic sea-ice cover, increased permafrost thaw and erosion of coastal villages o Arctic ocean will be ice free by middle of 21 century if melting rate continues o Seasonal sea ice averages 2m, used to be 3m o Melting may contribute to even higher Arctic temperatures in the future  Harmful to some northern animals o Calving of Canadian, Greenland and Antarctic ice shelves o Local warming in Canadian Arctic will exceed 3C during this century  If entire ice were to melt, global sea level would rise by 7m  Climate and Weather o Climate – atmospheric characteristics of a region over years or decades o Weather – atmospheric conditions of a region for shorter periods (days or weeks) o Climate is more than averages of temperature and precipitation  Two locales may have similar temperatures but different climates  Climate has warmed over most of the earth during the past century  Magnitude differed considerably from place to place o Some areas more wet, some more dry  The Atmosphere o Atmospheric composition  Comprises of nitrogen, oxygen and smaller amounts of other gases  Permanent gases o Concentrations do not change  Variable gases o Proportions of which vary in time and space  Permanent gases  Constitutes about 99% of all atmospheric gases o Nitrogen, oxygen and argon  Nitrogen plays an important role in climate when combined with other gases o Forms 78% of atmosphere o Especially oxygen  Oxygen is second largest component o Forms 21% of atmosphere  Argon third component o Last 1% of atmosphere  Contains small amounts of neon, helium, krypton, xenon and hydrogen  Variable gases  Constitute small portion of total mass of the atmosphere  Include carbon dioxide, water vapour, ozone, methane, nitrogen oxides and halocarbons  Carbon dioxide o Very small percentage, concentration very low o Part of the biogeochemical cycle o Released naturally through volcanic activity, plant/animal respiration, wildfires and organic material decay  Also through burning fossil fuel o Removed by plants, chemical weathering and sea water absorption o Concentration increasing since the Industrial Revolution  Production greater than absorption  Water vapour Brian Kwok 1 Chapter 12 and 9 – Climate Change & Drought and Famine  Produced by evaporation of water at Earth’s surface  Condenses to form clouds  Temperature primary control of the amount of water vapour in the atmosphere o Warm air increases evaporation  Holds more vapour than cold air  Ozone o Forms when oxygen atom bonds with oxygen molecule o Mostly found in stratosphere o Shields earth from UV radiation o Ozone in stratosphere protects us o Zone in troposphere, produced by smog, irritates lungs and eyes  Methane o Major component of natural gas o Forms through bacterial decay in moist places that lack oxygen  Marshes, swamps, bogs, coal mines, oil wells, rice paddies, landfills, livestock o Stays in atmosphere for about 12 years  Major contributor to global warming  Nitrogen oxides o Present in troposphere and stratosphere o Natural sources include microbiological processes in soils, oceans, wildfires and lightning strikes  Automobiles, power plants, aircrafts, fertilizers  Average residence time of about 114 years  Contributes to global warming  Halocarbons o Contain carbon and halogen elements o Entirely anthropogenic  Used in industrial processes, firefighting, fumigants, refrigerants and propellants o 25-100 years in atmosphere o Contributes to warming in troposphere and ozone depletion  Aerosols o Not gases, but microscopic liquid and solid particles in atmosphere o Natural sources include desert dust, wildfires, sea spray, volcanic eruptions  Burning forests, fossil fuel consumption o Can cause cooling or warming of war o Structure of the atmosphere  Troposphere – much of heat radiating from earth trapped here  Stratosphere – dry layer where water vapour occurs as ice crystals  Mesosphere and thermosphere – far from earth’s surface, little impact on climate and natural hazards o Atmospheric circulation  Warm air rises in troposphere in equatorial areas and moves north or south  Creates regions of high and low pressure near N. and S. poles  Wind produced by movement of air from high to low pressure areas  Climate change o Evidence that earth is warming is unequivocal o Most of the warming occurred between 1995-2010  Sea-surface temperatures rose Brian Kwok 2 Chapter 12 and 9 – Climate Change & Drought and Famine  Glaciers have receded  Permafrost is thawing o Global warming – concluded 90% that humans have contributed to it o Complex and far-reaching effects on planet’s environment  Changes caused by climate warming too rapid for many organisms to adjust o Cryosphere – frozen part of hydrosphere  Snow, sea and glacier ice, permafrost  Changes can impact climate o Glaciers – forms ice sheet flow from high areas to low areas under their own weight  Have inputs and outputs  Inputs – snow turning into ice  Outputs – melting, sublimation and calving of ice blocks  Advance when input greater than output o Alternates between glacial intervals and interglacial intervals  Glacial – continental glaciations  Interglatial – warmer climate with less ice coverage o Glaciations  Many glacial intervals, characterized by repeated advances and retreats of ice sheets  Pleistocene Epoch – last glaciations period  Covered about 30% of land area  Global sea level 130 m lower than today’s levels  Holocene Epoch – interglacial interval we live in today  Began 116000 years ago  10% covered by ice  Causes of glaciations  No single factor can explain glaciations, result of several factors  Positions of continents affect ocean and atmospheric circulation  Milankovitch cycle o Shape of earth’s orbit around sun o Tilt or wobble of the earth o Precession of the equinoxes o Can be combined to determine net changes in radiation that any point on earth receives  Correlate well with major advances and retreats o Greenhouse effect  Surface temperature determined by three factors  Amount of sunlight planet receives  Amount of sunlight reflected  Degree to which atmosphere retains heat  2/3 of radiation passes atmosphere and reaches surface of planet  Absorbed and warms surface and atmosphere  Some radiated back into atmosphere  Earth surface would be much colder than it actually is without the greenhouse effect  Layers of atmosphere act similar to glass in greenhouse  Greenhouse gases – carbon dioxide, methane, nitrogen oxide gases o Increases warming o Carbon dioxide accounts for 56% of anthropogenic greenhouse effect  Cores of glaciers have been recovered, air bubbles trapped show atmospheric air at the time of freezing o Global climate change over the past 800 000 years Brian Kwok 3 Chapter 12 and 9 – Climate Change & Drought and Famine  Reconstructed climate over past 800 000 years from changes of air in cores  Low temperatures coincided with major continental glaciations, high temperatures with interglacial intervals  Last major interglacial interval about 125 000 years ago  Total increase in global mean temperature since 19 century is about 0.8C, half of the increase in the past 25 years  Average global surface temperatures during the last few decades warmer than any comparable period in preceding four centuries and possibly past 1000 years  Average temperature in Canada warmed up 0.8C since 1900, arctic warmed much more than southern part  Small area of eastern Canada even cooled over this period  Larger-than-average increases in high mountain ranges  Predicted that many ice caps/mountain glaciers in Africa/S.America will disappear in next 10 years o Climate change on short timescales  Forcing factors – factors that influence climate on short timescales  Ocean circulation  Ocean conveyor belt – global-scale circulation of ocean waters o Climate system able to change so rapidly because of this  Carries warm surface waters northward, cools and becomes more saline as it approaches Greenland o Salt water that cools sinks to bottom and flows southward along the seafloor to around Africa  Heat from conveyor belt sufficient to keep N. Europe 5C-10C warmer than it would be if it didn’t exist  If conveyor belt shut down, planet would cool and N. Europe and E. Canada would become less habitable  Solar forcing  Variations in solar output should be evaluated as cause of climate change as sun is source of most of Earth’s surface heat  Found a way to estimate changes in solar output by looking at carbon-14 in tree rings  Measuring concentration of carbon-14 in tree rings of a known age, can determine changes in solar output back through time  Variability of energy output from the sun can partially explain climatic variability during past 1000 years o Effect is small  Volcanic forcing  Eruptions introduce large amounts of aerosols into atmosphere  Particles reflect sunlight and can cool atmosphere 
More Less

Related notes for GG231

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.