Climatic Variation

1. Climatic Variation Climate change is a result of imbalances in the flow of energy and the ways in which energy is exchanged between the Earth, atmosphere, and oceans. Climatic variation results from both natural and anthropogenic processes.

2. Climatic Variation Climate chg is a result of imbalances in the flow of energy and the ways in which energy is exchanged between the Earth. Climatic variation may be classified as short-term or long – term Short term climatic variation refers to period of a few thousand years.

3. Climatic Variation Climatic variation and climatic change are two different phenomena.

4. Short-Term Climatic Variation Variation in Solar Irradiance The flux of the Sun remains relatively constant. 1370Wm-2 is the solar constant. A watt is = to a joule / second The Sun provides the energy that controls Earth’s climate system. A drop in solar irradiance of just 1% may result in a glacial period on Earth. 13 Wm-2 chg could cause an ice age.

5. Short-Term Climatic Variation Sunspots -caused by magnetic storms on the Sun -represents areas of colder temp on the Sun. Follow an activity cycle of 11 years

6. Short-Term Climatic Variation The Maunder Minimum represents a period of time where very few sunspots were observed for 70 years. Between 1645 – 1715 A.D. This period corresponds to the Little Ice Age and may provide evidence of the link between sunspots and climate. No sunspots may provide cooler temps. THIS IS TRUE, see next slide.

7. Short-Term Climatic Variation If sunspots represent colder areas on the Sun, why would an increasing amount of sunspots correspond with a warming on Earth? Because the Sun Spots are cooler more radiation is heading to Earth. “FACULAE” – extremely bright areas around sunspots that emit high amounts of radiation.

8. Short-Term Climatic Variation Atmospheric Dust The amount of energy reaching the surface is affected by the transparency of the atmosphere. Dust particles absorb and scatter incoming radiation. A reduction in radiation impacting the surface by 1% will cool surface temperatures by 1*C

9. Short-Term Climatic Variation Atmospheric Dust Volcanic eruptions are major sources of aerosols and may result in a worldwide cooling of temperature. Cooling is typically noticed with eruptions that either contain SO2 or with eruptions that penetrate the stratosphere. SO2 reacts with water vapour to form sulfuric acid.

10. Short-Term Climatic Variation Atmospheric Dust Volanic Explosivity Index (VEI) scale is from 0 - 8 Mt. Tambora: VEI 7 index, Indonesia 1815, 1816 became the year without summer. Mt. Pinatubo: VEI 6 index, Philippines 1991

11. Long-Term Climatic Variation Long-term variation relates to the Earth’s outer composition, revolution around the Sun, axial tilt, and position in space. Milankovitch Theory: Proposes that three separate phenomena leads to a changing climate.

12. Variations in Earth’s Orbit Eccentricity: varies from circular to an ellipse in a 100,000 year cycle

13. Variations in Earth’s Orbit Precession: It is the wobble of the Earth’s axis, takes 22,000 yrs

14. Variations in Earth’s Orbit Obliquity: Chg in the tilt from 22* - 24.5* in a cycle of 41,000 years. Present value is 23.5*

15. Changes on the Earth’s Surface Theory of Plate Tectonics - the continents have moved over time 250 million years ago Present

16. Distribution of Continents The presence of large land masses in polar regions may enhance the likelihood and extent of ice ages. Mountain building episodes increase glacial and ice formation as well as disrupt atmospheric circulations.

17. Oceanic Circulation Variations Oceans play a major role in the transport and redistribution of energy on Earth. Shifting continents affects ocean currents and water temperatures. The extent of the interplay between the oceans and the atmosphere remains a question in climatology. What is the interplay between the oceans and atmosphere? Is one more important?

18. Oceanic Circulation Variations Figure 15.4

19. Feedback Mechanisms Positive feedback enhances climate change. Ex: Snow-albedo feedback, more snow increases reflectivity. Keeps air cooler. Encourages more snow.

20. Feedback Mechanisms Negative feedback weakens climate change Ex: Cloud feedback: as surface warms, more water evaporates. Results in more water vapour in the air brings more cloud cover, means less radiation impacting the surface, which will cool the surface. (this can be highly localized.

21. Impacts of Bolides The collision of an asteroid with Earth 65 million years ago is believed to be responsible for the death of the dinosaurs. Bolides are any object which came from outer space. This marked the boundary between the Mesozoic and Cenozoic eras. KNOW THIS BOUNDARY 65 MILLION YEARS AGO!

22. Effects of a bolide collision: crashes on land • Ash / dust cloud into the atmosphere. • Fires from intense heat of impact from the velocity (speed) of the object entering the atmosphere. • Soot / smoke • Destruction of vegetation, no fire trucks to stop the forest fires 65 million yr ago. • Acidic precipitation from sulfate particles. • Rapid cooling.

23. Impacts of Bolides It is generally accepted that a collision with a bolide of at least 1 km in diameter will have major worldwide climatic implications. Bolide collisions in recent history: 1908: 50 meters in diameter in Siberia. 1994: Jupiter hit by comets 3 kilometers in diameter created huge dust storms.

24. The Urban Bias When assessing climatic records, it is important to account for the bias caused by the urban heat island effect.