Orbit: Episode Two

    The second instalment of the series follows the Earth's journey from the start of January to the Spring Equinox in March. Available on iplayer. What did you think?

    Kate begins the film on a day with a very significant point in our Earth's journey - Perihelion. Kate climbs Aonach Mor mountain, one of the highest mountains in Scotland, which brings her as close to the Sun as she'll ever be for the entire year.

    This however is not because of where she is but because of the point the Earth has reached in its orbit around the Sun. In fact we kick started our blog on this day just over a year ago, when we explored the elliptical shape of our planet's orbit and how significant this was to our understanding of Earth's climate.

    Later in the film Helen explains how the proximity of the Earth to the Sun doesn't guarantee warmth - which brings us to the tilt of the Earth (23.4 degrees) - a theme we explore in further detail in episode three.

    Throughout this episode Kate and Helen explore the increase in solar radiation and how land and ocean respond to it.

    Kate drives over a frozen lake in Canada with an ice road trucker in one of the coldest places in that region and learns how important this ice formation is to connecting communities.

    In this film we also tackle ice ages and how over time, as Earth has repeated it's annual journey, it's climate has changed.

    Helen dives under water in Belize to discover how sea levels have risen and fallen over time due to ice age - and explores the three cycles that need to be right in order for another ice age to exist.

    What did you think of episode two?

    (There are a total of three episodes in this series)

    Behind the scenes: Physicist in freefall

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    Helen Czerski Helen Czerski | 17:00 PM, Wednesday, 23 November 2011

    Distance travelled ~ 840'555'200 km

    helen czerski


    Being surrounded by sky is not a natural place for a human being. We have evolved to scoot about on the bottom of the atmosphere, stuck to the ground, and we don't often look up. Even when we do, we tend to see the sky as flat - clouds, the moon and aeroplanes move sideways across the sky. It's easy to forget that the sky has depth too, and that air in the atmosphere moves up and down as well as sideways.

    Your perspective changes quickly when you're in freefall, three thousand metres above the Earth's surface and travelling downwards at 120 mph.

    sky full of cumulus clouds


    Skydivers relish the sense of freedom that falling through the sky brings. There is nothing to get in the way, nothing touching you and a whole extra dimension to play in. For the air in our atmosphere, three-dimensional movement is normal. At the place where I jumped out of the plane, in Arizona, air that starts about 10 miles up is gradually sinking towards the ground. The air doesn't make the squeaking noises that I did, but then it isn't falling nearly as fast - it's a few millimeters per second on average. I was falling through a giant atmospheric waterfall, but a very slow one.

    It's not just in Arizona that this happens. Although weather maps tend to show sideways winds, the air making up those winds is all rising and falling as it travels around the Earth. The paths of air parcels weave in and out of each other, making the Tokyo subway map look simplistic by comparison.

    tokyo subway map

    Image courtesy of Tokyo Metro

    All this is very interesting, but not much comfort to a plummeting physicist. I don't think that I really breathed during the 40 seconds of freefall. Then the parachute opened, everything slowed down, and my brain stopped panicking and started appreciating what was going on around it.

    Seeing the layers of the sky is fascinating. Floating down past a cloud is amazing - a fluffy cumulous cloud is telling you that there's been a little puff of air upwards in that location. We can't really see the structure of the atmosphere, but seeing a cloud from the side makes it easy to imagine the turbulent swirls that are mixing all that air up.

    After five minutes of sharing the three dimensions of the sky with the clouds, we arrived at the landing zone and my feet touched the ground again. I was very happy to feel something solid under my feet, but there was also a small sense of loss. I was back to crawling around on the bottom of our fabulous three-dimensional atmosphere, and my understanding of the depth of the atmosphere was again limited to hints given away by the clouds. But I remember what it felt like, and my view of the sky will never be quite the same again.

    In a constant search for equilibrium

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    Jonathan Renouf | 11:00 AM, Wednesday, 5 October 2011

    (Jonathan Renouf is an Executive TV Producer making documentaries for the BBC 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...

    cob web

    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.

    How often do the remains of hurricanes affect the UK

    Distance travelled ~ 647'488'000 km

    Hurricane Katia, currently in the western Atlantic is set to steam due east towards the UK and is expected to reach our shores as a post tropical storm later in the weekend . With it will come the risk of severe gales and heavy rain to parts of the UK. The strength and depth of this September storm is quite unusual, but similar storms that originated as hurricanes have affected the UK in the last 20 years several times.

    Hurricane Bill - 2009

    You only have to look back as far as 2009 to find a storm that crossed the Atlantic. Hurricane Bill formed on August 15th and reached the UK as a post tropical storm on August 25th, bringing severe gales and heavy rain two days after being downgraded from a hurricane to a tropical storm.

    Hurricane Alberto, Gordon and Helene - 2006

    In 2006, three post tropical storms reached the UK. Alberto, Gordon and Helene all brought wet and windy weather to the UK. Alberto combined with a cold front to the west of the UK whilst Gordon brought record warm temperatures as tropical air pushed north across the UK, but also strong winds that brought down power lines in Northern Ireland.

    Hurricane Isaac and Leslie - 2000

    These two hurricanes both affected the British Isles in the year 2000.

    Hurricane Karl - 1998

    Hurricane Karl made its way to southern Britain in 1998.

    Hurricane Lili - 1996

    Perhaps the most similar storm to Katia was in 1996 when the remains of hurricane Lili pushed across the UK just one day after being downgraded from a hurricane. The post tropical storm ran across Britain on 28th and 29th October. The storm brought gusts in excess of 90 mph, bringing widespread impacts across the UK and causing significant disruption.

    Hurricane Katia - 2011

    Katia is currently a category one hurricane off the east coast of the US and will run across the Atlantic through the weekend bringing the risk of severe gales and storm force winds in places later on Sunday and through Monday.

    Although it is expected to be windy everywhere, it is uncertain as to exactly which parts of the country will see the very strongest winds and therefore you should stay up to date with latest forecast warnings.

    Cyclone watch: 70% chance of tropical cyclone formation in next 48hrs

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    Aira Idris Aira Idris | 17:00 PM, Tuesday, 6 September 2011

    Distance travelled ~ 639'876'800 km

    Visible satellite images indicate that the shower activity associated with a low pressure area centred about 680 miles west-southwest of the southernmost Cape verde islands, is gradually becoming better organised and a tropical depression could form later today or wednesday.

    graphical tropical weather outlook


    Chances are that this system will move toward the west or west-northwest at about 15mph and has a high chance..........70 percent.........of becoming a tropical cyclone during the next 48 hours according to the National Hurricane Center.

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