1. Climate Change

2. Most solar energy is in the form of shortwave radiation (e. g
Most solar energy is in the form of shortwave radiation (e.g. light, uv rays)
Earth absorbs this energy and re-emits as longwave radiation (infra-red, “heat”)
Greenhouse gases (CO2, CH4 H2O) in the atmosphere absorb infrared radiation
This natural process allows the Earth to maintain an average yearly temperature of about 150 C (600 F).

3. Climate change in the geologic past
Early Precambrian Time (4-2.7 bya)
Sun was 20-30% fainter, delivered less energy
Effect offset by large greenhouse effect of Earth’s early atmosphere, largely composed of CO2, and H2O.
Late Precambrian to Permian (2.7 bya to 250 mya)
Severe ice ages occurred at least five times in this period

4. Climate change in the geologic past
Mesozoic to Present
Climate mostly warmer than today
Most recent ice ages occurred over the last 2 million years
Some scientists think the last 10,000 represent an interglacial warming episode and the ice will return
Recent records show mean temperature increase from the late 1800s

5. “Recent” Climate change data from the Summit Ice Core.

6. Figure 21. 4 Mean global temperature changes from 1880 to 2002
Figure 21.4 Mean global temperature changes from 1880 to The zero line represents the average from 1951 to 1980, and plus or minus values represent deviations from the average.
Fig. 21-4, p.503

7. Figure 21.5 Several methods, each with its own useful time range, allow scientists to determine historical and ancient climates. Source: Adapted with permission from T. Webb III, J. Kutzbach, and F. A. Street-Perrott in Global Change,T. .F. Malone and J. D. Roederer, eds.,pp. 212–218. Copyright 1985 by Cambridge University Press, U.K.
Fig. 21-5, p.504

8. Measuring recent climate change
Historical records – accounts recorded as records, or in stories
Vikings’ tales of the Little Ice Age ( )
Wine harvest records
Landscape paintings, other historical & archeological accountings chronicle changes over the span of human history

9. Climate Data from Historical Records

10. Measuring climate change
Tree rings – growth rings of trees hold climate information
Plant pollen – the pollen record records what was able to grow, which is linked to temperature and precipitation
i.e; 10,500 years ago pines replaced spruce in what is now northern Michigan, indicating warmer temperatures.

11. Measuring climate change
Oxygen isotopes in glacial ice
18O & 16O (common isotope) both occur
16O evaporates more readily (lighter)
Ice from Greenland and Antarctica show a record back >100,000 yrs
Glacial evidence – till, tillites, striations all give information on climate at that time
14C dating of organic material preserved in till

12. Comparing oxygen isotope analysis with temperature in coral
This figure shows a δ O18 ratios from a coral core. This record is plotted against variations from average annual sea surface temperature (SST) rainfall, and coral growth in order to observe how well these corals have recorded recent climate variability.
Red shows higher than average SST/ rainfall/negative δ O18 (expected for warmer temperatures)/more coral growth.
Figure courtesy of Dr. Julie Cole, University of Colorado.

13. Figure 21. 6 Scientists remove an ice core from a glacier in Greenland
Figure 21.6 Scientists remove an ice core from a glacier in Greenland. Studies of ancient ice provide information about past climate.
Fig. 21-6, p.505

14. “Recent” Climate change data from the Summit Ice Core.

15. Measuring climate change
Plankton and isotopes in ocean sediment
Shells and other “hard parts” preserved in marine rocks / muds give two lines of information
What was alive at the time gives climate information
16/18O ratios in biogenic carbonate
Rock and fossil record
fossils give much information, what lived when
Rock records formative environment

16. Figure 21.7 (A) A fossil fern indicated that a region was wet and warm at the time the fern grew.
Fig. 21-7a, p.506

17. Figure 21.7 (B) These fossils and dune cross-beds indicate that this region was dry at the time the dunes formed.
Fig. 21-7b, p.506

18. Causes of Climate Change
Astronomical
Natural Variations in the Carbon Cycle
Tectonic
Position of the Continents
Volcanic Eruptions
Human Activity

19. Astronomical Causes – Sunspot cycles
The sun’s output varies over time
Local activity such as sunspots and solar storms has effect on solar output
Some studies show relationship between changes in global temperature and sunspot cycles

20. Astronomical Causes – Milankovitch Cycles
Orbital Eccentricity
Earth’s orbit becomes more/less elongated, changing distance from the Sun.
This is a cycle on the order of 100,000 years.

21. Astronomical Causes – Milankovitch Cycles
Axis Shift
Earth’s equator is presently tilted at a 23.5 ° angle from the orbital plane
This changes from a minimum (22.5°) to a maximum (24.5°) over a period of approximately 40,000 years
This change influences length and severity of the seasons

22. Astronomical Causes – Milankovitch Cycles
Precession (Wobble)
Earth’s axis wobbles in a circle every 26,000 years.

23. Natural Variations in the Carbon Cycle
Carbon is primary material of biosphere.
5 times as much carbon in the crust and upper mantle as in the atmosphere from carbonate rocks.
Fossil fuels primarily carbon.
These materials cycle through atmosphere, changing the carbon concentration.

24. Carbon Reservoirs Fig. 21-9, p.508
Figure 21.9 Carbon reservoirs in the atmosphere, biosphere, hydrosphere, and solid Earth. The numbers represent billions of tons of carbon. Source: Wilfred M. Post et al., “The Global Carbon Cycle.” The American Scientist, 78, July–August 1990,p. 310.
Fig. 21-9, p.508

25. Tectonics and climate change
The position of the continents influences winds and ocean currents.
North and South America joined, separating Atlantic from Pacific in the tropics.
Current configuration of continents keeps Arctic Ocean landlocked.

26. Figure 16.12 Major ocean currents of the world.
Fig , p.384

27. Volcanoes and climate change
Volcanic eruptions can cause either warming and cooling of the atmosphere

28. Volcanoes and climate change
Volcanoes emit ash, particulates and sulfur compounds, which block sunlight and so cool the atmosphere.
Volcanoes emit large quantities of CO2, which leads to warming of the atmosphere.

29. Human contribution to the Greenhouse Effect
Humans release, fossil fuels,CFCs and other greenhouse gases into the environment.
Concentrations of these gases has increased in the recent past
The atmosphere has warmed 0.8oC during the last century

30. How CO2 in atmosphere relates to temperature

31. Changes in CO2 Concentration from 1958

32. Possible Consequences of Global Warming
Increased temperatures tend to decrease plant productivity.
Extreme weather events increase (hurricanes, heat waves).
Changes in biodiversity: increase in extinction rates.

33. Thermohaline circulation – how global warming could cause global cooling
Warmer sea surface temperature could slow or stop vertical currents
This would stop, or re-route the Gulf Stream, which would cool the Earth
Thermohaline currents have decreased 30% from 1988 – 2000
Stopping of Thermohaline currents in North Atlantic caused the Younger Dryas Event, 10-11,000 years ago.

34. Figure Some climate models indicate that warmer temperatures may shut off the Gulf Stream and North Atlantic drift, which could result in subsequent global cooling.
Fig a, p.519

35. Figure Some climate models indicate that warmer temperatures may shut off the Gulf Stream and North Atlantic drift, which could result in subsequent global cooling.
Fig b, p.519

36. Possible Consequences of Global Warming
Sea-level changes – sea-level has risen markedly from 1900 to 2000
water expands when warm
Glacial (ice on land) melting is increasing
Effects on people
Tropical diseases flaring up in new areas
Population stress on food and water supplies as well as other global systems

37. Possible Consequences of Global Warming
Sea-level changes – sea-level has risen markedly from 1900 to 2000
water expands when warm
Glacial (ice on land) melting is increasing
Effects on people
Tropical diseases flaring up in new areas
Population stress on food and water supplies as well as other global systems

38. Figure Atmospheric carbon dioxide concentration has risen by about 17 percent within the past century. The short-term fluctuations are caused by seasonal changes in carbon dioxide absorption by plants.
Fig , p.514

39. The Kyoto treaty on greenhouse warming
Dec. 1997, 160 nations met to discuss global warming
By Feb a treaty was ratified by many of them
Creates a global trading market for CO2 emissions
Sets limits and goals
Caps and goals tied to nations’ economies
Developing nations, eg China, India excluded from CO2 caps

40. The Kyoto treaty on greenhouse warming
The U.S. has never ratified the treaty
Treaty supporters argue:
Wealth not necessarily tied to fuel consumption
Curbing consumption and emissions could help the economy
Models show the longer we wait, the worse it will get
Consider the alternatives: runaway temperature changes, famine, global unrest.
The treaty expires in 2012 – the sequel is looking less than inspired.

41. Figure Carbon dioxide emissions from the top ten emitting countries in (B) Per capita carbon dioxide emissions from the top ten emitting countries in 1994.
Fig , p.520

42. Oxygen Isotope Analysis
Oxygen isotope changes during production of glaciers via seawater extraction. The ratio of to O18 to O16 in a sample is expressed by scientists as the deviation (designated by the Greek letter δ) from the ratio of isotopes in a standard, where δ O18 = (sample ratio/standard ratio) -1. Note how during low sea level (cold weather conditions, when glaciers are expanding) the ocean becomes enriched in O18, leading to a positive δ O18 value (+1‰), while the glacier becomes depleted in O18, giving it a negative value (-30‰).