1. Causes of Climate Change

2. What is Climate Change? Climate change is a significant and lasting variation in weather patterns over periods of time ranging from hundreds to millions of years Change can be gradual (millenia) or abrupt (decades)

3. Causes Biotic (causes by life processes) Ocean circulation Orbital variations (Milankovitch) Volcanoes Solar energy variations Plate tectonics Asteroid/Comet Impacts Anthropogenic (result of human activity)

4. Biotic Influences Photosynthesizers like plants and algae that remove CO 2 from the atmosphere (global cooling) Methane production by insects (global warming) Natural burning (forest fires & coal fires) of carbon-rich sources (global warming)

5. Ocean Circulation http://www.windowso nmaine.org/view.aspx ?objectId=7- 48&currentfile=0http://www.windowso nmaine.org/view.aspx ?objectId=7- 48&currentfile=0 Ocean currents transfer heat from equatorial regions to polar regions Shutting down or changing the circulation pattern interferes with the transfer Can result in wildly different climate swings

6. Orbital Variations Milankovitch Cycles –Eccentricity –Obliquity –Precession

7. Volcanoes Large volcanic eruptions with high amount of ash can block sunlight (global cooling) However, after initial cooling, gases lead to increased CO 2 content (global warming)

8. Solar Variations Sunspots have been linked to periods of climate change –Lack of sunspots show decreased solar activity and energy (global cooling) –Increased sunspot activity shows increased solar energy (global warming)

9. Plate Tectonics Positions of continents alters ocean currents and wind patterns –Growth of mountain ranges can block prevailing winds and weather Himalayans –Land bridges (like Panama) change circulation of ocean currents Continents can move north-south

10. Asteroid/Comet Impacts Similar to volcanic eruptions in that they fill the atmosphere with debris, blocking out the sun –Leads to “impact winter” – long cold periods Also can produce a “firestorm” adding ash to the atmosphere Impacting body must be large (0.5 km) for effects to be seen