Causes of Climate Change: Solar Radiation, Sunspots, Dust, Land Use, Milankovitch Cycles, Plate Tectonics, Ocean Current

1. Chapter 15 - Climate changes • Changes in solar radiation are primary cause for climates to change • ~10% change in solar radiation output can dramatically alter Earth’s climate • Longer term changes in total output • Milankovitch type variations • Shorter term • Sunspot activity (?), Human intervention

2. Short term cyclic • semi-cyclic in nature are Sunspots • Cooler areas on the Sun’s photosphere • Magnetic anomalies that trigger cooler conditions • Less than 0.01% change in energy

3. Linkage between # of sunspots and mean sea surface temp (a function of global temp).

4. Non-cyclic short term-- dust in atmosphere many causes volcanic explosions droughts meteorite impacts humans Example-1815 Mt. Tambora eruption in the East Indies created a year without a summer due to dust blocking sunlight

6. Drought and desertification can create either a negative or positive feedback loop drought triggers dust dust decreases temp temp decrease may trigger rain or or may further the drought

7. Dust storm in Sahara

8. Land use changes in Albedo different materials covering the land surface reflect solar radiation differently e.g., trees vs grass vs crops concrete vs blacktop, vs gravel Results in an Urban “Heat Island” or “Heat Bubble” effect surrounding cities Often cooler temps in agricultural vs city Often cooler temps in forest vs agricultural

10. Milankovitch cycles • small changes in Earths orbit around the sun and variability in its axis of rotation • Eccentricity - ellipicity of annual orbit • Obliquity - changes in tilt of Earth’s axis • Precession - change in position of earth along the annual orbit with respect to when the northern hemisphere is tilted toward the sun

11. Artists rendition of Chicxulub impact at time of impact

12. Plate tectonics Changes in location of continents affects global energy movement and absorption Influences position of and strength of oceanic currents

13. Plate tectonics - impact on continental location with respect to latitude and oceanic currents with respect to continuity of motion

14. Changes in ocean currents • Modern examples of El Nino and la Nina triggered widespread interest in this area • Showed how important ocean currents are in relation to global, regional, and local climates • global - El Nino-La Nina • regional - coastal desert in Peru • local - cooler temps along the Texas Gulf coast due to proximity to water and sea-land breeze

16. Volcanic ash plume from Mont Serrat

17. Ash from Mt St Helens

21. Before- 1964 After- 1990

22. Thematic mapper satellite image of Buffalo County, Nebraska

23. Greenhouse and other gases influencing climate change

24. Non-anthropogenic sources of green house gases • Volcanic activity • CO2; S02; H20; • Biological decay • CH4 - Methane