Weatherwatch: Those clouds that 'float on high o'er vales and hills'

Clouds have dominated the British summer this year, thanks to a pesky "jet stream" whose high level winds are tracking farther south than normal, spinning up low pressure systems over the Bay of Biscay and spitting them out to the south-west of the UK. Instead of the sunshine we might hope for, we've seen storms and flooding in recent weeks. June's leaden skies and persistent rain have been the product of frontal systems – moist, warm, air masses being forced to rise over cold, dry and dense air. As the warm air rises, it cools and condenses out, creating cloud along the line of the front. For much of June the clouds have been stratus: flat, grey and overcast. During a more typical British June we might have expected to see more cumulus clouds, like the ones that William Wordsworth so famously described: "I wandered lonely as a cloud / That floats on high o'er vales and hills". These cotton wool puffs often bubble up during summer afternoons, forming above columns of warm air, which rise up from ground being heated by the Sun. Naming clouds is easy, but their ephemeral nature and relatively small size make them a major headache when it comes to modelling them. And yet climate modellers can't afford to ignore clouds because they have a huge influence on Earth's climate – a 4% change in Earth's cloudiness would change the climate more than the current carbon dioxide induced global warming.