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In our journey so far we have explored the impacts of the Earth's Spin and Orbit on the weather and climate.

The final instalment of the series explores the influence of the tilt on the Earth's weather and climate, and how the Earth's relationship with the Sun affects the way we live our lives.

Originally the series was called 23 Degrees, (the angle of the tilt) as we considered this factor extremely significant to the variability in seasons our planet experiences. Although the series is now called Orbit, the tilt of the Earth continued to be an extremely important factor of the series. What do you think?

From the arrival of spring in the Hay river to the affects of the monsoon to the people in India, we wanted to uncover how Nature and culture respond to the variations in the Sun's energy.

Kate takes us through the ancient archeological site Chichen Itza, Yacatan region of Mexico. At its peak, in the 10th century AD it was a thriving city that sprawled over 25 square kilometres and was home to more than 40000 people.

We wanted to explore how ancient civilizations had developed a great understanding of our Earth's journey around the Sun, and Kate takes us there on a significant day; the March Equinox. How significant are sites such as temple of Kukulkan and Stonehenge to us today?

In this episode we also wanted to breakdown the key factors that drive the extremes of weather like the Monsoon, Dust storm and the Tornado.

Helen travels to Kerala, South of India to discover what drives the Monsoon and visits Tornado Alley with atmospheric Scientist Josh Wurman to explain 'What causes a tornado?'

A record six EF-5 tornadoes were confirmed in 2011, the most deadly being Joplin Missouri tornado (158 killed, 14 mile path length.)

What do you think about Episode three? How significant do you think the Earth's tilt is to our climate and weather? How far are we in understanding why one supercell drops a tornado and another doesn't? Has our cultural relationship with the Sun changed over time? Leave your comments on this post.

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Distance travelled ~ 552'669'600 km

(Eileen is the Assistant producer on 23 Degrees. From chasing the storms in the US to capturing the monsoon season in India, she has experienced a mixed range of our global weather)

As we drove through our 6th US state, our 5th consecutive day of torrential rain and the 17th playing of Stairway to Heaven from the cameraman's iPod, I wondered where it had all gone wrong... Just a week before, it was looking so promising. We were heading out to the USA's famous 'tornado alley' to shoot the ultimate weather phenomenon.

With a mountain of water-proofs, an SUV the size of a small English village and a crash course in weather lingo (note - if you want to sound like a storm-chaser, just call rain 'precip'), we were ready to go and had visions of bringing home a Hollywood style twister... And we had reason to be optimistic. We were going on the road with one of the world's most eminent tornado scientists, 2 of his state of the art 'Doppler on Wheels' radar trucks, 3 scientific support vehicles and a team of professional storm-chasers. If anyone could find us a tornado, it would be this lot...

But by Day 3, I realised I might have to revise the energetic, adrenaline-fuelled storm-chasing sequence I had in my head. It turns out that the real grunt work of tornado chasing is about as action-packed as a paint drying convention. Each morning our scientists would park themselves in the lobby of whatever glamorous motel we'd ended up in, fire up their laptops and stare intently at satellite pictures of weather. I mean it was pretty rigorous staring to be fair, sometimes with accompanying pointing and the occasional mumble about ridges and troughs, but not quite the gripping, high-drama telly sequence I'd had in mind...

After an agonizing 3 or 4 hours of this (during which I'd only just manage to resist posting a photo of them on Twitter with the heading 'Storm-chasing - Not as exciting as you might think...') a decision would finally be made about where we should head to for the best chance of tornadic activity and we would hit the road.

Ah the road. With romantic visions of how to make the perfect blend of 'classic American road movie meets classic force-of-nature movie' I knew things would start to look up once we hit tarmac.

And yet somehow, despite knowing that tornadoes are the product of 'severe thunderstorms', what I hadn't quite counted on was the rain. Not nice, gentle, intermittent British rain. No this was relentless, pounding, torrential rain that laughed in the face of our extreme weather gear.

But in true documentary filming style, we made the best of it and filmed whatever we could. Which was mainly our presenter Helen Czerski- in the rain. We filmed her walking, talking, sitting and driving in the rain. Looking up at the rain, down at the rain and through the rain. We had the makings of a truly great rain sequence totally covered...

By the beginning of Day 5, we'd driven over 2000 miles, but still no tornado. It was our final day on the road and we all knew it was our last chance.

By 6pm, we were ready to give up. We had a 5-hour drive ahead of us to reach Kansas City for our flight home the next morning. But there was 'one last storm' on the horizon that looked promising so we decided to give it one final go. We'd had many supposedly 'promising' storms already so expectations were low. But as we drove through the rain, a crackling voice came over the radio saying 'Tornado to our immediate North East - all vehicles use extreme caution'.

We turned a corner and there it was. A large, black, funnel-shaped twister travelling steadily across the Nebraskan countryside.

5 minutes later it was all over. But we had our footage, we'd seen a twister and were returning to London happy...

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Distance travelled ~ 538'572'800 km

(Dr Joshua Wurman created the Doppler On Wheels (DOW) mobile radars which observe tornadoes, hurricanes, wildfires, and other phenomena from close range. He has been actively chasing storms, for science, since 1995. One of the key objectives of the research carried out by him and his colleagues is to better understand what generates a tornado)

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HelenÌýCzerski - So we've got all this data that the truck is measuring, so what can we see?

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Dr. J

oshua Wurman - Well the radar can measure both winds and precipitation, rain and hail inside the storm. So we can see the red area here, which is precipitation, rain and hail in a super cell, and then these browns and blues here represent different wind speeds, different Doppler wind speeds.

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And then there are other fields, we can also look at the difference in the return from horizontal and vertical polarised microwaves and we can tell the difference between hail and rain. Rain, big raindrops look kind of like hamburger buns and they return more energy horizontally, and then vertically, so we can tell if it is heavy rain. Hail stones are very irregularly shaped and they are also tumbling, so if we look at a million of them in our radar volume they average out to zero orientation, so we can tell the difference between hail and rain, like in the areas we were just experiencing outside.

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Distance travelled ~ 521'206'400 km

(Following on from Henry Margusity's blog - 'Joplin tornado - one of the 10 deadliest on record?', George Kourounis shares his take on 2011's tornado season. George Kourounis Is the first storm chaser to ever be elected into the prestigious Explorers Club, and each spring he guides tornado chasing tours in the central U.S.)

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We all have a weather story... Perhaps lightning struck across the street from you or maybe you have vivid memories of that unexpected storm that rumbled through one afternoon and pelted you with hail while you were on your way to Aunt Susan's house. The weather is the one subject that we can all talk to each other about. It's not political, not religious, it affects us all and plays a role in just about every aspect of our lives. It's no wonder that whenever we try to make small-talk with a stranger on an elevator, we invariably lean towards the topic of the day's weather. "Sure is hot out today isn't it?"

I just happen to have more weather stories than most. As a storm chaser for the past 14 years, I've seen a lot of very, VERY bad weather. In fact, I've travelled the world, to all 7 continents and over 40 countries, documenting the most extreme forces of nature from tornado outbreaks in Kansas to the eye of landfalling hurricanes, I even got married on the crater's edge of an exploding volcano in the South Pacific.

The 2011 Tornado season in the U.S. has been unlike any I've experienced, not only for the record breaking number of tornadoes, but also the fact that many of these storms have struck densely populated urban areas, resulting in tremendous loss of life and widespread destruction.

In April, the deep south states of Mississippi and Alabama were hit hard by powerful, fast moving tornadoes that did incredible damage in places like Tuscaloosa. The peak of tornado season typically arrives in May and the deadly trend continued with Joplin, Missouri taking a direct hit on May 22nd. I chased that storm and our team arrived on the scene about 2 minutes after the tornado had passed and we had to instantly switch from being storm chasers to being first responders as we assisted with injured motorists on the side of the main highway. Others were not so fortunate and a large part of the city was simply leveled in a display of natural power that I've never seen the likes of before.

As the month progressed, another outbreak of tornadoes raked across Oklahoma, causing more devastation and loss of life. In total over 1,500 tornadoes have touched down so far this year with 5 of them being ranked as EF-5 on the Enhanced Fujita scale, the highest possible rating.

ÌýÌýÌýÌýÌýÌýÌýÌýÌýÌýÌýÌýÌýÌýÌý Image © George Kourounis

So what's to blame? How did this all happen?

Currently there is no direct link between climate change and tornado production, but the waning La Nina ocean pattern in the Pacific has caused the jet stream over North America to persist in an orientation that helps develop supercell storm that produce tornadoes. Couple this with the increasing population density that keeps expanding these regions and then add an unfortunate dose of bad luck to the mix and we end up with a tragic season like 2011 has been.

Tornadoes are a naturally occurring phenomenon but they only make the shift from "natural phenomena" to "natural "disasters" when they have a direct impact on communities of people unfortunate enough to find themselves in the path of these wicked winds. There is still much to learn and many improvements to be made in the warning systems for these communities and that's part of the reason I'll continue to find myself out there, prowling the great Plains for many more years to come.

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(Whilst the 23 Degrees team were trailing the Centre for Severe Weather Research DOW's on Monday 20 June in Nebraska, this amazing footage of the massive tornado was captured by team. For licence of this video please contact them directly)

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