“Climate change at the present is of great consequence to most species including humans.“
By Dr. John J. Hidore
November 15, 2017—-Planet Earth was formed about 4.5 billion years ago. Geologists have divided this long history of the planet into several pieces called eras. They are the Precambrian, Paleozoic, Mesozoic, and Cenozoic.
The Precambrian is the longest and each of the other three are shorter than the previous one. When considering climate change through geologic time, two aspects stand out. The first is that for most of geologic time Earth has been warmer than it is at present. How much warmer varied through time. The second feature that stands out is the intermittent ice ages when large portions of the earth were covered with ice.
Major Ice Ages
Relatively little is known about the long period of Precambrian time. Basically it was the period during which the earth cooled from its initial very hot state. The Paleozoic, Mesozoic, and Cenozoic eras encompass the rest of geologic time, about 570 million years. More evidence, and a greater variety of
evidence, is available about the environment during these eras. The climate of Earth varied widely during this time. However, it has been established that there were three known periods of glaciation in Precambrian time. They were:
Archeozoic 2250 million years ago (mya)
Early Precambrian: 950 million years ago
Late Precambrian: 750 million years ago
There were four major glaciations following that of the Precambrian era. They were:
Early Cambrian: 650 mya
Ordovician: 450 mya
Permo-Carboniferous: 350-250 mya
Pleistocene: 1.8 mya until recent time
Following the ice age at the end of the Precambrian, the earth rapidly warmed. For the remainder of the history of the earth, temperatures have averaged 5 degrees C (9°F) higher than at the present. These warmer conditions existed probably 90 percent of the time over the past 570 million years.
The Permo-carboniferous Ice Age
An ice age, called the Permo-carboniferous, began at the end of the Paleozoic Era. It began about 325 million years ago and lasted until about 250 million years ago. The South Pole was in the midst of the large land mass called Gondwanaland. Ice sheets moved over about half of this large land mass. What is now Antarctica and parts of Australia, India, Africa, and South America were covered with ice. The glaciation of each of these areas did not take place at precisely the same time, but they were all affected by the same climatic cooling. The Southern Hemisphere suffered widespread glaciation, but the Northern Hemisphere remained warm. The most appealing explanation for this situation is a different relative location of the land masses. The northern continents were nearer the equator and the southern land masses nearer the poles.
The Warming of the Earth
After the glaciation in the Permo-Carboniferous ice age, the earth again entered a long period of warm conditions. The period of warmth continued through most of the Mesozoic Era and the earth was free of glaciation. Temperatures were warm and rainfall was abundant on the land masses. Even the polar regions experienced mild weather. Initially, the warmer conditions resulted from the slow migrations of the large southern hemisphere land mass to the north. This carried areas that had been glaciated into warmer climates.
The Pleistocene Ice Age
The most important single environmental event since the human species has been on earth has been the oscillation between glaciation and interglacials during the Pleistocene Epoch. The epoch represents a large change from much of the last 570 million years. This ice age is the most recent of the major cold periods to occur over the history of the planet. During the time when the ice was most extensive over Earth, temperatures averaged about 4°C (7°F ) lower than those of the present. In the northern hemisphere it was perhaps 8 to 12 °C ( 14 to 22°F) lower than current temperatures.
There is no question but what the climate of planet earth has changed frequently, and sometimes drastically, over geologic time.
Climate Change Today
Climate change at the present is of great consequence to most species including humans. There is really no way of knowing how much change will take place in the foreseeable future nor how much is due to the activity of our species. What is known is the earth is warming rapidly at this time and that all evidence points to human activity as bearing the responsibility.
Now is the time to take international action and not only support the Paris Agreement, but take even more drastic measures to curtain the warming!
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