• E-mail
• Print
• Comment
• Font Size
• Digg
• del.icio.us
• Discuss article

Global Warming: If You Can't Stand the Heat

Posted on: Tuesday, 22 November 2005, 03:02 CST

By Baird, Stephen L

All of the top ten warmest years on record have occurred since 1990.

Introduction

In the early 1980s scientists began raising concerns about global warming and climate changes. Initially these concerns about human- induced climate changes were met with skepticism because there are natural cycles of climate changes that occur over hundreds of years. Those who tried to raise the importance of this issue, and suggest that perhaps we were over-consuming or unsustainably using our resources, were faced with a lot of criticism and ridicule (Shah, 2005). That early skepticism of the 1980s and 1990s has been replaced with a mainstream scientific consensus on global warming- that changes in our climate are real and that continued human- induced global warming cannot be ignored. Today, the body of research accumulated over the past 25 years indicates that humans are a major factor in the current climate changes. More and more we are realizing that the Industrial Revolution has changed forever the relationship between humanity and nature. There is real concern that by the middle or the end of the next century, human activities will have changed the basic conditions that have allowed life to thrive on earth. The results are uncertain, but if current predictions prove correct, the climatic changes over the coming century will be larger than any since the dawn of human civilization (UNEP/WMO, 1994).

Figure 1. Global warming can alter climate and weather patterns that can have a significant impact on land use and agriculture. Water and its distribution is a critical resource for all living things. Researchers at Sandia National Laboratories have developed software models they think might help not only regions and nations with critical water shortages, but also areas such as the Southwestern U.S. where sound water management policies might avert a crisis. (Sandia National Labs - Randy Montoya)

What is Global Warming?

Global warming is the progressive, gradual rise of the earth's average surface temperature, thought to be caused in part by increased concentrations of "greenhouse" gases (GHGs) in the atmosphere. According to the National Academy of Sciences, the Earth's temperature has risen by about one degree Fahrenheit in the past century, with accelerated warming during the past two decades. Analysis of the various human and natural influences on the global climate indicates that this warming cannot be explained without taking into account human emissions of GHGs. Current scientific data indicates that these "greenhouse" gases have been the dominant force driving temperature increases over the past 50 years. Human activities have altered the chemical composition of the atmosphere through the buildup of greenhouse gases-primarily carbon dioxide, methane, and nitrous oxide. The heat-trapping property of these gases is undisputed, although uncertainties exist about exactly how earth's climate responds to them (Environmental, 2005).

The Greenhouse Effect

The term greenhouse is used in conjunction with the phenomenon known as the "greenhouse effect." Energy from the sun drives the earth's weather and climate and heats the earth's surface; in turn, the earth radiates energy back into space. Roughly 30 percent of the total solar energy that strikes the earth is reflected back into space by clouds, atmospheric aerosols, reflective ground surfaces, and ocean surfaces, Figure 2. The land, air, and the oceans absorb the remaining 70 percent. Atmospheric greenhouse gases (water vapor, carbon dioxide, methane, nitrous oxide, and other gases) trap some of the outgoing energy, retaining heat much like the glass panels of a greenhouse. Without this natural "greenhouse effect," temperatures would be much lower than they are now and life as we know it would not be possible. Greenhouse gases are responsible for maintaining the earth's average temperature at approximately 60 degrees Fahrenheit. What has many people worried now is that, since the Industrial Revolution, humans have been artificially raising the concentration of greenhouse gases in the atmosphere, causing the greenhouse effect to get stronger, trapping more heat than needed and raising the average temperature of the earth's surface, which, if left unchecked, could eventually cause the planet to become much less habitable for humans, plants, and animals.

Figure 2. The Energy from the sun drives the earth's weather and climate and heats the earth's surface and, in turn, the earth radiates energy back into space. This effect is known as the "greenhouse effect," and roughly 30 percent of the total solar energy that strikes the earth is reflected back into space by clouds, atmospheric aerosols, reflective ground surfaces, and ocean surfaces. However, increasing amounts are not being reflected back into space, thus raising the temperature of the earth's atmosphere. (Courtesy of U.S National Park Service.)

Our factories, power plants, and cars burn coal and gasoline, pumping millions of tons of carbon dioxide into our atmosphere. We produce millions of pounds of methane through trash decomposition and by breeding large herds of methane-producing cattle. Nitrogen- based fertilizers, which we use on nearly all our crops, release unnatural amounts of nitrogen oxide into the atmosphere. Once these carbon-based greenhouse gases get into the atmosphere, they stay there for decades or longer. According to the Intergovernmental Panel on Climate Change (IPCC), since the Industrial Revolution, carbon dioxide levels have increased 31 percent and methane levels have increased 151 percent. Paleoclimate readings taken from ice cores and fossil records show that these gases, two of the most abundant greenhouse gases, are at their highest levels in the past 420,000 years. Many scientists fear that the increased concentrations of greenhouse gases have prevented additional thermal radiation from leaving the earth, in essence trapping excess heat in the earth's atmosphere and raising the average surface temperature (Weier, 2002). Much of the available climate data substantiates these fears. Temperature data gathered from many different sources all across the globe shows that the surface temperature of the earth, which includes the lower atmosphere and the surface of the ocean, has risen dramatically over the past century. Global mean surface temperatures have increased 0.5-1.0 degree Fahrenheit since the late nineteenth century. Recent decades have seen record-high average global surface air temperatures. In fact, all of the top ten warmest years on record have occurred since 1990. These record warm years are attributed to a century of global warming (PEW, 2001). In addition, changes in the natural environment support the evidence from temperature records:

* Mountain glaciers the world over are receding.

* The Arctic ice pack has lost 40 percent of its thickness over the past four decades.

* Global sea level is rising about three times faster over the past 100 years, compared with the previous 3,000 years.

* A growing number of studies show plants and animals changing their range and behavior in response to shifts in climate (Union, 2005).

The Big Unknowns

Scientists are concerned that our health, agriculture, water resources, forests, wildlife, and coastal areas are vulnerable to the changes that global warming may bring. But projecting what the exact impacts will be over the twenty-first century remains very difficult. Scientists are more confident about their projections for large-scale areas (e.g., global temperature, precipitation change, and average sea level rise) and less confident about projections for smaller areas such as local temperature and precipitation changes, altered weather patterns, and soil moisture changes. This is largely because the computer models used to forecast global climate change are still ill-equipped to simulate how things may change at smaller scales. Like many pioneer fields of research, the current state of global-warming science can't always provide definitive answers to our questions. There is certainty that human activities are rapidly adding greenhouse gases to the atmosphere, and that these gases tend to warm the earth. This is the basis for concern about global warming. Some of the largest uncertainties are associated with events that pose the greatest risk to human societies. The IPCC warns that "Complex systems, such as the climate system, can respond in non-linear ways and produce surprises. There is the possibility that a warmer world could lead to more frequent and intense storms, including hurricanes. Preliminary evidence suggests that once a hurricane does form, it will be stronger if the oceans are warmer due to global warming. However, the jury is still out as to whether or not hurricanes and other storms will become more frequent (U.S. Environmental, 2005).

How Do We Know That the Atmospheric Build-up of Greenhouse Gases Is Due to Human Activity?

Four decisive areas of scientific evidence prove conclusively that the recent build-up of carbon dioxide, methane, nitrous oxide, and other gases are directly related to human activities.

1. The nuclei of carbon atoms in carbon dioxide emitted by burning coal, oil, and natural gas (fossil fuels) differ in their characteristics from the nuclei of carbon atoms in carbon dioxide em\itted under natural conditions. Forty years ago scientists provided the first direct evidence that the combustion of fossil fuels was causing a buildup of carbon dioxide.

2. Technological advancements have allowed scientists to take more precise measurements globally, with the data showing convincingly that the levels of carbon dioxide and other gases have increased each year worldwide and are consistent with other estimates of the rise of carbon dioxide emissions due to human activity over the same time period (since 1950) the data has been collected.

3. A third area of evidence has been added since 1980. Samples of fossil air, some of them over 200,000 years old, have been retrieved by drilling deep into the Arctic and Greenland ice caps. Measurements from the youngest and most shallow segments of the ice cores, which contain air from only a few decades ago, when compared to older parts of the core, show that carbon dioxide amounts were about 25% lower than today for the ten thousand years previous to the onset of the Industrial Revolution.

4. The final line of evidence comes from the geographical pattern of carbon dioxide measured in the air. Observations show that there is more carbon dioxide in the northern hemisphere than in the southern hemisphere. The difference coincides with the fact that most of the human activities that produce carbon dioxide take place in the northern hemisphere.

Direct atmospheric measurements of other human-produced greenhouse gases have not been made in as many places or for as long a period as they have for carbon dioxide. However, existing data for these other gases do show increasing concentrations of methane, nitrous oxide, and chlorofluorocarbons over recent decades. Ice core data shows that methane and nitrous oxide concentrations began increasing over the past few centuries, after having been relatively constant for thousands of years. Chlorofluorocarbons are absent from deep ice cores because they have no natural sources and were not manufactured before 1930 (United, 2004).

Scientific Skepticism

While the general consensus among scientists is that global warming is real and its overall effects are detrimental, there are still some prominent scientists who feel that the threat of global warming has been greatly exaggerated. Skeptics take issue with the basic temperature data that demonstrate the earth's temperature has increased over the last century. Most of the pre-satellite, pre- 1970 data was collected in urban areas using many types of thermometers that were spread far apart. Such measurements are subject to human error and do not give a clear depiction of ocean temperatures. Until satellite data is collected for several more decades, some researchers feel that the temperature data is too unreliable to take at face value. Another point of contention is that no one has ever proven outside of the laboratory whether global warming occurs as a result of carbon dioxide. There is ample fossil evidence that shows that carbon dioxide levels in the atmosphere have risen as the earth grows warmer, but no one has yet shown that a rise in carbon dioxide is responsible for increased temperatures. Although these scientists feel that there is still too much that we do not understand about the climate, nearly everyone agrees that more research needs to be done (Weier, 2002).

Conclusion

As the earth continues to warm, there is a growing risk that the climate will change in ways that will seriously disrupt our lives. While, on average, the globe will get warmer and receive more precipitation, individual regions will experience different climatic changes, with different consequences for local environments. Some of the more severe consequences will be:

1. A faster rise in sea level.

2. More heat waves and droughts, resulting in more and more conflicts over water resources.

3. More extreme weather events, producing floods and property destruction.

4. A greater potential for heat-related illnesses and deaths, as well as the wider spread of infectious diseases carried by insects and rodents into areas previously free from them.

If climatic trends continue unabated, global warming has the potential to threaten our health, cities, farms, forests, beaches, wetlands, and other natural habitats (Union, 2005). Fortunately, we can take action to slow global warming. Global warming results primarily from human activities that release heat-trapping gases and particles into the air. The most important of these activities are the burning of fossil fuels (coal, gas, oil) and deforestation. To reduce the emission of heat-trapping gases such as carbon dioxide, methane, and nitrous oxides, we can curb our consumption of fossil fuels, use technologies that reduce emissions whenever possible, and protect the world's forests. Global warming is a grave problem. It will take everyone-governments, industry, communities, and individuals-working together to make a difference.

Learning Activities

The Union of Concerned Scientists (UCS) is an independent nonprofit alliance of more than 100,000 concerned citizens and scientists, who augment rigorous scientific analysis with innovative thinking and committed citizen advocacy to build a cleaner, healthier environment and a safer world. In order to help bring an awareness of global warming into mainstream society, the Union of Concerned Scientists has produced a set of teaching materials designed to accompany their science-based world map depicting the local and regional consequences of global climate change. Geared towards students and teachers in Grades 9-12, the curriculum guide activities engage students in an exploration of the impacts of global climate change on ecosystems and natural resources, on community, and on individuals and society. The curriculum guide can be downloaded for free; the corresponding map can be ordered from the Web site. (There is a shipping fee).

Visit www.climatehotmap.org to order the map or to download an MS PowerPoint version for free. Visit http://climatehotmap.org/ curriculum/ index.html to download the curriculum guide.

References:

PEW Center on Global Climate Change. (2005). Fact Sheet 1: Attribution. Retrieved September 2, 2005 from www.pewclimate.org/ docUploads/Fact %20Sheet%201%20Attribution%2Epdf

Shah, A. (2005). Climate Change and Global Warming. Retrieved September 5, 2005 from www.globalissues.org/EnvIssues/Global Warming/ Intro.asp

UNEP/WMO. (1994). Beginners Guide to The Convention. Retrieved August 22, 2005 from http://unfccc.int/resource/ beginner.html

Union of Concerned Scientists. (2005). Global Environment Retrieved August 18, 2005 from www.ucsusa.org/global_environment/ global_warming/index.cfm

United Nations Environment Programme-World Meteorological Organization. (2004). Common Questions about Climate Change. Retrieved September 7, 2005 from www.gcrio.org/ipcc/qa/05.html

U.S. Environmental Protection Agency. (2005). Global Warming. Retrieved September 1, 2005 from http://yosemite.epa.gov/oar/ globalwarm ing.nsf/webprintview/Climate.html

Weier, J. (2002). Global Warming. Retrieved August 22, 2005 from http://earthobservatory.nasa.gov/Library /GlobalWarming/

Stephen L. Baird is a technology education teacher at Bayside Middle School, Virginia Beach, Virginia and adjunct faculty member at Old Dominion University. He can be reached via e-mail at Stephen.Baird@vbschools.com.

Copyright International Technology Education Association Nov 2005

Source: Technology Teacher, The

More News in this Category