Climate Change

• Weather

  • atmospheric conditions at a certain place and time with reference to temperature, pressure, humidity, wind and other key parameters (meteorological elements)
• Climate

  • the average weather or the statistical description in terms of the mean and variability of relevant quantities over a period of time ranging from months to thousands or millions of years
• Factors of climate:

  1. temperature
  2. precipitation
  3. wind
• Climate:

  • 30 yr average (World Meteorological Organization)
• Climate change

  • Change in the state of the climate that can be identified by changes in the mean and/or the variability of its property, and that persists for an extended period
• Oxygen Explosion (2.5 Ga - 500 Ma)

  • The evolution of cyanobacteria, which produced oxygen as a bi-product of photosynthesis, that that O2 levels dramatically increased
• Paleocene-Eocene Thermal Maximum (55 Ma)

  • Records show a massive warming of between 5-8 C in just 20 000 years, possibly due to a sudden release of carbon into the atmosphere
• Examples of release of carbon into atmosphere:

  • methane from ocean bed or from within ice structures called clathrates
• Natural causes of climate change

  1. Plate tectonics and volcanism
  2. Ocean variability
  3. Solar output and variations
  4. Orbital variations
• Precession

  • wobbling of the Earth as it spins on its axis

  
• Eccentricity - Ellipticity of Earth’s orbit

  
• Tilt - Inclination of Earth's axis

  • 23.5 degrees
  • accounts for the earth's seasons

  
• Glacial period: cold period; time with large sheets in the northern hemisphere
• Interglacial period: warm period; time without large ice sheets
• Ice growth configuration

  • low eccentricity
  • low tilt
  • large earth-sun distance in summer
  • net effect: less seasonal contrast
• Ice decay configuration:

  • high eccentricity
  • high tilt
  • small earth-sun distance in summer
  • net effect: warmer summers, cooler winters
• The Milankovich cycles include precession (wobble), obliquity (tilt) and eccentricity (elliptical).
• Natural greenhouse gases emissions

  • volcanism
  • carbon dioxide
• If global volcanism slows, as would be the case when supercontinents stabilize, less atmospheric carbon dioxide would trigger global cooling.

  • increased volcanism results in more greenhouse warming
• Anthropogenic greenhouse gases emissions

  • produced by humans
• Paris agreement

  • agreement within the United Nations Framework Convention on Climate Change dealing w/ greenhouse gases emissions mitigation, adaptation, finance starting in 2020
• High global land-ocean temperature index --> low arctic sea ice
• Sea level rise is caused by 2 factors related to global warming:

  • added water from melting ice sheets and glaciers
  • expansion of seawater as it warms
• Responding to climate change:

  1. mitigation - reducing climate change
  2. adaptation - adapting to life in a changing climate
• Mitigation

  • reducing flow of heat-trapping greenhouse gases into atmosphere either by reducing sources of these gases or enhancing "sinks" that accumulate and store these gases
• sinks:

  • oceans
  • forests
  • soils
• goal of mitigation:

  • avoid significant human interference with climate system
• Adaptation

  • adjusting to actual or expected future climate
• Goal of adaptation:

  • reduce vulnerability to the harmful effects of climate change
• NDRRMC: National Disaster Risk Reduction and Management Council