I just found out the coolest thing about the Earth, and I just have to tell someone about it. I’m reading “Climate Wars” by Gwynne Dyer, a book about some possible future scenarios that might result from climate change. (I highly recommend it if you want to know more about this very important issue. It’s fascinating, scary, and hugely educational.)
Here’s the thing that blew my mind: The author says if you get an old-fashioned globe and spin it on its axis, the deserts of the world will blur into two brownish rings, one slightly above the equator and one slightly below it, at roughly 25 degrees latitude north and south. Since I don’t have one of those globes I found a map of the world’s deserts here. It’s clear from this map that the primary deserts really do line up at those latitudes. See how you could draw a line through the brown areas of the Northern Hemisphere and another one through the ones in the Southern Hemisphere? (Here’s another map that shows the latitude lines if that’s helpful.) That’s interesting by itself, but just wait until you find out why.
This is where Hadley Cells come in. Mr. Dyer explains it like this:
…an atmospheric circulation pattern called the “Hadley cells.” What drives this circulation pattern is the fact that warm, moist air is continuously rising at the equator — moist because there is high evaporation from the warm ocean surface, and rising because that is what warm air does. As it rises, however, it cools…and cool air cannot hold nearly as much water as warm air, so the moisture comes out in the form of tropical downpours. High above the equatorial regions, therefore, there is a constantly replenished layer of chilled, recently dried air –which is then pushed away, to both the north and the south, by more warm, moist air rising from below. This cold, dry air comes back down to the Earth’s surface some 2,500 to 3,500 kilometers away from the equator, and as it descends it heats up due to the increasing pressure (a process known as “adiabatic heating”). When it hits the surface, it is both hot and dry. This is what causes the world’s deserts.
Now I don’t know about you, but I don’t remember hearing the term “Hadley Cells” mentioned in all my years of schooling, so I’m just blown away by learning this simple fact about our planet.
This part of the book was an explanation of how precipitation patterns might change when the ocean temperatures rise over the next century — the Hadley cells will expand, pushing the hotter, drier air further from the equator into the areas where most of the world’s food is grown. On our continent, this means the American midwest would no longer be able to produce nearly as much food as it does now. Think about what that will mean for the seven billion people who live on this planet right now. It’s obvious why he called the book “Climate Wars.” I won’t even begin telling you about the fights that will be waged over water sources, because I’m sure you can imagine it for yourself.
One thing I do remember learning in school was that it’s my obligation as a citizen to be as well-informed as I can be. Thomas Jefferson said it this way: “If we are to guard against ignorance and remain free, it is the responsibility of every American to be informed.” I try to read as much as I can on both sides of an issue, hoping that I deserve my right to vote. It’s hard sometimes, but I think it’s an obligation all citizens should take seriously.
The more I read some of the reports that have been written by various governments around the world about climate change, the more I realize how ridiculous it is for us to be spending our time watching hillbillies grabbing monster catfish on tv, or discussing who wore the worst dress at some Hollywood event. We are all so distracted by tiny little things that don’t matter, when we should be doing all we can to understand what our planet needs in order to continue to be a suitable home for our species. Because really, what else matters if the planet can’t sustain us? I won’t be alive to see the worst of what’s coming, but I feel such a deep sadness when I think of what our intelligent species could have done if we’d just paid attention and stopped all the nonsense. What a shame it will be if the worst climate models turn out to be right. Maybe we should stop calling ourselves the smartest of all the animals until we can earn that title.