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Climate Change Homework Assignment

Here's a topic for every fifth-grader's science fair project. Or, if you are a "climate change skeptic" or if you would like to challenge your friends who are, this is a simple exercise.

Background: We know that the Earth's pre-industrial atmosphere contained certain trace gases that absorb heat energy. During the daytime, the sun warms half of the planet as it rotates on its axis. At night, some of the absorbed warmth is reradiated back into space. Without the atmosphere's greenhouse effect, all heat energy would be lost to space and the Earth would be very cold-- less than 32 degrees F. Water would be frozen and life as we know it could not exist.

So, the natural greenhouse effect created by water vapor, carbon dioxide, and a few other gases keeps the Earth a comfortable temperature for the life that has evolved over the past 3 billion years.

Since the industrial era began in the 1800's, however, humans have enhanced the natural greenhouse effect by emitting billions of tons of carbon dioxide, and by land use practices (plowing, forest cutting) that limit the Earth's capacity to absorb (sequester) some of the released carbon dioxide. As a consequence, the atmospheric greenhouse has become more and more effective in trapping re-radiated heat energy. This brings us to the homework exercise.

The Assignment: Since the atmospheric greenhouse works primarily at night, by absorbing some of the heat energy absorbed the preceding day, nighttime low temperatures are trending above average. This warming trend becomes apparent to anyone who pays attention to their local weather reports.

For the next 30 days, record your local nighttime low and the average nighttime low.

The null hypothesis(for your science fair project) is 'the actual and the average nighttime lows will not be significantly different over the 30-day period.'

Note: The average nighttime low for your area is based on a 30-year record, and it is updated every 5 years. You might have to find a weather information source that reports an "almanac" that gives nighttime low averages for that date.

If you believe 30 days is too few data points, try 60 days or 90 days or a year. If you search the weather/climate records for the last 10 or 100 years, you won't have to collect your own current date.

TV and radio weather presenters know about this trend, but due to commercial considerations on commercial stations, never mention it.

The distribution of grasslands, forests, and deserts across the Earth's surface is the result of many variables, among which climate is a major determinate--especially mean annual temperature and mean annual precipitation.

Climate warming affects the world's vegetation.

As the Earth's average annual temperature trends upward under the influence of modern industrial human activity, vegetational communities like forests and grasslands find themselves, as climatologist Stephen Schneider explains, ' stranded in the wrong climate.'

Rapid climate change (i.e. over decades and centuries) provides stresses that overwhelm plants adapted to the previous 'normal' conditions. Many die. Dying forests present a double impact, as explained in the illustration below. One is that dead trees either burn (increased forest fires in a new drier climate) or if they don't burn, they decompose. In either case, the fast burn of fire or the slow burn of decomposition both release all of the carbon that had been stored in the trees themselves. The second impact is that regions that previously supported forests no longer have trees that serve as a carbon sink.

Logical action to minimize this climate feedback loop would involve eliminating carbon emissions (the source of carbon dioxide in the atmosphere) and planting trees where trees can grow (the sink for carbon dioxide in the atmosphere). Eliminate the source; re-establish the sink.

Climate Feedback Loop 5. © Fred Montague — Climate Feedback Loop 5. © Fred Montague

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