Earth's Climate Before the Industrial Revolution
written by Laurie Jin, edited by Ada Praun-Petrovic
Climate change deniers often point to temperature fluctuations before the industrial revolution to evidence their claims. However, multiple scientists have confirmed that the most recent rise in global temperatures is not only caused by humans but also poses a serious threat to the survival of the human race.
Natural temperature changes occur due to both internal and external factors that influence Earth’s climate. The El Niño Southern Oscillation, a periodic change in wind and ocean patterns, is an example of short term climate fluctuation, which only causes a temporary 0.2˚C change. The most relevant gaseous contributor to global warming is most likely carbon dioxide. Although human emissions are the main cause of today’s global warming, volcanoes, metamorphic rocks, decomposition, and other natural occurrences also contribute to it. Earth’s internal climate system regulates the natural emission of carbon dioxide through its weathering thermostat: Chemical reactions with silicate minerals remove carbon dioxide and bury it in biomasses such as limestone. Other internal factors include earthquakes and volcanic eruptions, which release particles that reflect the sun’s energy, resulting in temporary cooling. For example, the Mt Pinatubo eruption in June 1991 lowered the entire world’s temperatures by 0.5˚C for 18 months. However, despite the cooling effects, these eruptions release tons of toxic particles that are detrimental to our environment. (For more information on this process, read our article about SCoPEx Research.) Additionally, earthquakes, caused by the shifting of plate tectonics, have changed Earth’s temperature by 30˚C over the last 500 million years. During this process chemically reactive rock is thrusted upwards – the shifting of tectonic plates – and more carbon dioxide is absorbed. Today, the doubling of the erosion rates of the Himalayas, Andes, and Alps has exposed such rocks, releasing more carbon dioxide and contributing to global warming. Furthermore, Earth’s orbital wobbles, or Milankovitch Cycles, occur every 100,000 years, causing as much as a 6˚C change in temperature as the amount of sunlight varies up to 25%. During these periods, Earth’s orbit changes - or “wobbles” - as the Sun, moon, and other planets change their relative positions. Types of changes can pertain to the orbit’s shape (eccentricity), variations in the directions of the rotational axis (precision), or variations in the rotational axis’ angle (obliquity). For example, during the Pleistocene Epoch (from 2,580,000 to 11,700 years ago), Earth entered and exited ice ages due to these wobbles.
External factors, though less common, also affect the Earth’s temperature. Many climate deniers point to the Sun’s energy as a cause for the recent rise in heat. Sunspots increase the Sun’s temperature, emitting more energy to Earth. However, scientists have deemed most of these effects negligible and harmless. Short term effects like solar cycles, when the Sun brightens and dims over an 11 year period, cause 0.1 to 0.3˚C of cooling. Similarly, the grand solar minima, decade long periods of reduced solar activity (from 0.04% to 0.08%) have little effect on Earth. Another external factor that could impact Earth’s climate is asteroids. If a massive asteroid were to strike Earth, the impact would expel an enormous amount of dust and other particles into the atmosphere, reflecting the Sun’s rays away from Earth and drastically lowering Earth’s temperature. If one hit an ocean or any other massive body of water, water vapor levels would increase enormously, leading to more rainfall. However, of the 190 asteroids that have hit earth, only one, Chicxulub, has caused a significant change in Earth’s environment. The asteroid that created the Chicxulub crater over 66 million years ago vaporized part of Mexico upon impact, cooling the Earth by 20˚C. However, after the cooling period, temperatures rose by 5˚C due to the vaporized biomass, which stored carbon dioxide that had entered Earth’s atmosphere.
Other notable contributors to Earth’s ever-changing temperature are igneous provinces and evolutionary changes. Igneous provinces are lava floods and underground magma that release large amounts of methane and carbon dioxide when they emerge, destroying the ozone layer and causing 3˚C to 9˚C of warming. They can also cause acid rain, acid fog, and mercury poisoning. Large provinces could lead to mass extinction, but such events were mainly active while Earth was still molten, before complex life existed. In fact, the evolution of certain lifeforms triggered mass periods of global cooling. Photosynthetic cyanobacteria, the predecessors of plants, emerged 3 billion years ago with the amazing capability of manufacturing its own food and, in turn, emitting oxygen. As more cyanobacteria emerged, carbon dioxide and methane levels fell, sending Earth into increments of below freezing temperatures for 200 million years.
Many of these events happened billions of years ago, but scientists are able to learn about them by examining Earth. For example, researchers found evidence of varying climate conditions from over 800,000 years ago by looking at ice cores in Greenland and Antarctica. Tree rings, pollen remains, and ocean sediments can also reveal patterns in the Earth’s internal climate system. Peter de Menocal, the dean of science at Columbia University and founding director of Columbia’s Center for Climate Life, looked at deep-sea sediments to understand the past. He saw that the current global warming, with a rate ten times faster than that of past Earth warmings, is unprecedented compared to the past 1300 years. When researchers input natural phenomena into their data models, they do not reproduce the changes that are occurring today.
Humans have contributed greatly to Earth’s current warming. During the industrial revolution, which started in the late 1700s, the use of factories gradually increased, emitting more toxic particles. Scientists believe that modern climate change signals appeared on a global scale as early as the 1830s. Now, carbon dioxide levels are 40% greater than they were before the industrial revolution, increasing from 280 ppm (parts per million) to over 400 ppm. Scientists believe that 80% to 100% of the unusual warmth we are currently experiencing is due to greenhouse gas emissions. Our atmosphere also contains 2.5 times more methane, a greenhouse gas whose short-term effects are 84 times more potent and detrimental than those of carbon dioxide, than it did ___ years ago. Although this toxic gas can emerge naturally from wetlands, sediments, volcanoes, and wildfires, the majority of the methane in our atmosphere today arises from livestock farming, oil production, and gas production. Additionally, oceans are the warmest they have been in 50 years because more heat energy has been entering the water than leaving. Oceans are also about 30% more acidic than they were at the start of the industrial revolution due to the massive amounts of carbon dioxide they have absorbed. Sea levels rose six to eight inches in the past century, endangering thousands of lives and forcing millions to relocate.
Despite all the available research, however, some people are still skeptical about the validity of climate change. Galvin Schmidt, the director of NASA’s Goddard Institute for Space Studies, disproved skeptic’s claims and identified the difference between natural and human made carbon dioxide. Many dissenters blame an increase in the Sun’s radiation for the rise in temperature; however, this would cause Earth’s entire atmosphere to warm. In reality, the stratosphere and mesosphere remain cool while the surface warms, a clear effect of greenhouse gasses. Furthermore, the Sun’s radiation has not significantly increased since at least 1978, when satellite monitoring of the Sun first began.
Another common claim is that the carbon dioxide in the atmosphere today is natural and not produced by humans. Carbon molecules from different sources have different numbers of neutrons. These varied molecules are called isotopes. Carbon molecules from CO2 released by fossil fuels and deforestation have lighter carbon isotopes than that of natural sources. Recently, scientists have observed an increase in lighter carbon molecules.
Natural climate fluctuations occur throughout the years, but the temperatures recorded in the past 5 years have been the highest in 300,000 years, the approximate duration of human existence. Global warming that occurred millions of years ago happened over thousands of years, but today’s warming has reached the same levels in only 150 years. For example, scientists estimate that the Permian Triassic extinction event, where seawater temperatures rose around 6˚C, may have taken as much as 150,000 years. The rapid changes we are experiencing today make predicting future consequences difficult.
Climate change deniers all around the world point to disproven evidence to try to convince others that climate change is fake. While more and more people are accepting the realities of climate change, dangerous “documentaries” such as The Great Global Warming Swindle can easily change people’s minds by displaying disproven or fabricated data in a professional and truthful light. Deniers often spread a notion of uncertainty around climate change, manufacturing doubt and providing people with an excuse to not take climate action. They point out that Earth was much hotter billions of years ago, but fail to realize that humans cannot survive in such an extreme climate. Temperatures must range from above 0˚C to below 44˚C to ensure human survival. Hundreds of thousands have already died because of climate change, and more will die if this trend continues.
While our planet’s system has regular temperature cycles, today’s unprecedented rise in temperature not only endangers humans, but also other animals who have evolved to survive in this climate. Climate change skeptics try to derail our path to a cleaner environment by spreading misinformation, but we can combat this by educating others about climate change and consciously making an effort to help clean the environment.
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