Review the Unit 12 Introduction
You have reached the end of Unit 12! Double-check the list of requirements on the Unit 12 Introduction page and the Course Calendar to make sure you have completed all of the activities listed there.
Review of the main topics and ideas you encountered in Unit 12.
- Plants turn carbon dioxide, water and sun’s energy into more plants and oxygen
- Other life forms “burn” plant with oxygen to get that energy
- If buried without oxygen, plant isn't burned, and heating makes fossil fuel
- Woody plants-->peat (in sediment; Bear Meadows) -->lignite (in sedimentary rock)-->bituminous (in harder sedimentary rock, western PA) --> anthracite (in metamorphic rock, eastern PA)
- Algae-->gas from bacteria (Bear Meadows)-->oil (with gas) (western PA)-->gas (eastern PA) (float up and escape to be burned unless trapped by geology)
Take It to the Limit
- Fossil fuels are NOT infinite:
- nature really is efficient at recycling
- oil & coal companies good, found the easy stuff
- not a lot set aside (ANWR oil estimated to equal only just over 2 years of US imports)
- World oil production peak likely in next decades
- At vaguely recognizable prices and current demand, probably close to a century of oil and gas, a few centuries of coal
- But demand rising rapidly, so less time
You’re in the Greenhouse Now
- Some gases let visible light through (sun) but partly block infrared (return from Earth)
- Makes planet warmer than otherwise, so we “glow” brighter to force energy past the gases
- We are increasing these gases (esp. carbon dioxide) a lot, and they will stay up for centuries, millennia or longer
With High Confidence
- Our greenhouse gases will warm world, amplified by feedbacks such as melting of reflective ice increasing warming (maybe 16oF over centuries if we really burn fossil fuels, vs. barely-noticeable 1oF so far)
- Positive and negative impacts on us, but mostly negative for warming more than a few degrees:
- Sea-level rise from ice melt, expanding ocean
- Summertime drying of grain belts
- Not-nice tropical heat
- We have to switch from fossil fuels; will we do so before or after we change the world?
- Reasonable estimates say switch needs few decades of serious research and 1% of economy
- This is in line with other clean-up costs now
- This is something like $400 billion per year now
- Not a lot of scientific disagreement on these points
- But much political, social, economic disagreement (which is completely expected, and in line with previous environmental issues)
Lions and Tigers and Bears?
- Why save biodiversity--medicines, other useful things from living types; more-diverse ecosystems produce more; living types “canaries in coal mine” to warn us of trouble; ethics
- Early and modern humans hard on biodiversity--next mass extinction?
- Smaller islands have fewer species (easier to eliminate smaller population), so isolating patches of wilderness in separate national parks will lose species in those parks
- Climate change will complicate, forcing migration when there may not be migration pathways
Reminder - Exercise #6 is due this week. Check the Course Calendar for the specific due date.
Following are some supplementary materials for Unit 12. While you are not required to review these, you may find them interesting and possibly even helpful in preparing for the quiz!
- Website: Arctic National Wildlife Refuge
Comments or Questions?
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