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1. Google Groups Help • http://groups.google.com/group/met-10 • Other available help • Office hours 8:15 – 9:00 a.m. Monday/Wednesday • Email at shaun@wunderground.com • Call me at (415) 205-2083 • Meteorology department help on 6th floor

2. Chapter 14: Climate Change • The earth’s changing climate • Possible causes of climatic change • Global warming

3. Why Climate Change Matters • Why should you be aware of climate change? • Climate is changing and your generation will be the one to make or break it • Climate change (whether nature or manmade) will directly affect you!

4. Determining Past Climates • How do we know what past climates were like? • Fossil evidence • Fossils of tundra plants in New England suggest a colder climate • Ocean sediment cores • Certain animals must have lived in a range of ocean temperatures • Oxygen isotope ratios • Differing isotope counts mean differing temperatures

5. Determining Past Climates • How do we know what past climates were like? • Ice cores • Sulfuric acid in ice cores • Oxygen isotopes (cold the air, the more isotopes) • Bubbles in the ice contain trapped composition of the past atmospheres • Dendrochronology • Examining tree rings to see growth patterns

6. Climate Through the Ages • Much of Earth’s history was warmer than today by as much as 15°C • Ice age • Most recently 2.5 m.y.a. • Beginning marked by glaciers in North America • Interglacial periods (between glacial advances) • When glaciers were at their max (18,000 – 22,000 years ago) sea level 395 feet lower than today • This is when the sea bridge was exposed • 20,000 years ago the sea level was so low that theEnglish Channel didn’t even exist.

7. Climate Through the Ages

8. Climate Through the Ages • Temps began to rise 14,000 years ago • Then temps sank again 12,700 years ago • This is known as the Younger-Dryas

9. Climate Through the Ages • Temps rose again to about 5,000 years ago (Holocene Maximum). Good for plants

10. Climate During the Past 1000 Years • At 1000, Europe was relatively warm. Vineyards flourished and Vikings settled Iceland and Greenland

11. Climate During the Past 1000 Years • From 1000-1300 • Huge famines due to large variations in weather. Crops suffered. • Floods and great droughts

12. Climate During the Past 1000 Years • From 1400-1800 • Slight cooling causes glaciers to expand • Long winters, short summers. Vikings died • Known as the Little Ice Age

13. Climate During the Past 1000 Years • Little Ice Age • 1816 – “Year Without A summer” • Very cold summer followed by extremely cold winter

14. Temperature Trend During the Past 100-plus Years • Warming from 1900 to 1945 • Cooling to 1960, then increasing to today

15. Temperature Trend During the Past 100-plus Years • Sources of temperature readings • Over land, over ocean, sea surface temps • Warming in 20th century is 0.6°C • Is global warming natural or manmade?

16. External Causes of Climate Change • How can we change the climate? • Changes in incoming solar radiation • Changes in the composition of the atmosphere • Changes in the earth’s surface • Emissions of CO2 and other greenhouse gases areby no means the only way to change the climate.

17. Climate Change and Feedback Mechanisms • Water vapor-greenhouse feedback • Explain it (is it positive or negative?) • Runaway greenhouse effect • Negative feedback mechanisms • Increase in temp…increase in radiant energy to space • What planet as a runaway greenhouse effect? • Snow-albedo feedback (what kind is it?)

18. Climate Change, Plate Tectonics, and Mountain-building • Theory of plate tectonics – moving of plates like boats on a lake • Evidence of plate tectonics • Glacial features in Africa near sea level • Fossils of tropical plants in high latitudes

19. Climate Change, Plate Tectonics, and Mountain-building • Landmasses at high latitude create glaciers • Arrangements of landmasses disturb ocean currents • Mountain building by plates running into each other

20. Climate Change and Variations in the Earth’s Orbit • Milankovitch theory • As Earth moves around the sun, three different movements affect solar radiation

21. Climate Change and Variations in the Earth’s Orbit • Eccentricity • Change in the shape of the orbit (from circular to elliptical • Cycle is 100,000 years • More elliptical, more variation in solar radiation Presently in Low eccentricity

22. Climate Change and Variations in the Earth’s Orbit • Obliquity • Change in the tilt of Earth’s axis • Cycle is 41,000 years • Smaller the tilt, the less seasonal variation • Axis tilts from 22° to 24.5° • What is our current tilt

23. Climate Change and Variations in the Earth’s Orbit • Procession • Wobble of the Earth as it spins • The Earth wobbles like a top • Currently, closest to the sun in January • In 11,000 years, closest to the sun in July

24. Climate Change and Variations in the Earth’s Orbit

25. Climate Change and Atmospheric Particles • Sulfate aerosols • Put into the atmosphere by sulfur fossil fuels and volcanoes • Sulfate aerosols are thought to cool the climate andtherefore counteract global warming to some extent.

26. Climate Change and Atmospheric Particles • Volcano aerosols • May get into the stratosphere and absorb and reflect sunlight • Thus, warms the stratosphere and cools the troposphere

27. Climate Change and Atmospheric Particles • Volcanic eruptions may be responsible for many of the climate’s cooling periods (Little Ice Age) • Eruptions were larger 2.5 m.y.a and may be responsible for the Ice Age

28. Climate Change and Variations in Solar Output • Sunspots – magnetic storms on the sun that show up as dark region • Maximum sunspots, maximum emission (11 years) • Maunder minimum – 1645 to 1715 when few sunspots happened

29. The Recent Warming • Radiative forcing agents – greenhouse gases that can disturb the radiative equilibrium • Climate models are used to see the future • They use data from Carbon dioxide, other greenhouse gases, aerosols, and more

30. Future Warming - Projections, Questions and Uncertainties • Questions and uncertainties • How fast will Carbon dioxide increase? • Can we stop deforestation? • Can we stop burning fossil fuels?

31. Future Warming - Projections, Questions and Uncertainties • Uncertain effect of clouds • More clouds, more reflection to space? • More clouds, more longwave radiation absorbed?

32. Possible Consequences of Global Warming • Projected temperatures • Temperatures will rise most in high latitudes • Expanding boreal forest will increase temps • Plants and animals will die • Precipitation will increase worldwide • Possible effects on global circulation • Weather shifts from normal pattern • More rain than snow in the West • Rise in sea level • Melting glaciers • Contamination of groundwater

33. Possible Consequences of Global Warming

34. Possible Consequences of Global Warming

35. Fig. 14-20, p. 407

37. Global Warming and Human Impact on the Earth’s Surface • Desertification – process of overgrazing and excessive cultivation of grasslands, causing desert conditions • An interesting theory • Plagues could be nature’s way of “curing” the Earth of Global Warming • Plagues kills us and our effects, allowing the Earth to heal (Gaia Hypothesis)

38. Curbing Global Warming • Kyoto Protocol • A format agreement by hundreds of nations to curb greenhouse emissions • Try to reduce emissions by 5% below 1990 levels by 2012 • Geoengineering • Trying to fix the atmosphere with technology • Idea to put sulfate aerosols into atmosphere to cool it