Page 379 - Geosystems An Introduction to Physical Geography 4th Canadian Edition

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Chapter 11 Climate Change 343
carbon through Earth systems, between carbon sources, areas where carbon is released, and carbon sinks, areas where carbon is stored (carbon reservoirs)—the overall exchange between sources and sinks is the global car- bon budget. The permafrost–carbon feedback and CO2– weathering feedback involve the movement of CO2 within Earth’s carbon budget.
Maunder Minimum (p. 319) Milankovitch cycles (p. 320) climate feedback (p. 320) carbon sink (p. 321)
global carbon budget (p. 321)
7. What is the connection between sunspots and solar output? What happened to sunspot activity during the Maunder Minimum? What was the status of solar activity in 2005 to 2010?
8. What are the three time periods of cyclical variation in Milankovitch cycles?
9. Describe the effect of volcanic aerosols on climate.
10. Name several of the most important carbon sinks in the global carbon budget. What are the most impor-
tant carbon sources?
11. Define a climate feedback, and sketch an example as
a feedback loop.
12. Does the CO2–weathering feedback work in a posi-
tive or negative direction? Explain.
■ List the key lines of evidence for present global climate change, and summarize the scientific evidence for an- thropogenic forcing of climate.
Several indicators provide strong evidence of climate warming: increasing air temperatures over land and oceans, increasing sea-surface temperatures and ocean heat content, melting of glacial ice and sea ice, rising global sea level, and increasing specific humidity. The sci- entific consensus is that present climate change is caused primarily by increased concentrations of atmospheric greenhouse gases resulting from human activities. The primary greenhouse gases produced by human activities are carbon dioxide, methane, nitrous oxide, and halogen- ated gases, such as chlorofluorocarbons (CFCs) and hydro- fluorocarbons (HFCs). The increasing presence of these gases is causing a positive radiative forcing (or climate forcing), the amount that some perturbation causes the Earth–atmosphere energy balance to deviate from zero. Studies show that CO2 has the largest radiative forcing among greenhouse gases and that this forcing surpasses other natural and anthropogenic factors that force climate.
radiative forcing (p. 331)
13. What is the role of multiyear ice in overall global sea-ice losses? What is the status of this ice today? (Check some websites such as those of the Canadian Cryospheric Information Network or the National Snow and Ice Data Center.)
14. What are the two most significant factors currently contributing to global sea-level rise?
15. What are the main sources of carbon dioxide? What are the main sources of atmospheric methane? Why is methane considered a more radiatively active gas than carbon dioxide?
16. What are methane hydrates, and how can they potentially affect atmospheric greenhouse gas concentrations?
■ Discuss climate models, and summarize several climate projections.
A general circulation model (GCM) is a complex comput- erized climate model used to assess past climatic trends and their causes, and project future changes in climate. The most sophisticated atmosphere and ocean submodels are known as Atmosphere–Ocean General Circulation Models (AOGCMs). Climate models show that positive ra- diative forcing and current temperature trends are caused by anthropogenic greenhouse gases rather than natural factors such as solar variability and volcanic aerosols.
general circulation model (GCM) (p. 335) Atmosphere–Ocean General Circulation Model (AOGCM) (p. 335)
17. What do climate models tell us about radiative forc- ing and future temperature scenarios?
18. How might we alter future scenarios by changing national policies regarding fossil-fuel usage?
■ Describe several mitigation measures to slow rates of climate change.
Actions taken on an individual level by millions of peo- ple can slow the pace of climate change for us and for future generations. The principal way we can do this— as individuals, as a country, and as an international community—is to reduce carbon emissions, especially in our burning of fossil fuels.
19. What are the actions being taken at present to delay the effects of global climate change? What is the Kyoto Protocol, and what is the Copenhagen Accord?
20. Take a moment and reflect on possible personal, local, regional, national, and international mitiga- tion actions to reduce climate-change impacts.