Reading

Freedman, B. (2018). Environmental science: A Canadian perspective. Halifax, Canada: Dalhousie University Libraries. See: FREEDMAN_Environmental-Science.pdf

Before you begin, look up: anthropogenic

Chapter 3 (Atmosphere Section) (pp. 52-56)
Chapter 17 ~ Atmospheric Gases and Climate
Change

Atmosphere Basics

Our atmosphere is made up of gases and aerosols (microscopic particles, like pollen and dust) that surround the Earth. Most of those gases, having some molecular weight, are pulled down toward the Earth’s surface by gravity. This is what cases air pressure. Essentially most of the gases are “piled” up in the bottom-most atmospheric layer—the troposphere—in which we live. It is in the troposphere that we live, and all our weather occurs because it is also where all of the water vapor is. It is the thickest of the atmospheric layers, stretching from sea level to about 10 miles (16 km) at the equator and only about 4 miles (6 km) thick at the poles.

Atmospheric layers depiction showing the troposphere from sea level to 9 miles in altitude, then the stratosphere with the ozone layer near the top, then the mesosphere, and finally the thermosphere.

Beyond the troposphere layer is the stratosphere. The stratosphere is where the ozone layer exists. The ozone layer, in some cases only 1/16^th of an in thick, protects us from harmful incoming solar radiation (insolation) from the Sun. Without it we would have too much dangerous shortwave electromagnetic radiation (EMR) from the Sun and we would die. Shortwave electromagnetic radiation from the Sun includes gamma rays, x-rays, and ultraviolet rays (the EMR that burns your skin).

The tropospheric gases are mostly nitrogen, oxygen, water vapor, and carbon dioxide. Ozone, an atmospheric gas, should be in the stratosphere where it belongs. When it is at ground level it is a pollutant.

Water vapor in the atmosphere is water in a gaseous form, however, it is not stem. The temperature would have to be 212-degree F (100-degrees C) for steam to occur. Water vapor in our atmosphere is what you call humidity.

Air constituents showing 78% nitrogen, 20% oxygen, water vapor 1%, carbon dioxide and other gases ,03%, and inert gases .97%.

Electromagnetic Radiation

The Sun gives off electromagnetic radiation (EMR) in the shortwave (SW) end of the EMR spectrum.

Electromagnetic radiation spectrum with short waves on the left (gamma, X, and ultraviolet), the visible light spectrum, then long waves (infrared, microwaves, radio waves).

The does not give off (much) longwave radiation (LW). You can, basically speaking, think of LW radiation as heat when it is near the light spectrum where it is infrared. Just think this: infrared longwave radiation = heat.

The energy from the Sun (as SW radiation) strikes the Earth. That SW energy that is not filtered out or reflected into space is absorbed by the Earth. The Earth re-radiates the converted energy as LW radiation near the infrared part of the EMR scale.

So, to be clear, the Sun does not heat the atmosphere. Rather, the Earth heats the atmosphere after converting the Sun’s energy to heat.

Greenhouse Effect vs. Global Climate Change (they’re NOT the same thing)

In short, the greenhouse effect is a natural phenomenon we cannot live without. It is NOT the same thing a global warming or global climate change.

Here is how the greenhouse effect works in simple terms:

Shortwave (SW) radiation from the Sun filters through the atmosphere, striking the Earth. (BUT this does not heat the atmosphere because it is not heat…yet).

The Earth re-radiates longwave (LW) radiation.

Greenhouse gases absorb the LW radiation, hold it, then re-radiate it within the troposphere.

That’s it. End of story.

Earth heats atmosphere, atmosphere re-radiates heat.

We’d freeze without this very simple process.

I didn’t mention anything about global warming or climate change. The greenhouse effect is NOT climate change. Students almost always conflate the greenhouse effect as being climate change.

Climate Change

You’ll read about this in more detail in Freedman, but climate change is based on the addition of more greenhouse gases into the troposphere. This can be natural (volcanoes, rotting wetlands, etc.) or it can be human created (anthropomorphic; burning fossil fuels, burning biomass, etc.).

If there are more heat-absorbing gases put into the atmosphere there will be more heat held in the atmosphere, this is what creates climate change—the addition of greenhouse gases, not the greenhouse effect itself per se.

Atmospheric Carbon Dioxide

The media below demonstrate how much carbon dioxide is increasing in our atmosphere and what the major contributors are. View these in light of the Freedman reading for this part of Module 2.

A Global Breakdown of Greenhouse Gas Emissions by Sector

2.1 greenhouse gasses by sector.JPG

Trends in Atmospheric Carbon Dioxide at Mauna Loa, HI - NOAA lab.

How does today’s level of carbon dioxide compare to when you were born (see interactive plots tab).

Atmospheric Carbon Dioxide