Climate Change Basics: The science behind rising temperatures.
The Earth is wrapped in a blanket of fleecy warmth made of greenhouse gases. I remember watching Al Gore’s documentary film an Inconvenient Truth almost twenty years ago, and being shocked when he said “that’s a good thing.” I thought we were fighting greenhouse gases! It turns out greenhouse gases fundamentally make the Earth habitable. The law of conservation of energy states that any energy put into a system has to be equal to the output of energy. If the Earth were merely to receive the energy of the sun, absorbing some of it and radiating the rest of it back into space, without its atmospheric greenhouse blanket, it would be a very cold place, likely uninhabitable by life as we know it. Thinking about how I might teach this to middle school students, the following analogy might work. My tea is hot because I heated the water on the stove (energy in) to pour into my mug. If I let it sit on the counter long enough, all the heat will dissipate (energy out), and I will be disappointed with a cold mug of tea. I need something to hold the heat in. If I put my hot tea into a thermos (like wrapping it in a blanket), it will stay warm quite a long time by trapping the heat. Insulation is needed, and a thermos provides that. Greenhouse gases in our atmosphere provide insulation for the Earth. But too much greenhouse gas is like layering too many blankets! Figure 2 shows the increase in annual temperatures from 1880 to the present. Note that the dates directly correspond to the increase in fossil fuel consumption and combustion post Industrial Revolution. (See Figure 2) The science behind solar radiation and greenhouse gases is complicated, but it may be enough just to begin with the greenhouse gas blanket concept for middle school age students. Gases actually hold warmth and radiate it back to Earth, with different gases having different warming potential. The Earth’s atmosphere and surface also reflects some of the sun’s rays, a term which scientists call albedo. That reflectivity also helps regulate temperature on the planet. With darker surfaces having a low albedo, absorbing more of the sun’s energy, and lighter surfaces having a higher albedo reflecting more energy.14
Figure 2. Warming trends attributed to climate change. Climate.nasa.gov15
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