Weatherwatch: no signposts in the sea – but clear tracks overhead

Ship condensation trails are wider and fainter than those left by aircraft, but are visible in satellite images

On a clear winter’s day, the sky is full of condensation trails from aircraft. More surprisingly, ships also leave faint trails in the sky, an effect not studied until the 1980s. Like aircraft contrails, ship tracks are formed when water in the atmosphere condenses around tiny particles.

A study in the 1990s set out to discover whether the ships’ exhaust was responsible, or salt crystals thrown up by their wake. A nuclear-powered aircraft carrier with no exhaust left no cloud trail, unlike diesel-powered ships in the same conditions, indicating exhaust particles were the main factor.

Related: Aircraft contrails bring warmer nights and conspiracy theories