Past Climate Change

• Climate change


  The average climate conditions of the planet that vary over time
• The earth has a history of going between warm (interglacials) and cold (glacial) periods
• Causes of climate change

  • Natural events
  • Humans
• Evidence of current climate change includes sea level change, melting ice caps, and warmer global temperatures
• Sea level change

  Eustatic changes due to melting ice caps and thermal expansion. Sea levels rose by 210mm from 1870-2010
• Melting ice caps


  By 2012, floating sea ice in the Arctic had shrunk to less than half the amount in 1979
• Warmer global temperatures


  The 10 hottest years on record have all occurred since 1998
• Milankovitch Cycles


  1. Eccentricity - The orbit becomes elliptical so at times the earth is further from the sun causing it to be much cooler

  2. Axial tilt - The angle of the earth's tilt changes so summers and winters are more extreme when this happens

  3. Precession - The earth sometimes wobbles on its axis and it changes seasons slightly
• Solar variation (sunspots)


  The amount of radiation the sun produces varies over time. Lower solar activity are likely to end in glacials. The Little Ice Age, between 1600-1800, has been linked to reduced sunspot activity
• Volcanism


  Large-scale eruptions can lead to lots of ash in the atmosphere, sometimes it's so great it can block out the sunlight reducing global temperatures. In 1991, Mount Pinatubo erupted, releasing 17 million tonnes of SO2. This was enough to reduce global sunlight by 10% and cool the planet by 0.5 C for a year
• Surface impact


  Asteroids and comets can impact the earth's surface and cause lots of ash blocking out sunlight and reducing global temperatures