How Warmer Climate Can Mean More Life
My interest here is the rise of mammals and climate change following the extinction of the dinosaurs and environmental changes that followed. Starting at 65.5 million years ago we have what is called the Paleocene epoch. This lasted until 56 million years ago. At this time mammals radiated across the ecological spectrum, as did giant flightless birds and other predators.
Then begins the Eocene epoch starting at 56 million years ago lasting until 34 million years ago. Cloven-hoof herbivores appeared in large numbers as did the first primates. Bats also appeared as did the earliest horses and primitive whales. Also appeared were ancestors to elephants and many other mammal species.
Then we enter the Oligocene epoch that lasted from 34 million years ago to 23 million years ago where plants and animals become very similar to what we see today evolved. By the end of the Oligocene continents were mostly in their present positions and sea level was approximately the same as today.
A substantial change from the Eocene to the Oligocene epoch was a massive drop in global temperatures. The Eocene epic was far warmer than it is today and that is the discussion for the rest of this article. These three epics are known collectively as the Paleogene.
By studying fossils and oxygen and carbon isotopes1 it's been determined that at the beginning of the Eocene epic deep-sea waters warmed by several degrees to 64 degrees F. This occurred in less than 3000 years and may have led to the release of methane from methane hydrate ice on continental shelves. What triggered this event is unknown.
The warmer temperatures resulted in an explosion of plant and animal life across entire continents. Palm trees were growing in Wyoming and their fossil remains could be found as far north as southern Alaska. What is England today had tropical forest similar to modern Malaysia.
Tropical forests ringed N. America, Europe, and Asia. Mongolia and New Mexico today barren desert teemed with life.
Of interest is Ellesmere Island in Canada. Ellesmere today lies north of the Arctic Circle, but even here the land was covered with lush forest. Plant fossils indicate that even in winter the island had a climate similar to Southern California. The fossil remains of large tortoises and alligators shows that even winter temperatures remained warm.
While CO2 and methane certainly contributed to greenhouse conditions the primary greenhouse gas once the process got going was water vapor. Greenhouse warming was stronger during the Eocene than it is today. Abundant water vapor contributed to the warming, the vast forests helped retain water and through a process of transpiration kept large volumes of water vapor in the atmosphere.
The end of the Eocene warming epic came when Antarctica became separated from Australia and South America. Circumpolar currents around the icy continent dropped ocean temperatures and large volumes of water vapor fell as snow and ice on the southern continent.
This led to the large-scale drying and spread of scrub, savannah, and deserts as forests died out across the planet. The loss of plants led to further drying on the continents. Many species of animals and plants became extinct, but would be replaced by forms we are more familiar with today.
Today satellite data shows that the earth is greening and the expansion of plants caused by higher CO2 levels and a slightly warming climate. This can also further alter the climate as more plants create more water vapor and water vapor leads to a warmer climate, thus more animals and plants. Warmer climate plus abundant water with plants equals an expansion of life. That is what the geological record shows us.
The Eocene warming event is very unlikely to happen again as Antarctica continues to moderate climate temperature. Ice continues to expand there and temperatures have hit record lows.
Hysterical environmentalists whose real gripe is humans are altering the planet as if it was some kind of sin ignore the fact the climate is constantly changing and has had far, far more drastic changes in the past than anything we can do today. Life did just fine and will continue to do so.
Ref. Earth System History by Steven M. Stanley P444-45.
1. Isotopes are atoms that have the same number of protons but differing numbers of neutrons. Oxygen has two stable isotopes 16 and 18 - Oxygen 18 has two extra neutrons and is heavier than Oxygen 16. While they have the same chemical properties organisms produce differing ratios depending on temperature. More Oxygen 18 means cooler environment. (See above.) Both isotopes have 8 protons.
Carbon has two stable isotopes 12 known as "light" carbon and carbon 13 with an extra neutron. (Atomic weight is the sum of protons and neutrons, atomic number is the number of protons.) Carbon has 6 protons. Heavier carbon 13 is distributed through the system differently than carbon 12 and organisms prefer carbon 12, but plants can evolve to use any ratio. Burial of organic material leaves a higher proportion of carbon 13 - fossil fuel burning produces more carbon 12, super plant food for some plants, not so much for others. Stanley P224.
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