I have wanted to do this experiment for a few years and now have finally had a chance to get to do it. You have always heard the horror stories of leaving an audio CD in your car and returning to a warped useless “coaster”. Ok if you did this you’re a moron… wait, I’ve done this a few times…
Sun damage from recordable media has been a topic that I have not been able to scrounge any information on so I set out to answer:

•  Do CDs and DVDs breakdown faster in direct sunlight?
•  Which degrades in data integrity fast, CDs or DVDs?
•  How long does it take for direct sunlight to make a disk unreadable?

For a CD-R disk to work, there must be a way for a laser to create a non-reflective area on the disc. A CD-R disc therefore has an extra layer that the laser can modify. This extra layer is a colored dye. In a normal CD, you have a plastic substrate covered with a reflective aluminum or gold layer. In a CD-R, you have a plastic substrate, a dye layer and a reflective gold layer. On a new CD-R disc, the entire surface of the disc is reflective -- the laser can shine through the dye and reflect off the gold layer.
When you write data to a CD-R, the writing laser (which is much more powerful than the reading laser) heats up the dye layer and changes its transparency. The change in the dye creates the equivalent of a non-reflective bump. This is a permanent change, and both CD and CD-R drives can read the modified dye as a bump later on.
Ok since a laser basically emits a specific type of light, visible or invisible, one would think that the sun would also “burn” a disk’s sensitive dye.

Lets Go!

I selected six media samples for the experiment. Three DVDr disks of different brands, same for the three cds.

Each of the six disks were burned with the four files listed below. I'm guessing that I even small data corruptions would show up during playback.

Today it was 103° at 1:45pm. I wanted to start the test at noon but, luckily, the temp stayed the same over the test period.

...the arrangement on a scrap piece of foamcore.

This is'nt a slam dunk accurate temp sampling of the CD/DVD surface but you can see the steel probe reached 120°.

All six disks were removed every ten minutes and scanned for file defects. The 40min mark revealed the first breakdown.

The CD (drive F) now showed an incorrect file size. Since it was a closed session - zero bytes for "free space" is correct.

For the DVD the "Total Size" is correct but the "Free Space" should also be zero. This now incorrectly shows 226MB

writable space available. Since this is not a re-writable and another closed session burn this should also be zero.

Oddly enough - all the media file play flawlessly.

At 180 minutes : all six disks were completly unreadable.

I recorded a the data in greater detail, specifically which brand and which format failed first. I'll post a data gird soon, too tired.