Originally dropping with Season 5's mid-update that introduced the Games of Summer, YouTuber TheXclusiveAce made a demonstration of the thermal scope's visibility before and after the patch dropped.
Before, the thermal scope had clearly defined silhouettes of the area it covered, including buildings, general terrain, and vehicles, with enemies shining through the gray tones of the scope appearing in all-white fashion, easy to spot.
Now, the image is darker and blurrier, making it considerably harder to spot a target from a long distance, enemies show up in black instead, only glowing with a dim white when they get extremely close to your location.
According to Ace's test, players will now start to spot glimpses of enemies at around 250 metres, but it would still require a lot of attention as you can easily miss targets due to them not being bright enough for you to catch.
There's speculation among the Warzone community the scope nerf is in preparation for a leaked Night Mode coming in the near future, aiming at making it useful under different circumstances.
It is worth pointing out, the thermal scope in the Spotter Scope, a piece of equipment that lets you spot and tag enemies for your squad to see, was not affected by this change, functioning in the same way it has before the patch dropped.
For more on Warzone, check out why vehicles disabled from the game due to a server crashing bug.