Evidence for Climate Change

• A large body of evidence from direct weather and climate observation, and from computer simulation, supports the hypothesis that human activity is one of the causal factors in the climate changes that are being currently observed.

• No single study or observation is proof of climate change (natural or human-caused), but there is an international consensus of climate scientists on the anthropogenic climate change hypothesis.

Evidence for Climate change

1. Rising Temperatures2. Carbon dioxide (and other GHGs) level increases from direct

measurement and glacier ice cores

3. Melting Glaciers, Ice sheets and Sea ice4. Rising Sea Level5. Changes in Severe weather6. Changes in Precipitation Patterns7. Tree ring evidence (compared to known climate records)

Rising Temperatures

• Earth’s average temperature has generally increased from 1880-2006.

Melting Glaciers

• Over the last few decades, the average size of glaciers all over the world have decreased.

• Melting could cause serious water shortages.

Athabasca glacier, Alberta Canada

• Glacier Bay National Park

Why is Arctic sea ice important?

• Arctic sea ice keeps the polar regions cool and helps moderate global climate. Sea ice has a bright surface; 80 percent of the sunlight that strikes it is reflected back into space.

http://svs.gsfc.nasa.gov/vis/a000000/a003800/a003802/SSMIgraph2010labeled.m4v

• Tour of the cryosphere video– http://svs.gsfc.nasa.gov/vis/a000000/a003600/

a003619/

• http://svs.gsfc.nasa.gov/vis/a000000/a003800/a003802/SSMIgraph2010labeled.m4v

• http://www.teachersdomain.org/resource/ess05.sci.ess.earthsys.esglaciers/

Larsen ice shelf collapseIn 2002, a 3,250-square-kilometer (1,255-square-mile) section of the Larsen Ice Shelf rapidly collapsed

http://earthobservatory.nasa.gov/IOTD/view.php?id=2288

Rising Sea Level

• Global sea level has risen significantly over the past 120 years.

• Even small increases can result in devastating floods.

• Glacier and sea ice melt can cause sea levels to rise.

• May explain why sea level rise is accelerating.

• Thermal expansion is also an issue (warm water takes up more volume than cold water)

Albedo effect

• http://svs.gsfc.nasa.gov/vis/a010000/a010000/a010020/albeldoCU.mpg

If the ice melts interactive

• http://www.teachersdomain.org/resource/ess05.sci.ess.watcyc.icemelt/

Studying Climate Change1. Ice Cores

– Ice in polar regions contain trapped air bubbles.

– Bubbles can be analyzed for various GHG

– Ratios of heavy to light oxygen content can determine temperatures.

– Dust layers in ice can also give information on precipitation and volcanic eruptions.

More on Ice Cores

Ice cores

• http://www.youtube.com/watch?v=RaENQj77iPA&feature=related

Tree Rings

Tree Rings– Warm years produce

thick rings and cold years produce thin rings.

– Scientists assemble clues from living and dead trees to collect records of climate going back 10,000 years.