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Elementary Science Education

Global Warming and climate change

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      Bernard Nebel

       With so many climate change/global warming deniers still sounding off, I think it is important to understand the basic facts and reasoning behind the issue. 

      Basic Concept

      Any body that does not have its own heat source will both give off heat to, or absorb heat from its surroundings until it reaches the same temperature of its surroundings. Consider an ice cube tray of water placed in a freezer (it gives off its heat to the colder surroundings and cools) then left on the counter (it absorbs heat from its surroundings and warms). 

      If the earth were not continuously heated by the sun, it would radiate its heat to outer space (near absolute zero), cool to that temperature, and become nothing more than a totally frozen rock. Happily, the Earth’s loss of heat is compensated for by continuous heat input from the sun. However, this heat loss and heat gain is a delicate balance. 

      To illustrate this balance consider a pan of water (about a quart) set over a long-burn candle flame. Monitor its temperature rise. It does not get hotter and hotter until it vigorously boils. Its temperature rises to a point then levels off. Why? It is absorbing heat from the candle flame, but it is also radiating heat to its surroundings. As a body warms it gives off proportionately more heat to its surroundings. It levels off at point where where heat input (from the candle flame) is balanced by heat output (radiation of heat to its surroundings)

      Relating the concept to our planet

      Turning to our planet earth, the temperatures (climates) we experience should be seen as the ongoing balancing between heat input (solar radiation) and heat output (radiation to outer space). Have kids relate day-night and winter-summer temperatures to the duration and height of the sun in the sky.

      Back to our pan of water over the candle flame. Can we cause the temperature of the water to rise further without increasing the flame (heat input) below? Yes! How? Put insulating wrapping around the pan and over its top to retard heat loss. We find that the temperature of the water increases to a new level. Recall that radiation of heat is proportional to the temperature. Thus, the insulation, by retarding heat loss, results in temperature rising to a new point where radiation of heat outward again balances the rate of heat input.

      What does this have to do with climate here on Earth? More than 120 years ago, Svante Arrhenius a Swedish scientist, in 1896 observed that CO2 strongly absorbs infra red (heat) radiation. The earth’s atmosphere is essentially transparent to incoming solar energy (light radiation). As sunlight hits objects, however, it is absorbed and converted to heat. The heated objects give off heat as infra red (heat) radiation. (Witness hot sand or pavement under the summer sun.) 

      From this, Arrhenius hypothesized that CO2 in the atmosphere is instrumental in maintaining the global temperature. It followed logically: more CO2 in the atmosphere —> more absorption of outgoing infra red (heat) radiation  —> higher global temperatures. In short, Arrhenius proposed that more CO2 in the atmosphere would have the same effect as putting insulating wrapping around the pan of water over the candle flame.

      Our modern world burns prodigious amounts of fossil fuels (coal, oil refined into gasoline and other liquid fuels, and natural gas) for energy needs. All such fuels are based on carbon and, on burning, yield CO2. Are we increasing the atmospheric concentration of CO2?

      Actual Measurements

      Starting in the 1950s Scientists took serious interest in this and set up a sophisticated monitoring station on a mountain top in Hawaii. This site was chosen because it is far removed from industrial sources that might influence results. The results are shown at the link below: (scroll down)

      The dark line is the average CO2 concentration. The squiggly line (red) is actual measurements taken monthly; the squiggles are due to photosynthesis being more pronounced during the summer months drawing down CO2, and respiration more pronounced during winter months returning it. 

      The graph clearly shows a steady increase in the atmospheric concentration of CO2 over the years shown. Additionally, the graph corresponds with mathematical calculations based on knowing the total volume of the atmosphere and how much CO2 we add to it each year. (Actually, calculations reveal that we produce more CO2 than shows up in the atmosphere; the missing CO2 has dissolved in oceans causing increasing acidity, another very serious problem. Google: ecological effects of increasing ocean acidity.)

      Finally, we are witnessing ever increasing effects attributable to global warming ranging from increases in glacial melting to forest fires, more frequent and devastating hurricanes, and a list of ecological effects too long to get into here. 


      In short, we developed a hypothesis: Increasing atmospheric CO2 will cause climate warming.

      We have conduced the experiment: We have increased the atmospheric concentration of CO2.

      Result: We are experiencing global warming and the numerous ill effects that derive from that.

      What should we conclude?

      Please post comments, and/or questions 

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