Global Warming

Introduction

A build–up of greenhouse gases in the atmosphere due to the use of fossil–fuels and other industrial processes has led to an increase in the earth’s temperature. Since 1896 it has been known that these gases (carbon dioxide, methane and nitrous oxide) help stop the earth’s infrared radiation from escaping into space and it is this that maintains the earth’s relatively warm temperature. The question is whether the measurably increasing levels of carbon dioxide in the atmosphere over the last century will lead to elevated global temperatures, which could result in coastal flooding and major climatic changes and have serious implications for agricultural productivity.

The following experiment allows students to compare the thermal properties of carbon dioxide with that of air and can be extended further to include water vapour.

Equipment Required

• DrDAQ data logger connected to a PC
• Two DrDAQ external temperature probes (Part no DD100)
• Two 2 litre plastic pop bottles
• Two clamp stands, bosses and clamps
• Carbon dioxide e.g. from a SodaStream
• Two heat lamps or flexible spotlights (at least 60W)
• Plasticine

Experiment Set up

• Prepare plastic pop bottles by removing the labels and drilling holes in the tops big enough to allow the temperature probes to go through
• Setup clamp stands and heat lamps, etc being careful not to place the lamps so close that the plastic bottles will melt
• Fill one of the bottles with carbon dioxide screw top on and plug any gaps with plasticine
• Prepare bottle full of air by plugging any gaps with plasticine
• Monitor temperature of both bottles until they are approximately the same, at this point switch on the heat lamps and start the DrDAQ software recording
• After 20 minutes switch the heat lamps off but continue recording the temperature for a further 20 minutes

Results

Even over a small time period such as 20 minutes we are still able to get a difference of 4 degrees in temperature between the two samples. Students may not be impressed with such a small temperature difference in the lab. However, it needs to be stressed that scientists are in general agreement that an average increase of just 2 degrees celsius across the planet could have catastrophic effects on crop production and cause sea levels to increase significantly resulting in major flooding.