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(Jonathan Renouf is an Executive TV Producer making documentaries for the Ö÷²¥´óÐã Science department. His most recent projects are 'Wonders of the Universe' with Brian Cox, history of global warming "Earth: The Climate Wars", the BAFTA nominated "Earth: Power of the Planet" and the highly popular and critically acclaimed 'How Earth Made Us', which transmitted in January and February 2010. Here he shares his insights on making 23 Degrees (working title) due to transmit early 2012.)

Distance travelled ~ 713'844'800 km

A couple of days ago my baby son woke me up early, and even though I got him back to sleep, I was too awake to settle down. Eventually, at about 6.00, I gave up, got out of bed and decided to go out on my bicycle. I live in Cookham, close to a picturesque stretch of the River Thames, so I cycled down the lane towards the river. As soon as I left our suburban close behind, my heart leapt. A mist lay over the fields - just a few metres thick, but dense, and tinged magenta by the dawn light. Down by the river the mist hung over the water, and a grebe drifted into view on the mirror flat surface. In the distance I heard an early train clanking along the branch line towards London. A few last stars flickered above me as the sky lightened. And all around there were cobwebs thick with dew. I settled down to take some photos of the cobwebs, happily absorbed in the task of trying to capture their fragile, jewel-like beauty.



Isolated in my riverside reverie it would be easy to forget that we are hurtling through space, on a planet that is tilted over on its axis, spinning as we go, travelling on an orbit that takes us closer and then further from the Sun. And yet one of the wonderful things about working on 23 degrees is that it has given me a magical new perspective on mornings like this. Intensely local phenomena such as the dawn mist I experienced are also part of a much bigger picture. Dawn mists are a consequence of the longer - and therefore cooler - nights, which in turn relate to our 23 degree tilt and the seasons it creates. 



But the most revealing insight I've gained from the series is the notion that all our weather is driven by gradients - and by the way the Earth seeks to even them out. Gradients are created whenever two (or more) parcels of air (or water or ground) are next to each other, but with different properties - for example, a hot parcel of air next to a cool parcel of air. This means there is a temperature gradient between them, and the Earth system always seeks to even out these differences. The trouble is, there are constant energy inputs creating (or adding to) these differences. Put another way, the climate system is in a constant search for equilibrium, but our journey around the Sun keeps throwing the system out of kilter.



Gradients exist at every scale of the climate system, and crouched down with my camera in the cool, clammy air, I was experiencing one very directly. As the nights lengthen into Autumn, the ground radiates more and more heat back to space. The land cools down, setting up a temperature gradient between the land and the air above. The ground cools the air - attempting to equalise the gradient - until the air reaches its condensation point, forming mist. But then, as the Sun rose, the ground warmed, the air warmed with it, and within a few minutes the mist vanished - the gradient gone.

When I got home almost an hour after leaving I was relieved to find the house still quiet. Just enough time to download this photograph...

Working on 23 Degrees has given me terrific new insights into how our world works, why it is the way it is, and what makes it change. Hopefully when the series is transmitted early next year, you'll get to enjoy those insights too.

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