Skip to main content

Currently Skimming:

6. Global Warming
Pages 63-77

The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.


From page 63...
... This principle, known as the greenhouse effect, explains why gases produced by human activity will probably cause the earth's average temperature to increase within the lifetimes of most people living today. The 1980s were the warmest decade recorded on a global basis, but scientists are still uncertain, and will be for years, whether the warm spell was a normal climatic fluctuation or a response to the billions of tons of carbon injected into the atmosphere each year by human activities.
From page 64...
... Trace gases such as water vapor, carbon dioxide, methane, chlorofluorocarbons, tropospheric ozone, and nitrous oxide create a greenhouse effect by trapping heat near the earth's surface, and the concentrations of many of these gases are increasing in the atmosphere. Because of these increases, the gases are expected to trap more energy at the earth's surface and in the lower atmosphere, in turn causing increases in temperature, changes in precipitation patterns, and other as yet unpredictable changes in the global climate.
From page 65...
... Only in the last decade have scientists become aware that other, trace greenhouse gases can also be important contributors to global warming. Concentrations of many of these trace gases are known to vary naturally, but there is widespread agreement that human activities are contributing to the current increases.
From page 66...
... Apart from their role as greenhouse gases, when CFCs rise to the upper atmosphere, or stratosphere, they release free chlorine, which then catalyzes the breakdown of ozone, the protective layer that shields the earth from ultraviolet radiation. The two most prevalent CFCs are CFC-12, which per molecule has 20,000 times the capacity of carbon dioxicle to trap heat, and CFC-~l, which has 17,500 times the capacity.
From page 67...
... The most likely conditions Include significant cooling of the stratosphere, warmer surface temperature (which would be felt disproportionately at high latitudes) , and changes such as rising sea level, reductions in sea ice, and increases in total global precipitation (which again would be nonuniformly distributed around the gIobe)
From page 68...
... If current emissions trends continue, the combined greenhouse effect of all trace gases would commit us to an "effective carbon dioxide doubling"-the point where carbon dioxide and other trace greenhouse gases combined trap the same amount of energy that carbon dioxide would trap alone if its concentration doubled from the preindustrial level possibly as early as 2030. Although the climate models are intricate and require massive amounts of computer time, they are stark, simplistic representations of the complex realities of the real climate system.
From page 71...
... The climate mode! results shown in the box are based mainly
From page 72...
... Schneider, a climatologist at the National Center for Atmospheric Research in Boulder, Colorado, and Norman Rosenberg, director of the Climate Resources Program for Resources for the Future, note that another decade or so of observations will enable scientists to assess how well present estimates predicted the sensitivity of climate to increasing trace gases. But, they add, "While scientists debate, the real climate system continues to perform the experiment for us." All of the predictions about climate change are based on only five models (although there are many attempts to model portions of the earth system on more limited scales of time and space)
From page 73...
... that predict the ways in which temperature, humidity, wind speed and direction, soil moisture, sea ice, and other climate variables evolve through three dimensions and over time. They use mathematical equations to express the basic physical, chemical, and biological processes that govern the global climate system.
From page 74...
... As Schneider explains, "Perhaps the most perplexing question about climate models is whether they can ever be trusted enough to provide grounds for altering social policies, such as those governing carbon dioxide emissions." How can models so fraught with uncertainties be verified? Schneider explains that there are three main tests that together can provide evidence about a model's credibility: whether the mode!
From page 75...
... This depends, in turn, on behavioral assumptions as to how much fossil fuel burning will take place. (This graph neglects biospheric effects such as carbon dioxide emissions due to deforestation.)
From page 76...
... We are transforming the environment that sustains us. How much warmer the climate becomes, and how quickly the warming occurs, depend on whether societies decide to act to slow emissions of carbon dioxide and other trace gases.
From page 77...
... Schneider is a vocal proponent of what he has dubbed the "tiein" strategy, in which individuals, firms, and nations would take steps to slow down the rate of buildup of greenhouse gases and at the same time tackle other societal problems. As insurance against the surprises that would be more likely the faster the cInnate change occurs, he urges accelerated testing of alternative non-fossil fuels, development of strains adapted to wider climate ranges, adding flexibility to the management of water systems, and coastal planning to deal with rising sea level and storm surges.


This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More information on Chapter Skim is available.