The scientists found evidence that snow and ice was being darkened, accelerating the rate of melting.

这些研究人员发现证据可以证明雪和冰会变暗，从而加剧融化的速度。

A major new study in the polar ice sheets has discovered that the rate of melting has accelerated in the past 20 years. David Shukman is our science correspondent.

有关极地冰原的重大研究表明，冰原的融化速度在过去20年间已经加速。科学记者David Shukman报道。