Chapter 18

• Saltwater intrusion


  Saltwater bubbling up from the ground and flooding the streets, sidewalks, and lawns
• Saltwater intrusion is a relatively new phenomenon in Miami, the result of rising sea levels caused by global climate change
• The world's oceans rose 20 cm in the 20th century as warming temperatures expanded seawater and caused glaciers and ice sheets to melt
• All coastal cities are facing challenges from flooding and increased storms that arise from the sea level increase
• Southern Florida


  • Lies on flat, porous limestone, making it especially vulnerable to flooding from the ocean
• Climate


  An area's long-term atmospheric conditions, including temperature, precipitation, wind, humidity, barometric pressure, and solar radiation
• Factors that influence climate

  • The sun, which provides light and warmth
  • The atmosphere, which prevents major temperature shifts from night to day
  • The oceans, which store and transport heat and moisture
• The sun supplies most of the Earth's energy, which the atmosphere absorbs or reflects most of it before it even reaches the surface
• Aerosols


  Microscopic droplets that can have either a warming or cooling effect when present in the atmosphere
• Soot particles ("black carbon aerosols") cause warming by absorbing solar energy, while most other aerosols (such as sulfur) reflect solar energy and have a cooling effect
• Greenhouse gases


  Atmospheric gases having three or more atoms in their molecules that tend to absorb infrared radiation given off by the Earth's surface and re-emit it back downward
• Greenhouse gases


  • water vapor (H2O)
  • carbon dioxide (CO2)
  • methane(CH4)
• Global warming potential


  The relative ability of a greenhouse gas molecule to contribute to warming
• Methane is 84 times more potent than carbon dioxide
• Combustion of fossil fuels transfers carbon from underground deposits to the atmosphere, and clearing of forests reduces the biosphere's ability to remove carbon dioxide
• CO2 concentrations have increased from 315 ppm in 1958 to over 400 ppm today
• 150 million years ago, CO2 levels may have far exceeded those of today, when dinosaurs roamed the land
• Humans may have contributed to a net accumulation of greenhouse gases in the atmosphere over the past 250 years, primarily due to the release of carbon in fossil fuels during combustion
• Nitrogen oxide (NOx)


  Not a greenhouse gas
• Aerosols would have a net cooling effect on the Earth's surface temperatures
• Michael Crichton: '"Historically, the claim of consensus has been the first refuge of scoundrels; it is a way to avoid debate by claiming that the matter is already settled."'
• Climate scientists can analyze tiny bubbles of atmosphere that collected as ice formed in glaciers, sediment cores, tree rings, and coral reefs to study past climate conditions
• Greenhouse gases can be both the cause and effect of warming
• Average surface temperatures (both land and ocean) have risen by about 1.1°C in the past 100 years, with most of this increase occurring since the 1970s
• The Earth may have been warmer during earlier periods of human history, such as the Roman Empire
• For large portions of geological history, the Earth was ice free, with the last time being 50 million years ago
• Feedback loops involving water vapor can have both positive (accelerated warming) and negative (cooling) effects on climate
• Milankovitch cycles, which are changes in the Earth's orbit and tilt over thousands of years, also naturally vary the Earth's climate
• Estimating sea level rise

  1. Calculating mm per year from 30-year graph

  2. Calculating total mm by 2100

  3. Converting to inches
• NOAA projects sea level increases that vary from a few inches to about 7 feet by 2100
• Dam-building has slowed down sea level rises
• The "hockey stick graph" controversy involves differences between the 1990 and 2001 IPCC reports on climate data and methodology
• The Viking settlement in Greenland lasted from 985-1450 AD
• Mitigation strategies for climate change

  • Improving energy efficiency
  • Switching to clean energy sources
  • Preserving forests
  • Recovering landfill gases
  • Protecting soil quality
• Electricity generation produces the largest portion (40%) of U.S. carbon dioxide emissions
• Energy conservation technologies can reduce energy use and emissions by 30% or more, and switching to cleaner energy sources also reduces emissions
• Mass transit solutions like buses, subways, and light rail can reduce the number of cars on the road and greenhouse gas emissions
• Carbon trading


  A system where permits are traded for the emission of carbon dioxide, with the government setting a cap on total emissions
• Carbon trading is riddled with fraud and "greenwashing"
• Geoengineering


  Risky ideas involving directly altering the Earth's climate, such as fertilizing phytoplankton, injecting aerosols, or deploying mirrors