Human Effects on Climate

Key Terms
natural "greenhouse" effects
enhanced "greenhouse" effects
Why the term "greenhouse" is a misnomer?
Sources and sinks of greenhouse gases; greenhouse gas concentrations, trends, lifetime, and degree of forcing relative to carbon dioxide
Renewable and nonrenewable resources; fossil fuels
Carbon storages in the Earth's climate system
Time scales of carbon cycling, and related processes
Photosynthesis and respiration
Missing carbon sink
Uncertainties of global warming
GCMs and their performance in simulating climate change
Ozone hole
The role of ozone as a greenhouse gas and a pollutant

Review Questions

What are the three categories of UV radiation? Which of these are considered to be biologically harmful?

What is ozone column depth? In what units is it measured?

How do nitrogen and chlorine catalyze the destruction of ozone?

What role do polar stratospheric clouds play in the formation of the Antarctic ozone hole?

Why is a springtime ozone hole observed over the Antarctic but not over the Arctic?

What strategies have been adopted for reducing or eliminating the use of freons?

Critical-Thinking Problem: Is ozone depletion of proven significance enough to warrant government regulation of CFC's? P.Zurer would argue Yes for the following reasons:
  • Because CFC's work catalytically , a small amount of CFC's can deplete a huge amount of ozone. CFC's take up to 15 years to reach the stratosphere but can stay in the atmosphere from 50-200 years. This means that the relatively small depletions in ozone seen now will get much larger as CFC's that have already been released accumulate in the stratosphere.
  • Large amounts of lab evidence prove a number of pathways by which chlorine and bromine destroy ozone in carefully simulated stratospheric conditions.
  • There is more than sufficient evidence for significant CFC-caused ozone depletion. The simultaneous rise of CFC's and free chlorine in the stratosphere coupled with a corresponding decrease in ozone have been repeatedly shown, both over time and and latitude as one approaches the south pole:

Relative concertrations of atmospheric chlorine vs Antarctic Ozone

  • Al Globus adds a summary in favor of intervention: There are readily available examples in both math and science where small changes made to apparently stable systems radically change the system. Making poorly understood global changes to vital resources, such as the air we breath, is unwise.


Additional Readings:

Last updated on 12/08/09 02:52 PM by Zong-Liang Yang