Global warming: facts, causes, and effects

Here's why you should care.
Maia Mulko
Earth melting.bestdesigns/iStock

The term “global warming” refers to the heating of the Earth caused by the long-term increase in the planet’s average air and ocean surface temperatures. 

These temperatures have been on the rise since 1880 at a rate of 0.14° F (0.08° C) per decade, rising to 0.32° F (0.18° C) per decade since 1981. In fact, the warmest years in the records of the National Oceanic and Atmospheric Administration (NOAA) are 2016, 2020, and 2019. 

Average global temperatures are currently around 0.98ºC (1.76ºF) above pre-industrial levels, and this will probably reach 2.7ºC (4.9ºF) by the end of the century —with all of what that implies for the Earth’s climate— if individuals and industries don’t reduce their carbon footprint and act to reduce global warming.

But what is this all about, exactly? 

What are the causes of global warming?

Although there are a few natural causes of global warming — such as volcanic eruptions and changes in solar activity — 97% of scientists agree that natural causes cannot explain the statistics by themselves. Research has demonstrated clearly that human activity has been accelerating the process of global warming since the Industrial Revolution. In fact, global warming is believed to have started in the 1830s. But why? 

The main cause of global warming is the greenhouse gas emissions that absorb radiation and trap heat in the Earth’s atmosphere, producing the greenhouse effect. These gases are mostly carbon dioxide (72%), methane (19%), and nitrous oxide (6%). 

Gases by source - EPA
Source: EPA 

 Carbon dioxide mainly comes from the combustion of fossil fuels (such as coal, natural gas, and petroleum) that we use for activities such as transportation, heating, manufacturing, and the production of electricity. 

In addition to this, deforestation means there are fewer trees to absorb the excess carbon dioxide from the atmosphere, which they use to perform photosynthesis. Therefore, forest clearance is a contributing cause of global warming, due to the lower absorbance of carbon dioxide emissions.

Methane comes from the production of oil and natural gas, coal mining, organic waste in landfills, and livestock. Methane is even more harmful to the environment than carbon dioxide, but it has a shorter atmospheric lifetime (12-15 years vs 300-1000 years).

Nitrous oxide comes primarily from the agriculture sector, particularly from animal waste and fertilizers. It is 300 times more damaging than carbon oxide and stays in the atmosphere for 114 years.

What are the effects of global warming?

Global warming is leading to a rise in the Earth's average temperatures that can have dramatic effects on the climate system and directly affect ecosystems. 

Ice melting and rising sea levels

According to the US Environmental Protection Agency (EPA), when averaged, absolute sea levels have risen at a rate of 0.06 inches (1.15 mm) per year from 1880 to 2013, however, "since 1993, average sea level has risen at a rate of 0.12 to 0.14 inches per year—roughly twice as fast as the long-term trend." 

This is because the Earth’s warmer temperatures are already melting the glaciers and ice sheets, especially in Greenland and West Antarctica, and, as the water warms, it expands slightly.

Melting glacier in Iceland
Source: Matteo Basilici / Imaggeo

Already, rising sea levels have contaminated the groundwater in some low-lying areas, making agriculture difficult or impossible, and this is set to increase as waters rise. Rises in sea levels also increase the threat of flooding, which could have a severe impact on cities and coastal communities, including along the U.S. Gulf Coast and heavily populated cities like Tokyo and New York. 

Permafrost, a subsurface layer of soil that remains below freezing point throughout the year, is also at risk of thawing due to global warming. Many northern villages in Russia, Canada, Greenland, and Alaska are built on it. People in these places are already losing their homes and infrastructure due to the loss of permafrost. Their health can also be in danger because permafrost contains toxic mercury and antique pathogens that are released into the environment when it thaws.

Permafrost thawing
Thawing permafrost on Herschel Island, Canada. Source: GRID-Arendal/Flickr

Last but not least, permafrost contains organic carbon that can turn into carbon dioxide and methane, two greenhouse gases that increase global warming. 

Ocean warming 

The oceans absorb much of the excess heat that the greenhouse gas emissions trap in the atmosphere. This way, they reduce some of the effects of global warming at the expense of rising ocean temperatures—something that is highly detrimental to marine ecosystems. While the ocean absorbs around one-third of the atmosphere’s excess carbon dioxide, this also results in a more acidic ocean.

For example, changes in the temperatures of the ocean surface are already stressing corals and leading to mass bleaching and die-offs. In response to that stress, corals release the symbiotic algae that live in the coral polyps—which leads to coral bleaching. Corals need algae to carry out photosynthetic processes and obtain energy and nutrients. When they lack it, they’re weak and susceptible to disease and starvation. 

Coral bleaching in Keppel Islands
Bleached corals in Keppel Islands, Great Barrier Reef, Australia. Source: Acropora/Wikipedia

This is important because coral reefs support the development of many marine species, such as sea turtles, starfishes, crabs, shrimps, etc., providing food to other marine animals, sea birds, and humans. 

Coral reefs also act as natural seawalls that reduce the impact of waves on the coast. Without them, seaside towns are at higher risk of storm floods.

Storm tides in Port William
Storm surge contained by a harbor wall at Port William, Scotland. Source: David Baird/Geograph UK

Another example is the impact on species that need specific water temperatures to thrive. For example, the most abundant tuna species, skipjack, and yellowfin tuna prefer water temperatures between 20 and 30o Celsius (60 to 86o Fahrenheit). As ocean temperatures rise, there will be fewer of these tuna, and those that remain are predicted to migrate eastward, affecting the livelihoods of the people who rely on ocean fisheries.

Ocean warming also contributes to ice melting at the Earth’s poles, with all of the subsequent effects this will have on marine ecosystems. 

Global warming vs climate change

Global warming is not the same as climate change. It is, in fact, a cause of climate change. 

Due to global warming, hot weather can be more intense and long-lasting as soil moisture is reduced. This can lead to extreme water shortages, drought, dried-out vegetation and wildfires, which affect flora and fauna. 

Wildfire from the air
Source: Salam2009/Wikimedia Commons

Heatwaves can also impact human health due to a higher risk of heatstroke.  They can decrease economic productivity and cause problematic water and power outages. They can also lead to droughts, which can last longer, causing shortages of drinking water and crop losses (which affect food supplies). 

Drought in Algeria
Cracked ground during a ground in Bou Hanifia, Algeria. Source: Hydrosami/Wikimedia Commons

A modeling-based study by the Geophysical Fluid Dynamics Laboratory of NOAA determined that air and ocean warming also produces more severe tropical storms with increased wind speeds. The frequency and intensity of tropical storms and hurricanes, for example, have both been increasing, and this trend is set to accelerate as warming also increases. Average numbers of tropical storms in the North Atlantic Basin have risen from around 11 annually between 1966 and 2000 to around 15. 

What can we do to slow or stop global warming?

Human activity is the major cause of global warming. This is because we produce too many greenhouse gas emissions. If we stopped them, the oceans would gradually release the heat that they are storing into the surface. Eventually, that heat would dissipate as the amount of heat-trapping gases in the atmosphere would stabilize.

The experts recommend reducing your “carbon footprint” by minimizing your waste, car trips, meat consumption, and non-clean energy utilization. Instead, you should recycle, walk/bike or buy an electric vehicle, eat more locally-grown vegetables, unplug the devices that you are not using or, better yet, switch to energy-efficient appliances and/or power your home with renewable energy.

Global warming: facts, causes, and effects
Solar panels and wind turbines produce renewable, clean energy.
Source: yangna/iStock

In fact, the Environmental Protection Agency (EPA) reports that the primary sources of greenhouse gas emissions in the United States are the burning of fossil fuels for transportation, electric energy production, and industries. 

But there is a debate regarding how significant individual actions are on this matter. Especially when we look at statistics, it’s clear that in order to obtain better results, we should change much more than little habits —we should all switch to cleaner energies in all aspects and at a more structural level

In this sense, new policies to reduce greenhouse gas emissions from big companies and below could be the definite global warming solution.

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