Geography, why it matters

When I was a kid I was what you might call a "climate nerd." I would be at a party my parents took me to and pour over atlases and maps, as well as descriptive books on climatology, just to pass the time. Though it was just a phase I have kept a lot of that knowledge with me, and I've found it really useful. Many times I'm shocked at how ignorant many of my friends are of geography. If one was to choose between learning technique or information (e.g., math vs. history) I would pick technique because my own feeling is that technique is very versatile. But in the real world we don't choose, we mix & match. We combine a theoretical model of the world with a dense network of empirical data. A few weeks ago I was chatting with a friend of mine and it became clear that he thought China was placed "very far north." I told him to look at a map and he was shocked. The reality is that China is to a great extent a subtropical country, with a small portion even to the south of the Tropic of Cancer.

One of the main things I recall from my childhood climate phase is the importance of physical geographical parameters in combining to produce a particular regime. Additionally, one can work with a few rules of thumb to make predictions. For example, the wider a landmass east-west is the greater the difference in mean winter temperature will be between the west coast and the east coast, with the former generally being far milder than the latter. But let's make this concrete.

    Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
  Lat Average temperature in celsius
New York 40.6 0 1.39 5.83 11.39 16.9 21.7 24.7 23.9 19.7 13.9 8.33 3.06
Lisbon 38.2 10.5 12.5 14 15 17.5 22 23.5 23 21.5 18 13 11.5
Beijing 39.8 -3.5 -1 5.5 13.5 13.5 19 23.5 26 20 13 4.5 -1.5
Eureka 40.9 8.5 9 9 10 11 12.5 13.5 13.5 13.5 12.5 10.5 8.5

And here's a chart:

I assume a substantial proportion of the readership of this weblog are aware of the locations of Lisbon, New York City and Beijing. Eureka is just to the south of the Oregon border, to the north of San Francisco, on the California coast. What you are seeing here is the pattern of eastern coastal cities exhibiting a more continental weather regime. To some extent this is just a function of the spin of the earth, around 40 degrees north (and south) the dominant winds come from the west. This means that the western coasts tend to be characterized by a maritime climate. In contrast, eastern locales are often subject to winds from the interior, which in winter or summer are characterized by temperature extremes because of the differential physics of heating up water and the earth's surface. Also note the difference between Beijing and New York; the surface area of the interior of Eurasia is far larger than of North America, so the continental affect is more notable.

Of course there are many other factors, such as ocean currents and the distorting influence of mountain ranges. In any case, there's a map of the Koppen climate classification system (click for larger image):


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Another element is oceanic circulation: warm currents from the south in Europe and the North American western coast make winters a lot milder than would be otherwise. Certainly the Gulf Stream is extremely important to keep Europe warm, not just Lisbon but, specially, much farther north. Siberian winds do affect Europe (and Saharan ones too) but the Oceanic high and low pressures dominate and keep their effect limited and in general tend to push them back. When the Siberian high pressures manage to temporarily dominate though, this becomes like the Ice Age.

Instead both Eastern coasts are affected by cold streams from the arctic.

Quite pedagogical anyhow. I was not really aware that I live north of New York (similar latitude yes). :)

I used to tell people that Winnipeg was the coldest city that bog in the world (wintertime). Since then, I've found that a few cities in Mongolia and Siberia are more or less as big, and colder. But it's not just how far north you are, but how far inland.

By John Emerson (not verified) on 03 Jun 2008 #permalink

Climate affects how bad of a pathogen load the place will have, and that affects everything else, so that's a big reason to pay attention. Most academics don't realize this due to bi-coastal bias, both coasts being nightmares disease-wise compared to the Mountain Time Zone, for example. I haven't seen a single mosquito here -- at worst, the odd group of gnats. And no ants, camel crickets, or other creepy crawlies that could act as disease vectors.

One thing I'd like to look at is how the boundaries affect pattern formation. Like, let's say you had an epidemic disease spreading in Italy, and assume it had an activator-inhibitor feel to it. Murray proved that if you have an animal with a tail, and it has both spots and stripes, the part of the tail near the body will always have just one (I forget whether stripes or spots). Everyone's looked to see, and it's held up.

Peninsulas are like tails attached to the larger continental body, so there should be something similar going on there. Like you'd only get either bands of disease prevalence or patches of disease, at the part of the peninsula closest to the body.

both coasts being nightmares disease-wise compared to the Mountain Time Zone

assman, you haven't lived on the west coast. i've lived on the west coast, the intermontane west, as well as the northeast and midwest. the first two resemble each other in terms of stuff like mosquitos. it doesn't rain in the summer, which minimizes pools of stagnant water (i'm assuming the artificial wetlands of the central valley aren't that great, but they're not natural).


You got it backwards.

The east coasts of America and Eurasia have warm water currents coming up from the south. The Gulf Stream in the case of North America, and the Japan Current of the case of Eurasia.

The Gulf Stream warms up the east coast of North America and Western Eurasia because the current is relatively close to each.

On the other hand, the Japan Current has little effect on eastern Eurasia other than Japan because eastern Eurasia , other than Japan, is a bit too far away. And western North America is much too far away for the Japan Current to have any effect on it at all.

I don't know anything about the surface currents running south along the west coast of Eurasia. I do know there's a substantial deep current that carries a lot of the flow brought up by the Gulf Stream.

In contrast western North America is cooled down by the California Current. Which is essentially the Japan Current after being turned south by the Gulf of Alaska and chilled by the Bering sea and the Gulf of Alaska. Were it not for the California Current my home town would get hotter than Oran, Algeria, because it's south of Oran, Algeria.

Mosquitoes are a very poor example. Arctic mosquitoes can kill a newborn horse by depleting its blood. Minnesota is among the worst places for mosquitoes.

I don't remember ants as disease vectors either.

By John Emerson (not verified) on 04 Jun 2008 #permalink

Climate is what you expect, weather is what you receive. Can't recall where I read that but it is important to recognize.
One thing that should be pointed out is that Koppen devised this map not looking at the weather patterns, rather he examined the vegetation that grew in the particular locales. (And he didn't even do that, he sat in his office in Berlin and examined reports from those locales.) So the climax vegetation was determined to be the best indicator of the climate. Although this is for the most part reliable, there is the danger of skewed data. Consider the case of irrigation. I'm not thinking of the plants that are the recipients of the irrigation, rather the flora that is deprived by the diversion. That landscape changes as a result and so does the "climate."
One more thing into the mix, how does economics affect the cultivated cropland? Is there more than one "climate." As recently as the 1970's, Japan was the #3 producer of citrus in the world. Bring down a few trade barriers, increase the cost of land, and now it's #12. Has the climate changed or was the cultivation so close to the edge that it was no longer profitable? The answer is - China. Mao had millions of citrus tress cut down during the Cultural Revolution. Deng had those millions of trees replanted. As they came into bearing, China went from #13 to #2 and the now export their crop to the closest market. Funny thing is that while Japan's imports doubled, their share of total world imports remained the same. Japan's physical subtropical climate still supports citrus production but its economic climate does not support it.

By Onkel Bob (not verified) on 04 Jun 2008 #permalink

Just looking at the map, incidentally:

There's a guy here in Minnesota who has put together a fantastic arboretum which includes plants and trees from every continent (except Antartica, obvs). What he's done is calculate the altitude at which Minnesota's climate is approximated elsewhere, and then gathered plants from there. At the equator, for example, a plant growing at xxxx feet will be hardy enough to survive Minnesota winters.

It's a very rough equivalence since there aren't winters and summers at the equator, but he's made it work.

The guy has over a hundred willow species, for example. He's spent all his spare time and money for over fifty years doing this single-handed and self-funded. The botanists at Minnesota universities will consult with him occasionally, even though he's completely self taught. (Self-taught out of university textbooks he bought, that is. He didn't figure it all out from scratch.)

End of digression.

By John Emerson (not verified) on 04 Jun 2008 #permalink

It does snow alot in most parts of China, and paintings often disproportionately depict pines and decidious trees in the snow, so it is common to think of it as cold.


I like your math vs history comparison. In the brief time each day that I can devote to self-improvement, I always hit up against that issue. My natural tendency is to focus on technique until I hit a wall, and my lack of the necessary dense-web-of-facts prevents any further progress.

The frustrating thing about information is that, for me at least, it fades. I can reach into the intellectual toolbag and use a technique I mastered years ago. But finding a once-learned fact is harder.

I'm also old enough (mid-30s) that I've had the experience of re-learning forgotten facts. It's a bit depressing to realize that I once knew some fact that I now have to look up.

I think there's actual neuroscience to back up my suggestion though. Factual data requires more regular rehearsal to maintain the network. But technique has more of a learning to ride a bike flavor to it.

Presumably there's also an age component, with factoids memorized while young holding a privileged position vs facts learned later. So the ROI of informational learning decreases as we age.


It also reminds of a seemingly smart, successful woman I know. Yet she honestly thought there were 50 million people in Sweden, 150 million in Germany, and 30 million in Mexico. And she'd lived in all those countries! She was basically innumerate. But she had a master's degree in psychology. And she thought of herself, and was treated by others, as an intellectual -- mainly because she had traveled so extensively, I think.

"i'm assuming the artificial wetlands of the central valley aren't that great, but they're not natural"

Extensive rice cultivation occured in California due to the existence of large areas of seasonal marshland. Prior to extensive white settlement, the Central Valley, Sacramento Delta, San Francisco Bay, Oregon's Willamette Valley, Puget Sound and much of Southwest Washington State were areas of extensive swamps and tidal marshes. It is estimated that the area of wetland in the Delta-Bay complex is only 10% of the size it was 200 years ago.

You got it backwards.

The east coasts of America and Eurasia have warm water currents coming up from the south. The Gulf Stream in the case of North America, and the Japan Current of the case of Eurasia.

The Gulf Stream warms up the east coast of North America and Western Eurasia because the current is relatively close to each.

It's more complicated it seems. Neither you nor I have it completely straight. The Gulf Stream warms up the US Southeast but it gets into the Ocean at the latitude of Virginia, becoming the North Atlantic Drift (aka Gulf Stream too) that fans out to warm up all Atlantic Europe. North of Virginia you have the Cabot Current that is a southward flow of cold water from near Greenland.

A similar pattern happens in the Pacific Ocean with the North Pacific Drift, that leaves the Asian coasts at the latitude of Tokyo (replaced by a cold current there) to cross the ocean and reach North America at Vancouver island roughly. The derived coastal flow warms up Alaska and cools somewhat the Western coast of the USA.

See this (large) map:…

When I taught limnology, I gave my students a map of the world with rivers and lakes, and a list of the world's major rivers, lakes, and inland seas. The assignment was to label the map and bring it to every class.

By Jim Thomerson (not verified) on 04 Jun 2008 #permalink

I was another one those kids poring over maps and stuff as a child. :)

I still do. I subscribe to "ocean currents" on google alerts and was informed about this post of yours. You should check it out too.



The world does have a bad habit of being complex, don't it? :)

Sure. I'm still trying to understand why the Ice Age did not cover Siberia of ice, when it's now the coldest region of Eurasia.

This may look somewhat offtopic but certainly it's the same thing: understanding the why of climate. And really, I don't understand this part at all.

Luis, it's very simple. Ice ages don't mean that summers are automatically extinct. To begin glaciation, you don't need just colder winters, you also need enough snowfall during the winter so that it doesn't all melt during the summer. If the snow melts, the clock is reset; if it doesn't, it starts a self-reinforcing process, as snow reflects light well and the next year will be cooler if it starts with snow.

Deep inland Siberia is very dry, as you'd expect for the location and prevailing winds at the latitudes (from the west). Much more favourable places like Scandinavia will begin growing glaciers first and that will tie up some of the world's water, so during ice ages Siberia gets even drier. Siberia will also be downwind the European ice sheet and massive ice sheets generate dry local climates. The European ice sheet will of course grow into Siberia, but the further it gets, the harder it gets for it to grow.

That's a pretty reasonable explanation. Thanks, Jaakeli. :)

Not an easy one to figure out on my own really. True that I've never been in Siberia but typically I figure it almost like Antarctica, at least in the northern latitudes. Obviously a wrong stereotype.

That's not entirely inaccurate, as it's possible for a place to be so ridiculously dry that it remains ice free even in Antarctica:

An ice age would turn much of Siberia into similar desert, but it would also create vast ecoregions unlike anything seen today, as vast cold regions would exist at far lower latitudes than they do today, so there'd be tundra with much higher sunlight than seen today (Google steppe-tundra if you want to). Most of Siberia is taiga today and theoretically similar to inland Finland, but biodiversity is way higher there.

Thanks again for your explanations. Pretty interesting, certainly.

What about permafrost? Another thing that puzzled me is that while permafrost (that obviously requies water ice, even if under the soil) is known to have reached as far south as Beijing in the LGM, Siberia as a whole remained mostly ice-free, at least on he surface. How can there be permafrost and not surface ice, specially in such a vast extension?

Though guess the answer is in the dry winds, not affecting the underground water ice, right?

Why not? The deep underground doesn't respond to season changes that much. Permafrost just means that a deep layer of soil remains frozen year round. It's wet/frozen soil, not pure water/ice, so a melted top has no trouble existing on top of frozen soil during the summer. Tundra is simply the region where the summer isn't warm enough to melt the deep frost but where the temperatures do spend enough time above zero to melt a top layer of soil and allow some vegetation ("tundra" comes from the Finnic word for treeless areas - deep permafrost is a hard place to grow roots).

(BTW if you like visualizing, tundra is still not likely to be literally dry during the summer, as the meltwaters are trapped in the surface layers by the frozen deep soil. It might get as little rain as Sahara and still be a swamp. Take your rubber boots with you if you ever visit ice age Beijing.)

Guess it takes a Finn to understand (and explain) the machanics of the cold north. Very informative exchange. Thanks again.

"The reality is that China is to a great extent a subtropical country, with a small portion even to the south of the Tropic of Cancer."

Actually, from the map, it looks like only like one third or less of China is subtropical.

Actually, from the map, it looks like only like one third or less of China is subtropical.

i meant china proper (tibet and xinjiang have generally not been part of the geographic domain which is termed 'china').

I suggested to my kid to use an educational game Settera 3.0 for map pointing purpose. It helped him to some extent learning Geography, at least the Place names.