Climate Change

Climate Change

1. Climate

   • Definition: long-term atmospheric and surface conditions for area
   • long-term average of daily weather conditions
     • Typically takes decades or centuries to change a global climate
       • Intervals of...
         • hothouse/Greenhouse - much warmer climate
           • atmosphere composition
             • Greenhouse Gases
               • Carbon Dioxide (CO2)
                 • low atmospheric abundance is important because it absorbs sunlight reradiated from Earth's surface
                 • 0.04%
               • Nitrogen (N2)
                 • 78%
               • Oxygen (O2)
                 • 21%
               • Argon (Ar)
                 • 0.9%
               • Water vapor
               • Methane
               • Chlorofluorocarbon (CFC)
               • Greenhouse Effect
                 • Process of heat absorption by greenhouse gases in Earth's atmosphere
                   • Incoming sunlight enters atmosphere as visible light (short wavelength)
                     • Some sunlight absorbed by the Earth and is reradiated as heat energy (infrared radiation with longer wavelength
                       • Heat energy is absorbed by greenhouse gases, which results in warming
                 • Keeps Earth habitable
                 • Human activity has increases greenhouse gas abundance
                   • Controls on Atmospheric CO2 Abundance
                     • Volcanism
                       • Adds CO2
                       • volcanic eruptions release gases (mostly H2O, CO2, CO, N2)
                       • volcanic eruptions are the source of most gases in the atmosphere
                     • Burning Fossil Fuels
                       • Adds CO2
                       • burning any C-based fuel produces C)2 gas
                         • organic carbon + O2 --> CO2 (gas) + heat
                     • Photosynthesis
                       • Removes CO2
                       • Using light energy, plants convert CO2 gas into food (chemical energy)
                         • CO2 (gas) + sunlight --> Organic Carbon (sugar) +O2
                           • Reverse of fossil fuel combustion
                             • decrease of plants --> increase in atmospheric CO2
                     • Respiration
                       • Adds CO2
                       • reverse of photosynthesis
                       • plants and animals use stored chemical energy to carry out life functions
                 • Geologic Examples
                   • Early Earth/Early Precambrian (4.6-3 billion years ago)
                     • hothouse climate
                     • End of Mesozoic/Beginning of Cenozoic (100-50 m.y.a)
                       • hothouse climate
                       • caused flooding of continents)
                         • glaciers melt, sea levels rise
                       • high CO2 (7-10x more than today) from volcanism
                         • Rapid seafloor spreading
                         • opening of Atlantic Ocean
                       • Cenozoic Cooling (50-2 m.y.a)
                         • cooling
                         • Mainly due to plate tectonics
                           • India began to collide with Eurasia, causing enormous mountain range (Himalayas
                             • Himalayas caused chemical weathering of silicate and carbonate rock
                               • steep slopes eroded quickly and exposed fresh rock
                                 • decreased levels of CO2 gas, causing global cooling
                         • End of Paleozoic (250 m.y.a)
                           • Ice Age
                           • glaciers in several continents located near South Pole in single landmass (Pangea) with large temperature extremes
                             • Distribution of Land and Water
                     • Atmospheric CO2 abundance 98% (compared to current 0.04%)
                     • Atmospheric pressure 60 (compared to 1 today)
                     • temp. avg: 290 degrees C (compared to 16 today)
             • Volcanic Dust
               • Massive, explosive volcanic (ash fall) eruptions send huge amounts of dust-sized volcanic ash into stratosphere for months-years
               • Dust and associated SO2 gas oxidizes to sulfate aerosol, reflects sunlight and causes short-term cooling (months-years)
               • Tambora, Indonesia
                 • 1815 eruption - Largest historic volcanic eruption sent huge amount of volcanic ash and SO2 gas into stratosphere and caused global cooling
                 • 1816 - Year Without Summer
                 • Crop failure, worldwide famine, 90,000 deaths
         • icehouse/Ice Age - much colder climate

2. Importance

   • Effect on Sea Level
     • Future warming
       • if current glaciers melt, water (now on land) drains into the oceans
         • Sea level rises
           • floods coastal cities
     • Future Ice Age
       • If glaciers enlarge, ocean water transferred to land (ice)
         • lowers sea level
         • During previous Ice Age, glaciers connected Siberia and Alaska through a land bridge
         • Glaciers effect on Landscape
           • Carve Mountain Peaks
           • Formed Great Lakes
           • Flatten landscape and disposition of glacial sediment
           • Glaciers' Potential for Catastrophic Floods
             • as glaciers melted in the last Ice Age, created very large lakes
               • Lake Missoula, Montana
                 • dam of ice (glacial sediment) holding water suddenly gave way and huge amounts of water raced across Washington
                   • flood created Channeled Scablands
                     • rough, soil-free land (washed away by flood waters
                   • Ripples 10 feet high
                   • moved boulders
               • Starved Rock at the end of Illinois River
   • Impact on Agricultural Productivity, Ecosystems, Population Migration
     • if major global warming, some areas become much drier (others wetter), causing deserts
       • Decrease in agricultural productivity
     • if major glacier advance, huge impact on agricultural productivity and environmental refugees
   • Impact on Severe Weather and Tropical Diseases
     • if major global warming, increase in severe weather
       • Increase in tropical diseases, like sleeping sickness, malaria, and yellow fever
   • Predict Future Climate Change
     • Understand geologic past to help predict future
       • Inverse uniformitarianism
   • Effect of sun's intensity on climate
     • Sunspots
       • sun's energy dominant heat source to Earth's surface, variable solar energy received by Earth can affect climate
       • Solar energy can vary with sunspot activity
         • increased number of sunspots = slight warming
     • Albedo
       • Solar energy varies with reflectivity of Earth's surface
         • Dark surfaces (dark soil, deep blue equatorial seawater, green leaves) absorb more solar power
         • light surfaces (snow, ice, polar seawater) reflect more solar energy
           • as glaciers enlarge (increases snow and ice coverage), more sunlight is reflected and makes Earth colder
     • Variations in Earth's Orbit, spin, rotation
       • Variable solar intensity from regular variations in Earth's orbit explains regular oscillations of icehouse and hothouse climates over past 2 million years (Pleistocene)
       • glaciers restricted to polar latitudes