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Greenhouse Effect and Pets in Automobiles

  1. Jul 6, 2014 #1
    I have a question about the greenhouse effect that I hope you all can answer.
    My neighborhood went bonkers last night b/c an older woman left her dog in her car at 10:30 pm to do some grocery shopping. It was dark, but it was 84 degrees.

    I know this would be extremely dangerous if the sun was shining. I think this has something to do with sunlight coming in through the windows, being absorbed by the car's interior, but then not being able to escape as it radiates from the interior b/c the heat is trapped. I've been told the greenhouse effect.

    Here's my question: Since it was dark and the interior was previously cooled by the car's AC (according to the woman) was the dog in danger?
    I really feel bad for this woman (the neighborhood is ready to send a lynch mob and has contacted the media and her employer!), but don't want to support her unless the dog was truly not in danger.

    Please try to keep your answers as simple and staight forward as possible since I will be relaying them to interested neighbors. Thank you so much for any information you can offer to help educate non-physics people!
  2. jcsd
  3. Jul 6, 2014 #2


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    The dog was in little danger since the sun wasn't shining. The interior cannot get hotter than the exterior without a source of heat, like sunlight.
  4. Jul 6, 2014 #3


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    Almost ... glass blocks IR, so any heat generated by the dog would be trapped inside the car, minus leakage through the rest of the vehicle. When the car is in direct sunlight the visible light gets inside, is mostly absorbed by the coverings, and the extra energy is re-radiated in the IR.

    So the net effect depends upon other sources of heat transfer from the interior.
  5. Jul 6, 2014 #4


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    Still, bottom line, it wasn't very pleasant for the dog, even if it wasn't potentially lethal. Even though the car A/C had been recently run, it doesn't stay cool in the interior of a car very long because you can't insulate a car very well, what with metal body parts and all that glass. Plus, the parking lot pavement stores a lot of heat during the day, which is slowly released at night, meaning the car is being indirectly heated while parked.
  6. Jul 6, 2014 #5


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    Sorry, but it's dark and the outside temp is 85 degrees. I seriously don't think that dog was in danger of anything but loneliness unless it was left inside for several hours.
  7. Jul 6, 2014 #6
    Some neighborhood! looking out for the disadvantaged is admirable, but they I suspect they be extremely ( because of theuir reaction) misguided in this case. If it is a type of pug nose then more diligence from an owner is necessary than for other types.

    Are they always this attention attracting. Contacting the employer is just mean spirited. You should attempt to find out who did that and be very wary of that person.

    Dogs lose heat through their panting over their tongue. If the dog showed none of thes signs then it suffered no ill effects.

    Drooling, or slight frothing at the mouth would be a one of the signs that a dog is having trouble keeping cool, although the dog is not yet in immediate danger.

    I will have to agree that the dog was in no danger. Where I come from, the dogs used to run around in 95 F or more weather with the sun shinning and love it, except that they used to enjoy lapping up a gallon of water afterwards and then park in the shade.

    What are these people going to do next? Reprimand anybody who takes their out for its walk in the daytime on a hot day?
  8. Jul 6, 2014 #7
    Oh, I certainly understand that the dog was not comfortable, and I think paging the owner in the store was appropriate. I just want to make sure the dog was not in imminent danger.

    Neighbors seem to throwing out a lot of data they've heard on the local news/weather that are accurate for a sunny, clear day. This is far from that, sun completely set for more than an hour and the outside temp was continuing to cool, correct?

    Btw, she did receive a warning from the sheriff.
  9. Jul 6, 2014 #8


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    In fact, your car will radiate heat if the night is clear, which will result in it being noticeably cooler inside than outside. That's why you get condensation and/or frost on the windows.

    The dog was not in any danger.
  10. Jul 7, 2014 #9


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    I'd lodge a complaint with someone about her receiving a warning. It was entirely unnecessary.
  11. Oct 5, 2015 #10
    I have done "experiments" measuring the temperature inside a car compared to atmospheric temperature. The inside temperature can increase by as much as 30 degrees F on a sunny clear day. Opening the windows has little effect unless there is a really brisk wind. And the effect of air conditioning doesn't last long, a few minutes. Of course, this is for my car only. I didn't feel comfortable going around the parking lot and repeating this. :oldshy:
    In shade, temperatures increased by only 5-8 degrees F. A reflective windshield cover further reduced this to 1-2 degrees F if facing the sun. I did all this to decide on whether to take my dog with me when going out. It paid off when a zealous citizen called the cops. I was able to show my data, and the inside temperature was quite comfortable for my dog. They were impressed, no ticket, no broken windows. (I was a TA for 4 years in weather and climate. So far this has been the only benefit.) :oldcry:
  12. Oct 5, 2015 #11


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    The dog was in no danger, and it bothers me that people were contacting the employer and sheriff. Contacting someone's employer for a non work-related incident is never acceptable, and contacting the sheriff was dramatic overkill for a situation that was not dangerous (and could have easily been resolved in person with no police involvement).
  13. Oct 5, 2015 #12


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    I agree, the dog was probably in no danger in this case. However unless the owner leaves a note bystanders may have no idea how long the owner has already left the dog in the car without water. Has he just arrived? Been there 5 hours without water already? In the UK it would be quite acceptable to use the 999 emergency number to call the police if you believe the animal is in danger.
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