If you have ever seen a documentary that shows the Earth from space, you have seen that thin blue line that surrounds our planet. This is our atmosphere. It contains a variety of gases, some of which we call “greenhouse gases.”
This name comes from their function: they allow light through, but keep heat from escaping, like a greenhouse. Sunlight passes to the planet, which provides energy. When the Earth radiates the light back (as heat), some goes out into space, but greenhouse gas molecules trap the rest. This is a good thing. Without it, Earth would be a very different place; an average of 33C (60F) degrees cooler.
As always it is possible to have too much of a good thing. The more greenhouse gases are concentrated in the atmosphere, the more heat is trapped. Carbon dioxide (CO2) is one of these greenhouse gases.
CO2 naturally occurs in the atmosphere. Animals exhale it when they breathe and plants need it to grow. In fact, carbon naturally circulates between plants, animals, the atmosphere, soil, and the oceans. The amount of carbon on the planet hasn’t changed. We have always had the same amount. What is changing is WHERE it is.
All living things are made up of several elements, carbon being one. When plants and animals die, the carbon is trapped in the dirt, bonding with minerals like iron to be stored in rocks. Or, with enough time (millions of years), heat and pressure, carbon turns into fossil fuels. Most carbon on Earth is “stored” in this way.
Enter human beings. When we burn fossil fuels, the carbon leaves its oily storage space, reacts with oxygen, forms CO2 and returns to the atmosphere. In the atmosphere, it begins to trap the heat from the sun. Since the start of the Industrial Revolution (mid 18th century), humans have added 400 billion tons of carbon to the atmosphere; and we continue to add more at a faster and faster rate. Seventy years ago the annual rate of increase was about 0.7 ppm per year; by 2014 it had tripled to 2.1 ppm/year.
This additional carbon in the atmosphere is causing the surface temperature of the Earth to rise: global warming. But, the rising temperatures aren’t the only effect. The climate and weather systems of the planet are changing. “Climate change” refers to all of the varying impacts of increased greenhouse gases: rising temperatures, extreme weather events, rising seas, shifting habitats, even cooling temperatures in some areas.
And how does all of this impact the 71% of Earth that is the ocean? Most directly, the ocean itself is heating up. Both faster and at deeper depths. 2018 was the hottest year on record for the ocean.
In addition, the ocean is absorbing much of this extra CO2; 93% of the excess CO2 since the 1970s. To put that into perspective, if all of the heat absorbed by the ocean in the last 70 years were suddenly released, air temperatures would rise by 97F/36C degrees!
The consequences of continued global temperature rise can be overwhelming: droughts, severe storms, extinctions, flooding, food and water shortages. And undoubtedly there are more to come of which we are not even yet aware. Here are some of the ocean impacts we are already witnessing.
Glaciers & Ice Sheets Melting
Glaciers and ice sheets cover roughly 10% of the Earth’s land mass and contain nearly 69% of all of the freshwater on Earth. These vast areas of ice help to regulate the air and water temperature and reflect heat from the sun. Unfortunately, parts of the polar regions are warming three times faster than any other part of the planet. Arctic sea ice has decreased by an average of 4% and Antarctic sea ice by roughly 1.5% per decade in the past forty years.
Sea Level Rise
There are two primary factors contributing to sea level rise. First, and most obviously, the melting of glaciers and polar ice caps. Between 2012 and 2016, this has contributed to a 1.2mm rise annually (a 700% increase over 1992-2001). Secondly, water expands when it absorbs heat. As the oceans get warmer, the water expands, causing additional sea level rise. It is currently rising at a rate of 3.3mm (0.13 inches) per year; greater than the average rate over the last 2000 years.
Global warming leads to unexpected climate changes. Larger and more intense storms are becoming the norm. Huge amounts of rain are followed by longer droughts. Periods of extreme marine heatwaves are more frequent; causing coral bleaching events. Wave intensity has also been shown to be increasing. The ocean has regulated climate for millennia but is becoming less and less predictable.
Oxygen is essential to life in the ocean – fish and other marine species need it to live. As ocean temperatures rise, oxygen levels decrease. Oxygen is less soluble in warm water so warmer water contains less. If the oxygen level is depleted below 2 mg/L, there is no longer enough to support most marine life. There are an increasing number of “dead zones,” with these low levels of oxygen, in the open ocean.
As CO2 dissolves in seawater it forms carbonic acid and decreases the pH level of the ocean. With the ocean absorbing increasing amounts of our CO2 emissions, the ocean is increasing in acidity. This most directly affects animals with shells or skeletons made of calcium carbonate (like bivalves and coral). Excess carbon causes the amount of carbonate ions in the water to decrease which means fewer are available to marine animals for shell or reef building.
The habitats of many marine species are already being disrupted by rising temperatures. Krill, a primary food source for many marine animals, have moved four degrees south to find cooler waters. Closer to the tropics, invertebrates, fish and mammals are relocating as temperatures change. This increases competition for resources in new habitats as new species move in which can lead to localized population declines or extinctions.
Coral Reef Destruction
Coral reefs have existed for over 500 million years. During this time, they have successfully adapted to a wide variety of temperatures and climates. But adaptation takes time. With the current rate of temperature change, especially in the shallow waters favored by coral, corals are decreasingly able to adjust. With climate change causing more frequent and longer marine heatwaves, corals are even more at risk. The last 25 years have seen unprecedented mass bleaching events across the tropics (1998, 2010, and 2016).
Overall, the causes of increased greenhouse gases contributing to global warming can be summarized into three factors.
Burning Fossil Fuels
This is the biggest contributor to global warming and the one we hear the most about. Fossil fuels include coal, crude oil, and natural gas. These were all formed from the decomposing remains of plants and animals that lived millions of years ago. The organic material from these plants and animals is carbon. This carbon was trapped in the ground, and after millions of years and exposure to extreme temperatures and high pressure, these carbon-rich materials formed. As we remove coal, oil and gas from the earth and burn it, the carbon is released back into the atmosphere.
Other Greenhouse Gas Emissions
While fossil fuels are the most discussed, they are not the only source of greenhouse gas emissions. Livestock and other agricultural practices, organic waste decay, and wastewater treatment all add greenhouse gases. Refrigerators, air-conditioners, foams, and aerosol cans contribute “high global warming potential” gases.
Our destruction of nature also adds to the problem. Trees, plants, and soils store carbon and keep it out of the atmosphere. (Soils contain more carbon than the atmosphere and all plants combined!) As we disrupt soils, excavate for agriculture, and cut down forests we release that carbon back into the atmosphere. The sea bed also stores carbon – by disturbing the ocean floor, bottom trawling releases as much carbon annually as air travel.
Destruction of Carbon Sinks
The destruction of nature has double the impact. Not only does it release stored carbon into the atmosphere but also a source to absorb and store more carbon. A carbon sink is anything that absorbs more carbon from the atmosphere than it releases: plants, the ocean and soil. Marine ecosystems, like kelp forests, seagrass beds, and mangrove forests absorb huge amounts of carbon. For example, mangroves take up 0.5% of coastlines but account for 10% of coastal carbon storage capacity. The planet has natural ways to combat global warming. We must stop destroying them.
At this point, stopping global warming, let alone returning greenhouse gases to pre-industrial levels, will take decades at best and centuries at worst. The latest international treaty to address global warming is the 2015 Paris Agreement. This agreement aims to limit the temperature increase to 1.5°C. However, in 2019, a UN report stated that the world is on track for a 3.2°C increase.
We all have a responsibility to stop making it worse. On a personal, national, and global level, we all have a role to play. We must stop greenhouse gas emissions and give the planet time to adapt.
Support Conservation Efforts
Remember that global warming is everyone’s problem so we must all be part of the solution.
Nearly every conservation organization is working to spread the word and encourage personal, community, national and global change to address the climate change crisis. We are ALL responsible for our contribution and for allowing governments and corporations to continue with the status quo.
Please learn more about what these organizations are doing to help and support their efforts.
Association for Coastal Ecosystem Services
Inland Ocean Coalition
The Ocean Foundation
Global Youth Taking Governments to Court Over Climate Change
Future generations are standing up and demanding action. And it’s working. A number of lawsuits have been filed against national governments for not taking enough action to mitigate climate change. “The cases are most often centered around the idea that future generations have a right to live in a world that is not completely decimated by the climate crisis.” The number of climate litigation cases have doubled since 2017 and the future seems to be winning.
Norway Creates Zero Emissions Zones in World Heritage Fjords
In 2018 the Norwegian Parliament adopted a resolution creating the world’s first marine zero emissions zone. By 2026, only emissions-free cruise ships and ferries will be allowed to enter Geirangerfjord and Nærøyfjord, beautiful fjords and popular tourist destinations. Last year more than 300,000 cruise ship passengers visited the fjords. The regulations cover emissions to air, discharge of grey and black water, and visible exhaust in hopes of convincing ship owners to build sustainable ships.
Royal Dutch Shell Ordered to Cut Carbon Emissions, The Netherlands
In May 2021, a Dutch court ruled that Shell petroleum company is responsible for for its CO2 emissions and must cut global carbon emissions by 45% (compared with 2019 levels) by 2030. This is the first time a multinational corporation is held accountable for contributing to climate change. The lawsuit was brought against Shell by Friends of the Earth with over 17,000 co-plaintiffs. Shell was found guilty of violating Articles 2 & 8 of the European Convention on Human Rights (the right to life and the right to family life) by causing a danger to others when alternative measures could be taken.
Climate Activists Gain Three Seats on Exxon Mobile BOD
Shareholder elections at the largest petroleum company in the US took a surprising turn in early 2021. Three board seats have gone to activists pushing the company to address climate change. While this likely won’t lead to massive changes immediately, it does send a message that a shift in focus to climate change issues is a priority for shareholders. Hopefully this trend continues.