What if the Earth turned in the other direction?

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The Earth turns in the same direction as the sun, and has done since its formation around 4.5 billion years ago. But what would happen if it suddenly started to turn the other way? 

According to a computer simulation presented recently at the European Geosciences Union in Austria, in such a case, desert would cover North America, and arid dunes would replace the expanses of the Amazon forest in South America and the luxurious green countrysides of central Africa and the Middle East.

In the course of the Earth’s year long orbit around the sun, the Earth completes a full rotation on its axis (from the South Pole to the North Pole) every 24 hours, turning at a speed of around 670 km/h (measured at the equator). The direction of its rotation is called “prograde”, meaning West to East, similar to all the other planets in our solar system, except for Venus and Uranus.

As the Earth gradually turns, the push and pull of its momentum creates ocean currents which, along with atmospheric winds, produce an array of weather models around the world. These models lead to abundant rains in the tropical jungles, or divert moisture away from dry areas, for example.

In order to study how the Earth’s climatic system is affected by its rotation, scientists recently mathematically simulated the Earth’s rotation, but in the opposite direction.

The simulated rotation appears to maintain all the major characteristics of the planet’s current topography, such as the sizes, shapes and positions of the oceans and continents. This new configuration however allows ocean currents and winds to interact differently with the continents, generating entirely new climatic conditions throughout the whole world.

All in all, the researchers discovered that an Earth that rotated from East to West would be a “greener” Earth. The proof is that global desert coverage would go from around 42 million kilometers squared to around 31 million kilometers squared. Grass would sprout in half of the current desert areas, and woody plants would emerge and cover the other half. However, desert would appear in areas in which it never was before: in the South West of the United States, in the South of Brazil and in Argentina, as well as in Northern China.

Reversing the rotation would also alter global wind trends, bringing temperature changes to subtropical regions and to middle latitudes. The Western side of continents would cool down, while the Eastern sides would heat up, and winters would become much colder in the North West of Europe.

Ocean currents would also change direction, heating up the sea’s eastern boundaries and cooling the western ones, according to the researchers during the conference. The Atlantic Meridional Overturning Circulation (AMOC), an important ocean current which regulates the climate in the Atlantic, would die out, to resurface in the Northern Pacific, bringing heat towards Eastern Russia. In this hypothetical case, the modification of marine currents in the Indian Ocean would also allow cyanobacteria to dominate the region, which they have never managed to do with the current rotation.