⏳ Estimated Reading Time: 5 - 7 minutes

Identify the threats to human health and the environment posed by an increase in greenhouse gases.

Increasing Greenhouse Gases

Greenhouse gases (GHGs) include water vapor, carbon dioxide, methane, nitrous oxide, HFCs, ozone, chlorofluorocarbons (CFCs), and a few others.

Water vapor is the most important GHG, since globally it is the most abundant of these gases, although it varies from 0-3% in a given location. Because water vapor has a short residual time in the atmosphere and it is not a human-produced greenhouse gas, scientists are not concerned about it as one of the gases involved in climate change. Human-produced GHGs, though, are of great concern to climate scientists, and much effort is going into monitoring, studying, and modeling of climate change in response to those GHGs. Greenhouse gases are released from a variety of sources. The graph below summarizes global GHG gas emissions by economic sector since 1990. Which sector emits the most greenhouse gases? Do any of these surprise you?

Did you notice the category "fugitive emissions" in the graph above? No, that doesn't refer to greenhouse emissions from fugitives escaping the law! Fugitive greenhouse gas emissions refer to gases that are unintentionally released into the atmosphere from various sources.

The graph below depicts the global average abundances of the major, well-mixed, long-lived greenhouse gases - carbon dioxide, methane, nitrous oxide - since 1850. It’s obvious that the trend for each of these GHGs is up and to the right indicating significant increases of these human-produced gases.

Human-produced greenhouse gases are on the rise worldwide. This is the reason that climate scientists are concerned that rising temperatures on Earth are linked to rising amounts of GHGs.

Effects of Increasing Greenhouse Gases

In the next lesson, we will learn more about the effects of global climate change (GCC), which is caused by excessive greenhouse gases in the Earth's atmosphere. For now, let's just discuss the broad impacts.

As the average global temperature has increased, amphibian extinctions have already started increasing on mountains. A cascade of effects will happen as the temperatures change above preindustrial temperatures. Explore the infographic below to see the changes that occur at each degree above pre-industrial levels:

These events occur because as the climate changes from what living organisms, whether terrestrial, aquatic, or oceanic, are adapted to withstand. As we learned earlier in this course, organisms have 3 choices when the environment changes. They can....

🔄 adapt to the new conditions

📦 move somewhere else

🪦 die

There are some benefits to climate change, depending on your perspective. For example, warm-adapted species (including disease-carrying insects) could have increased ranges, and areas of the planet that are too cold for people, animals, and plants to live, could become habitable. Also, places that are highly susceptible to droughts could get more rainfall, becoming more productive.

Essential Knowledge

Global climate change, caused by excess greenhouse gases in the atmosphere, can lead to a variety of environmental problems including rising sea levels resulting from melting ice sheets and ocean water expansion, and disease vectors spreading from the tropics toward the poles. These problems can lead to changes in population dynamics and population movements in response.

AP Exam Tip

You should understand some of the broad effects of increasing greenhouse gases in the atmosphere.

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