The 'greenhouse effect' in cars

TUCSON, AZ (Tucson News Now) - It's only early April, but we've already had our first report of an infant found in a hot car in Tucson. We talk about this every Spring and Summer in Arizona: the dangers of cars heating up in the sun.

Afternoon temperatures are about 20 to 25 degrees lower now than they will be in June, but it's still hot enough to raise the temperature up to 120 degrees in about 45 minutes.

The air inside the car heats up so fast because of the "greenhouse effect". Here's what it means:

Incoming solar radiation, known as "shortwave radiation", shines through the windows and is absorbed in the car's interior.

The heat released from the interior is known as "longwave radiation", and is much weaker than the shortwave radiation. The heat becomes trapped inside the car. Heat continues to enter the car, but struggles to exit.

It only takes 10 to 15 minutes for a car in direct sun light to heat up above 100 degrees when it's 80 degrees outside, even if the window is cracked. When the air temperature climbs above 100 degrees here in June, the temperature inside a car can soar above 150 degrees to 170 degrees in less than an hour.