You’ve probably heard of greenhouse gases before, but what exactly are they and why do they matter?
Greenhouse gases are gases in Earth’s atmosphere that trap heat. They let sunlight (solar radiation) pass through the atmosphere, but they prevent the heat that comes with it from leaving the atmosphere. The main greenhouse gases are:
|• water vapour
• carbon dioxide (CO2)
• methane (CH4)
• nitrous oxide
Some greenhouse gases in the atmosphere are essential for keeping the planet from becoming too cold. However, as you will see, when too much of these greenhouse gases build up in the atmosphere they prevent excess heat from escaping, and lead to many effects that can be disruptive to life on Earth.6
Carbon dioxide and methane are two of the greenhouse gases that have been building up in the atmosphere rapidly since the industrial revolution.3 The graph below outlines the carbon cycle and how carbon cycles through the biosphere, geosphere and atmosphere.
The carbon cycle describes the process in which carbon atoms continually travel from the atmosphere to the Earth and then back to the atmosphere.
On Earth most carbon is stored in rocks and sediments. The rest cycles through the ocean, the atmosphere and in living things. These represent the carbon reservoirs, or sinks.
Carbon is constantly being released into the atmosphere. As organisms die, forests burn and volcanoes erupt, these carbon sinks send carbon into the atmosphere. As carbon builds up in the atmosphere, much of it is cycled back to the Earth where it can be absorbed by the ocean’s surface water, or sequestered by photosynthesizing plants.
The carbon cycle has been relatively stable and predictable for millennia. The major problem we face today is that far more carbon is being released into the atmosphere than the Earth’s carbon cycle can regulate. Humans play a major role in the carbon cycle by burning fossil fuels and developing land, and as a result the amount of CO2 in the atmosphere is rising rapidly. As the carbon cycle becomes unbalanced and overwhelmed, it puts added pressure on the rest of the system to keep up. Let’s take a look at how the ocean is reacting to this increased burden.
Ocean Acidification – how the oceans are being overwhelmed by excessive CO2
The Ocean has absorbed more than 25% of the greenhouse gas that has built up in the atmosphere — this includes CO2.5 As CO2 is absorbed it increases the acidity of ocean water, which has many detrimental effects on the organisms that live within it.
Some of these effects include:
- Coral bleaching (die off)
- Shells dissolve (shellfish die off)
- Food chain disruption — this effects economic activities such as fisheries, aquaculture and tourism.4
As you can see, the effects of climate change impact the land and the ocean. The entire system is interconnected! With this interconnection comes many indirect impacts of climate change. To illustrate these impacts, lets take a look at how a warmer climate is melting the polar ice caps and the feedback loops that contribute to accelerating climate change.
Melting Polar Ice Caps and Climate Change
The melting of polar ice is a fundamental example of what scientists refer to as a positive feedback loop.
(Source: The National Academies of Science, Engineering and Medicine)
Polar ice helps modulate the effects of climate change in several ways: It prevents evaporation of ocean water below the sea ice; it insulates ocean water against the atmosphere — helping to slow acidification — and it reflects the sun’s energy back into space, cooling Earth in the process.7 This effect of reflecting the sun’s light, rather than absorbing it, is called the albedo effect.
As the Earth loses its polar ice, more of the sun’s energy is absorbed by the land and ocean, further warming the climate. This additional warming contributes to more ice melt, resulting in even less solar radiation being reflected into space. This cycle of ice loss leading to warming, which causes more ice loss and so on, is an example of a positive feedback loop. The global climate system is effected by many feedback loops that combine to form the interconnected nature of Earth’s geological, biological and climate systems.7 As these systems affect the Earth’s warming, the change in temperature affects the systems themselves. Some “downstream” effects of polar ice melting include:
- sea-level rise
- changes in ocean currents
- changes in ocean nutrient cycling and food systems
All of these changes have global implications, and it will take effort from around the world to mitigate, adapt to and overcome these challenges.
Now that we understand how climate change is studied and how it works, lets examine what effect the changing climate may have on our country and community.