Global Warming
The Heat is On: Global Climate Change Revisited
Written by: Lisa Ayers Lawrence, Virginia Sea Grant, Virginia Institute of Marine Science
Summary
Using Mauna Loa and greenhouse gas data, evaluate trends over the past 50 years as well as seasonal variations in sea level.
Objectives
- Recognize the role of greenhouse gases in relation to global warming.
- Interpret and graph atmospheric carbon dioxide concentrations from the Mauna Loa data record.
- Predict and assess global climate trends.
- Compare renewable energy sources.
Vocabulary
Global warming, Kyoto protocol, Greenhouse gas, Atmospheric carbon dioxide
Introduction
Scientific
evidence has revealed that a warming trend occurred in the last century - on
that there is consensus. The debate is about whether or not this is a natural cycle and how to respond to the
evidence. The scientific uncertainty surrounding global warming makes it
particularly difficult for public policy makers, who must decide whether or not
to implement costly greenhouse gas reduction policies. The views of our
political candidates sometimes vary widely on climate change and the Kyoto Protocol, an
international treaty to reduce greenhouse gas emissions. Let's investigate the
topic further and examine some data so that you can cast your vote on this
issue.
Global
warming refers to an increase over time of the average temperature of the
Earth’s atmosphere and oceans. The
majority of qualified scientists believe that most of the warming observed over
the last 50 years is due to the continued emission of greenhouse gases produced
by industry and agriculture. Greenhouse gases are so named because they trap
heat in the atmosphere by allowing sunlight through but preventing some heat
from escaping into space, thus acting like the glass in a greenhouse. The
majority of this greenhouse effect is natural, keeping the Earth's average
temperature at a pleasant 60° F (15° C), as opposed to the frigid 0° F (-18° C)
we would experience otherwise. However, the atmospheric concentrations of
several greenhouse gases have been rising as a result of human activity. Levels
of carbon dioxide, which is released primarily by the burning of fossil fuels
such as coal, oil and natural gas, have increased by nearly 30% since
pre-industrial times. Levels of methane—emitted during the production and
transport of coal, natural gas and oil, and released from the decomposition of
organic wastes in municipal solid waste landfills and the raising of
livestock—have more than doubled, and levels of nitrous oxide—emitted during
agricultural and industrial activities, as well as during combustion of solid
waste and fossil fuels—are increasing, too.
If average global
temperatures continue to rise, they would, at some point, be expected to cause
changes in precipitation frequency and intensity patterns, changes in soil
moisture, and a rise of global sea level. Sea level would rise as a result of
warmer air temperatures because ocean waters expand when heated, and many
mountain glaciers would melt. Significant sea level rise would eliminate beaches and plague coastal
towns and cities with flooding. Certain islands and low-lying countries such as Bangladesh would be particularly at
risk. In addition to the loss of property and historically and culturally
significant landmarks that would be caused by flooding, mosquito-borne illnesses
and other diseases would increase in incidence. Coastal marine ecosystems would
be severely affected by a combination of sea level rise and warmer
temperatures. The potential impacts of global warming are numerous.
It has recently
been discovered that the polar ice caps have been thinning and shrinking, and that
the Earth’s
permafrost is thawing. Most
scientists believe that the chances of the ice shrinkage being due to natural
cycles are slim. If Arctic ice continues to melt at its present rate, in a few
decades it could be nonexistent during summer months. The Arctic would become a huge heat
collector, absorbing 80% of the sunlight that reaches it, rather than
reflecting it back into space as it does now. Major ocean currents that
exchange energy from the tropics to the poles would be altered, as would world
weather patterns.
In the past 100
years, Earth's average temperature has increased by 1° Farenheit.
When deciding what to wear in the morning, this seems trivial; however,
consider the fact that during the last Ice Age, the planet was only 9° F cooler
than it is now. It doesn't take much to seriously
affect climate patterns and ecosystems. If greenhouse gas emissions continue to rise, projections for temperature increases in the
next century range from 1.8° F to 6.3° F (assessments by the U.S. National
Academy of Sciences and the United Nations' Intergovernmental Panel on Climate
Change (IPCC)). During that same period, sea level is projected to rise six
inches to as much as three feet. If future climate change occurs at this
magnitude, 21st century Earth would experience the fastest warming in the
history of civilization and the warmest temperature since the evolution of
modern humans. What does this mean for our existence? We cannot possibly know.
We are conducting an experiment in real time.
Some scientists
believe that too much "gloom and doom" is being predicted, and that
the potential impacts of global warming could be negligible
or even positive. They say that correlations of temperature and greenhouse
gas concentrations indicate that the greenhouse effect has had little, if any,
effect on global climate change. In the May 1992 report of the George C.
Marshall Institute, scientists stated that the greenhouse warming produced from
a doubling of CO2 in the next century will be "less than 1° C,
and may be as small as 0.5° C." The report contends that differing levels
of solar activity provide a much more likely explanation for increases in
average global temperature.
Data Activity
The longest
continuous record of atmospheric carbon dioxide measurements in the world dates
back to 1958 and comes from a site in Mauna Loa, Hawaii. This site
is considered one of the most favorable locations for measuring undisturbed air
because possible local influences of vegetation or human activities on
atmospheric CO2 concentrations are minimal, and any influences from
volcanic vents may be excluded from the records. Because of the favorable site
location, continuous monitoring, and careful selection and scrutiny of the
data, the Mauna Loa record is considered to be a
precise record and a reliable indicator of the regional trend in the
concentrations of atmospheric CO2 in the middle layers of the
troposphere.
In the
TOPEX/Poseidon activity Analyzing Greenhouse
Gases and Global Temperature Data Over Time,
you will graph the Mauna Loa data as
well as three other data sets representing other greenhouse gases (methane,
chlorofluorocarbon (CFC), and nitrous oxide). You will look for trends in the
data and project the curves for another 50 years. You may also want to try the Ocean
Seasons activity, in which you will examine seasonal variations in sea
level and discuss how such data can help scientists to better understand
patterns and changes in global climate. After completing your projections for
the 50 years following 1988, you can compare your CO2 values (1989
to present) with the actual data from the Mauna Loa record (click on Digital
Data for a table of numbers, or Graphics for a chart).
Various
ideas exist for dealing with the pollution which may be causing climate change.
Many of us could take steps in our daily lives to reduce our consumption of
energy. There are also good reasons for switching to renewable energy sources. These
energy sources are rapidly replaced, unlike fossil fuels, and are generally
less polluting. Examples of renewable energy sources are solar power, wind
power, hydropower, geothermal energy, and biomass energy.
For more
activities and resources, check out the Bridge's Climate & Atmosphere page, as well as the following sites:
