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  • Sunday, December 24, 2006
    As global mean temperatures continue to rise moving the Earth into its warmest period in 10 million years, New York City has begun to feel an immediate impact. While rising ocean levels have not inundated and converted the metropolis into a new Atlantis, precipitation levels have increased and winter temperatures have risen, an early indicator of global warming.
    While heat waves and periods of unusually warm weather, ocean warming, arctic warming, melting glaciers and shrinking ice caps, gradual rises in the sea-level, and even the historic hurricane season of 2005 have received significant publicity, “harbingers” such as spreading disease, earlier thaws, acceleration of evolution including adaptations seen in some insect and plant species, coral reef bleaching, along with an increase in extreme weather have only begun receiving press coverage. Yet two symptoms of global warming have quietly been present in New York City since 1971 and 1950.

    Since 1971, fueled by a rising number of severe downpours and heavy snowfalls, New York City has undergone a shift in precipitation patterns. Since official record keeping began in 1869 through 1970, a 102-year period, New York City had 12 years in which 50 or more inches of precipitation had fallen. From 1971 through 2006, even though the year is not finished yet, New York City has already experienced 15 years with 50 inches or more of precipitation. Accordingly if one extrapolated the 36-year period from 1971-2006 over 102 years, it would result in an astonishing 42.5 years of 50 inches or more of precipitation versus the 12 year figure for the period ending in 1970.

    Not surprisingly, the period from 1971-2005 has a mean precipitation figure that is 7.22 inches or 16.8% higher than the mean precipitation figure from 1869-1970. It is likely to rise even higher when 2006, which has already seen more than 55 inches of precipitation through November 21st is factored in.

    Likewise, considering the higher precipitation figures since 1971, it is also not surprising that nine out of the 12 monthly precipitation records have occurred subsequent to the transition to wetter weather as illustrated by the below table:

    New York City Monthly Precipitation Records
    January: 10.52 Inches 1979
    February: 6.87 Inches 1869
    March: 10.54 Inches 1983
    April: 14.01 Inches 1983
    May: 10.24 Inches 1989
    June: 10.27 Inches 2003
    July: 11.89 Inches 1889
    August: 12.36 Inches 1990
    September: 16.85 Inches 1882
    October: 16.73 Inches 2005
    November: 12.41 Inches 1972
    December: 9.98 Inches 1973

    With the elevated precipitation levels fueled by an increase in severe downpours that often leave in excess of 2 inches of rain and heavy snowfalls, it is not surprising that the 59 year-old snowfall record fell earlier this year when New York City received a record 26.9 inches of snow from February 11-12 versus the old record of 26.4 inches that had fallen during the Blizzard of 1947 from December 26-27. In addition, New York City has seen two 20+ inch snowstorms in the last 11 years (20.2 inches in 1996 and 26.9 inches in 2006) versus the 59 years it took for the last two (21.1 inches in 1888 and 26.4 inches in 1947). Furthermore three out of New York City’s top five snowstorms since record keeping, have occurred since 1996: 26.9 inches (2006), 20.2 inches (1996, which also saw a record 75.6 inches of snow for 1995-96 winter since modern record keeping, eclipsing the 63.2 1947-48 mark) and 19.8 inches (2003) and five out of the City’s top ten have occurred since 1978.
    New York City’s Top 10 Snowstorms[1]
    26.9 Inches – February 11-12, 2006
    26.4 Inches – December 26-27, 1947
    21.0 Inches – March 12-14, 1888
    20.2 Inches – January 7-8, 1996
    19.8 Inches – February 16-17, 2003
    18.1 Inches – March 7-8, 1941
    18.0 Inches – December 26, 1872
    17.7 Inches – February 5-7, 1978
    17.6 Inches – February 11-12, 1983
    17.5 Inches – February 4-7, 1920
    Even more astonishing, since 2000 there have been five snowstorms that have dumped at least a foot of snow on New York City. Aside from the two listed in the above table, 14.0 inches fell from December 5-6, 2003, 13.8 inches from January 22-23, 2005, and 12.0 inches on December 30, 2000.
    Consistent with New York City’s snowfall records, seven out of the top ten annual precipitation records have also occurred since 1971:
    New York City’s Top 10 Yearly Precipitation Totals80.56 Inches – 198367.03 Inches – 197265.11 Inches – 198961.21 Inches – 197560.92 Inches – 1990 58.56 Inches – 200358.32 Inches – 1903 58.00 Inches – 191357.23 Inches – 197357.16 Inches – 1889
    Last, prior to 1971, the record of consecutive years for 50 or more inches of precipitation was two, which occurred twice (1888 and 1889 with 53.32 inches and 57.16 inches, respectively and 1902 and 1903 with 52.77 inches and 58.32 inches, respectively). Since 1971, the record is currently four consecutive years (2003-2006 with 58.56, 51.97, 55.90 and 55.83 inches through November 21, 2006) followed by three consecutive that had been set from 1971-1973 when 56.77, 67.03, and 57.23 inches, respectively had fallen. Not coincidentally, with the increased precipitation totals, New York City is currently experiencing a record four consecutive years with 40 or more inches of snowfall (Winter 2002-03 through Winter 2005-06).
    Aside from increased precipitation, New York City has also experienced a dramatic decline in extreme cold sub-zero Fahrenheit temperatures. Since 1950, New York City has seen the temperature drop below zero with a low of -2° Fahrenheit on only a handful of occasions, a far cry from the early years (1869-1949) when readings fell far deeper below zero including -15° Fahrenheit in 1934. Below is a comparative table of extreme sub-zero readings as measured in Central Park from 1869-1949 and 1950-2006:
    New York City Below Zero Temperature Readings1869-1949:-15° Fahrenheit – February 9, 1934-13° Fahrenheit – December 30, 1917
    -8° Fahrenheit – February 15, 1943
    -7° Fahrenheit – December 31, 1917 and February 8, 1934
    -6° Fahrenheit – December 30, 1880, January 24, 1882, February 10, 1899, December 29, 1917, February 5, 1918, and December 30, 1933
    -5° Fahrenheit – February 17, 1896 and January 14, 1914
    1950-2006:
    -2° Fahrenheit – February 2, 1961, February 8, 1963, January 17, 1977, January 21, 1985, and January 19, 1994
    -1° Fahrenheit – January 9, 1968, January 23, 1976, and December 25, 1980

    Since the start of the 21st century, the mercury has yet to fall below zero in New York City. With the “Big Apple’s” growth and expanding “heat-island” effect, it is possible that until global warming is effectively addressed, New York City may have seen its last sub-zero reading for decades and even centuries to come.

    Another sign of New York City’s warming is the absence of annual snowfall records since 1950 despite the rise in precipitation. While the 1971-2005 mean precipitation totals for November, December, January, and March run 30.3%, 16.7%, 24.6%, and 21.3% higher, respectively than the 1869-1970 figures (February is an exception in which the 1971-2005 mean actually runs 6.8% lower than the 1869-1970 figure), only three winters from that period rank in the top eleven as far as snowiest seasons go. Below is a table of the eleven snowiest seasons:
    Top 11 Snowiest Seasons:
    1. 75.6, 1995-962. 63.2, 1947-483. 60.4, 1922-234. 60.3, 1872-735. 55.9, 1898-996. 54.7, 1960-617. 53.4, 1993-948. 53.2, 1906-079. 52.0, 1933-3410. 51.5, 1966-6711. 50.7, 1915-16, 1916-17, 1977-78
    However, despite the adversity of warmer weather and wetter winter precipitation, the 1971 transition has had an impact when it comes to consecutive winters with 40 or more inches of snow. The old record of two consecutive winters set on four different occasions has been broken as illustrated below:
    Consecutive 40 or More Inch Snowfall Seasons:
    1882-83: 44.0 Inches1883-84: 43.1 Inches
    1895-96: 46.3 Inches1896-97: 43.6 Inches
    1915-16: 50.7 Inches1916-17: 50.7 Inches
    1947-48: 63.2 Inches1948-49: 46.6 Inches
    2002-03: 49.3 Inches2003-04: 42.6 Inches2004-05: 41.0 Inches2005-06: 40.0 Inches
    Based on New York City’s transition to a wetter climate starting in 1971 and to a warmer winter commencing in 1950, the imprint of global warming is already present from a microcosmic meteorological standpoint. Thus global warming is not a theory. It is a scientifically proven fact that must be dealt with. Until carbon-based fuels are replaced with clean alternatives such as hydrogen or a catastrophic natural event such as a significant or even super volcanic eruption occurs, the latter which can be equally as devastating, the Earth’s warming will continue threatening not only the mild repercussions that New York City has seen to date, but significant climactic changes that will not only adversely affect the global economy through famine, disease and increased storm-related damage to such a level that it “could devastate [it] on a scale of the two world wars and the depression of the 1930s,”[2] but also to accelerating mutations and the extinction of rising numbers of species that cannot adapt to the changing conditions or fall prey to other migrating species originally alien to their habitats as competition for food and other scarce resources heightens.
     
    posted by sasikala at 12:27 PM | 0 comments
    The Earth may be much more sensitive to global warming than previously thought, according to the first results from a massive distributed-computing project.

    The project tested thousands of climate models and found that some produced a world that warmed by a huge 11.5°C when atmospheric carbon dioxide concentrations reached the levels expected to be seen later this century.

    This extreme result is surprising because it lies far outside the 1.4°C to 4.5°C range predicted by the Intergovernmental Panel on Climate Change (IPCC) for the same CO2-level increase - a doubling of CO2 concentration from pre-industrial times. But it is possible the IPCC range was wrong because its estimate is based on just a handful of different computer models.
    "We have anecdotal evidence that people tend to tune their models to be similar to other people's," says David Stainforth, from the University of Oxford, UK. "Nobody wants to have a model that's terribly different, particularly when there are only 8 or 10 in the world," he explains.

    Stainforth and his colleagues set up www.climateprediction.net to see what happened when models were not tuned in this way. They start with a climate model that divides the Earth's surface into boxes hundreds of kilometres square and then change some of the 29 or so parameters that govern aspects of the atmosphere and weather.
    These tweaked models are farmed out to volunteers who run them on their home computers via a screensaver. Models that accurately simulate today's climate are then dosed with carbon dioxide, to give double pre-industrial levels, and projected forward 45 years to see how the climate responds.


    "Quite scary"

    Since the project launched in 2003 more than 95,000 people from over 150 countries have donated spare computing time. The results have now come back from 60,000 simulations and the team have analysed around 2000 of these, focussing on six parameters.

    While most of the models showed the global mean temperature rising by between 3°C and 4°C, some experienced much stronger heating. "When you see large areas of the northern hemisphere at 11°C above pre-industrial levels, you think this is quite scary," says Stainforth.
    Geological data shows the Earth's climate has been much warmer in the past. Temperatures were around 6°C higher during the Cretaceous period, for example, when dinosaurs roamed the Earth. But Bob Spicer, an expert in the palaeoclimate at the Open University in Milton Keynes, UK, says there is no evidence that temperatures have ever been as high as in some of the climateprediction.net simulations.


    Missing factors

    Some iterations of the models showed the climate cooling after an injection of CO2, but these were discarded after close examination because the temperature fall resulted from an unrealistic physical mechanism, says Stainforth. In these scenarios, cold water welling up in the tropics could not be carried away by ocean currents because these were missing from the models.

    There are no obvious problems with the high temperature models, he says. The climateprediction.net team were left with a range of 1.9°C to 11.5°C. "The uncertainty at the upper end has exploded," says team-member Myles Allen.
    Clouds, which climate scientists have already recognised as the Achilles' heel of climate prediction, were the main cause of the variability in the high temperature models. The two most sensitive parameters governed the humidity at which clouds form and convection in the tropics. More observations of these critical processes could now help to narrow the uncertainty in the climate models' prediction.

    But the climateprediction.net team stress that they are not saying we will see double-digit temperature rises if CO2 emissions go unchecked. "We're saying we can't rule it out," says Stainforth.

    The next batch of climateprediction.net models will be making predictions of the timescales over which these changes might be seen, says Stainforth. "We need a lot more help, and we encourage people to continue getting involved."

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    posted by sasikala at 12:24 PM | 0 comments