will cause a decrease in the
number of frost days in the southwestern states, an increase in
precipitation intensity in southeastern states, and an increase in
heat-wave intensity in the southern tier of states, according to a
new study. The study looks at the weather impact of El Nino events
on weather extremes in North American if, as is often predicted,
global warming raises temperatures by a degree or two in coming
decades.
El Nino is the name for a huge ocean-atmosphere
interaction and transfer of energy across the tropical Pacific Ocean
between South America and Asia. El Nino events occur irregularly in
intervals of between two and seven years and can have a large impact
on weather in places around and beyond the Pacific basin. Gerald
Meehl (meehl@ncar.ucar.edu) and his colleagues at the National
Center for Atmospheric Research (NCAR) in Boulder, Colorado have
attempted to model what happens when El Nino events occur in a
hypothetical warmer world, especially for weather patterns in the
US.
The model, first of all, does a pretty good job of simulating
weather extremes (such as number of frost days-days when the
temperature goes below freezing---and intense precipitation) in the
world as it is now. Furthermore, the same model has been used to
demonstrate that the temperature increase over the US in recent
years has been mostly due to human-related “forcings” over and above
any natural fluctuations in effect. Giving the model a new slightly
higher base temperature, a number of specific changes in weather
extremes (during El Nino events) in the US emerge, such as those
shifts in extremes mentioned above. (Meehl et al., Geophysical
Review Letters, current issue.)
Egyptian Pyramids, Dinosaur Extinction, The JFK Assassination:
all were studied by Berkeley physicist Luis Alvarez. Alvarez won a Nobel Prize for his discovery of new particles using a bubble chamber, but some of his fame comes from his work applying physics
principles and methods outside the normal physics-research world.
In the November issue of the American Journal of Physics, Charles
Wohl of the Lawrence Berkeley National Lab (cgwohl@lbl.gov) looks at
three notable examples of Alvarez’s extracurricular effort.
(1) To
search for possible hidden chambers in the Chephren pyramid in
Cairo-one of the three great pyramids built in the third millennium
BCE-Alvarez designed an experiment in which cosmic rays would strike
a detector set up inside a known chamber beneath the pyramid.
Observing the penetrating muons from cosmic-ray showers, this
detector would discern any intervening empty spaces in the overlying
pyramid structure. The upshot: no hidden chambers.
(2) In scrutinizing the so called “Zapruder film,” a short filmed
sequence that caught the assassination in progress, experts had been
puzzled by the backwards jerk of President Kennedy’s head after one
of the bullet impacts. Some took this to be evidence for another
assassin shooting from in front of the president’s car. Alvarez and
some of his colleagues performed impromptu experiments at a shooting
range, and also considered the conservation of momentum and the
forward-moving matter from the wound. From this they concluded that
the movie sequence was consistent with a shot coming from the rear.
(3) Most famous of all was Alvarez’s hypothesis, made in
collaboration with his son Walter Alvarez, that a thin but
conspicuous layer of the otherwise rare element iridium in numerous
places around the world, all at a geological stratum corresponding
to the era just around the boundary between the Cretaceous and
Tertiary periods (the KT boundary), signified a large asteroid
impact at that time. This impact, it was further thought, cast
enough dust into the air from a long enough time as to kill off many
living things, including a large portion of dinosaurs.
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