ES2- 2Tues Systems

8/9/2019 ES2- 2Tues Systems

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Read any newspaper article with a scientifically critical eye.

What dont they tell you?What assumptions are made?

What would they have you believe with no evidence?

Are there discrete conclusions or are you left to infer?

Tell the person next to you about it. - NW.


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The Textboo! is ready" The Textboo! is ready"

#f you didnt already order it$

%tep &$ 'o( on to https$))students.universityreaders.com)store).

%tep *$ +reate an account or lo( in if you have an existin(

account to purchase.

%tep ,$ asy-to-follow instructions will (uide you throu(h the restof the orderin( process.


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%%T/$ A set of components that function to(ether as one.


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0eedbac! is the response of part of a system to chan(e in or

information from another.

1 2ositive feedbac!$ tends to amplify the stimulus or chan(example- compound interest

1 Ne(ative feedbac!$ tends to reduce or dampen chan(e

xample- friction


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2ositive 0eedbac!

Ne(ative 0eedbac!


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3A#%WR'3

Albedo$ 4bri(htness5 of surface. 0raction of li(ht reflected.

Water dar!est6 then forest6 then (rass6 desert6 ice.


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A chan(e in one part of the system affects the behavior of

other components within the system.

1 3ia(nostic challen(e

-+hic!en and e(( problem

1 2otential positive feedbac!s-Runaway chan(e and collapse

1 2ositive feedbac!s may mas! chan(e

-Not observed until too late


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bservation$ woodland chan(ed to (rassland7ypothesis$ +attle (ra8in( and elephant dama(e !illed trees


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/asai (ra8in( (oats

lephants

dama(e trees


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Test 7ypothesis

#s tree loss proportional to amount of (ra8in(?Number of elephants?

No.

%o what other factors are there in the system?

Rainfall increased. 7mmm9

%alt from la!e bed soil rose to tree roots- !illed trees

lephants compounded the problem


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2olar ice and temperature

-As ice melts6 white is replaced by blac! water

-absorbs more sunli(ht

-increases temperature

-melts faster9

:pposite of 3aisy-world;


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Desertification of Sahara

-%unli(ht was decreasin( in intensity due to orbital chan(es

-3ar! ve(etation warmed re(ion and !ept moisture in system

-ventually could not 4!eep up5 with decreasin( insolation

-cosystem collapsed


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2ositive feedbac!s can become ne(ative6 !eepin( the

system within bounds.


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xponential (rowth if rate of increase is proportional to

present stoc!. :'i!e continuous compoundin(;N:t;< Noe

!t

so if !., < &.,@


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N:t;< Noe!t

3oublin( Time Approximation

0or N to be twice No:doublin(;6 e!t< *. %olve for t.Ta!e natural lo( of both sides9

!t < ln:*; < >.B, so t < ln:*;)!

#f ! :(rowth rate; is in percent6 you multiply by &>>6 so

3oublin( time t < B.,)! < >)! :easy to remember9;


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4The present is the !ey to the past.5

2rocesses observed now can explain past conditions.

The present is uniCue because it includes human perturbations

Dncontrolled experiment with local and (lobal environment.

We have pushed parts of the system to levels not seen for

millions of years.

%- perhaps the past is the !ey to understandin( the future"


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Eiew that the history of the arth is dominated by sudden

and sometimes devastatin( events.

Feolo(ically6 this view su((ests that most of the roc!record preserved bi( events li!e floods or storms6 rather

than every-day processes.

nvironmentally6 su((ests that the system is controlled by

maGor disruptions6 and prone to positive feedbac!s.


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Stock- The amount of somethin( stored in a 4reservoir5

Flux- The rate at which somethin( enters or leaves reservoir

Equilibriumwhen input and output are balanced

Residence time- stoc!)flux

Fround water

+*2eople

'ehi(h

Heach sand+onveyor belt

arths radiation

Tropical forests

0ish'obsters?

/ineral ores


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Example- Water in a dammed reservoir

Residence time is volume)outflow

Time any dissolved pollutants :/TH; remain

in la!e is environmentally important

#f pollutant decays faster than residence6 output is clean

3ama(e limited to :concentrated in; reservoir

:/ost pollutants 3NT decay9;

vaporation further concentrates pollutants


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Linear system-output chan(e is proportional to input chan(e- sprin(

- twice fertili8er < twice (rowth

onlinear system-output amplifies or buffers input :feedbac!s;- (laciation

- ve(etation and rainfall

!ncertainty- unpredictability of nonlinear systems

&. Removable co(nitive$ fixed by better measurements6 etc.

*. #rremediable co(nitive$ cant improve because of nonlinearities

,. Eoluntative$ stemmin( from human decision-ma!in(

:%ee 2iel!e et al. on Hlac!board;


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0rom physics- the act of observation alters what is bein( observed

0eedbac! with uncertainty

Wal! across crowded mall- +annot plan route a priori

-people chan(e paths in response to your presence


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arth system contains many nonlinearities and uncertainties.

"hallen#e$#dentify those aspects that are most sensitive to environmental

chan(es caused by natural and anthropo(enic activities.

-3etermine critical thresholds

-/onitor chan(in( conditions

-3evelop remediation measures.


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arth formed I. b.y. a(o - solar nebula

/aGor events in life correspond to maGor environmental chan(es

- photosynthesis$oxy(en

- land plants$less +*- intelli(ence$many disruptions

cosystem$ +ommunity and its physical environment

xist at all scales

Rely on internal interactions between componentsHio(eochemical cycles and ener(y flow

Hiosphere$ Re(ion where all life exists.


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1 'ife affects its physical environment

1 'ife has altered its planetary environment such that it persists

1 'ife controls the (lobal environment on purpose

'ife ma!es arth a self re(ulatin( system :7omeostasis;

-!eeps surface temperature in liCuid water

-ne(ative feedbac!s


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3A#%WR'3

:7omeostatic system;

% if ! h h i it h d t l


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9%o if we !now so much6 why is it so hard to solve

environmental problems?

&. 2ositive feedbac!s

*. 'a( time - by the time you see the effect6 it is too late to

alter the cause. :overshoot and collapse;

,. Reversible vs. irreversible impacts

I. 3iscount rates

@. 'ow probability6 hi(h impact events

- meteor

- maGor volcano6 tsunami6 etc.

- deadly epidemic


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ES2- 2Tues Systems

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