UCSD Physics 12

An Aside on GrowthAn Aside on Growth

Another Limited Time OfferAnother Limited Time Offer

UCSD Physics 12

Developing Exponential IntuitionDeveloping Exponential Intuition

• When the rate of increase depends directly on how When the rate of increase depends directly on how much stuff there is, we get exponential growthmuch 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 timeImportant 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

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UCSD Physics 12

Bacteria in JarBacteria in Jar

• Imagine bacteria with a doubling time of one Imagine bacteria with a doubling time of one minuteminute– a little fast, but still: one splits to two every minute

• Start the jar with just enough bacteria to Start the jar with just enough bacteria to completely fill the jar in exactly 24 hourscompletely fill the jar in exactly 24 hours– provide adequate food, etc.

• Start culture at exactly midnight (12:00 AM)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?At what time is the jar half full?

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UCSD Physics 12

We’re going to need more jarsWe’re going to need more jars

• When the jar is 1/16When the jar is 1/16thth full (at 11:56 PM), some full (at 11:56 PM), some visionary (laughed at for predicting full jar) visionary (laughed at for predicting full jar) decides to strike out on a quest to find more jarsdecides to strike out on a quest to find more jars

• Good news! Three empty jars available!Good news! Three empty jars available!• After 24 hours, and 1440 generations in this After 24 hours, and 1440 generations in this

stinking jar, we’re stinking jar, we’re savedsaved!!• Okay, but for how many more minutes?Okay, but for how many more minutes?

• And how many more Earths do you think we’ve And how many more Earths do you think we’ve got available this century?got available this century?

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UCSD Physics 12

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A note on graphs: log vs. linearA note on graphs: log vs. linear

• Many graphs in the book are on logarithmic scalesMany graphs in the book are on logarithmic scales• This condenses wide-ranging information into a This condenses wide-ranging information into a

compact areacompact area• Pay attention, because you could warp your Pay attention, because you could warp your

intuition if you don’t appreciate the scaleintuition if you don’t appreciate the scale• Log scales work in Log scales work in factors of tenfactors of ten• A given vertical span represents a constant ratio A given vertical span represents a constant ratio

(e.g., factor of ten, factor of two, etc.)(e.g., factor of ten, factor of two, etc.)• An An exponential increaseexponential increase looks like a looks like a straight linestraight line

on a logarithmic scaleon a logarithmic scale

UCSD Physics 12

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Example PlotsExample Plots

Exponential plot is curved on linear scale, and straight on a logarithmic scale

UCSD Physics 12

Shall We Continue Growth?Shall We Continue Growth?

• We associate We associate growth growth with with progressprogress– cars, TVs, air travel, iGadgets,…

– quality of life improves

– investment pays interest

• Let’s look at Let’s look at physical growthphysical growth ( (energyenergy))

• Surplus energy Surplus energy (beyond the bare amount needed for survival) (beyond the bare amount needed for survival) has translated into:has translated into:– more food available, more people, more industry, economic growth

• Our energy use, now at Our energy use, now at 12 TW 12 TW globally, has historically grown globally, has historically grown at at >2%>2% per year per year

• What will this mean if we continue expanding energy use at this What will this mean if we continue expanding energy use at this rate?rate?

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UCSD Physics 12

U.S. Energy Historical Energy Growth: 2.9%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

16501650 2050 2050

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UCSD Physics 12

power output of sun

1400

yea

rs

power output of the entire Milky Way galaxy

2500

yea

rs

421

yr

solar power reaching Earth’s upper atmosphere

336

yr

solar power reaching Earth’s land

The Road We’re NOT OnThe Road We’re NOT On

all solarland

12 TW today(1.2×1013)

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factor of 10 each century

UCSD Physics 12

Waste Heat Boils Planet (not Global Warming)Waste Heat Boils Planet (not Global Warming)

body temperature

water boils

paper burns

steel melts

sun surface temperature

global warming?

thermodynamic consequence ofarbitrary energy technology on Earth

59°F

99°F

212°F

450°F

75°F

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UCSD Physics 12

Reality CheckReality Check

• This calculation shows how This calculation shows how ridiculousridiculous, , absurdabsurd, , fantastical fantastical any notion of exponential growth becomesany notion of exponential growth becomes

• Many reasons prevent us from continuing growth Many reasons prevent us from continuing growth trajectorytrajectory– obviously, we won’t cook ourselves

– continued growth presupposes population growth

– we certainly can’t get far along the curve using finite fossil fuels

• The lesson: our future The lesson: our future must abandon growthmust abandon growth, at some point, at some point– yet most economists and planning commissions assume growth

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UCSD Physics 12

The Allure of the Growth NarrativeThe Allure of the Growth Narrative

• Our Our narrative narrative is one of is one of growthgrowth

• It’s what our parents, grandparents, great grandparents, etc. It’s what our parents, grandparents, great grandparents, etc. have known: have known: we are reluctant to give it upwe are reluctant to give it up

• We tend to think that even if population levels off, that if We tend to think that even if population levels off, that if energy availability levels off (or even goes down), we can still energy availability levels off (or even goes down), we can still manage economic growth by:manage economic growth by:– bringing up standards of living (even without extra energy)

– efficiency gains (do more with less)

– technology innovations (new gadgets keep economy humming)

• But such things cannot become the But such things cannot become the wholewhole economyeconomy– at the end of the day, we’re tied to the physical/energy streams

provided by the natural environment

– divorcing our economy from physical limits is pure fantasy

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UCSD Physics 12

Yup, There is an End to Growth!Yup, There is an End to Growth!

• Physical growth is undoubtedly boundedPhysical growth is undoubtedly bounded– independent of energy technology: thermodynamic conclusion

• There There areare viable mechanisms for economic growth viable mechanisms for economic growth requiring requiring little or no physical growthlittle or no physical growth– examples abound (and bubble and burst sometimes)

• But their But their reach is limitedreach is limited; can’t skip off into la-la land forever; can’t skip off into la-la land forever– existence of examples does not mean that 99.99999% of our economy

could be driven by non-energy activities (making limited energy ~free!)

– meanwhile, everything takes some energy: physical limits don’t disappear

• Therefore: Therefore: Economic Growth Must EndEconomic Growth Must End– failure to adopt steady-state economy results in overshoot/collapse

– Adam Smith saw growth as a transient phase, until all land was used

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UCSD Physics 12

A Look at PopulationA Look at Population

Semi-log plot straight line in thisplot is exponential behavior

slope indicates growth rate

0.035% per year(2000 yr doubling)

1%/yr(70 yr)

(10,000 B.C.)Spring 2013 14

UCSD Physics 12

Surplus Energy Grows Babies Surplus Energy Grows Babies

0.4%/yr

0.8%/yr

1.9%/yr(36 yr)

1865

1950

industrial (coal) revolution

Green (oil) Revolution

0.09%/yr

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UCSD Physics 12

Our Problem: Approaching “Full Earth”Our Problem: Approaching “Full Earth”

• The Frontier Earth model no longer appliesThe Frontier Earth model no longer applies– imagine building an interstate system from scratch

today in the U.S. (was possible 50 years ago)

– now everything we try to do hits constraints

• Not surprising: we’ve populated ourselves into a Not surprising: we’ve populated ourselves into a crowded, resource-constrained existencecrowded, resource-constrained existence

• Earth has a finite “Earth has a finite “carrying capacitycarrying capacity””– we may well have exceeded it in an overshoot mode

– estimates range from 1 billion humans to over 10 billion

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UCSD Physics 12

Perspective on Our Joy RidePerspective on Our Joy Ride

• This cartoon is from an energy/environment textbook, pointing This cartoon is from an energy/environment textbook, pointing out how out how special special this moment in history really isthis moment in history really is

• We found the We found the Earth’s batteryEarth’s battery, expending it , expending it as fast as we canas fast as we can– effectively a short circuit

• Treating the last 200 years as “normal” is Treating the last 200 years as “normal” is perilousperilous

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UCSD Physics 12

What Happens Next?What Happens Next?

• The future beyond our fossil fuel surge is The future beyond our fossil fuel surge is not writtennot written

• A return to more primitive ways is a A return to more primitive ways is a distinct possibilitydistinct 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.)

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UCSD Physics 12

Sustainable Option 1: Level Out HereSustainable Option 1: Level Out Here

• Leveling out at today’s scale means roughly Leveling out at today’s scale means roughly 1/5 U.S. standard1/5 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 Could we even sustain today’stoday’s physical throughput? physical throughput?– pollution, fisheries, rain forests, soil quality, aquifers, minerals, etc.

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UCSD Physics 12

Sustainable Option 2: Everyone Lives LargeSustainable Option 2: Everyone Lives Large

• If we wanted the world to live like Americans, we need If we wanted the world to live like Americans, we need 10×10×– 5× for today’s population at today’s standards, 10× for a bit of growth

in both aspects

• Pull back to Pull back to 5×5× to allow efficiency, etc. to allow efficiency, etc.

• Makes the amazing Makes the amazing fossil fuel ridefossil fuel ride look like a blip look like a blip

• What makes us think we can do this? What makes us think we can do this?

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UCSD Physics 12

Stepping UpStepping Up• A kid might A kid might reallyreally want a pet pony want a pet pony

• A smart parent might approach the problem step-wiseA smart parent might approach the problem step-wise

1×

2×

3×

4×

5×

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UCSD Physics 12

We’re Not Taking Care of Our GerbilWe’re Not Taking Care of Our Gerbil

• We’re having tremendous difficulty managing the We’re having tremendous difficulty managing the 1×1× case 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 What makes us think we deserve deserve a pony?a pony?– are we deluding ourselves about our capacity to manage?

• Do we then Do we then deserve deserve to be brandishing the word “to be brandishing the word “sustainablesustainable?”?”– we have no clear idea what it means, or at what level we can expect to

operate

• This fossil fuel joy ride has This fossil fuel joy ride has clouded our judgmentclouded our judgment– we tend to attribute our progress to our smarts, not to surplus energy

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UCSD Physics 12

Breaking News: NYT Science ScreenshotBreaking News: NYT Science Screenshot

• From April 3, 2013From April 3, 2013– ahem: today

• Not unusual for energy Not unusual for energy stories to dominate stories to dominate science newsscience news

• This isn’t going to go This isn’t going to go awayaway– as this century progresses,

we’ll be ever-more tuned in to energy news

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UCSD Physics 12

Announcements/AssignmentsAnnouncements/Assignments

• Reading:Reading:– Chapter 1 of Ristinen and Kraushaar– also read the Appendix

• Optional Reading from Do the Math (DtM)Optional Reading from Do the Math (DtM)– Galactic Scale Energy (#1)– Can Economic Growth Last? (#2)– numbers refer to chronological list on Guide to Posts page

• First homework will be due Friday, April 12First homework will be due Friday, April 12– see main course website for assignment

• First quiz by Friday (midnight), April 12First quiz by Friday (midnight), April 12• Transmitter use (iClicker) starting Friday, April 5Transmitter use (iClicker) starting Friday, April 5

• Discussion Session today (I’ll join partway through)Discussion Session today (I’ll join partway through)

• Matt’s office hours: Thursday 2:30−3:50, SERF 434Matt’s office hours: Thursday 2:30−3:50, SERF 434

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