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THIS  is why cars get hot inside, if they sit in the sun

with all the windows rolled up

          Regardless of how many people understand it, and how many don't, the basic truth is that global warming (and climate change, sea level rise, etc.) is being caused by EXACTLY the same process that occurs, when the interior of a car gets unusually hot, if the car is left sitting in the sun, on a hot and cloudless summer afternoon, with all the windows rolled up.

          And, EVERY intelligent adult living in the US already knows about that process. They've seen it, for themselves. They've experienced it, for themselves. They don't have to be convinced that it actually happens, because they already know it does.

          Therefore, a strategy that might be helpful, in persuading people who are not yet convinced that global warming is indeed happening, and needs to be slowed down, might involve explaining, to them, why car interiors get hot, if they sit in the sun, with all the windows rolled up.

          So, here is a serious attempt to explain it, in terms that non-experts can understand. This is the basic reason why the air inside a car gets hotter than the outside air, if a car sits in the sun, with the windows rolled up:

          (1) Since any non-tinted glass in the windows and windshield of a car or truck is clear, that means that all of the visible spectrum of wavelengths, in sunlight, can readily pass that through that type of (clear) glass. If some type of glass is NOT clear, that means it is either absorbing, or reflecting off, at least some portion of the visible wavelengths. For example, if glass is tinted red, that means that at least some of the blue, green, and other "non-red" wavelengths are either: (1) reflecting off the surface of the glass, so that they cannot enter the glass and pass through it; or, (2) being absorbed, by the tinting substance which is either embedded within  or, coating a surface of  that red-tinted glass.

     This picture is a simple depiction of how VISIBLE light will pass through CLEAR glass. It also shows  for reasons described below  that ONLY A SMALL FRACTION of any heat-carrying INFRA-RED wavelengths will pass through the types of glass that are used to make car windows and windshields, while MOST of that INFRA-RED energy will reflect off the surface of the types of glass used in automobiles.

          (2) The "visible light" energy which is carried by sunlight INTO A CAR, through the windshield and windows, will `hit’ the dashboard, seats, steering wheel, and anything else in the car which is NOT clear. And, when visible light `hits’ an opaque surface, some part of the energy in that visible light will be absorbed, in a way which turns that energy, into heat. For example, if the top surface of a dashboard, directly under the windshield in a car, is a blue color, that means that the plastic or polymer surface of that dashboard will be reflecting off some portion of the blue part of the spectrum, while absorbing the other colors and wavelengths within the visible spectrum, And, whenever a solid surface absorbs some of the visible wavelengths, carried by sunlight, that means that that solid surface is absorbing the energy which is being carried, by those wavelengths.

          (3) When the plastic, polymer, or other material which covers the surface of a dashboard, car seat, steering wheel, or any other item inside a car, becomes hot, then . . . well, the next paragraph describes what happens. And, this effect, and result, and process, is central, critical, and absolutely crucial, to understand “the greenhouse effect”. 

          When things become hot, they begin trying to get rid of that heat (to stay in balance with their surroundings), by emitting (i.e., sending out) their own energy-carrying radiation.

          However, any heat-carrying radiation will be strongly shifted to the “heat-carrying” INFRA-RED portion (or range, segment, etc.) of the spectrum of wavelengths.

          Why? Because, plain and simple, INFRA-RED wavelengths are the wavelengths that carry the most heat energy. As a simple example and illustration, here's a picture of a "HEAT LAMP" bulb, of the type that is used to warm food. These types of specialized light-bulbs can be found at any large hardware store, or online by searching on Amazon, Google, etc., for "heat lamp".













          Infra-red heating lamps are standard equipment, in most restaurants and fast-food outlets, since they offer the best way to keep food hot, after the food has been cooked. At fast-food places, they usually are positioned over baskets that hold hot food. In sit-down restaurants, they usually are suspended (pointing downward) from the top of a wide horizontal window with no glass in it, which passes through a wall between the kitchen and the main rooms. A cook -- in the kitchen -- can set a plate of hot food on a stainless-steel shelf which forms the bottom of that window, and the food sitting on that shelf will stay hot (because of the infra-red lamps, shining their heat-carrying IR radiation downward, onto the food), until a waiter or waitress picks up that plate with the food on it, and carries it to a customer.

          (4) But now, here is where the problem arises, inside a car sitting in the sun with the windows rolled up. Infra-red light can NOT pass through the type of glass that is used to make car windshields, and windows. Instead of passing through that type of glass, infra-red wavelengths will be reflected by (i.e., they will bounce off of) the inside surface of a windshield, or window pane, in a car. And, when that happens, they are trapped, inside that car. They will bounce off of the inside surface of a car window or windshield, in some direction created by the angle of the glass at that location, and that will send the reflected infra-red rays directly back toward the interior of the car – where they will then transfer the heat they are carrying, to whatever surface they happen to hit next (such as, the dashboard, or a seat, or the steering wheel).

          And, when those infra-red rays (reflecting off the inside surface of a window or windshield) hit a solid surface (such as a dashboard, seat, steering wheel, etc.), they will heat up that surface, even more. And, THAT – the fact that those heat-carrying infra-red rays are bouncing off the inside of the glass, and are being reflected directly back into the car interior, causing anything they hit to become EVEN HOTTER . . . is why the air, inside a car that is sitting in the sun with the windows rolled up, will become substantially hotter than the outside air.

     Below is a picture which attempts to create a visual image, which attempts and hopes to illustrate, reinforce, and support (and drive home, and make memorable) the verbal description above.












          In the hope of helping more people understand what is happening, here is an analogy: to get a mental grasp of what "infra-red rays" can do, think of them as analogous to a swarm of angry and unpleasant little insects we'll call "heat bugs" -- worse than gnats, not as bad as hornets, somewhere on about the same level as a bunch of hungry mosquitos. When they feel threatened, disturbed, angry, etc., they will flap their wings, to try to get away from the problem. But, when they flap their wings, that ends up generating -- and releasing -- some level of heat. That is not some bizarre science-fiction fantasy; whenever energy is burned, to turn it into mechanical power, the process is never 100% efficient, and some that energy will be converted into unwanted heat. That happens whenever any kind of engine is run, such as a car engine, diesel engine, jet engine, steam engine, or any other kind of fuel-burning engine; and, even electric motors get warm, and sometimes hot, when they are run. So, assume, for the sake of the analogy, that when "heat bugs" flap their wings, some portion of the stored biochemical energy that is being "burned", to generate mechanical energy (i.e., the movement of their insect muscles), will be turned into heat, instead, as an inefficiency.

          Continuing the analogy . . . if these "heat bugs" are trapped inside a car which is sitting in the sun, with all the windows rolled up, then they will feel threatened, and they will get upset and angry, when the inside of the car starts to get warm. So, following their insect-level instincts, they will begin flying around, inside the car, trying to get away from the heat. The problem is, when they start flying around, they begin generating, and releasing, even MORE heat . . . and, since they are trapped inside that car, because all of the windows are rolled up, THAT process makes the inside of the car even HOTTER. And, THAT makes the insects get EVEN ANGRIER -- which causes them to begin flapping their wings EVEN HARDER . . . which releases EVEN MORE HEAT, at an even faster rate . . . which makes the inside of the car EVEN HOTTER, STILL . . . which makes the bugs even angrier, still . . . which makes them . . .

          Hopefully, anyone reading this will have realized, by now, that a "vicious circle" situation would be created, if "heat bugs" were real, and if swarms of them happened to get trapped inside of cars with all the windows rolled up, sitting in the sun. That type of "vicious circle" problem is described and illustrated, in these two slides:











          Shifting back out of that analogy, it is entirely serious and reasonable to refer to heat-laden infra-red rays as acting like "heat demons" when they are trapped inside a car, with all the windows rolled up. As the seat, dashboard, and other solid surfaces inside a car get hot, the infra-red rays become even more intense, and carry even more heat energy, and yet, they still remain trapped inside that car. So, they begin heating up the interior surfaces, inside the car, EVEN MORE! And, THAT causes the next round of infra-red radiation to carry EVEN MORE (!!) HEAT . . . and THAT causes . . . well, it creates exactly the type of "vicious circle" that is illustrated above, using hypothetical "heat bugs" instead of infra-red rays, to help people develop a stronger and more solid mental grasp and understanding of what actually happens, and why, inside a hot car on a summer day.

          That EXACT SAME PROCESS, AND PRINCIPLE, explains how and why greenhouses – made of glass window panes mounted on a frame made of thin metallic supports – are widely used in the northern climates, to grow flowers and sometimes crops. Sunlight (with wavelengths that spread across the entire visible spectrum) enters a greenhouse (because the glass panes are clear, which means that the entire visible spectrum can pass through them). That sunlight warms up anything that the visible-spectrum radiation hits, which is not clear (such as the leaves of the plants inside the greenhouse, any wood or steel which was used to make any shelves which hold the plants, and the mulch, rubber mats, or whatever material covers the walking surfaces, inside that greenhouse). When those things warm up, they send out infra-red rays . . . and THAT is where the plot thickens, and things become both active, and interesting. THOSE rays – because they have a new, shifted, and different wavelength which can NOT travel back out of the greenhouse, through its glass windows – get trapped, inside the greenhouse. The infra-red rays reflect off the insides of the glass panes, and go back inside, in some inward direction, until they hit something else. That transfers their heat energy to whatever they happen to hit, inside the greenhouse. Plain and simple, that heat energy – which is being carried by infra-red radiation – is trapped inside the greenhouse, and cannot get out through the glass panes; and, so, that heat energy warms up whatever the infra-red rays hit, inside the greenhouse.

           Now . . .  why is any of that important, to understanding climate change, global warming, and "the greenhouse effect?”

          Because EXACTLY that same process is occurring, in the earth’s atmosphere, where carbon dioxide, in the atmosphere performs EXACTLY the same role as a pane of glass, in a car windshield (or in a greenhouse).

          Here are the facts, about how and why that happens: When sunlight passes through our atmosphere, and hits the surface of the earth, it will warm up whatever land, water, ice, or other surface it happens to hit, in exactly the same way that sunlight passing through a car windshield will heat up any dashboard, seat, or other surface it hits.


          Then, when the surface of the earth (land, ocean, etc.) grows warmer, it tries to stay “in balance” by emitting some of that heat, BY MEANS OF RADIATION WHICH WILL BE IN THE (HEAT-CARRYING) INFRA-RED PART OF THE SPECTRUM.


          BUT . . .  those infra-red rays cannot travel back upward, through the atmosphere, and dissipate out into the vacuum of space, IF THE ATMOSPHERE CONTAINS TOO MUCH CO2 (or certain other gases, notably including methane).


          Instead of being able to go back out into space, and dissipate into the black vacuum of deep space, a portion of those infrared rays will be bounce off of the CO2 and methane gases, in the atmosphere, and will be trapped inside our atmosphere, and will be reflected back downward, to the earth’s surface once again – where, those infra-red rays will transfer their heat energy to whatever they happen to hit, on that “second pass”.


          In exactly the same way that a set of glass windows, enclosing the air inside a car, will cause the air inside that car (as well as any solid surfaces, inside that car) to get hotter . . . in exactly that same way, a layer of gas having too much CO2 and methane, which completely encircles this planet, will create what becomes, effectively, an “enclosed system” that can no longer get rid of heat in the same way (and to the same extent) it previously did (i.e., by sending infra-red radiation out into deep space).

          So . . . THAT is the crucial, central fact, of global warming. That is a scientific description, of the process which is involved.


          And . . . pretty much ANYONE and EVERYONE (at least, of adult age) knows, perfectly well, that cars do indeed get extra-hot inside, if they are left sitting in the sun, with all the windows rolled up.

          Since, they know that THAT happens, anyone who is trying to explain global warming, to someone who is trying to deny that it is happening, or deny that it is being caused by burning fossil fuels (which creates and releases carbon dioxide), then they can be asked whether they are aware of the fact that cars get hot, if left sitting in the sun with the windows rolled up.

          Begin with that, as a starting point, and then build on it, using one logical step at a time.

          And, if people want to, they can create live demonstrations, to prove any or all of the points described above. Anyone who puts the back of a hand directly below or in front of an IR bulb will realize, within seconds, the truth that THOSE are the wavelengths that carry heat. If someone wants something more elaborate, the drawing below shows how two infra-red heating bulbs can be used, to show that: (i) a standard IR heating bulb will cook an egg, until it turns white, within about 30 minutes (e.g., while candidates are talking to an audience); but, (ii) a sheet of glass will reflect and block enough of those IR rays to prevent an egg from being cooked, over that same span of time.

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