How would global weather patterns change if Earth were to rotate in the opposite direction?
Nick Canning
Coleraine, County Londonderry, UK
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Local weather is produced by the interaction of landmasses with the air and sea currents that transport heat and water. Changes in these flows would profoundly alter the weather, resetting the climate on each continent. Patterns of arid versus verdant land would change across the world.
On an Earth with reversed spin, the direction of Coriolis forces – the deflection of air movements to the right in the northern hemisphere and left in the southern due to the spin of Earth – would reverse. So wind circulation around low-pressure zones would reverse from anticlockwise to clockwise in the northern hemisphere (and vice versa in the southern hemisphere).
The jet stream would reverse direction, so weather fronts would travel from east to west over Europe, reducing the annual rainfall in the UK. Thermally driven sea currents north of the equator would change direction from north-east to north-west, disrupting the Gulf Stream and making the UK colder in winter.
A indicates that the tropics would remain warm and humid, deserts would form mainly in the Americas and would no longer dominate North Africa and the Middle East, and western Europe would become much colder.
Mike Follows
Sutton Coldfield, West Midlands, UK
One of the most obvious manifestations of weather patterns is the associated winds, caused by air moving from high to low pressure. If Earth rotated in the opposite direction, it would lead to prevailing winds reversing. So, instead of western Europe and the eastern seaboard of the US experiencing westerlies, these regions would be subjected to easterlies. The regional climates would probably swap over too, such that western Europe would have a more continental climate and cold winters, while the eastern US would have a more maritime climate and might have warmer winters.
Graham Smith
Werribee, Victoria, Australia
If a uniform Earth rotated in the opposite direction, there would be little change in the north/south components of the winds, which are largely driven by temperature differences. However, all of the east and west wind components would be reversed. For example, the south-east trade winds would become south-west trade winds at the same latitude.
However, Earth isn’t a uniform ball. A continent in a very large ocean would experience reversed east-west climate. For example, the south-east trade winds bring rain to the east coast of Australia, which mostly drops on the mountains of the Great Dividing Range along the east coast. The water quickly flows back into the sea, leaving arid land on the west side of the mountains. In a reverse-rotation world, the south-west trade winds would bring rain to Western Australia, which would penetrate much further inland because there are no significant mountain ranges for several thousand kilometres.
It is harder to predict the effect on the northern hemisphere because the continents cover much more of the surface area. However, the Indian monsoon currently comes from the south west. In the alternate-rotating world, the monsoon from the warm waters of the Indian Ocean would come from the south-east and dump on the Arabian Peninsula instead of India.
Earth and its history would be very different if the rotation of the planet was different.
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