Ice Age part II

Last week we talked about ice ages. Today I will try to explain what causes ice ages and are we heading for another one at this time?  We start out with the time period known as the Pleistocene epoch. Pleisto means most recent.  It is typically defined as the time period that began 1.8 million years ago and lasted until about 11,700 years ago.  The most recent ice age occurred then, as glaciers covered huge parts of the planet Earth.  There have been at least five documented major ice ages during the nearly 5 billion years since the earth was formed. At one point, during the recent ice age, sheets of ice covered all of Antarctica, large parts of Europe, North America and South America and small areas in Asia. In North America the ice stretched over Greenland and Canada and parts of the northern United States.  The remains of glaciers of the latest ice age can still be seen in parts of the world, including Greenland and Antarctica.  During this time there were about 20 cycles when the glaciers would advance and retreat as they thawed and refroze.

So what are some of the theories put forth to explain ice ages?  The consensus is that several factors are important. One that has been put forth is the change in the earth’s atmosphere. During the recent period of the last 100-1000 years, the sharp increases in human activity, especially the burning of fossil fuels, has caused the parallel sharp and accelerating increase in atmosphere greenhouse gases which trap the sun’s heat. Some scientists feel the resulting gases cause the increase in global warming and thus the chief contributor to the accelerated melting of the remaining glaciers and polar ice.

Others say the activities of the human species first began not in the 18^th century with the advent of the industrial era, but dates back to 8,000 years ago, due to intense farming activities of our early ancestors.  It was at that time that atmospheric greenhouse gas began to increase.  Some say it was the introduction of large-scale rice agriculture in Asia, coupled with extensive deforestation in Europe that caused the warming of the atmosphere during the last 1000 years.  Warmer climate caused warmer ocean waters and thus less efficient storehouses of carbon dioxide.  Theories, theories, theories! The geological records also appear to show ice ages start when continents are in positions which block or reduce the flow of warm water from the equator to the Poles and thus allow ice sheets to form. The ice sheets increase earth’s reflectivity and thus reduce the absorption of solar radiation.  The earth cools, ice sheets continue to grow which further increases reflectivity and the cycle continues. Another popular theory is variations in earth’s orbit  (Milankovich’s theory.) Of particular importance are the changes in the tilt of the earth’s axis, which affect

the intensity of seasons.  It is widely believed that ice sheets advance when summers become too cool to melt all of the accumulated snowfall from the previous winter. Of course, this is just another theory and not completely accepted by the scientific community. However, it does make a lot of sense.  Another theory is that the sun outputs varying amounts of energy. Scientists are skeptical about this theory. They think the variation in the sun’s output is so small as to have little effect on our climate.

How about volcanism?  Could volcanic eruptions be the cause of ice ages?  Volcanoes can contribute to high amounts of carbon dioxide in the atmosphere when they erupt.  Carbon dioxide from volcanoes probably contributed to periods with highest overall temperatures.  With regard to volcanoes, they also spew tremendous amounts of soot and ash into the atmosphere.  This can circulate around the globe in the upper atmosphere for years and years.  Could this block out the radiation from the sun and cause an ice age? Many, many questions, very few answers.  Remember, ice ages last for millions and millions of years.  I believe the cause or causes of such occurrences have to be long lasting.  If one wanted to press me for my thoughts, I would have to think the variations in the earth’s orbit around the sun, (Milankovich theory) has the most credibility. This may work in coordination with other factors to bring on an ice age. 

 

Ice Age part 1

We talked about the year without a summer, 1816. Periodically we have periods of cold weather but that is not an ice age. By definition, an ice age is a period of long-term reduction in the temperature of the earth’s surface and atmosphere, resulting in the presence or expansion of continental and polar ice sheets and alpine glaciers. Within a long-term ice age, there are intermittent warm periods we call interglacial periods.  We are in an interglacial period right now.

Before we go too far into the talk on ice ages, it is important to put “time” into perspective.  I really don’t know when our universe was created, the so-called “big bang”.  Theory has it our sun was born approximately 15 billion years ago.  Our earth came into being some 5 billion years ago. When did man make his appearance on earth?  Well, let’s shrink the earth’s 5 billion year history into a single year.  Man did not appear in January, not even the beginning of December. On December 15th man still has not appeared on earth.  Not even on December 30th.  On December 31st at noon time, man is still not present.  At 11 pm, no sign of man.  At 11:59 pm still no sign of man.  The final seconds tick off on New Year’s Eve.   11:59 and 50 seconds, no man.  Finally, at 11:59 and 59 seconds man appears on earth.  Out of the entire year, man has existed on earth for only one second.  Having this in mind, it is easier to understand ice ages.

Let’s go way back…during the past billion (that’s a b) years, the earth has fluctuated between warm periods (even ice free) and cold periods when glaciers scoured the continents. The current earth cooling started about 70 million years ago and continues today.  We can determine that by examining marine sediments.  We have a fairly continuous record of earth’s climate change. This record indicated decreasing deep-water temperatures along with the build-up on continental ice sheets.  Much of the deep-water cooling occurred in three major steps…36, 15 and 3 million years ago…the most recent continues today.  Filling in the blanks, between 20 & 16 million years ago the earth warmed up.   About 7 million years ago the glaciers began to grow and by 5-6 million years ago glaciers continued to grow. Then came a warming period between 5 & 3 million years ago.  In fact, during that period it became much warmer than it is today...

Seems like a long time to us, but geologically speaking it is only the blink of the eye.  Then about 3 million years ago, temperatures started falling as we entered another glaciation period.  We are still in the midst of the third major cooling period.  During this time, glaciers have advanced and retreated over 20 times, often blanketing portions of North America with ice.  Our climate today is actually a warm period between these many periods of glaciation.  The most recent period of glaciation, which many people think of as “the ice age” was at its height approximately 20,000 years ago. About 10,000 years ago, the earth began to warm up.  Currently, all that remains of the continental ice sheets are the Greenland and Antarctic ice sheets and a few smaller glaciers.  A typical interglacial period lasts about 12,000 years.  Are we about ready to begin to slide into another glaciation period?  Scientists differ on this.  Some say it is just around the corner, others say it is 28,000 years off, others say it is 50,000 years in the future.

We should consider ourselves extremely lucky.  The majority of the time, the earth is in the midst of “an ice age”.  Everyone living on earth today has been blessed with, as they say, a “friendly sun”.

The question always comes up about climate change.  Does the climate change?  Of course it does.  Are human beings responsible for these changes?  Well, as mentioned earlier in this blog, many times in the past the earth has been much warmer than it is today.  Mankind was not around to cause that warming. Perhaps we can influence the climate to a small degree, but I think climate changes because of factors way beyond our control. Could we stop the tide from coming in?  Could we stop lava from coming out of a volcano?  Could we change the course of a hurricane?  No, of course not.  Climate change occurs over millions and millions of years.

Next week I will examine some of the theories put forth explaining the causes of ice ages.  None have been so plausible as to be able to predict the next ice age.

Hurricane part 2

Last time we talked about the hurricane, how and where it formed (over warm ocean waters).  We mentioned hurricanes generally form from June 1 through November 30^th in the Atlantic and May 1 to November 30^th in the Pacific Ocean.  We talked about the surge of water that comes ashore with a hurricane, the storm surge and then mentioned the scale that measures the strength of hurricanes called the Saffir-Simpson.  Today we are going to investigate these storms a little more. 

I get asked this question many, many times.  What is the difference between a hurricane, a typhoon and a cyclone?  The answer is, basically nothing except location.  In the Atlantic Ocean, the Gulf of Mexico and the eastern Pacific Ocean, these tropical storms are known as hurricanes.  In the western Pacific Ocean, these same storms are called typhoons and in the Indian Ocean, the Bay of Bengal and Australia these storms are called cyclones. So, same type storm, just named differently in different parts of the world. 

Years ago, there were no satellites, no radar, no TV, not even radios.  The major hurricane that hit Galveston, Texas in 1900 took the public by complete surprise.  There were a few reports being spread around that Cuba had a hurricane but that “news” was dismissed as hearsay.  While this storm was approaching Galveston, many curious folks went to the seashore to examine the angry seas.  Finally, the storm surge arrived on shore and washed thousands of onlookers out to sea.  In all, when the storm had passed, 16,000 people had lost their lives.  Today, that would never happen.  We have come so much further than back in those days.  In the 1950’s hurricane hunter planes began flying into the eyes of hurricanes.  One of my high school students, who was part of the weather club I organized at the high school, is now the director of research of the national hurricane center.  He is in charge of the hurricane hunter division.  He has asked me numerous times to fly with him into a hurricane on the hurricane hunter plane.  I refuse each time because I am chicken.  He does tell about some harrowing experiences he has had, but insists they have never had a passenger death or lost a hurricane hunter in over 60 years of flying into hurricanes. My student tells of his experiences, saying the flight is 95% boredom and 5% sheer terror.  Anyway, he has flown though the eye of hurricanes over 300 times.  These hurricane hunter planes usually fly into, through and around the eye of the hurricane at all levels to get very accurate readings concerning the storm and then send all the data back to the hurricane center where it is put into computers to improve the forecast of the future speed, strength and direction of the storm.

Of course, also being relayed back to the hurricane center are pictures of the storm from space.  Satellite imagery has improved greatly over the years.  As the storm gets closer to land, radar is then utilized.  Now they can get an exact fix on the location of the storm and track its exact movement.  Forecasts are then made and ready for distribution.  Again, one of my students from the high school weather program is the executive vice president of the largest weather corporation in the world.  Millions and millions of people are notified immediately by radio, TV, and internet that a storm is threatening their location.  Mandatory evacuations are issued in areas that are in eminent danger.  Never again will a hurricane “sneak up” on a location.  When storms are just beginning, they are picked up by the satellites and followed.  When then get closer to land, the planes fly out to examine them.  Then radar goes into play.  Computer programs forecast future movements…. we are well protected…. follow the watches and warnings. 

Usually a watch means a weather situation is possible in the next 12-36 hours.  A warning means a weather situation is expected in the next 24 hours.  For example, a hurricane warning means hurricane conditions are expected in your area within 24 hours and all precautions should be taken immediately, including evacuation if necessary.  Within the last 10-20 years, beachfront property has become a very popular location.  A major hurricane, category 4 or 5 will be catastrophic. Some people will refuse to evacuate, others may be unable to evacuate.  Time will tell how this is going to work out.  There are indications a major hurricane may threaten the east coast of the United States from September 17th to 19^th, 2015.  That’s this year!  Of course, making an outlook like this is like shooting a bullet out of the sky with another bullet, but we will watch.