Growth - Energy and the Environment - Lecture Slides, Slides of Energy and Environment

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Course Introduction Spring 2013 Lecture 2 1 An Aside on Growth Another Limited Time Offer Developing Exponential Intuition • When the rate of increase depends directly on how much stuff there is, we get exponential growth – interest earned depends on balance – more bacteria or rabbits are born if the population is larger • Important concept is doubling time – A 1% yearly increase doubles in 70 years • 1.0170 = 2.0 – A 5% increase doubles in 14 years • 1.0514 = 2.0 – Law of 70: doubles in (70 / % rate) periods Bacteria in Jar • Imagine bacteria with a doubling time of one minute – a little fast, but still: one splits to two every minute • Start the jar with just enough bacteria to completely fill the jar in exactly 24 hours – provide adequate food, etc. • Start culture at exactly midnight (12:00 AM) – so jar reaches full at midnight on next day • At what time is the jar half full? We’re going to need more jars • When the jar is 1/16th full (at 11:56 PM), some visionary (laughed at for predicting full jar) decides to strike out on a quest to find more jars • Good news! Three empty jars available! • After 24 hours, and 1440 generations in this stinking jar, we’re saved! • Okay, but for how many more minutes? • And how many more Earths do you think we’ve got available this century? Docsity.com Course Introduction Spring 2013 Lecture 2 2 A note on graphs: log vs. linear • Many graphs in the book are on logarithmic scales • This condenses wide-ranging information into a compact area • Pay attention, because you could warp your intuition if you don’t appreciate the scale • Log scales work in factors of ten • A given vertical span represents a constant ratio (e.g., factor of ten, factor of two, etc.) • An exponential increase looks like a straight line on a logarithmic scale Example Plots Exponential plot is curved on linear scale, and straight on a logarithmic scale Shall We Continue Growth? • We associate growth with progress – cars, TVs, air travel, iGadgets,… – quality of life improves – investment pays interest • Let’s look at physical growth (energy) • Surplus energy (beyond the bare amount needed for survival) has translated into: – more food available, more people, more industry, economic growth • Our energy use, now at 12 TW globally, has historically grown at >2% per year • What will this mean if we continue expanding energy use at this rate? U.S. Energy Historical Energy Growth: 2.9% Sum of all forms of energy used in the U.S. (fossil fuels, nuclear, hydro, wood, etc.) Red curve is exponential at 2.9% per year growth rate logarithmic plot of the same 1650 1650 2050 2050 Docsity.com Course Introduction Spring 2013 Lecture 2 5 Perspective on Our Joy Ride • This cartoon is from an energy/environment textbook, pointing out how special this moment in history really is • We found the Earth’s battery, expending it as fast as we can – effectively a short circuit • Treating the last 200 years as “normal” is perilous What Happens Next? • The future beyond our fossil fuel surge is not written • A return to more primitive ways is a distinct possibility – most say 2200 will be as unimaginable to us as 2000 would be in 1800 – I agree: who could have imagined we’d be clubbing each other over the heads with half-gnawed bones 200 years after the height of the fossil fuel age?! – let’s have some humility, and not be unjustifiably asymmetric (6000 B.C.) Sustainable Option 1: Level Out Here • Leveling out at today’s scale means roughly 1/5 U.S. standard – because U.S. is 5% of population, 25% of energy – inequalities are difficult to justify in no-growth world • Could we even sustain today’s physical throughput? – pollution, fisheries, rain forests, soil quality, aquifers, minerals, etc. Sustainable Option 2: Everyone Lives Large • If we wanted the world to live like Americans, we need 10× – 5× for today’s population at today’s standards, 10× for a bit of growth in both aspects • Pull back to 5× to allow efficiency, etc. • Makes the amazing fossil fuel ride look like a blip • What makes us think we can do this? Docsity.com Course Introduction Spring 2013 Lecture 2 6 Stepping Up • A kid might really want a pet pony • A smart parent might approach the problem step-wise 1× 2× 3× 4× 5× We’re Not Taking Care of Our Gerbil • We’re having tremendous difficulty managing the 1× case – we have not demonstrated that we can take care of our gerbil – pollution, CO2, fisheries, rain forests, soil erosion, aquifer depletion, etc. • What makes us think we deserve a pony? – are we deluding ourselves about our capacity to manage? • Do we then deserve to be brandishing the word “sustainable?” – we have no clear idea what it means, or at what level we can expect to operate • This fossil fuel joy ride has clouded our judgment – we tend to attribute our progress to our smarts, not to surplus energy Breaking News: NYT Science Screenshot • From April 3, 2013 – ahem: today • Not unusual for energy stories to dominate science news • This isn’t going to go away – as this century progresses, we’ll be ever-more tuned in to energy news Docsity.com