Evidence

• How do Ice cores provide LONG-TERM evidence for climate change?

  1. As ice forms, tiny bubbles of air are trapped in the ice. 
  2. The trapped air contains a record of the carbon dioxide and methane levels at the time.
  3. the more CO2 the warmer the temperatures were.
  4. Scientists in Cambridge have found clear evidence of a rapid increase in temperature in recent decades.
• How does melting ice provide evidence for climate change?

  1. The world’s ice sheets are decreasing in size.
  2. Over the last 30 years, the Arctic ice has thinned to around half its earlier thickness.
  3. There are fears that the Arctic could become ice-free by 2100.
• How does rising sea levels provide SHORT-TERM evidence for climate change?

  • Sea levels have risen by 19 centimetres since 1900 and are expected to continue to rise.
• Describe why sea levels are rising

  • When temperature rises + freshwater ice melts, more water flows to the seas from the glaciers +ice caps.
  • When ocean water warms, expands in volume – thermal expansion.
• How does glacier retreat provide SHORT-TERM evidence for climate change?

  1. Photographs of glaciers taken in the Alps : high mountain ranges since the mid-1800s highlight changes in the Earth’s climate.
  2. Glaciers globally = shrinking + retreating.
  3. Estimated = disappear fully, 2035.
• How does increase in extreme weather events show evidence for climate change?

  • More energy = more intense tropical storms.
  • In 2011 the IPCC : extreme weather more common due to global warming
  • The atmospheric circulation may be affected, floods - dry regions + heatwaves - cooler areas.
• Migration patterns

  • The timing of natural seasonal activities such as tree flowering and bird migration is advancing.
  • 65 species of bird were nesting an average 9 days earlier in the 1970s compared to the mid 1990s.
• Long-term evidence

  • Ice cores
  • Pollen analysis
• Short-term evidence

  • Glacier retreat
  • migration patterns change
  • Sea level rise
  • More extreme weather events : droughts