Why do climate models project that the frequency of very large hail (30 mm or larger) will increase in a warmer world, even though warmer air melts hail more quickly?

Answer: Warmer air holds more moisture, strengthening updrafts that feed hail growth.

Warmer air holds more moisture, strengthening updrafts that feed hail growth. ✓ — Correct. Warmer air can hold more water vapor, so storms can draw in more moisture, fueling stronger updrafts. These updrafts carry more supercooled water droplets into the hail growth zone, allowing hailstones to grow larger before they fall. Although warmer air also increases melting, the enhanced updrafts can keep hailstones aloft longer, and the net effect is that the largest hailstones become more frequent, while smaller ones decline.

Storm clouds become colder overall, promoting hail formation. — This is a common misconception. Warming does not make storm clouds colder overall; in fact, the atmosphere generally warms. The key is not the temperature of the cloud itself, but the increased moisture and stronger updrafts that allow hail to grow larger despite warmer conditions.

Less rain falls beneath clouds, allowing hail to reach the ground. — Not quite. The amount of rain below the cloud is not the primary factor. Hail forms inside the storm cloud, within the updraft, before it falls. The critical factor is the strength of the updraft and the availability of supercooled water, not the rainfall beneath the cloud.