The Carbon Cycle and Global Warming Chapter 19

1. The Carbon Cycle and Global Warming Chapter 19

2. The Carbon Cycle: A Review • Carbon is found in the atmosphere as carbon dioxide. • There are several sinks for carbon including limestone rock, the oceans, forests, and fossil fuels. • The two processes that naturally balance out the carbon in the world are photosynthesis and aerobic respiration (one releases carbon dioxide into the atmosphere while the other absorbs it).

3. Continued • The typical amount of carbon dioxide in the atmosphere is 0.036%. • The amount of carbon dioxide found in the oceans is significantly greater than that found in the air. • Carbon dioxide in water will react to produce carbonic acid. This gives natural rainwater a pH of about 5.6. • The pH of seawater is about 8.

4. What is the greenhouse effect? • Some of the light energy reaching the earth from the sun is converted into infrared radiation (heat) as it reaches the surface of the earth. • Clouds, water vapor, and gases (like CO2) are heated when they absorb this energy as it is transmitted back to space. • The clouds and greenhouse gases then radiate out the infrared energy in all directions. • Some of this energy radiates back into space, but some warms the earth’s surface and troposphere.

5. Greenhouse gases-molecules in the atmosphere which help to trap infrared radiation • Carbon dioxide • Water • Methane • Chlorofluorocarbons • Nitrous oxide • Carbon tetrachloride • Halons • Hydrofluorocarbons • Hydrochlorofluorocarbons

6. Comparison of heat trapping capacities • SubstanceLength of timeHeat factor • Carbon dioxide 50-500 years 1 • Methane 9-15 years 24 • Nitrous oxide 120 years 360 • CFCs 11-20 years 1500- 7000

7. Some factors actually help to cool the Earth • Evaporating water absorbs heat, rises, condenses high up in the atmosphere where it releases heat  helping to cool the earth • Cloud cover helps to cool the earth (reflects light back into space before it is converted into heat) • Albedo effect (light colored surfaces reflect heat back to space). Ice/snow are especially important for this. • Aerosols (suspended liquid particles) and dust in the atmosphere also help to cool the earth (this is mainly from pollution and volcanic activity). Some volcanoes (like Mt. Pinatubo in the Phillipines) have released so much ash that they have lowered the average temperature measurably.

8. Carbon dioxide levels and Global Warming • Is there a connection between the rise in global levels of carbon dioxide and rise in global temperature? • Carbon dioxide levels have been recorded at Mauna Loa observatory in Hawaii since the 1950s. • They have noted an increase in carbon dioxide levels which some link to increased temperatures. • Increased carbon dioxide levels are blamed on human activities, primarily the burning of fossil fuels.

9. Is this part of a natural cycle? Some evidence suggests that carbon dioxide levels rise following temperature increases. • There have been periods of warming and cooling in the past (before humans had any influence). There are natural cycles of warming and cooling. Could this current period of warming be part of a natural cycle? Possibly connected to solar cycles (changes in solar radiation coming from the sun)?

10. Measuring Climate Change • Ice core samples • Sediment core samples • Current temperature data and trends • World-wide data • Reaching a consensus • IPCC

11. How May Humans Be Influencing Global Climate Change? • IPCC report in 2007 says that it is very likely that the troposphere is getting warmer and that human activities are largely responsible. • Increase in certain greenhouse gases associated with human activities, especially the burning of fossil fuels. • Other activities include • Deforestation and clearing of grasslands • Raising of livestock which release methane in digestion • Rice paddies and use of inorganic fertilizers which release nitrous oxides

12. Evidence of a warming world • 20th century was the hottest on record in past 1000 years. Global average rise in temperature is 0.6 degrees Celsius. • Glaciers and sea ice are melting and shrinking at rates faster than they can be reformed. • The world’s average sea level has risen between 4-8 inches in the last century. • Plants have been observed blooming earlier in spring. • Migrating animal species may arrive too late for their food source

13. Ice Caps Melting…So what?? Polar ice caps and glaciers have a high albedo. If there is less snow and ice, there will be less of an albedo effect and more warming. More warming means less snow and ice and so on. Melting glaciers and land ice will contribute to sea level rise. Melting floating ice does not contribute to sea level rise, but will affect the salinity of salt water and can affect currents and weather patterns. The poles experience greater climate change than anywhere else. Biggest concerns are ice sheets in Greenland and Antarctica. Reduction in glaciers means reduction in fresh water supplies.

14. Melting permafrost in Alaska • Releases large amounts of carbon dioxide and methane from the soil (both are greenhouse gases). • Damages man-made construction. • Trees are dying and bent over. • Spruce bark beetle is becoming prominent. • Economic benefits include longer growing season and more tourist dollars.

15. Polar Bears • Extinct by the next century?? • Melting sea ice makes it difficult for them to hunt for seals • Melting ice increases likelihood of drowned bears.

16. Effects of Global Warming • Sea level rise (from melting glaciers and land ice and thermal expansion of water) • Salt water intrusion • Extreme weather • Loss of biodiversity • Agriculture changes (areas become warmer and drier…agricultural belts moving north?) • Human Population (will it crash?) • Human Health (diseases from the tropics moving north?) • Forests • Water Resources (increases evaporation and changes rainfall patterns) • See page 507 for effects as temperature rises.

17. Global Oceanic Conveyor Belt • Shallow and deep water ocean currents are connected and act like a conveyor belt transferring carbon dioxide and warm and cold waters between the surface and the abyss and between the poles and the tropics. • Differences in temperature and salinity (creating density differences) contribute to the rising and sinking of the water and its movement. • If too much land ice melts, this could change the salinity of the water in the conveyor belt, slowing or disrupting its flow, possibly leading to a global cooling for some areas.

18. Slowing Global Climate Change • Three essential prevention strategies: • Improve energy efficiency • Switch to renewable energy resources • Prevent deforestation of tropical forests • Reducing population increases would enhance the effects

19. Other Suggestions • Carbon Capture and Storage (CSS): Remove carbon dioxide from smokestacks where coal is burned and store it. • Geoengineering: • Use balloons, planes to inject sulfate particles into the stratosphere to reflect sunlight • Pump up nutrients from the bottom ocean to create massive algae blooms to remove carbon dioxide • Wrap glaciers in insulating material to slow melting

20. Kyoto Protocol • 2,200 delegates from 161 nations met in Kyoto, Japan in 1997 to negotiate a treaty to slow climate change. • Requires that 36 developed nations reduce emissions of greenhouse gases including carbon dioxide, methane, and nitrous oxide (5.2% below 1990 levels). • Businesses can earn and trade credits to help with the associated costs. • The United States did not sign. • It is hoped that rapidly developing nations will join in the next phase.