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Anthropocene Epoch | Geological Periods and Climate Change

Upcoming geological periods

With climate change ruling the environment discourse, the sudden warming of the Earth in contemporary times prompted an official expert group to present a recommendation to the International Geological Congress to declare the geological period beginning since 1950 as the Anthropocene epoch. Since 2009, the Working Group on the Anthropocene (WHA) has been working to set up a working model for the Anthropocene Epoch. The epoch would be said to mark the impact of modern civilization on the climate and environment of the Earth involving humankind’s impact on global climate.

The beginning of Anthropocene age, marked by the numerous nuclear tests and consequent detonations that had dispersed radioactivity in areas around the world, also would have to take into account for large-scale environmental effects caused by anthropogenic interventions such as plastic pollution, greenhouse gas emissions, environmental contamination, and several other effects. Although the changes have been said to be initiated, statigraphers cannot yet come to a conclusion on bringing changes to the geological time scale.

Talk of the Anthropocene epoch is taking place because the current epoch – the Holocene – is marked by largely stable climate over the last 12,000 years since the previous age – the Ice Age.

The Holocene epoch is the period within which all of human civilization developed, and many experts are calling for its end with large scale changes such as greenhouse gas emissions, sea level rise, development activities, destruction of ecosystems, and the extinction many animal species (Carrington, 2017), which should alter the planet to an extent similar in scale to a change in epoch, and is said to be principally manifested in its genesis as climate change. Human civilization has so far inhabited a planet that has seen no massive planetary shifts in climate, in a period of relative stability.

However, the changes that human intervention have initiated are so aberrant that it is expected that climate change will not be the only defining feature of this epoch, with the introduction of an incredible array of chemicals in the soil, water and atmosphere; and incredible changes to the geomorphology of the planet; that could change the entire biosphere at a pace not witnessed before in the history of life on Earth.

On the other hand, it is argued that new basis of planetary order could arise, such as the electronic medium, which for now is in the realm of popular science. The full effects of anthropogenic changes on the geology of the planet could have rather serious and tragic implications that until now have not been fully charted. However, based on trends in changes in geological periods, we can get a sense of one important aspect of the effects of anthropogenic interventions on transitional aspects of geological periods – climate change.

Climate Change and Geological Periods

The driving aspect of climate change is the rising up of the Earth’s temperatures by the accumulation of greenhouse gases, primarily CO2 in the atmosphere, which act to trap the solar heat that is reflected back from the Earth’s surface, leading to a rise in temperatures.

Although the Earth since its formation is said to be gradually cooling down cumulatively, in the more recent time scale since the Ice Age, temperatures have increased, although in the present Holocene epoch, they have remained quite stable in general. The comparative stability of plate tectonics in the last 50 million years allows geologists to better study geological periods since about this time.

These epochs thus fall within the broader period among geological periods called the Cenozoic Era. Generally the Earth has been cooling, and this follows a fairly warm period about 45 to 55 million years ago called the Eocene Optimum, when much of Antarctica was without an ice cover. The cooling process post the Eocene Optimum is said to have begun 34 million years ago during the Eocene-Oligocene boundary climate transition when due to the cooling of the Earth, an ice sheet had formed over Antarctica.

Atmospheric CO2 during this period is said to have fallen to below 750 ppm. Evidence from sedimentary cycles from the Ross Sea point towards glacial cycles between 34 to 31 million years (Galeotti et al., 2016).

Cenozoic

Fig: The Cenozoic Era among Geological Periods, which includes the recent epochs
Source: hoopermuseum.earthsci.carleton.ca

However, within these epochal transitions, the Earth’s climate, including its temperature, showed wide variations. Going by fossil records, the Eocene Optimum displays evidence of an abundance of forest areas, with most species being species adapted to tropical conditions, although there were arid conditions as well.

In the Ice Age, although most species were those adapted to cold conditions, tropical species thrived in the lower latitudes. With changing climatic conditions over time, certain species adapted while others went extinct.

Climatic variations could be due to conditions on earth itself or due to extra-terrestrial reasons such as due to changes in the amount of heating provided by the Sun. Geological evidence however, makes a strong case for Earth’s own volition rather than in extra-terrestrial reasons. Climatic patterns have largely fluctuated somewhat even though the long term trend has been the cooling down of Earth.

For example, climate during the Ice Age was particularly unstable, with frequent temperature fluctuations ranging more than 10 degrees Fahrenheit. The fluctuations largely follow changes in the tilt of the Earth’s axis and in the shape formed when the Earth orbits the Sun.

These are defined as Milankovitch Cycles, and are caused by the gravitational forces in the Solar System caused by the Moon and other planets besides the Sun. However, Milankovitch Cycles do not result in as large of fluctuations in temperature as were said to have occurred over geological periods, unless there were factors on Earth, those influencing climatic patterns that would aggravate the warming effect. The Earth exhibits certain intrinsic characteristics that lead to a rise in temperatures and a change in climatic patterns between geological periods and within them, over time.

Due to bubbles containing air from the Ice Age preserved in glaciers in the Arctic and Antarctic, it is possible to evaluate the atmospheric composition of the period with certain accuracy. Evaluation of earlier geological periods is more difficult, and the composition of marine sediments as affected by oceanic CO2 and studying its effect on fossilized leaves of plants from these geological periods are some examples of methods used to evaluate the atmospheric composition in these geological periods.

Although investigations reveal that the Earth’s overall cooling process has been accompanied by a gradual decrease in CO2 levels along with certain other greenhouse gases, their levels have fluctuated in between that have caused significant changes in the Earth’s climatic patterns.

CO2 levels during the extremely warm Eocene Optimum were said to be between 2,000 and 3,000 ppm while those for the much colder Ice Age are said to be about 200 ppm (Menke, 2014). In pre-industrial times in the current Holocene epoch, CO2 levels had reached to about 280 ppm. By 2016, the CO2 levels reached to over more than 400 ppm (Jones, 2017).

However, atmospheric CO2 is not the only determining factor in raising Earth’s temperatures. Other factors can also be involved such as other greenhouse gases, amounts of ice cover and persistent cloud cover, which reflect sunlight back into space, and other possible concomitants can be the amounts of areas on the Earth covered by forests and oceans, which absorb heat.

Although evidence is altogether unsatisfactory on whether greenhouses gases alone could have caused the high global temperature levels in the Eocene Optimum, rising to about 5 to 6 degrees Celsius above previous levels (De Conto et al., 2017), global climatic models suggest that such high levels of warming could only have occurred due to the proliferation of greenhouse gases.

This rise in temperatures during the Eocene Optimum eventually led to the melting of the polar ice caps, such that sea levels rose to 200 feet above previous levels (Menke, 2014). Data suggests that climate change, although slow to begin, could accelerate over time if left unchecked. A rise in greenhouse gas levels similar to previous warm epochs such as the Eocene Optimum, which was the warmest period in the Earth’s recent history, could be devastating for most living things not adapted to warm climates.

It is said that during the Eocene Optimum, cold-blooded creatures like crocodiles inhabited areas close to the polar regions such as present-day Greenland. Though there is uncertainty as regards the exact levels of CO2 during the geological period when the polar ice caps had largely melted, the rate of increase in CO2 levels can be determined based on cumulative estimates.

Modern levels of atmospheric CO2 are accelerating at a pace unprecedented in the history of previous geological periods. The annual rate of increase for atmospheric carbon di oxide levels in the late 1950’s was 0.7 ppm/ year, while between the years 2005 to 2014 this had increased to 2.1 ppm/ year.

Although the effects are slow to be realized, with the IPCC predicting the possibility of a rise in global temperatures by 3 degrees Celsius by 2080 (Jones, 2017), the longer term effects with an increasing rate of acceleration in global atmospheric CO2 levels could have devastating effects on the Earth’s climatic patterns.

A full estimate of the effects of this process cannot be definitively ascertained due to the vastness of the scope, but there is no doubt that this uncertainty adds to the need to form better estimates of the effects, which are extremely difficult to define and attribute. Although we know that global CO2 levels annually are accelerating, there cannot be any estimates over how the trends are going to play out in the coming years. Without a global concerted effort towards checking carbon emissions, humankind is exploring uncharted territory. The in depth study of geological periods although should help us better understand the effects of climate change.

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