It's Sensitive. Really. - New York TimesThe tusk started out as a tooth; the research was led by an adventurous dentist. It makes a bizarre sort of sense; anyone with an exposed tooth root or broken tooth knows how sensitive teeth can be to temperature. Invert the tooth, put the soft tissue on the outside, and you have a weather sensor.
The find came when the team turned an electron microscope on the tusk's material and found new subtleties of dental anatomy. The close-ups showed that 10 million nerve endings tunnel from the tusk's core toward its outer surface, communicating with the outside world. The scientists say the nerves can detect subtle changes of temperature, pressure, particle gradients and probably much else, giving the animal unique insights.
Evolution works with the tools at hand. The Narwhal is now Darwin's poster child.