CONTACTS
SUBJECTS
Climate Change Ice age Global Warming Glacial Interglacial Periods
0703 -
0703 - ..
0704 - Summary/Objective
0705 -
070501 - Follow up
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070503 -
070504 -
070506 - ..
0706 -
0707 -
0708 - Progress
0709 -
070901 - Yesterday, Morris explained theories on causes of ice ages from
070902 - warming and cooling of the earth. He taught this subject as part of
070903 - a class on "Green Electrical Engineering.
070905 - ..
070906 - Morris seemed to indicate the major causes of ice ages are
070907 - fluctuations in thermal energy from the sun that occur over 100s of
070908 - thousands of years, together with insulation from cloud cover, i.e.,
070909 - moisture in the atmosphere. He seemed to indicate that changes in the
070910 - tilt of the earth's axis is a minor factor.
070912 - ..
070913 - This evening, research on the Internet found...
070914 -
070915 - 1. What causes ice-ages?
070916 -
070917 - http://culter.colorado.edu/~saelias/glacier.html
070919 - ..
070920 - Quatenary - seems to be the most recent and current ice age.
070921 -
070922 - 1. Fluctuations in the amount of insolation (incoming solar
070923 - radiation) are the most likely cause of large-scale changes
070924 - in Earth's climate during the Quaternary. In other words,
070925 - variations in the intensity and timing of heat from the sun
070926 - are the most likely cause of the glacial/interglacial
070927 - cycles. This solar variable was neatly described by the
070928 - Serbian scientist, Milutin Milankovitch, in 1938. There
070929 - are three major components of the Earth's orbit about the
070930 - sun that contribute to changes in our climate. First, the
070931 - Earth's spin on its axis is wobbly, much like a spinning
070932 - top that starts to wobble after it slows down. This wobble
070933 - amounts to a variation of up to 23.5 degrees to either side
070934 - of the axis. The amount of tilt in the Earth's rotation
070935 - affects the amount of sunlight striking the different parts
070936 - of the globe. The greater the tilt, the stronger the
070937 - difference in seasons (i.e., more tilt equals sharper
070938 - differences between summer and winter temperatures). The
070939 - range of motion in the tilt (from left-of-center to
070940 - right-of-center and back again) takes place over a period
070941 - of 41,000 years. As a result of a wobble in the Earth's
070942 - spin, the position of the Earth on its elliptical path
070943 - changes, relative to the time of year. This phenomenon is
070944 - called the precession of equinoxes. The cycle of equinox
070945 - precession takes 23,000 years to complete. In the growth
070946 - of continental ice sheets, summer temperatures are probably
070947 - more important than winter.
070949 - ..
070950 - 2. How does the ice build up?
070951 -
070952 - Throughout the Quaternary period, high latitude winters
070953 - have been cold enough to allow snow to accumulate. It is
070954 - when the summers are cold, (i.e., summers that occur when
070955 - the sun is at its farthest point in Earth's orbit), that
070956 - the snows of previous winters do not melt completely. When
070957 - this process continues for centuries, ice sheets begin to
070958 - form. Finally, the shape of Earth's orbit also changes. At
070959 - one extreme, the orbit is more circular, so that each
070960 - season receives about the same amount of insolation. At
070961 - the other extreme, the orbital ellipse is stretched
070962 - longer, exaggerating the differences between seasons. The
070963 - eccentricity of Earth's orbit also proceeds through a long
070964 - cycle, which takes 100,000 years. Major glacial events in
070965 - the Quaternary have coincided when the phases of axial
070966 - tilt, precession of equinoxes and eccentricity of orbit
070967 - are all lined up to give the northern hemisphere the least
070968 - amount of summer insolation.
070970 - ..
070971 - 3. What makes the ice melt when the glaciation is over?
070972 -
070973 - Major interglacial periods have occurred when the three
070974 - factors line up to give the northern hemisphere the
070975 - greatest amount of summer insolation. The last major
070976 - convergence of factors giving us maximum summer warmth
070977 - occurred 11,000 years ago, at the transition between the
070978 - last glaciation and the current interglacial, the Holocene.
070979 - During the late Pleistocene, the Rocky Mountain regions of
070980 - Canada and the regions farther west were almost engulfed in
070981 - the Cordilleran Ice Sheet, while most of Canada east of the
070982 - Rockies and the north-central and northeastern United
070983 - States were covered by the Laurentide Ice Sheet. The divide
070984 - between the two ice sheets lay east of the Rockies, with
070985 - the two ice bodies meeting near the U.S.-Canadian border in
070986 - eastern Montana. The Laurentide ice sheet is thought to
070987 - have been as much as two miles thick at the center.
070988 -
070990 - ..
070991 - 2. Mail Online
070993 - ..
070994 - Natural tilts in earth's axis cause ice ages, says Harvard
070995 - scientist - and their cycles could help predict the next one
070996 -
070997 - http://www.dailymail.co.uk/sciencetech/article-2095571/Natural-tilts-earths-axis-alter-temperature-cause-ice-ages-says-Harvard-scientist.html
070998 -
070999 - http://www.dailymail.co.uk/sciencetech/article-2095571/Natural-tilts-earths-axis-alter-temperature-cause-ice-ages-says-Harvard-scientist.html#ixzz2IByQAsEI
071001 - ..
071002 - By.................... ROB WAUGH
071004 - ..
071005 - Date.................. 02 February 2012
071006 -
071007 - 1. The idea that slight shifts in Earth's axis might have been
071008 - enough to trigger the ice ages is a century old. But a
071009 - Harvard earth sciences Professor Peter Huybers has finally
071010 - proved it, using computer models to test competing ideas -
071011 - and finding that earth's tilting axis is the only one that
071012 - works.
071014 - ..
071015 - 2. The finding could have profound implications for our
071016 - understanding of our planet's climate - and could, its
071017 - author says, be crucial to 'predicting long-term changes in
071018 - future climate.'
071020 - ..
071021 - 3. Two 'cycles' in the way Earth's axis spins have an effect
071022 - on the cycle - one lasting 10,000 years and one lasting
071023 - roughly 40,000 years.
071025 - ..
071026 - 4. When they align correctly, ice melts. At the other
071027 - extreme, glaciers advance.
071029 - ..
071030 - 5. The idea that these could dictate the cycles of glaciation
071031 - in Earth's climate was first proposed by Serbian
071032 - geophysicist Milutin Milankovitch in the first half of the
071033 - twentieth century
071034 -
071035 - 6. 'These periods of deglaciation saw massive climate
071036 - changes,' Huybers said. 'Sea level increased by 130
071037 - meters, temperatures rose by about 5 degrees C, and
071038 - atmospheric CO2 went from 180 to 280 parts per million.'
071040 - ..
071041 - 7. We ought to understand what caused these massive changes in
071042 - past climate if we are to predict long-term changes in
071043 - future climate with any confidence.'
071044 -
071045 - 8. 'And at least now we know with greater than 99 percent
071046 - confidence that shifts in earth's axis are among the
071047 - factors that contribute to deglaciation.'
071049 - ..
071050 - 9. When both cycles align 'correctly', the glaciers retreat
071051 - rapidly.
071053 - ..
071054 - 10. 'When you get that alignment, the radiation that the
071055 - Northern Hemisphere receives during summer increases by
071056 - tens of watts per meter squared, and if large Northern ice
071057 - sheets are present, they tend to disintegrate.'
071059 - ..
071060 - 11. 'These statistical findings agree exactly with what Milutin
071061 - Milankovitch, a Serbian geophysicist, proposed in the first
071062 - half of the 20th century.'
071064 - ..
071065 - 12. Huybers emphasises that these cycles are only one factor
071066 - among many.
071068 - ..
071069 - 13. 'It could also be that orbital forcing causes a rise is
071070 - atmospheric CO2, and that it?s the increased CO2 that
071071 - drives the loss of ice sheets,' he said.
071073 - ..
071074 - 14. 'In all likelihood, both CO2 and increased summer radiation
071075 - contribute to deglaciation. They?re both expected to push
071076 - the climate system toward less ice.'
071077 -
071079 - ..
071080 - 3. Wikipedia
071081 -
071082 - http://en.wikipedia.org/wiki/Ice_age
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