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View Diary: How Hot Has It Been? (and why you should be alarmed) (232 comments)

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  •  I know that. (4+ / 0-)
    Recommended by:
    melfunction, PaloAltoPixie, pico, Nulwee

    But we are always furthest from the sun during the Northern Hemisphere's summer.  This year, last year, 1375.  Always always always.

    It is the angle of the earth's axial tilt that determines our seasons.  We (in the Northern Hemisphere) are tipped towards the sun now, which means we are in summer.  The Southern Hemisphere is tipped away, which means they have winter.  

    •  If you know that, why are you asking for the (5+ / 0-)

      diarist to fix a statement that is the truth?  Steven's point was that we're having all these heat records when the earth is at the farthest point from the sun and inviting us to imagine what the temperatures might be if things were different and we were closer in the orbit (like if we were on the southern hemisphere where their summer comes during our closest part of the orbit).    I see no reason Steve should change this.

      •  Because our orbit is our orbit and isn't (3+ / 0-)
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        Rube Goldberg, PaloAltoPixie, pico


        Because the Southern Hemisphere's weather isn't what's being discussed?

        Because I can't even with this conversation?

      •  cai's point is that it's always hottest in (3+ / 0-)
        Recommended by:
        maryabein, Nulwee, AkaEnragedGoddess

        the Northern hemisphere during aphelion, so it makes no sense to bring it into the conversation as a "worrying" factor.   Or a factor at all.

        Think of this way: if someone said "I'm especially worried that we're seeing maximum record temperatures during the summer", you'd probably think, ... well, isn't that when we'd expect to see them, rather than winter?  But that's ultimately what the diarist is saying, intentional or not.  Distance to the sun isn't even a factor, and makes no sense in this context.  

        That's cai's point.  I had the same reaction reading that part of the diary.

        Saint, n. A dead sinner revised and edited. - Ambrose Bierce

        by pico on Fri Jul 06, 2012 at 10:47:52 PM PDT

        [ Parent ]

        •  Well, distance from the Sun is a factor (3+ / 0-)
          Recommended by:
          pico, billlaurelMD, AkaEnragedGoddess

          in some climate-related contexts. Specifically, Milankovich cycles (variations in Earth's orbit over periods of millenia) are tied to natural climate changes.

          However, the annual variation in our distance from the Sun is irrelevant to the conversation because of precisely what you said: of course Northern Hemisphere record highs are going to be set in summer (if at all).

          "Let’s just move on, treat everybody with firmness, fairness, dignity, compassion and respect. Let’s be Marines." - Sgt. Maj Michael Barrett on DADT repeal

          by kyril on Sat Jul 07, 2012 at 01:21:17 AM PDT

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      •  it makes sense to me (1+ / 0-)
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        as a rebuttal to one of the deniers' arguments about high temps being linked to solar influences (including distance from the sun) rather than our domestic effects.

    •  actually, that *isn't* true (3+ / 0-)
      Recommended by:
      AkaEnragedGoddess, kyril, zett

      We are now closer to the sun in NH summer than winter.  Cool summers result in ice ages because there's not enough solar insolation to melt all the snow and ice that accumulates over the northernmost parts of the continents that accumulate over the previous winter.  Then the positive feedback from increase in reflectivity due to snow, and within about 1000 years, voila!  An ice sheet, advancing southward.

      There are three cycles going on that affect solar insolation.  The earth's axis wobbles like a top, tracing out a circle every 26,000 years. This changes the time of year in which the seasons occur and is called the "precession of the equinox". The angle of the earth's axis relative to the sun (the "obliquity") also shifts about 2° up and down, resulting in subtle, but important, in the angle of the earth relative to the sun, and thus the difference between solar heating in summer versus winter. This cycle takes about 40,000 years.  Finally, there is a cycle in how oval the earth's orbit is around the sun (the "eccentricity of the earth's orbit), which will also affect the intensity of sunlight reaching the earth.  That cycle takes about 100,000 years.

      These are called Milankovichcycles, named after the Serbian scientist Milutin Milankovich who published the first journal article on this topic in 1920, with followups in 1930 and 1941.

      You'll be happy to know that using the cycles, solar insolation will gradually increase over the next 25,000 years, and is not expected to decrease enough to result in a new ice age over the next 50-to-100,000 years.  So don't expect any help from Milankovich cycles to get us out of the global warming predicament!

      "Mitt Romney has more positions than the Kama Sutra." -- me "Social justice is love, made public." -- Cornel West

      by billlaurelMD on Sat Jul 07, 2012 at 06:46:21 AM PDT

      [ Parent ]

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