4.3.2 - The Atmosphere (KQ3): Greenhouse Gases and Climate Change

Climate Change.  We've all heard it, know there's something controversial about it, but may not know the science behind it.  We were introduced to some effects of climate change in the hydrosphere unit (sea level rise, etc.), but how does climate change work?  More specifically, what have humans done to contribute to it?  And, what can we do about it?

Greenhouse Gases

To understand how climate change works, we must first study the greenhouse effect, caused by greenhouse gases.  Think about a greenhouse...those glass-walled structures used to grow plants.  Radiated heat from the sun is moving so fast that it passes right though the walls.  After it rebounds, the infrared waves do not have enough energy to pass back through, and thus get trapped.  This causes the structure to get warmer, resulting in accelerated growth of plants.  A diagram of this is below.

You can think of greenhouse gases in our atmosphere as acting like the panes of glass in a greenhouse.  They let the radiation from the sun in, but trap the infrared waves in the form of heat on the Earth.  Let's get this straight...WE NEED GREENHOUSE GASES!  Without them, the Earth would be too cold for life to exist.  BUT, we are pumping so much into the atmosphere that it's like making the panes of gas thicker...they trap more and more heat, changing the climate of the Earth.  Gas concentrations have changed over the history of the Earth, but usually slowly over  thousands over years.  We are seeing the highest amount of CO2 (a major greenhouse gas) in the past 400,000 years, as evidenced by the graph below (courtesy of NASA).

We can get that CO2 data by looking at ice cores in arctic areas.  It's harder to measure historical temperature, but we do have reliable global data since 1880, as evidenced by the graph below.

 Here's a diagram of the process:

We tend to focus on carbon dioxide, because we make A LOT of it, but there are other greenhouse gases as well.  The relative abundances of greenhouse gases are shown in the infographic below.

We need to work on reducing all of the greenhouse gases, but as you can plainly see, carbon dioxide will be the easiest for us to reduce because we make so much of it via combustion of fossil fuels for electricity(coal), transportation (oil), and industry (both). Methane is a big problem as well, because it actually has a stronger greenhouse impact over carbon dioxide.  It's a big player from cattle/agriculture.

Predictions for Climate Change

The evidence is fairly overwhelming that the Earth as a whole is warming, and it's unnaturally accelerating due to human contributions.  It makes sense.  Does that mean we'll not have any cold times?  NO!  It will just change the average temperature overall in an increasing way.  We will still have snow storms, maybe even more intense because of the climactic changes.  But, what are the predictions for the future and how do we make those predictions?  What do leading scientists think will happen?  Watch this video from the SciShow for some insight.

So, to summarize the impacts, a warming climate may result in:

- Melting of polar ice caps

- Flooding of coastal areas

- Massive migrations of people inland

- Alteration of rainfall patterns

- Deserts becoming farmland and farmland becoming deserts

- Significant losses in crop yields

- Stronger and more frequent storms (due to more water evaporation during formation)

How soon or if these events will come to pass is up for debate, but we are seeing some impacts now.  It is imperative that we address climate change, as even the threat of these events warrants action.