The change in climate on planet Earth is called ‘global warming’.
Planet Earth: An Illustrated History - Photo Essays - TIME
The invasion of North America from Asia (with a little migration from North America to Asia), while important, was not as dramatic as what happened in Africa a few million years later. About 24 mya, Africa and the attached Arabian Peninsula began colliding with Eurasia. The once-vast Tethys Ocean had finally been reduced to a strait between the continents, and one of Earth’s most dramatic mammalian migrations began. By about 18 mya, proboscidean had migrated from Africa and they reached North America by 16.5 mya. An left Africa but stayed in Asia. As with the North American interchange with Asia, however, the greater change came the other way. Rodents, deer, cattle, antelope, pigs, rhinos, giraffes, dogs (including the ), and cats came over, along with small insectivores and shrews. Most of the iconic large fauna of today’s African plains originated from elsewhere, particularly Asia. Asian animals invaded and dominated Europe and Africa, and became abundant in North America. In general, Asia had more diverse biomes and was the largest continent, so it developed the most competitive animals. That principle, which Darwin remarked on, became very evident when the British invaded Australia in the 18th century: imports such as rabbits and foxes quickly prevailed, and . The most important Miocene development for humans was African primate development, but that is a subject for a later chapter.
The Earth from Space - Photo Essays - TIME
In recent years, Neogene temperatures have been the focus of intensive research. What appears to be the proximate cause of elevated temperatures was a dramatic change in global ocean currents. The final closing of the , the isolation of Antarctica, the creation of , and the opening and closing of land bridges, such as in the Bering Sea and ultimately the land bridge between North and South America, created dramatic changes in ocean currents and global climate. One result was fluctuating . Its production declined beginning about 24 mya, and its weakness lasted until about 14 mya. Consequently, Earth’s oceans were not stratified as they are today, and warm water extended far lower into the oceans than it does today. Also, it reduced the temperature gradient between the equator and poles, which drives global currents: the greater the differential, the more vigorous the currents. It was still an Icehouse Earth, but the “mid-Miocene climatic optimum” was relatively warm. The past three million years are the coldest that Earth has seen since the that ended 260 mya, but this . While the steadily declining carbon dioxide levels of the past 150-100 million years is the ultimate cause of this Icehouse Earth phase, relatively short-term and regional fluctuations have had their proximate causes rooted in other geophysical, geochemical, and celestial dynamics.