Causes of Climate Change
Earth’s climate has never been exactly the same. The present day climate is far different from the climate Earth had to begin with. Changes in the tilt of Earth’s axis caused by the gravitational pull of Jupiter and Venus affected the amount of direct sunlight that reached Earth. This created cold periods, known as ice ages, with warm periods in between. Usually, the climate change that has occurred on Earth has been slow and gradual, happening over thousands or millions of years, giving species a chance to adapt. For the past 10,000 years, after the last ice age ended, the climate was reasonably mild, with only slight fluctuations in the average temperature. However, this stability might not last for much longer. Average temperatures have risen by about 0.8º Celsius. But what exactly brought about such a change? Because of increased emissions in so-called greenhouse gases such as carbon dioxide, the planet is rapidly warming up.
The greenhouse gases are the cause of this global warming. They are the gases that trap thermal energy in the atmosphere, such as carbon dioxide (CO2), water vapor (H2O), and methane (CH4). When incoming infrared heat strikes the Earth, the Earth absorbs some of it and “glows” in infrared heat. It radiates the infrared heat back into space, but some of it gets trapped and reflected back toward the surface by greenhouse gases. This warms up the planet, and the greenhouse effect has kept Earth from becoming a huge ball of ice. But if there are too much greenhouse gases present in the air, not much heat can can escape into space, and all the heat will keep getting radiated back to Earth, and the planet will get pushed toward the fate of Venus.
Venus may most likely have been a very Earthlike planet billions of years ago, with oceans of liquid water. Venus at that time would probably have been as likely to harbor life as Earth. Temperatures were mild and there was a good amount of water on Venus. However, when carbon dioxide began accumulating in the atmosphere, it became so hot that it is now the hottest planet in the solar system; even Mercury has lower temperatures. However, Venus and Earth had about the same amount of carbon, and still do. However, most of Earth’s carbon is stored in carbonate (CO32-) rock when the ocean absorbs atmospheric carbon dioxide, and that used to be true for Venus, too. However, Venus was too close to the sun, so the slightly higher temperatures started to cause the reactive carbonate rock to change to carbon dioxide. This greenhouse gas went into the atmosphere, where it trapped more incoming heat and caused more carbonates to react into carbon dioxide. This is known as a positive feedback loop, where the occurrence of one thing causes something else, which creates more of the first thing, and the positive feedback loops always accelerate. Soon on Venus, the oceans boiled away. That made the problem even worse. Now, when volcanoes erupted, there weren’t any oceans to absorb the carbon dioxide in the atmosphere, so it just kept building up until Venus became hot enough to melt lead, and the atmospheric pressure became 90 times that of Earth. Even the hardiest organisms could not survive on Venus.
There are many positive feedback loops involved in global warming. One of the effects which global warming has is melting the polar ice caps, and this does many things. It helps global warming accelerate. Ice is the most reflective natural surface and seawater is the darkest, making it able to absorb more heat. When more ice melts, it exposes more surface to absorb heat, making Earth warmer. This melts more ice, exposing yet more seawater to absorb more heat. This means that eventually, the process can accelerate enough so it will get out of control. Ice in involved in another positive feedback loop: permafrost. This is ground that stays frozen all year, and it contains a lot of organic matter. Global warming is starting to thaw the permafrost, exposing the organic matter, which rots, releasing carbon dioxide in a decomposition reaction. The carbon dioxide traps more heat, rotting more permafrost, which releases more carbon dioxide, and so on. These positive feedback loops accelerate global warming to the unstoppable point.
Each of these positive feedback loops gets triggered by more greenhouse gases trapping in more heat, but how do scientists know it is carbon dioxide? Since Earth warms more at night and winter than during daytime and summer, it is not increased solar output. Also, higher temperatures were accompanied by a sharp increase in the amount of carbon dioxide. The level of it usually stayed below 300 parts per million, but since the Industrial Revolution, it has skyrocketed. In fact, most of our emissions are greenhouse gases.
Consider a computer. Carbon dioxide was created in the process of smelting the metal and metalloid ores. Also, the factories where the computer was made was most likely coal-powered, and generated liberal amounts of greenhouse gases, along with other toxic gases. Then, when the computer was ready for use, it got its electricity from coal or methane power plants mostly, which also produced greenhouse gases. In fact, every combustion reaction, which is what powers civilization, generates carbon dioxide. An example is shown below. If mostly everything involves greenhouse emissions, how will people change their lifestyles so that emissions will be much lower?
Methane Combustion: CH4 + 2O2 — — — — — — — — → CO2 + 2H2O
Iron Smelting: 2Fe2O3 + 3C — — — — — — — — → 4Fe + 3CO2
Carbon dioxide, the main byproduct of civilization, is the reason Earth is warming. What is happening on Earth now has not happened for 300 million years, during the late Permian, which destroyed 90% of species on Earth. The greenhouse gases have to be present in the right proportions to help Earth be a life-sustaining planet. What happened on Venus is an example of what climate change can do to Earth. The positive feedback loops of global warming make it accelerate, which means at some point, it will be unstoppable. Scientists are now sure it is carbon dioxide. Most of what people do now involves greenhouse emissions. However, there are ways to stop the runaway train of climate change. People need to act fast. Because if they do not, the planet will undergo drastic changes, such as sea levels rising and flooding coastal cities, stronger storms, and the Amazon drying up into a desert. The Earth and its life may not be ready for such changes in the basic way of living.
