2. The Enhanced Greenhouse Effect and Global Warming
Atmospheric concentrations of greenhouse gases have increased significantly
since the Industrial Revolution due to human activities (fossil
fuel combustion, deforestation, raising livestock, coal mining and
drilling for oil and natural gas, rice cultivation, decomposition
of garbage in landfills).
See the EPA global warming website for lots of depressing news.
Global warming, the progressive rise of the Earth’s surface temperature,
almost certainly causes changes in global climate patterns. Earth
has undergone many periods of global warming (and others of global
cooling) due to natural causes, so how do we know whether, and how
much, humans have contributed to the current episode (about 100
yr old) of global warming?
Geologists study paleoclimates (literally, ancient
climate) by investigating proxies that are sensitive to climatic
variables, such as temperature and precipitation, e.g. tree rings,
ice cores, marine sediments, and fossil pollen.
Long-lived ice masses, called glaciers, are storehouses of old
air. Ice starts out as layers of snow, a light fluffy material mixed
with air. As snow layers accumulate, their weight compresses the
bottom layers, forming ice that traps some bubbles of “stale” air.
The cyclicity of snowfall and snowmelt produces layers that can
be counted like tree rings to provide an icy chronology.
In the image above, note the correlation between elevated temperatures
and elevated levels of CO2. CO2 fluctuates naturally, but monitoring
since the late 1950s shows a true enhanced rate of CO2 concentrations.
Scientists have drilled deep into the Greenland and Antarctic ice
sheets, extracting cores that represent thousands of years of precipitation.
There is a clear connection with human influence.
In this activity, students explore how many dilutions it takes
to achieve a parts-per-million dilution of a common substance (food
coloring). This can provide a basis on which to better understand
concentrations of gases in our atmosphere that refers to parts per
million. Please note: the table of gas and PPM illustrated within
the teacher resource is out of date. The more appropriate PPM for
CO2 is 370.
|Teachers experiemented with different dilutions
of food coloring using ice cube trays.
Here, instructor Ellen Metzger plots the class data.
Despite the amount of data on the enhanced greenhouse effect, some
continue to argue that climate change is influenced by changes in
the solar cycle.
To learn more go to Page 3...