Monday 20 January
Ancient past climate
Water & water vapour played a key role, enabling the creation of life forms but also nearly wiping them out through at least two extreme temperature swings caused by positive feedback effects. See http://www.snowballearth.org/ & http://www.bbc.co.uk/nature/ancient_earth/Snowball_Earth
BBC site noisily illustrates how extreme temperatures came about, and left evidence in rock formations.
Here is my feedback diagram:
Another course participant, Takver Takvera writes a climate change blog with a very full description of this process: http://takvera.blogspot.com.au/2014/01/exclimate-ice-albedo-feedback-mechanism.html
Recommended reading about climate records:
What are climate change records?
Met Office: http://www.metoffice.gov.uk/climate-change/guide/science/explained/observations
Rocks, ice cores and tree rings provide evidence for the state of the atmosphere at different times and locations, including temperature, amount of radiation and atmpspheric composition
How do volcanoes affect climate change?
Volcanos: http://earthobservatory.nasa.gov/Features/Aerosols/
Volcanic eruptions deposit vast amounts of dust in the atmosphere over large parts of the glove, causing increased albedo and short term reduction in temperature.
How is today’s warming different from the past?
"Natural variations" in the past several thousand years have not included the sudden rise in temperature accompanied by the similar sudden rise on atmospheric CO2 taking place over the past 100 years, and occurring even more rapidly today.
What is the role of isotopes in determining temperatures from the past?
Role of isotopes: http://www.giss.nasa.gov/research/briefs/schmidt_01/
The rate of radioactive decay of isotopes can be measured very precisely, enabling samples of rock or ice which contain an isotope to be accurately dated, which in turn dates the climate evidence contained in the samples.
The rate of radioactive decay of isotopes can be measured very precisely, enabling samples of rock or ice which contain an isotope to be accurately dated, which in turn dates the climate evidence contained in the samples.
How have trees been used to reconstruct different climate variIce cores: http://www.earthobservatory.nasa.gov/Features/Paleoclimatology_IceCores/ables across the world?
Tree rings: http://web.utk.edu/~grissino/principles.htm#1
The spacing and contents between the rings which grow around the tree every year, provide evidence of the amount of biological activity resulting from solar radiation, humidity and temperature during that year. Counting the rigs inwards dates each ring, or in older tree relics, carbon dating is used.
The spacing and contents between the rings which grow around the tree every year, provide evidence of the amount of biological activity resulting from solar radiation, humidity and temperature during that year. Counting the rigs inwards dates each ring, or in older tree relics, carbon dating is used.
How can ice cores provide a record of atmospheric composition?
Ice cores: http://www.earthobservatory.nasa.gov/Features/Paleoclimatology_IceCores/
Snow is deposited on the ice surface each year, and its texture and chemical compositon changes in summer and winter. As each layer of snow is overlaid by another, the lower layers become compressed so that many thousands of years of ice layers may be examined by extracting a deep ice core.
400 parts per million
Two things are remarkable about CO2 reaching 400ppm:
1. No previous climate records reached this level with similar rapidity,
2. It is correlated closely with the known output of CO2 caused by extraction and burning fossil fuels during the industrial era
The last time CO2 reached similar levels was during the Pliocene period between 3.3-3.0 mya, when the average climate was 2-3 degrees C warmer and sea levels were 25 m higher. The higher temperature resulted from near-complete absence of ice, however this period was marked by overall cooling and appearance of polar ice caps. It began with extensive forestation which disappeared as the climate cooled.
Reflection:
Disappointed to achieve 9/15 in the test, having dropped 6 points on the aerosols and proxy records. I should have gone for only one answer rather then try to find all the correct answers. Instead, I scored 0, and need to study the correct ones. I believe volcanic eruption and desert dust to be aerosols, and trees rings and ice cores provide climate proxy records.
Important themes: Climate history, how it has been determined, and causes of variation
Most difficult: Multiple choice questions with more than one correct answer - can I get a correct score with just one answer? Also, video segments include lots of entertainment but I get impatient looking out for the key points.
Most interesting: What kinds of changes or events cause positive feedback loops to stabilise and then reverse? Volcanic eruptions, asteroid impact, Milankovitch cycles
Own research: Geo-engineering by seeding water vaapour - to do
Websites: Takver Takvera's blog at http://takvera.blogspot.com.au He has a whole day ahead of me to develop his website in Melbourne, but it's very impressive even so! I'm interested to see what other course participants are producing.
Important themes: Climate history, how it has been determined, and causes of variation
Most difficult: Multiple choice questions with more than one correct answer - can I get a correct score with just one answer? Also, video segments include lots of entertainment but I get impatient looking out for the key points.
Most interesting: What kinds of changes or events cause positive feedback loops to stabilise and then reverse? Volcanic eruptions, asteroid impact, Milankovitch cycles
Own research: Geo-engineering by seeding water vaapour - to do
Websites: Takver Takvera's blog at http://takvera.blogspot.com.au He has a whole day ahead of me to develop his website in Melbourne, but it's very impressive even so! I'm interested to see what other course participants are producing.
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