Week 2 - Reflections on Past Climate Change 3-2-2014

 

      This discussion is for an assignment in Week 2 of the Climate Change course from Exeter University.  Section 2.8 asks for our reflections the week's topic, "Past Climate Change."
      This week's material  dealt with both ancient and more recent climate changes.   The significance of understanding these changes is that they are pathways to understanding what changes are occurring in our climate now, what trends we have set in motion, and to what kind of future climate these projected trends could lead.
      Ancient Climate Change:  One of the most interesting things about the history of Earth over the long haul is how the climate has "self-regulated" for most of that time to be habitable for life.  Consider: 

1. The age of Earth is about 4.5 billion years.
2. Earth has been covered in water for about 4.2 billion years.
3. Life on earth began as far back as 3.8 billion years ago.
4. The sun was 25 to 30% cooler then, which would work out to 44 degrees F. colder, and Earth would have been frozen.
5. However, it was actually warmer then, due to a higher amount of greenhouse gases--in particular, CO2 and water vapor.
6. So today, with the sun much warmer, we should be far hotter, but we are not.
7. The reason is that CO2 has been greatly reduced compared to 4.5 billion years ago, due to chemical and biological processes which transferred CO2 through the ocean and into sedimentary rocks.  The higher the temperature, faster this process occurred--so we have stayed within a range that supports life.

    However, there have been two "Snowball Earth" episodes, once 2.2 billion years ago, and again 700 million years ago.  In these episodes Earth froze over completely.  It is not known exactly what touched it off.  It is thought that ice completely covered Earth even at the equator, though there may have been more of a "slushball" effect in places.  In any case, when the 700-million-year-ago event occurred, life had only evolved to the level of very small organisms, all living in the oceans.  (After the thaw, the "Cambrian Explosion" of forms of life took place.)  The fact that life survived at all was one of the arguments against the theory that the snowball ever occurred.  That objection was not dispelled until rather recently, when it was discovered that in the Antarctic, there was enough light under 5 meters of ice--provided it was clear ice--to support photosynthesizing and eukaryotic life.
     A Russian researcher developed the Snowball Earth theory in the 1960's, having worked out mathematically that if the earth froze such that it reflected about half the sun's energy (equivalent to glaciers reaching to about Texas), there would be a runaway cooling effect.  He was unable to explain how the effect would not have remained permanent, so the theory was stalled for a while.  Finally by 1998 it was theorized and accepted that CO2 from volcanoes would have gradually accumulated in the atmosphere enough to start the thawing process.  Normally the CO2 would not have accumulated so much--see point 7 above--but the ice everywhere prevented the CO2 from being transferred into the earth's crust.  Of course, it took...  10 million years!
      The story above is quite simplified.  However, three things amaze me:
          1)  that such extremes can occur when a particular "tipping point" is reached, 
          2)  that the original mathematical prediction of runaway cooling was correct, and 
          3) that CO2 is such a powerful and long-term determinant of Earth's climate.
 
(Relatively) Recent Past Climate Change:  This deals with periods from several million to just the last few hundreds of years.  Some of the influencing factors are predictable, like changes in the Earth's axis, wobble, and orbit.  It takes about 100,000 years, for example, for the Earth's orbit to change from nearly circular to more elliptical and back again.  Other factors are unpredictable, such as cooling effects due to ash clouds from volcanic eruptions.   For example, the Medieval Warm Period (around 11th century) occurred during a period of increased solar activity.  However, it happened only in the Northern hemisphere, and was not part of a global effect.  The warm period was followed by the "Little Ice Age" for a few hundred years, and there is evidence of more volcanic activity at that time.   These climate changes were tiny compared to the ancient ones, but still they had major effects on European history.  Records like tree rings, ice cores and pollen samples help us recreate "recent" past climate changes.  

The present and future:  The dramatic temperature increase over the last 100 to 150 years cannot be explained by changes in solar activity or vulcanism.  The major predictive determinant is the rise in carbon dioxide.  
      One of the most striking things I learned from this week's recommended reading is that today's warming is happening at a very fast rate compared to climate changes of the past.  It is useful to compare today's rate of change to the rate of warming at the end of the last ice age.  Part of NASA's website, called "Earth Observatory," notes that over the last century, global warming is happening five to ten times faster.  The prediction of next century's warming is that it will happen at a rate twenty times faster than when the last ice age ended.

      One final note from my own further web-exploring:  http://www.truthdig.com/report/item/carbon_output_will_climb_29_by_2035_20140208

     BP’s Energy Outlook 2035 says CO2 emissions are likely to increase by 29% in the next two decades because of growing energy demand from the developing world.

   

This will be the new location for my class notes from the University of Exeter's "massive on-line open course" (or MOOC) on:

CLIMATE CHANGE:  CHALLENGES AND SOLUTIONS

Week One: Climate Change: Challenges and Solutions 1-13-2014

Week One: Climate Change: Challenges and Solutions              1-13-2014 

 This is a transcript of my notes from Week One of University of Exeter's Massive Open Online Course (MOOC) on Climate Change.
 Offered via: www.futurelearn.com Course beginning date: Jan. 13, 2014   [I started 1/23.]
 Professor: Tim Lenton  (all sections are presented by Dr. Lenton unless otherwise noted.)

1.1 Reflective Learning 

Guest presenter, Dr. Damien Mansell, suggests that the participants use social media to enhance “reflective learning;” specifically, set up a blog using a blog hosting site such as Word Press or Blogger to record your insights, case studies, examples, and so on. Students may then post their documents on the discussion boards and invite others to comment. At the end of the course, you can create a summary post.

 1.2 Key Principles of Climate Change

GREENHOUSE EFFECT: Short wave radiation comes in from the sun, strikes objects on the Earth, and re-emits heat radiation at long wavelengths that are invisible to us. 

• SUNLIGHT is visible, short wave radiation.  We see it as light.
• Long wave radiation is "infrared heat" and is not visible to us.
• The "Greenhouse Effect" doesn't really work exactly like a greenhouse.  A greenhouse works mostly by trapping air.  The sunlight passes through the glass, strikes the ground or plants or objects in the greenhouse, which warms them up, which in turn warms some of the air in the greenhouse, and then the air is kept within the greenhouse by the glass. The glass itself only traps a little bit of the heat radiation on the way out.  But in the atmosphere, the greenhouse gases absorb some of the radiation bouncing back from the earth, and become warmer, and some of that heat radiates back to earth as long-wave radiation.
• Short-wave radiation (sunlight) is either absorbed by or reflected from the surface according to how high its albedo is.  Albedo is a measure of "shinyness" or reflectiveness.  The higher the albedo, the more light is reflected.  The average albedo of the Earth is 0.3, which means 30% of the light is reflected (and in turn means 70% of the sunlight radiation reaching earth is absorbed.)
• If the absorption of 70% of the sun's energy were the only factor, Earth's temperature would be -18 degrees Celsius (-19 C per the I.P.C.C.), which is right about zero Fahrenheit (-0.4 F to -2.2 F).
• But, Earth's average temperature is about 15 degrees Celsius (59 F) because of our atmosphere.  Certain gases absorb some of the radiation, and some of that comes back to the surface.   That's a total difference of 33 C (59.4 degrees F) warmer because of our greenhouse gases.

THE GREENHOUSE GASES:
        These are the important greenhouse gases in our atmosphere:  Water vapor, methane, ozone, nitrous oxide, and CO2.  The last four exist in much smaller amounts than water vapor. These are Earth's "thermal blanket."

1.3 Blanket Earth - more information, from NASA's website

NASA says most scientists agree that :

"... the main cause of the current global warming trend is human expansion of the "greenhouse effect"-- warming that results when the atmosphere traps heat radiating from Earth toward space."

Greenhouse gases are those which trap some of the heat being radiated back from the Earth.  Those which are long-lived and do not react physically or chemically to temperature changes are considered to be "forcing" climate change; those which do respond physically or chemically to temperature changes are considered feedbacks to the system.

• Water Vapor:  This is the most abundant greenhouse gas.  Because it responds physically or chemically, increasing with warmth but then carrying more clouds and rain, it is considered an important feedback in the climate system.
• Carbon Dioxide (CO2):  Minor [in amount] but important component of the greenhouse effect.  It has increased by one third since the industrial revolution began.  It creates a "forcing" of climate change because it is long-lived, semi-permanent in the atmosphere, and does not respond physically or chemically to changes in temperature.
• Methane:  Comes from natural and human sources.  It is a hydrocarbon.  Sources are: decomposition of wastes, e.g. from landfills, also from ruminants and rice cultivation.  It is less abundant than CO2 but more potent.
• Nitrous Oxide:  Very powerful.  Comes especially from fertilizers, and burning fossil fuels or biomass.
• Chlorofluorocarbons (CFCs): Human origin; now regulated.

The NASA article also contains a good disputation about Solar Irradiance factors in global warming.  Some data shows that global warming increases cannot be from increases in solar irradiance, because the irradiance has been decreasing lately.  Or, some sources believe it cannot account for more than 10% of global warming.
 This is a link to the NASA article:  http://climate.nasa.gov/causes

1.4  What Is Climate?

An Introduction to the Climate System, especially defining the difference between climate and weather, via a video from the U.K. Met [Meteorological] Office:

WEATHER:  Temperature, wind and precipitation, changing by the hour and by the day.
CLIMATE:  How weather changes over a long period, typically at least 30 years.

A CLIMATE SYSTEM is comprised of many interactions and factors, such as oceans, ice sheets, land masses, vegetation, sunlight, and atmosphere.  Atmosphere affects world climate greatly.  The greenhouse effect was discovered 150 years ago.

1.5 DISCUSSION:  What is the difference between Weather and Climate?  Give examples. 

(Please see the January 26, 2014 blog post, titled "Assignment: Weather vs. Climate")

1.6  The Climate System, Feedbacks, Cycles and Self-Regulation

Components of the climate system:

1. Atmosphere

1. Hydrosphere 

1. Biosphere

1. Cryosphere  (ice)

1. Lithosphere   (surface of Earth's crust)

LINKS:  We will see that there are a whole series of cycles that act as the active links--the interactions between components that power the climate system.  For example, in the hydrologic cycle, water can re-enter the hydrosphere or the cryosphere.

The Hydrologic Cycle (Water Cycle)--illustrates the coupling between components of the climate system:

• Water vapor rises

• then condenses (forms clouds)

• falls as rain or snow

• rain enters ground or aquifers, or rivers and lakes, then oceans; or

• plants

• snow or ice can evaporate directly into atmosphere

At many points, humans can influence the system.

FEEDBACKS:   "Feedback Loops" are "closed loops of cause and effect."  Cycles also create feedback loops.  There are three key feedbacks:  1.  Water Vapor feedback. 2. Ice Albedo feedback. 3. Radiation feedback.










(MORE TO BE ADDED LATER...  )

Difference between Weather and Climate 1-26-2014

The Difference between Weather and Climate          1-26-2014

   This discussion is for an assignment in Week 1 of the Climate Change course from Exeter University.  Section 1.5  calls for discussion and examples of "weather" vs. "climate.

  "Weather" concerns relatively short-term events or forecasts of temperature, precipitation, wind, storms, and so forth.  A trend in the climate is measured over a much longer span, typically thirty years or more.
    We've had some extreme "weather" here in Austin in the last few days:  Friday, Jan. 24, we woke to a quarter inch sheet of ice formed by freezing rain and sleet, which shut down the city.   Ice is rare here--our unprepared and inexperienced drivers had 274 car wrecks.  Low, 25 F (-3.9C). By the next afternoon, it was 67F (19.4C).
    It is harder to know what changes to attribute to climate change.  I've lived here since 1967, and I remember we used to have infrequent cold snaps down below 20F (-7C), which would  break pipes all over the city and you wouldn't be able to get a plumber for days.  I don't think we've gotten that cold since the 1980's.
       People often move and don't have a base of comparison.  A friend of mine who grew up in Austin, which is now 10 times more populous, remembers seeing as a child (which would have been in about the 1950's) such large thick flocks of monarch butterflies crossing Highway 183 that the driver couldn't see and had to pull over.  Now the flocks are insignificant.  Monarchs migrate south yearly, all wintering in a tiny area in the mountains of Mexico, where their numbers are observed to have fallen.  Many factors including agriculture practices may impact them.  Perhaps climate change does also.   They fly north for three generations, then the fourth generation flies back all the way to Mexico.  To have that specific destination so programmed in some way into their genetics makes it difficult to see how they could adapt to much climate change.  Many other species of animals and insects have been observed shifting their habitats northward.
    Addendum:  Since writing the above, I encountered this article that describes the reasons for Monarch migration slowing to a trickle.  It does include climate change.

 Why Has The Magnificent Monarch Butterfly Migration Slowed To A Trickle? | ThinkProgress

http://thinkprogress.org/climate/2014/01/31/3230561/monarch-migration-decline/

Addendum (March 4, 2014):  Monarchs have reached their lowest numbers ever. In California, the population has fallen 80% in 15 years.  The National Resources Defense Council has called for regulation of the use of glyphosates (Roundup) in agriculture. http://www.latimes.com/science/sciencenow/la-sci-sn-monarch-butterfly-roundup-20140224,0,1342942.story#axzz2uuu1VHk3

INTRODUCTION: Why Study Climate Change? 1-24-2014

INTRODUCTION: Why Study Climate Change?                         1-24-2014

 I recently signed up for a "MOOC" (Massive Open Online Course) from the  Exeter University on the subject of climate change.  The introductory material suggests that we share our reasons for wanting to take the course.  For me, it was this:

A recent article on the alternative news site, Truthdig, got me thinking even more than I usually do about climate change.  The title was "Are We Falling Off the Climate Precipice?"  Dated 12-13-2013, at this link:

http://www.truthdig.com/report/item/are_we_falling_off_the_climate_precipice_20131219/

It is already clear that climate change is underway.  But I have wondered:  Where is the tipping point for unacceptable (or catastrophic, or runaway) climate change? 

 I certainly have previously read alarming arguments in any number of places.  This article and its associated links have brought some of those thoughts into sharp and uncomfortable focus.  Three of them are:  1) The most recent data coming in, including from a purpose-built satellite, shows trends that exceed projections.  2) Even considering the widespread agreement among climate scientists (97% is quoted often these days), scientists tend to want to be conservative and avoid sounding alarmist.  3) If you factor in the lack of political progress on setting and meeting climate-protecting goals, well... 

So there you have it.  Is it time to panic? Despair? Hope?  Even if when the course is done I may agree or disagree with its conclusions, I do seek a stronger foundation of scientific knowledge of climate-change processes.  Hopefully with more and more of us gaining a deeper knowledge of the subject, it will lend us more effectiveness toward whatever measures each of us undertakes toward dealing with the challenge.