view of Earth from space at night - SCANDINAVIA

The Planet We Inherited

“We got here according to the laws of physics. There are no miracles, we are now in charge.”

Sandra Faber, Professor Emerita of Astronomy and Astrophysics
Cosmic Knowledge and the Future of the Human Race

Some 10-12 billion years ago, quantum fluctuations in energy density interacted with interstellar dust particles about the size of particles of cigarette smoke. Thus began the formation of our galaxy and our planet Earth.

In their 2006 book The View from Center of the Universe, renowned astrophysicist Joel Primack and science historian Nancy Abrams contend that every society has a centering cosmology to answer the questions of where its people came from, how they were created, and for what purpose. The heavens, they say, always played a central role. Then a few centuries ago, Copernicus, Galileo, Newton, Kepler, and their successors subordinated the heavens to science. Now that science gives us the answer to how we were created, they suggest that our sense of purpose was removed, leaving people adrift.

Cosmologist and astrophysicist Sandra Faber has a somewhat different view; she thinks our purpose has become “progress,” the relentless pursuit of using more energy, which goes hand-in-hand with economic growth. Growth is like a drug: the more you do it, the more you want. But things add up over time, and the resources supporting growth are finite.

“Earth is finite and we are ignoring that. Any society that functions in contradiction to its cosmological truth is doomed.”

The world GDP is now growing by 3.5% per year – that’s a factor of 16 in a single human lifetime (80 years). Every item that goes towards the calculation of  GDP is subject to limitations and availability. Can the earth actually produce 16 times more food, shelter and fuel in the next 80 years? We already use 1 out of every 2 drops of water before it goes to the ocean, says Faber, and 95% of potentially arable land is already farmed.

The Nobel laureate economist William Nordhaus gives one-in-three odds that better than expected economic growth would result in emissions that exceed the U.N.’s worst-case scenario for business as usual. In other words, if our purpose has become growth, it too is about to die. The beginning of our cosmology is planet Earth and, says Faber, “Earth is finite and we are ignoring that. Any society that functions in contradiction to its cosmological truth is doomed.”

To give us a moral compass for the future, to guide our response to limits and possibilities, Faber poses two questions:

First, is Earth safe? Can it provide a livable future over cosmic time? Answer: Probably. The major threat is from super volcanoes and they seem to happen only every 100 million years or so.

Second, is Earth rare? Are we alone? Answer: We don’t yet know. We are still investigating the likelihood that more planets have emerged from the faintest of energy perturbations and microscopic dust particles with the exact combination of factors required to support life as we know it:

Artist conception of planet collision that formed the moon
A major contributing factor to Earth’s biological evolution is our moon, which formed when a Mars sized planet collided with Earth. (Artist’s conception of the collision.)
  • The planet needs to be in a star’s “habitable” zone, the area not too close and not too far from the star where liquid water can exist on the planet’s surface. Every star has a habitable zone, but not all can support life. If the star is too big and bright, its lifetime would be too short to support the eons required for the development of biological life. If it’s too small, its planets would likely be tidally locked – not rotating but always facing the star with the same side of itself. A short rotation period is essential for the development of life.
  • Planet size and composition are also factors. It can’t be too big or too gaseous. If it’s too small, it may not have enough gravity to hold on to its atmosphere and its water, as was the case with Mars.
  • The planet must also have plate tectonics, or convection cells lubricated by water that “recirculate” material from the planet’s core to the crust. This is what forms continents and also removes excess CO2 from the atmosphere, acting as a “thermostat” to maintain a stable climate over billions of years.
  • To maintain its atmosphere, a planet must also have geo-dynamics, a magnetic field to deflect the solar winds and its damaging particles. Though Venus once had massive amounts of water, without the forces of plate tectonics and a magnetic field, it eventually got much too hot—hot enough to lose all its water and melt lead.
  • A major contributing factor to Earth’s biological evolution is our moon, which formed when a Mars-sized planet collided with Earth. It set our axis off enough to create the short days that allow photosynthesis to occur.

Though we don’t yet have the definitive formula for determining Earth’s rarity, the identification of each new factor exponentially decreases the odds of more Earth-like planets. Faber believes that we will find the Earth is indeed rare—meaning that in a cosmic sense, we have been given an amazing gift that we are failing to appreciate and care for.

Elements of Earth’s Climate

The Intergovernmental Panel on Climate Change (IPCC) defines Earth’s climate as a complex, interactive system consisting of the atmosphere, land surface, snow and ice, oceans and other bodies of water, and living things.

The atmospheric component most obviously characterizes climate. Climate is often defined as “average weather” and usually described in terms of the mean and variability of temperature, precipitation and wind over a period of time, ranging from months to millions of years (the classical period is 30 years).

Volcanos block some of the sunlight from reaching Earth and thereby cooling temperatures.

The climate system evolves in time under the influence of its own internal dynamics and as a result of changes in external factors that affect climate, or “forcings.” External forcing factors may be natural phenomena such as volcanic eruptions and solar variations, as well as human-induced changes in atmospheric composition.

The climate system is powered by solar radiation, the balance of which can be changed in three fundamental ways:

  1. By changing the incoming solar radiation, for example, by changes in Earth’s orbit or in the sun itself.
  2. By changing the “albedo,” or fraction of solar radiation that is reflected, for example from changes in cloud cover, atmospheric particles or vegetation.
  3. By altering the infrared radiation from Earth back towards space; e.g., by changing concentrations of the gases that trap heat in the atmosphere, known as the greenhouse effect. Earth’s main greenhouse gases are carbon dioxide, methane, ozone, nitrous oxide and chlorofluorocarbons.

Climate responds directly to such changes, as well as indirectly, through a variety of feedback mechanisms that can either amplify (“positive feedback”) or diminish (“negative feedback”) the effects of a change in climate forcing. Detecting, understanding and accurately quantifying these feedbacks are a key focus of current scientific research.

For example, Earth’s natural “greenhouse effect” – the process by which gases in Earth’s atmosphere trap heat from the sun – makes life as we know it possible. Without it, the average temperature at Earth’s surface would be below the freezing point of water. However, human activities, primarily the burning of fossil fuels and clearing of forests, have greatly increased the amount of carbon dioxide in the atmosphere which in turn increases the amount of water vapor, intensifying the natural greenhouse effect and causing global warming. 

As Earth’s climate warms, snow and ice begin to melt. This melting reveals darker land and water surfaces that were beneath the snow and ice, and these darker surfaces absorb more of the sun’s heat, causing more warming, which causes more melting, and so on, in a self-reinforcing cycle. This feedback loop, known as the “ice-albedo feedback,” amplifies the initial warming caused by rising levels of greenhouse gases.

A Short History of Earth’s Climate

During the 4.6 billion years since Earth was formed, its climate has undergone many dramatic feedback forcings that impacted the evolution of the planet and its inhabitants.

We are now in an interglacial (warm period) that began about 11,000 years ago and includes the whole of the development of human societies and civilizations.

Some 225 million years ago, the end-Permian mass extinction event, also known as “The Great Dying,” occurred when oceans absorbed vast quantities of carbon dioxide from the air, depleting the oxygen in the water and triggering a worldwide bloom of a sulfur-emitting anaerobic bacteria. The seas became spiked with acid and the air was filled with poisonous gas. The result was an event even more cataclysmic than the later extinction of the dinosaurs. This event is presently under active investigation given the rate at which we humans are now warming and acidifying the oceans.

At least five major ice ages – millions to tens of millions of years, when large areas of the earth are covered by glaciers and global temperatures are relatively cold – have been documented over Earth’s history. The current ice age began about 3 million years ago and includes all of human history. Within a major ice age are shorter periods called “interglacials” (when glaciers retreat and global temperatures warm) and “glacials” (when glaciers advance and temperatures drop). In the last million years, a major glacial has occurred approximately every 100,000 years. We are now in an interglacial (warm period) that began about 11,000 years ago and includes the whole of the development of human societies and civilizations.

The Pleistocene Epoch

The first epoch of the Quaternary Period and the sixth in the Cenozoic Era, the Pleistocene Epoch is typically defined as the period that began about 2.6 million years ago and lasted until about 11,700 years ago at the start of the current interglacial period. During this epoch the climate was chaotic. While parts of the globe experienced a climate that was reasonable, much of Eurasia and North America was buried under ice several kilometers thick. The climates across the northern continents swung from the depth of glacial frigidity to a relative mildness in the space of a few years. This erratic pattern was a feature of virtually the whole of the last 100,000 years of history.

Landsat photo of lake Toba
The largest volcanic eruption during the last 2 million years created Lake Toba in Sumatra.

About 72,000 years ago, in the early part of the last major glacial, the largest volcanic eruption anywhere on Earth for the past 2 million years occurred at what is now Lake Toba in Sumatra. Scientists agree that a supereruption of the scale at Toba must have deposited a layer of ashfall about 6 inches thick over the whole of South Asia, the Indian Ocean, and the Arabian and South China Seas and injected as much as 6 billion tons of noxious sulfur dioxide into the atmosphere. This would have had worldwide effect on weather and climate; a sudden cooling may have resulted in a sharp decrease of the human population to between 15,000 and 40,000, leaving 3,000 to 10,000 surviving individuals. Earth has experienced at least nine “volcanic winters” since Toba.

About 12,000 years ago the planet began to warm. The glaciers that carved out the Great Lakes melted to form an immense lake in modern Canada, Lake Agassiz, that was larger than all the Great Lakes combined and held more water than all the world’s lakes today. Then suddenly, after thousands of years of warming, within the course of a decade or less the planet slipped back into a 1,300-year glacial period known as the Younger Dryas. Did a geological event, perhaps the failure of an “ice dam,” free the water in Lake Agassiz, and enough freshwater flowed into the Atlantic to shut down the ocean conveyor belt that brings warm water from the tropics to the poles? Scientists who study rapid or sudden climate change continue to search for answers about the origin and disappearance of Lake Agassiz that may provide clues to our future climate.

The Holocene Epoch

“I think that if the climate would have been stable fifty thousand years ago [civilizations] would have started then. But they had no chance.”

After the final paroxysms of the last major glacial came to an end around 12,000 years ago, the world warmed dramatically over the next two millennia. Earth entered the Holocene Epoch and the Neolithic Era began. Earth’s climate has been relativity stable for the past 10,000 years, which is widely recognized as the central reason for the explosive development of societies and civilizations.

According to paleoclimatologist J.P. Steffense “…[the] ice age was so climatically unstable that each time you had the beginning of a culture they had to move….Then comes …ten thousand years of very stable climate. The perfect conditions for agriculture…. Civilizations in Persia, in China, and in India start at the same time, maybe six thousand years ago. They all developed writing and they all developed religion and they all built cities, all at the same time, because the climate was stable. I think that if the climate would have been stable fifty thousand years ago it would have started then. But they had no chance.”

Collapse of the Bronze Age Civilizations: End of the First Era of Global Trade

In spite of relative stability, humanity in the Holocene has seen a number of significant climate-induced setbacks. From about 1800 BCE until around 1200 BCE, civilizations developed in the Aegean, Egypt, and the Near East. Commerce flourished in the region to the point that it can be described as the earliest known example of global trade. Then after nearly two thousand years of growth and prosperity, a series of catastrophes caused the final collapse of the Bronze Age civilizations.

A severe change in climate certainly played a role. Toward the end of the 13th and the early decades of the 12th century BCE, a drought lasting about 300 years appears to have affected the entire region. This would obviously have caused crop failures, famine, and human migrations. Scarcity of resources would have caused problems including violence at home and overseas.

“Fire of Troy” by Kerstiaen de Keuninck.

We know from recent research by archaeoseismologists, that Greece, as well as much of the rest of the Aegean and Eastern Mediterranean, including Ugarit, was struck by “earthquake storms” – a series of earthquakes that began about 1225 BCE and continued over fifty years, until about 1175 BCE. Although there is evidence of repetitive rebuilding, quake-caused damage likely disrupted trade.

The Bronze Age Collapse resulted in the destruction of almost every major city in the eastern Mediterranean world. It took four centuries before Greek society re-emerged, entering what we know as the Archaic Period. The historian Eric Cline, author of 1177 B.C.: The Year Civilization Collapsed, suggests that there are lessons here for our own time: “We must now turn to the idea of a systems collapse, a systemic failure with both a domino and multiplier effect, from which even such a globalized international, vibrant, intersocietal network as was present during the Late Bronze Age could not recover.”

Subsequent Cooling Events

There were many instances subsequent to the Bronze Age collapse where climate-induced conditions contributed to severe setbacks. A hundred-year cooling period in the Northern Hemisphere occurred in the 6th and 7th century CE following three immense volcanic eruptions in the western Pacific. The extreme weather events of 535–536 CE were the most severe and protracted short-term episodes of cooling in the Northern Hemisphere in the last 2000 years. The effects were widespread, causing unseasonal weather, crop failure, and famine worldwide – though not nearly at the scope of what we expect in our future if the current warming goes unchecked.

Another centuries-long period of global cooling started in the early 14th century and extended to the mid-19th century, causing considerable agricultural distress in Europe. The year 1816 is known as the Year Without a Summer (also the Poverty Year and Eighteen Hundred and Froze To Death). Severe climate abnormalities caused average global temperatures to decrease by 0.7–1.3°F, resulting in major food shortages across the Northern Hemisphere. European peasants suffered famines, hypothermia, bread riots and the rise of despotic leaders brutalizing an increasingly dispirited peasantry.

Mount Tambora from the air
The 1815 eruption of Mount Tambora in present-day Indonesia was one of the most powerful volcanic eruptions in recorded history.

The cooling was likely caused mainly by the 1815 eruption of Mount Tambora on the island of Sumbawa in present-day Indonesia, one of the most powerful volcanic eruptions in recorded history. It may also have been impacted by the Dalton Minimum (a period of relatively low solar activity) which ran from December 1810 to May 1823. May 1816 in particular had the lowest sunspot number (0.1) to date since record keeping on solar activity began. The lack of solar irradiance during this period may have been exacerbated by atmospheric opacity from volcanic dust.

It would be a mistake to think that humanity had no role in these climate feedback events or in determining the impact. Over-hunting, depleting agricultural practices, massive burning, tribal warring over scarce resources, scapegoating in the face of disaster – all were human responses that exacerbated the outside forces and contributed to the outcomes.

Externally-caused factors continue to pose threats; for example, a dozen or more earthquake storms of varying magnitude have been identified in the 21st century. But clearly, the greatest threats now to the stability of Earth’s life-supporting climate are those we humans are creating (and exacerbating) – at an unprecedented and truly alarming rate. James Zachos, who studies the nature of rapid and extreme climate transitions in Earth’s past, points out that 56 million years ago, an increase of 5,000 gigatons of carbon dioxide warmed the arctic by 18 degrees F – an increase that occurred over a period of tens of thousands of years. In contrast, we humans are on track to produce 10,000 gigatons of carbon dioxide in just the next 100 years.

It is also a mistake to think that because Earth has had major climate shifts before, that all will be OK. Recent research shows that no previous climate event over the past 2,000 years was even remotely equivalent in degree or extent to the warming over the past few decades. The planet and climate will survive in one form or another, but humans will not be OK. Fortunately, for the first time in history, we are in a position to know what’s happening, the impact we are having, and what will happen if we do nothing. We also have the means to intervene.

Andreas Bohnenstengel, Wikimedia Commons

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