Global Climate Change

1
Global Climate Change

• What we know, what we are fairly confident about,
  and where the uncertainties lie.

2
What do we know?

• CO2, methane, CFCs, water vapor trap heat (
  greenhouse gases).
• Global average temperature has risen 0.3-0.6 C
  in the last 100 years.
• Global average sea levels rose 10-25 cm over the
  last 100 years.
• The global climate system is very complex.

3
What do we confidently conclude?

• The rise in CO2 is the largely the result of
  human activity.
• More CO2 will probably mean further rise in
  global average temperatures and sea levels.
• Sulfate aerosols have been counteracting the
  warming trend.

4
What do we not really know?

• Regional changes are very hard to predict at
  present. Local conditions may change much more
  than the global average.
• Whether regional weather patterns are becoming
  more extreme or variable.

5
Major sources of uncertainty

• Clouds warming may mean more clouds, but these
  could cool or warm the planet.
• Oceans the fate of CO2 over the long term in the
  ocean is not known.
• Interactive effects. Poorly known links in the
  climate system may lead to surprising changes.