Thoughts on Global Warming from a UGA Ecology Major

Five weeks ago none of us had to go to class because the skies had painted white treasure upon campus. At the same time facebookers were declaring their love for the miracle, but not all of them left out an accompanying “What global warming?!”. Whether or not it snowed this past January in Georgia, that event does not negate the 0.74˚ C increase in global average temperature. I know that does not mean a lot to some people, but imagine what would happen if your blood temperature rose 1.3˚ F. It is important to consider larger spatial and temporal scales when analyzing global climate change.

Weather refers to singular events, while climate refers to weather patterns over a long period of time (temporal). The physics of the Earth and the chemistry of water and air lead the constant movement of the two mediums. Hot air is less dense than cold air and can also hold a lot more water, so when the sun hits the equator a lot of hot, moist air rises to a higher elevation. As that air rises to a higher elevation it begins to cool and loses its water, which explains why tropical forests (hot, humid areas) are at the equator. It also creates a pocket of suction in that area, and air from higher latitudes (up to 30˚ N/S) is sucked down to the equator. This suction creates a circular effect and the hot air that had originally risen and began to cool and lose its water, it becomes more dense and eventually becomes very cold (while also carrying very little water) and drops right around 30˚ N/S. This would explain while most of the deserts in the world are located at those latitudes (Figure 2.) The process of this transfer of air is called the “Hadley cell.” There are two other cells: the “Ferrel cell” and the “Polar cell.” The Polar cell operates in the same direction as the Hadley cell, but the Ferrel cell operates in the opposite direction. As air in the Ferrel cell moves towards the pole along the surface of the air, it picks up water and drops it at the subtropical regions along 60˚ N/S. An important feature of the planet to note is that the earth has a different circumference per latitude. Velocity is distance over time, and the distance gets smaller but a year can never be shortened. Therefore the velocity at the equator is the fastest, and as air from the Hadley cells comes down to the equator from higher latitudes, the air curves away from the direction of the earth (as you can see in the figure, whether or not the air is going towards the equator or the poles it will turn left or right).

These winds create currents in the oceans. Water is much better at holding heat than air. Have you ever noticed that Europe which is at a similar latitude to Canada, experiences a similar climate to the US? It is because the “Westerlie” in the Northern Atlantic Ocean. This refers to the North Atlantic Oscillation. The portion of it with which you may be familiar is the Gulf Stream current (in which water goes North and then East), which drags warm water from the Caribbean to Europe. This water allows for a similar climate as our nation, and also explains the rainy days in London. However, as polar ice caps are melting, floods of fresh, cold water are invading the North Atlantic surface water and can potentially stop this stream of water mitigating the effect of the Gulf Stream on Europe and leading to a much colder climate in that region of the world having devastating effects to their native flora and flauna and agricultural practices. I point this out because it is important to emphasize the importance of the term “climate change” versus “global warming” and to differentiate between local and global trends. It may be getting warmer globally, but that is leading to more variable climate conditions at specific locations (i.e. harsher winters and hotter summers). Just remember, it may have snowed five weeks ago but it’s the beginning of February and the high of the past few days has been in the high 60s. I can’t wait to see what July is going to be like…and don’t forget, the average high in Athens, Ga for July last year was 94.6˚ F (the third highest year to date since 1944).

* Historical temperature data from 1944 to 2010 comes from the weather station at Athens-Ben Epps Airport, National Weather Service ID (AHN).

 

 

 

 

 

 

 

 

 

-Alex Wright

*We would like to give a special thanks to our guest blogger Alex Wright, a third-year Ecology major at the University of Georgia.

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