Global Warming
Midterm 2 Scores Class average: 40/50 # of students Exam score
Learning Objectives (LO) Lecture 19: Global Warming and Energy Use Read: Chapter 14 Homework due Thursday Nov. 5 What we ll learn today:! 1. 1. Describe the geologic time scale and how it is organized!
Mass Extinctions Influence the Evolution of Life.
Geologic Time! Major divisions! Cenoz66-2.5 m.y.a Cenozoic! Mesoz245-66 m.y.a. Mesozoic! Paleo542-245 m.y.a. Paleozoic!! pre-542 m.y.a Precambrian!
Precambrian (4.6 Ga 542 Ma)! Comprises 88% of Earth History! First continents, plate tectonics! Rock record poorly preserved! Life evolves, but rarely preserved as fossils!
Paleozoic Era (542 Ma - 245 Ma)! Continents are widely separated! Continents collide - Pangea! Reptiles & amphibians!
Mesozoic Era (245 Ma 66 Ma)! Breakup of Pangea! Opening of Atlantic Ocean! Dinosaurs, mammals, flowering plants!
Cenozoic Era (66 Ma - present)! Mammals & grasses! India-Asia collide! Australia moves N.! Rocky Mts. form!
Learning Objectives (LO) Lecture 19: Global Warming and Energy Use Read: Chapter 14 Homework due Thursday Nov. 5 What we ll learn today:! 1. 1. Describe the cause of modern climate change! 2. 2. Describe how heat distribution on Earth depends on circulation in the oceans and atmosphere! 3. 3. Explain what causes the amount of greenhouse gas in the atmosphere to change! 4. 4. Identify human activities that contribute to climate change!
The Climate Crisis
The Greenhouse Effect 1) Carbon dioxide 2) Water vapor 3) Methane 4) Nitrous oxide Solar Radiation Powers the Climate System
Industrial Pollution
Deforestation
2014 hottest year on record http://www.giss.nasa.gov/research/news/20150116/
Day After Tomorrow Map: Ideas about what will happen if global average temperature rises by 4 C
Climate: long-term average weather pattern in a region Climate Change: any large-scale change in climate over time Global Change: changes to climate on a whole-earth scale
Structure of Earth s Atmosphere We live in the troposphere
Atmospheric Convection: Hadley cells explain global wind patterns On Earth: Three Cells Trade winds are part of the Hadley Cell
Hadley Cell Circulation Explains approximate locations of deserts and rainforests Exceptions: based on topography, ocean circulation, local wind patterns, continental shapes Equator
The Global Ocean Thermohaline Circulation: Ocean circulation depends on ocean geometry, seawater temperature, and seawater salinity
The Greenhouse Effect Determines Earth s Heat Budget
The GreenHouse Effect http://www.youtube.com/watch?v=hi3eres0h84
The Greenhouse Effect greenhouse ~ car parked outside all day (in the sun) Glass windows/roof allow sunlight to enter, be absorbed, & heat up car/greenhouse Warmed interior radiates energy back - infrared waves (longer wavelengths) infrared HEAT Glass is opaque to infrared energy - the heat is trapped sunlight in HEAT infrared out
Greenhouse Gases Certain gases act like glass in a greenhouse/car Gases transparent to visible energy (sunlight) but opaque to infrared energy - carbon dioxide - methane - nitrous oxide - water vapor
Consider the Energy Balance of an Average Square Meter Incoming radiation: about 250 Watts Outgoing radiation: about 250 Watts in steady state Solar Radiation is equivalent to 2.5 100 watt bulbs for every square meter Additional greenhouse gasses absorb more heat: Outgoing radiation is slightly smaller! Result: Each meter of Earth is heated by about 0.6 Watts (one christmas tree bulb) James Hansen Explanation: (6:00-11:00): http://www.ted.com/talks/james_hansen_why_i_must_speak_out_about_climate_change.html
Greenhouse Gases Carbon Dioxide: Most abundant, long-lived Methane: Powerful greenhouse gas, short-lived CFCs: Being phased out Ozone: Very short lived Nitrous Oxide: Increasing
Greenhouse Gases: Abundance Through Time
The Keeling Curve: Atmospheric Carbon Dioxide Through Time Pre-industrial Levels: 280 ppm Ralph Keeling, UCSD May 2013: Reached 400 ppm for the first time!
Carbon Dioxide and The Green House Effect http://www.youtube.com/watch?v=pjpk8orzqyu
Where is Carbon Dioxide Coming From? Increase in atmospheric Carbon is caused by burning of fossil fuels (~6 Gt C/yr) Eventually, this carbon will become dissolved in seawater, but the process is slow Storage volumes (Giga-Tons of Carbon) Flux Ranges (Giga-Tons of Carbon per year)
Human Activities are Increasing Atmospheric Carbon Dioxide
The Long-Term Carbon Cycle Removal of Carbon from surface systems: Chemical weathering (removes from atmosphere) Limestone formation (removes from oceans) Burial of organic sediments (Oil and Coal) Addition of Carbon to surface systems: Volcanic Outgassing (of subducted carbon)
Temperature and atmospheric carbon dioxide are tightly linked Climate Records from Ice Cores
The Ice Ages Caused by changes in solar radiation Changes in atmospheric carbon dioxide were caused by the temperature changes. We are doing the reverse experiment today: Carbon dioxide changes causing climate change
Global temperatures have increased with Carbon Dioxide