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Ocean Currents Explain Why Northern Hemisphere Is Soggier

Posted by Unknown on from the stealing-the-rain dept.

vinces99 writes "A quick glance at a world precipitation map shows that most tropical rain falls in the Northern Hemisphere. The Palmyra Atoll, at 6 degrees north, gets 175 inches of rain a year, while an equal distance on the opposite side of the equator gets only 45 inches. Scientists long believed that this was a quirk of the Earth's geometry – that the ocean basins tilting diagonally while the planet spins pushed tropical rain bands north of the equator. But a new University of Washington study shows that the pattern arises from ocean currents originating from the poles, thousands of miles away. The findings, published (paywalled) Oct. 20 in Nature Geoscience, explain a fundamental feature of the planet's climate, and show that icy waters affect seasonal rains that are crucial for growing crops in such places as Africa's Sahel region and southern India."

35 comments

  1. Junk Science by Anonymous Coward · · Score: -1, Troll

    This study is junk "science". The lack of rainfall in the Southern Hemisphere is a direct result of Anthropogenic Global Warming. Anyone that claims otherwise is an idiot or an oil company executive.

    It's so obvious sheeple!

    1. Re:Junk Science by i+kan+reed · · Score: 3, Interesting

      Yes, very nice straw-man, but the real concern here is that if the sub-surface ocean currents cause rainfall in the northern hemisphere, climate change is bad news for northern-hemisphere populations. We've seen noticeable drop-offs and changes in those currents correlated quite strongly(and explained quite thoroughly by thermodynamic principals) with increasing ocean temperatures.

    2. Re:Junk Science by Anonymous Coward · · Score: 0

      bad news for northern-hemisphere populations

      Pfft. As if anyone lives north of the Equator.

    3. Re:Junk Science by Anonymous Coward · · Score: 2, Insightful

      Yes, very nice straw-man, but the real concern here is that if the sub-surface ocean currents cause rainfall in the northern hemisphere, climate change is bad news for northern-hemisphere populations. We've seen noticeable drop-offs and changes in those currents correlated quite strongly(and explained quite thoroughly by thermodynamic principals) with increasing ocean temperatures.

      Not really. Not only do the currents correlate with thermodynamics, they are caused by it.
      You can worry all you want about the gulf stream stopping or changing direction but thermodynamics tells us that if it does a new stream will have to warm up the northern hemisphere.
      There aren't many places for such a stream, the question is really if it will flow west from Africa and along the east coast of America before a part of it splits back or if it will change direction and flow directly north from Africa with a part of it split of to go down along the east coast of America.
      The latter will lead to a slightly warmer Spain and slightly cooler Florida. UK and everything north will be mostly unchanged.

    4. Re:Junk Science by OakDragon · · Score: 2

      bad news for northern-hemisphere populations

      Pfft. As if anyone lives north of the Equator.

      All the cool people do.

      Get it? Get it?

      --
      Dark Reflection
    5. Re:Junk Science by Mr+D+from+63 · · Score: 1, Troll

      Whatever the reason, it is completely unfair and we must to something about it. I think a global precipitation tax is a good place to start.

    6. Re:Junk Science by PPH · · Score: 3, Insightful

      Actually, the real concern here is that we are still building and refining atmospheric and oceanographic models. Models that some people have already tried to use to initiate political and economic changes.

      Good science, just too early to use for anything important.

      --
      Have gnu, will travel.
    7. Re:Junk Science by Anonymous Coward · · Score: -1

      Whatever the reason, it is completely unfair and we must to something about it. I think a global precipitation tax is a good place to start.

      OMG! It seems so obvious now that you have said it. Only this can possibly save us from certain death.

      Tax the rain. Or set fire to it. Or something...

    8. Re:Junk Science by disposable60 · · Score: 2

      We're still refining models of planetary motion.
      And plate tectonics.

      The models are never 'done,' but we can use what we think we know to get stuff done.

      --
      You're looking for quotes? See my journal.
    9. Re:Junk Science by Immerman · · Score: 1

      > thermodynamics tells us that if it does a new stream will have to warm up the northern hemisphere.

      Not necessarily - both the major air and ocean currents are driven by the global thermal differentials, and yes they will thus continue in some form. However, one of the major effects of global warming is that it is uneven - the poles are warming much faster than the equator, due in large part to the melting ice caps reflecting away less incoming sunlight. That means that the thermal differential is shrinking rapidly, and the currents it drives will thus be correspondingly weaker. And out in the chaotic real world that doesn't mean you'll get the same currents with less strength behind them - instead you will get far more meandering and fragmented currents as regional influences play a relatively larger role in determining the course.

      And hopefully it's obvious that as the major currents become slower and more chaotic they will play a less driving role in weather patterns. The most likely outcome being that weather patterns will tend to move more slowly and chaotically - meandering slowly over territory that they once would have quickly traversed. And that means more floods and droughts as a slow-moving storm drops all its rainy payload over one region instead of spreading it across several.

      --
      --- Most topics have many sides worth arguing, allow me to take one opposite you.
    10. Re:Junk Science by Rob+Riggs · · Score: 1

      We're still refining models of planetary motion.

      If we can navigate our space probes to Kuiper Belt objects using multiple slingshot maneuvers, I think our models of planetary motion are "good enough".

      --
      the growth in cynicism and rebellion has not been without cause
    11. Re:Junk Science by Anonymous Coward · · Score: 0

      If we can navigate our space probes to Kuiper Belt objects using multiple slingshot maneuvers, I think our models of planetary motion are "good enough".

      If all you are ever going to do is to slingshot probes, certainly.

      And Newtonian physics is good enough for building bridges and elevators but that doesn't mean that you never want a more accurate model.

      The question is how good our climate models are. Are they good enough for climate engineering yet?

    12. Re:Junk Science by disposable60 · · Score: 1

      I'm old enough to remember when a 'pretty good' 5-day weather forecast was a big deal. Now we have 'pretty good' 10-day forecasts. 'Pretty good' 10-week, -month and -year forecasts are on the way. All of which will good enough for something new.

      --
      You're looking for quotes? See my journal.
    13. Re:Junk Science by Immerman · · Score: 4, Insightful

      Actually, the real concern here is that we are still building and refining atmospheric and oceanographic models. Models that some people have already tried to use to initiate political and economic changes.

      There are of course flaws in the climate models, just as there are flaws in our models of gravity, subatomic physics, etc,etc,etc - we are imperfect beings and it is the nature of scientific knowledge to evolve as our understanding expands. Those models are still far and away the best guides we have to predicting the future though, and their accuracy and reliability far exceeds the economic and sociological models that are currently driving most of the world's political process.

      The point is that all the science for the last many decades has agreed with ever-increasing certainty and detail that we will be facing major human-caused climate problems in the next century, though the exact manner in which those problems will unfold is still being understood. And the longer we put off dealing with those problems the more drastic and expensive the eventual solutions will have to be. Had we headed the scientists in the '60s and started mitigating oil usage, or at least dedicated some noteworthy resources to developing alternative energy sources, then we would now have only a moderate challenge in front of us. Instead fusion research funds have been continuously dwarfed by fossil fuel subsidies (as just one example), solar is only just starting to become economically viable, and we are likely already past the point where it will be possible to maintain the global climate in a state similar to the last several thousand years.

      If we wait another 50 years for the climate models to have all the details hammered out we'll be far too late to even start building the infrastructure we'll need to weather the transition and adapt to the new reality. As one example, several years ago an extremely high-resolution regional climate-change simulation was done for California, using the most well accepted global-scale climate change predictions as the input. Even using the most conservative numbers for global climate change, their model predicts the near-total elimination of mountain snow-pack in California by mid-century, and probably considerably sooner. That translates into *much* worse winter flooding and summer droughts, which will be devastating to both agricultural and population centers unless there have been a lot of dams built by then, and to get them built properly in time we need to start planning them now.

      Now obviously we can just keep on with life as usual and hope for the best - after all that's what our species has done for the last 100,000 years, but three things are different this time:
      1) We can see it coming, so we have the opportunity to start adapting preemptively at a much lower cost.
      2) We are the forcing factor - had we reacted sooner we could have prevented the drastic changes from coming at all (or at least delayed it by a few hundred or thousand years), as it is we may still be able to moderate the changes.
      3) There's seven-plus billion of us on the planet, and we're already over-utilizing the available ecological resources, and global climate change will drastically reduce those resources, at least for a few centuries until a new equilibrium is reached. The resulting famine and wars will dwarf anything our species has ever seen. If nuclear or bioweapons see much usage (as they may with most nations on Earth struggling for survival) then we may be lucky to survive this change even as well as we did the last ice age, when the global human population was reduced to only a couple thousand people.

      --
      --- Most topics have many sides worth arguing, allow me to take one opposite you.
    14. Re:Junk Science by HiThere · · Score: 2

      I wouldn't like to trust our climate models. The problem is, we've got to. Saying "Assume things will stay the same." is also a climate model, after all. And the evidence so far seems to show it's wrong...though not usually drastically wrong in the short term. But changes are cumulative, so when you project further out, you get larger amounts of uncertainty.

      OTOH, even a primitive climate model says that the climate between, say, 1930 and 1980 was unusually stable and favorable (unless you lived in a place where it wasn't favorable, of course). That means NO MATTER WHAT you should expect an increase in unseasonable storms and droughts. That's even without thinking about global warming. So currently I don't believe that global warming has had as many effects as people are crediting. But changes are cumulative, so one shouldn't expect that to continue to be true (except, of course, in every short term).

      --

      I think we've pushed this "anyone can grow up to be president" thing too far.
    15. Re:Junk Science by Anonymous Coward · · Score: 0

      I am still skeptical about climate science for the following reasons: weather is a chaotic system, therefore it's conceivable that climate also has some chaotic component. In this case, small imprecisions may lead to (exponentially) large errors later on. Although I am confident that climate scientists have tuned their models to eliminate most such errors, they may not have eliminated all of them.
      Since I am not a climate scientist, I am forced to rely on the specialists' assessment. However, I am generally skeptical of modeling that isn't amenable to rigorous proofs.

    16. Re:Junk Science by Immerman · · Score: 1

      Water motion is chaotic - you can sit on the beach for days watching the waves, getting a sense of how they behave, but like the weather you'll never be able to predict the details of where any given wave will reach, and occasionally you'll be taken completely by surprise. Climate though is more like the tide - still complex and prone to unexpected quirks on occasion, but the primary forces driving it are predictable. and it moves slowly enough that you can mostly see what's coming long before it gets to you.

      We have discovered many significant feedback systems that alter the climate predictions, most of the big ones though are self-reinforcing, the thawing of permafrost or the melting of undersea methane hydrates for example will release massive quantities of additional greenhouse gasses. It's not impossible that there is some other unpredicted feedback system that could throw the brakes on the process, but do you really want to gamble the future of your civilization on something that nobody has managed to think of?

      As for the effects of climate change - well the world has done this sort of thing several times before, and the geological record gives us a good idea, in a broad sense, of what the eventual "new normal" is likely to be. Except for the fact that the modern forcing factors are in excess of anything on record, which will likely accelerate things significantly, and the fact that humanity is already at the center of one of the larger extinction events in history, which combined with a climate-driven extinction event could drive biodiversity down to dangerous levels.

      As for the changes along the way - well that's where things get dicey - waves riding the tide on an unfamiliar beach, there's no telling exactly what will unfold. One thing we can say for sure is that there will be more energy in the system, and fewer forcing factors as the major jet streams and ocean currents are all driven by thermal differences between the equator and poles, and that is becoming ever smaller as the poles melt and start absorbing their fair share of sunlight. That's a recipe for more chaotic and slower-moving weather, and that's not good for agriculture, which isn't good for humans. We're seeing the first signs already - storms that would once have covered half the continent with water are beginning to get trapped by regional weather patterns, causing severe flooding or snowstorms in one area, and leaving droughts downwind. And the tide will be moving faster every year for the next century at least, making next years weather patterns even more difficult to predict. How do you farm efficiently when you don't know where the rain will fall? It's not even just a matter of planting the right seeds, you also need all the infrastructure for processing the crop. How much will it cost to move the US grain belt into Canada?

      --
      --- Most topics have many sides worth arguing, allow me to take one opposite you.
  2. What about elevation? by justthinkit · · Score: 4, Interesting

    Isn't most of the land in the Northern Hemisphere? When clouds are forced to go upward to pass over a land mass, they are more inclined to drop their rain load. Isn't that basically how it all works?

    --
    I come here for the love
    1. Re:What about elevation? by TWX · · Score: 1

      Isn't most of the land in the Northern Hemisphere?

      Which means, by default, that the Southern Hemisphere is soggier, given that it's got more water sitting on it and all...

      --
      Do not look into laser with remaining eye.
    2. Re:What about elevation? by ShanghaiBill · · Score: 4, Informative

      Isn't most of the land in the Northern Hemisphere?

      Yes. But that doesn't explain why the Northern Hemisphere gets more rain even thousands of miles from any significant land mass. The Palmyra Atoll is in the middle of the Pacific Ocean, about as far from any continent as possible. Yet it still gets significantly more rain than similar islands south of the equator.

  3. It's simple physics by RivenAleem · · Score: 4, Funny

    Northern hemisphere is on top, southern hemisphere is underneath, rain falls downwards. TBH it's a miracle that rain falls in the southern hemisphere at all. I think they use magnets.

    1. Re:It's simple physics by alex67500 · · Score: 1

      It's a good thing Europe was civilised first, otherwise it would the other way around...

    2. Re:It's simple physics by wallsg · · Score: 1

      Northern hemisphere is on top, southern hemisphere is underneath, rain falls downwards. TBH it's a miracle that rain falls in the southern hemisphere at all. I think they use magnets.

      We should launch rockets from Australia. All you have to do is let them go and they'll fall into orbit. It would save a lot of fuel.

    3. Re:It's simple physics by RivenAleem · · Score: 1

      Did you know also, that because of its location, all the air pools down in the southern hemisphere, so much so that its density is higher than that of cork, which is why Australians wear it on their hats to help them stick to the ground better.

  4. Right by justthinkit · · Score: 1

    The Southern Hemisphere's oceans are very soggy. That's what you meant, right?

    --
    I come here for the love
    1. Re:Right by bondsbw · · Score: 1

      I've been under the impression that the oceans are all equally soggy, regardless of hemisphere.

      --
      All my liberal friends think I'm a conservative, all my conservative friends think I'm a liberal.
    2. Re:Right by TWX · · Score: 2

      A given quantity of ocean is as soggy as any other equivalent quantity of ocean, and there's more of that ocean in the southern half of this planet. Hence the southern hemisphere is more soggy, QED.

      --
      Do not look into laser with remaining eye.
    3. Re:Right by Anonymous Coward · · Score: 0

      Whoosh!

    4. Re:Right by Anonymous Coward · · Score: 0

      Untrue, a square inch of water from a warm ocean is not the same amount of water as a square inch from a cold ocean.

  5. Land mass, altitude, etc... by Anonymous Coward · · Score: 4, Interesting

    From what I remember of my climatology course, rainfall is tightly tied to the oceanic currents. In the northern hemisphere there are a lot of things going on. We have more land mass, resulting in more "circles" of currents. The axis of the earth impacts insolation and global wind patterns, which create areas of evaporation and condensation at particular lattitudes on the earth. These currents change with the elevation of land mass, but by and large hard rock doesn't hold heat nearly as well as water, so you get a (sometimes drastic) temperature difference and condensation above land, which of course results in various wind patterns and rainfall. What is also interesting is look at the deserts of the northern hemisphere, notice how they are all at the same latitude?
      This stuff has been known for years, I'm not sure how this is really "news".

    1. Re:Land mass, altitude, etc... by Mr+D+from+63 · · Score: 1

      My first thoughts... the ocean currents are not the cause. Its the damn shape of the continents and ocean floor that is the real cause. Oh, wait, its the tectonic forces over millions of years... but hang on, its more the heat resulting from gravitational compression that.....oh no, basic physics is to blame for this unfairness.

    2. Re:Land mass, altitude, etc... by Anonymous Coward · · Score: 0

      my climatology course

      I was going to take that, but I didn't think I could afford the tithe and I would have had trouble making it to all of the prayer services.

    3. Re:Land mass, altitude, etc... by riverat1 · · Score: 1

      But man, it's an awesome religion with actual empirical evidence to back it up.

  6. The rains down in Africa by Kozz · · Score: 1

    From TFS:

    The findings, published (paywalled) Oct. 20 in Nature Geoscience, explain a fundamental feature of the planet's climate, and show that icy waters affect seasonal rains that are crucial for growing crops in such places as Africa's Sahel region and southern India."

    The musical act Toto was unavailable for comment.

    --
    I only post comments when someone on the internet is wrong.
  7. depressing by Anonymous Coward · · Score: 0

    More evidence of hemispherism. Will true social justice ever be attained?