Heavy Precipitation Over the US: Has it Increased as Some have Predicted it Should?

Discussion in 'Environment' started by daveman, Sep 2, 2012.

  1. daveman
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    daveman Diamond Member

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    Heavy Precipitation Over the US: Has it Increased as Some have Predicted it Should?
    Background
    Noting that "extreme events of precipitation have a potential for impacting our social and economic activities," Mahajan et al. state that it is "essential to determine if there has been a systematic change in the extremes over the past years and what awaits us in the future owing to global warming," especially in light of the fact that "climate model projection studies suggest that intense precipitation would be on the rise as global temperatures increase due to increased greenhouse gas forcings in the future (Meehl et al., 2000a,b; Cubasch et al., 2001; Zwiers and Kharin, 1998; Kharin and Zwiers, 2000)," which future, obviously, has already begun, as well over a decade has passed since the writing of the cited papers.

    --

    What was learned
    Mahajan et al. report that trends estimated from the two data sources they employed "straddle the margin of statistical significance, and hence a definitive answer to the question of increasing trend of heavy precipitation over the US cannot be arrived at by looking at observational data." And with nearly half (9 out of 20) of the GCMs employed in their study predicting trends that are "significantly different from the observations," they are forced to conclude that "the GCMs are not yet fully capable of simulating extremes of precipitation at a regional level," as they say that only "one GCM simulation of the twentieth century does demonstrate a statistically significant upwards trend in monthly heavy precipitation."

    What it means
    When all was said and done, the four scientists concluded the report of their research by writing "we cannot definitively answer if the heavy precipitation in the US has been increasing in the past century." Yet they continue to repeat the ominous refrain that "GCM integrations suggest that it is very likely to increase in the future." We shall see.​
     
  2. daveman
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    daveman Diamond Member

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    So, how are those models working out?
     
  3. Katzndogz
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    Katzndogz Diamond Member

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    From reports given by legitimate meterologists, we are entering the same kind of cycle that we were in during the 40s and 50s, which is increased hurricane activity in the Carribean. Just like experts in California are predicting an increase in earthquake activity after a period of quiet.

    The problem with liberals is that everything is brand new, it never happened before. It's global warming and if it's cold, it's climate change because its cold.
     
  4. RollingThunder
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    RollingThunder VIP Member

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    Oh wow, some distorted and spun-up scientific misinterpretations from an idiotic denier cult blog. Very unimpressive. What is actually happening is that precipitation has definitely increased in the farther northern and southern latitudes and decreased in the equatorial regions and this averages out to only a slight upward trend globally.

    National Oceanic and Atmospheric Administration
    National Climatic Data Center
    Hydrological Cycle (evaporation and precipitation) impacts

    (excerpts)
    Globally-averaged land-based precipitation shows a statistically insignificant upward trend ... ...precipitation changes have been spatially variable over the last century. On a regional basis increases in annual precipitation have occurred in the higher latitudes of the Northern Hemisphere and southern South America and northern Australia. Decreases have occurred in the tropical region of Africa, and southern Asia. The measured changes in precipitation are consistent with observed changes in stream flow, lake levels, and soil moisture (where data are available and have been analyzed).


    Early Warning Signs of Global Warming: Downpours, Heavy Snowfalls, and Flooding
    (excerpts)
    An increase in global temperatures will lead to an intensification of the hydrological cycle. This is because an increase in surface air temperature causes an increase in evaporation and generally higher levels of water vapor in the atmosphere. In addition, a warmer atmosphere is capable of holding more water vapor. The excess water vapor will in turn lead to more frequent heavy precipitation when atmospheric instability is sufficient to trigger precipitation events. Intense precipitation can result in flooding, soil erosion, landslides, and damage to structures and crops. Parallel to the likely increase in heavy precipitation events in winter, increased temperatures will also amplify the drying out of soils and vegetation due to increased evaporation in the summer. This is likely to result in more severe and widespread droughts where and when atmospheric conditions do not favor precipitation (see Droughts and Wildfires).

    The largest changes in precipitation are expected at mid- to- high latitudes (Kattenberg et al., 1996). Climate models predict an increase in average precipitation in winter at high latitudes due to poleward transport of evaporated moisture from lower latitudes. There is also an increase in the expected frequency and areal extent of intense precipitation over the continents. Predictions for soil moisture changes are less certain; however, models show an increase in soil moisture in high northern latitudes in winter. Consistent with model predictions, weather observations over the last century indeed indicate an increase in precipitation over land in the high latitudes of the Northern Hemisphere (Nicholls et al., 1996). For the United States, precipitation since 1970 has averaged about 5% more than in the previous 70 years (Karl et al., 1996), and cold season precipitation has increased by almost 10% during the last century. Over the period 1950 to 1990, annual snowfall increased by about 20% over northern Canada and by about 11% over Alaska (Groisman and Easterling, 1994). An increase in snowfall was also observed in the 1960s and 1970s in China. A recent analysis indicates a trend toward increasing streamflow in most regions of the United States (Lins and Slack, 1999), consistent with the observations of a wetter climate.

    Some regions have also experienced an increase in extreme precipitation events, as predicted in model simulations (Nicholls et al., 1996). Observations for the last 100 years indicate that extreme precipitation events (more than 2 inches in 24 hours) in the United States have increased by about 20% (Karl and Knight, 1998). Increases in heavy precipitation have also been reported for Japan and northeastern Australia. An increase in the intensity of precipitation increases flood potential. The magnitude of the human influence relative to natural variability is much larger for temperature compared to precipitation and atmospheric circulation, meaning that a "fingerprint" of anthropogenic warming in precipitation records will emerge much more slowly (Wigley et al., 1999). It may be decades before an unmistakable human signal emerges from the natural background noise.
     
  5. Katzndogz
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    Katzndogz Diamond Member

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    The Sahara Desert used to be a sea. Lebanon was once a forest.

    I don't know who is doing the filtering in these rather odd climate predictions, but climate is not the same as weather. There aren't a lot of climate zones. There is polar, desert, tropical, sub tropical, humid continental and arctic, with several subsets of climate. Climate changes over thousands of years. The Sahara sea becomes a desert, the tropical prairie becomes grassland. Mountains form and become alpine in climate. Climate changes all the time, but to our eyes, it is imperceptible. The Salton Sea is in the process of becoming part of the desert and has been doing so for a couple of hundred years.

    Weather, on the other hand, changes quickly. The weather is a result of atmospheric changes in the various jet streams of air current. It is cyclical. We have periodic droughts and floods. Hurricanes follow a 40 year cycle because the jet stream follows a 40 year cycle.

    Decades ago, Issac Asimov wrote a story called Nightfall. It was about a planet whose orbit allowed sunset only once every 500 years. Civilizations would collapse into chaos when night fell because the people were convinced that the night would be permanent. They felt this way even though there was a historical record of the regularity of nightfall. Scientists expecting nightfall tried in every way to affect the orbit and rotation of the planet to stop nightfall. Something they could do, on a planetary basis, would stop sunset. If the whole world got together and acted quickly, night would not come.

    Night came, every nation on earth collapsed into barbarism and the cycle of civilization repeated for the next 500 years.

    That's what this reminds me of. We could be aztecs believing if we only could sacrifice enough virgins. If we just found the way to affect the orbit, rotation, sunspots and that darn jet stream, we would control the weather and the climate. Meanwhile the arctic will not grow tropical ferns (although we have a fossil record that it once did). Florida will not become a desert and Siberia will still be quite cold. It just won't always be like that.
     
  6. Old Rocks
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    Old Rocks Diamond Member

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    Well, one can always expect our local ignoramouses to be denying the obvious. In 2011 we had such an extreme weather pattern that the Mississippi and Missiouri rivers were at flood stage or above from March to September. This year, we have had such a nearly continent wide drought that there is major damage to homes because of soil drying and shrinking in 40 of the 48 states. Damages to private homes that totals to over a billion dollars.

    Once more, we are having a year world wide in which extreme precipitation events, too much or a lack of precipitation, are happening at a far higher rate than in the past decades.
     
  7. daveman
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    daveman Diamond Member

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    ...and world socialism is the only thing that can save us.

    Right, Chicken Little?
     
  8. RollingThunder
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    RollingThunder VIP Member

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    Once again, little retard, you demonstrate that this debate is, for you, not about the science but only about the politics. And of course, even there, politically, you've been bamboozled into believing some really idiotic nonsense about the implications of any world action to curb CO2 emissions. Just some clever propagandists pushing your 'hot' buttons and making you dance to their tune and parrot their bullshit.
     
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  9. RollingThunder
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    RollingThunder VIP Member

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    What a completely idiotic and pointless post, Katzhitbrainz. Your scientific mistakes are not even worth a comment.

    In the area of science fiction though....

    Anybody who has actually read Asimov's story can see how badly you've mangled it, you pathetic retard. The "scientists" in that story did not try in any way whatsoever "to affect the orbit and rotation of the planet to stop nightfall". That's utterly ridiculous on the face of it and particularly in the context of that story where the planet only had a low level of technology. This bullshit here - "Something they could do, on a planetary basis, would stop sunset. If the whole world got together and acted quickly, night would not come." - is entirely your own invention and has nothing to do with that story. Every time on that planet (in the story), after generations of continuous daylight from multiple suns that obscured everything else in the sky, things would line up just right so that nightfall and full darkness would finally arrive, people would see the stars for the first time (many more stars than here) and freak out massively, go insane, and start fires, burning their cities, trying to blot out the reality of larger universe (they thought their few suns and their world were the only ones in existence). The 'scientists' in that story were just trying to create some sort of storage vault for their records that might survive the time of burning. If anything, the story might be an analogy to you reality denying cultists who can't handle the truth of our current situation in regard to the climate and would destroy the world in your foolish and futile attempts to avoid facing the fearsome reality.
     
    Last edited: Sep 2, 2012
  10. asterism
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    asterism Congress != Progress

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    Because there was no dust bowl in the 1930s? No massive flood in 1927?
     

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