8.Humans and Climate

8/18/2019 8.Humans and Climate

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www.earthobservatory.sg

ES8007 Climate and Climate ChangeES1007 Oceans, Atmosphere and Climate

© NEA-MSS

Humans and Climate-Part II

Asst. Prof. WANG

Xianfeng

Asian School of theEnvironment

Nanyang Technological

University5 April, 2016


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ES8007 Climate and Climate ChangeES1007 Oceans, Atmosphere and Climate

© NEA-MSS

Humans and Climate-Part I

Asst. Prof. WANG

Xianfeng

Asian School of theEnvironment

Nanyang Technological

University5 April, 2016


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All objects emit radiation as long as they have a non-zero temperature on the kelvin

(K) scale. x °C = (273.15 + x) K

KEY QUESTIONS

How did climate afect hma!evoltio!"

How cold ice volme #sea level$cha!ge afect hma! migratio!"


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(K) scale. x °C = (273.15 + x) K

HU%&N E'O(UTION T)EE

(Ruddiman, 2014, Earth’s Climate: Past and Future)

1. Humans originated and evolved in East Africa.

2. The last ~5 million years span the evolutionaryline from primitive apes (particularlychimpanzees to the australopithecines (!southern apes"# ~$%& million years ago to our

o'n genus# Homo (~2 million years ago# andfinally our o'n species# Homo sapiens(!intelligent man"# !anatomically modernhumans"# ~2# years ago.

). *ipedalism (+eing a+le to 'al, upright on t'olegs# an energy%saving mechanism for travelinglong distance- 'as pro+a+ly developed ~$%&million years ago# and has +een considered asthe defining characteristic that separated thehominins from the hominoids (humanli,e apes#pro+a+ly the single most important event inhuman evolution.


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(K) scale. x °C = (273.15 + x) K

(Stanley, 2009, Earth System History; Ruddiman, 2014, Earth’s Climate: Past and Future)

1. harles /ar'in 'as among the first to suggest a lin, +et'een the African arid savanna andhuman evolution.

2. The uplift and su+sidence of the East African 0ift resulted in a comple topography that+loc,ed the effective moisture from transferring inland from the ndian 3cean# hence causedintensified aridification and ever%epanding savanna in Africa# and then stimulated human

evolution +y +ipedalism developing.

&*)I+&N TO,O-)&,HY

The East African 0ift4

All of the early () 6ahominin fossil sites arelocated along the narro'

+elt of the East African 0ift.

Hominin footprints# 7aetoli#

Tanzania# ~).& 6a.


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(K) scale. x °C = (273.15 + x) K

)O(E O* +(I%&TES&'&NN& HY,OTHESIS

This hypothesis ties human evolutionto long%term drying in Africa andglo+al climate processes.

Through the last 5 million years# 'hileplanet is cooling# Africa is getting

dryer and less forested. The tropicalrainforests in Africa largely have+ecome semi%arid grasslandsavannas.

This 'ould force hominins to adapt

from forests to an open environment#and force them to move rapidly tocover longer distances to survive.

auses of drying may +e many4tectonic uplift# ice volume# lo'er 32#

and monsoons.(Ruddiman, 2014, Earth’s Climate: Past and Future)

+/ vs +0

1la!ts


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(K) scale. x °C = (273.15 + x) K

HU%&N %I-)&TION OUT O* &*)I+&

Hominin spreading

1. Homo sapiens

2. Neanderthals

3. Homo erectus

?

8or most of the last ) million years# hominins onlydeveloped slightly +eyond the most primitive level of9tone Age of life4 e.g.# control of fire and gradually moresophisticated stone tools.

Ho'ever# 'hen our species appeared# the pace of change+ecame faster. The early human !culture" 'as developed4

cave paintings# figure statues# shell :e'elry# etc.(Stanley, 2009, Earth System

?


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(K) scale. x °C = (273.15 + x) K

I+E +O)E )E+O)2

(Petit et al., 1999, Nature3arm tem1.4 low ice volme4 high sea level5 cold tem1.4 low sea level

~1!

~"#

~1$%1


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(K) scale. x °C = (273.15 + x) K

%ONSOON&( +I)+U(&TIONS

(Ruddiman, 2014, Earth’s Climate: Past and Future)

Seasonal monsoon circulations

n summer# more rapid heating of landsurfaces than of the ocean producesrising motion over the continents anddra' moist air in from the ocean#producing precipitation over the land.

n 'inter# more rapid cooling of the landsurface than of the ocean producessin,ing motion over the continents andsheds cold dry air out over the 'armocean# shifting most 'inter precipitationout to sea.

A similar pattern can +e found on longertimescales. ;enerally spea,ing#summer monsoon is strong ininterglacial periods# +ut 'ea, in glacialperiods.


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(K) scale. x °C = (273.15 + x) K

6NO)TH 'S. SOUTH 2IS,E)S&( %O2E(7

1

1


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(K) scale. x °C = (273.15 + x) K

,EO,(IN- O* NO)TH &%E)I+&

(Stanley, 2009, Earth System

The megafaunalpopulation 'ashighly diverse untilthe late stages ofthe most recentdeglaciation in@orth America. *utmost of the largemammal species+ecame etinct'ithin a short timeperiod centered on

~12#5 years ago.

/id climate cause the megafaunal

etinction directly=

9harp spear pointsand over,ill hypothesis


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(K) scale. x °C = (273.15 + x) K

2&3N O* +I'I(I8&TION

3ur invention of agriculture coincides 'iththe onset of the sta+le climate of the past~1# years.

This is ~1# years of climatic

sta+ility that ena+led humanity toevolve and cultures to develop.

Agricultural revolution in the moist andfertile land4 several ,inds of agriculture

originated in the 8ertile rescent regionnorth and east of the 6editerranean# andgradually spread into Europe# @orth Africa# and other parts of Asia.

(Alley, 2007; Ruddiman, 2014, Earth’s Climate: Past and Future)

Holocene# the current interglacial period#is characterized +y a 'arm and relativelysta+le climate. A strong monsoon prevailsin the +road regions of Africa and Asia.

The region also sa' the developmentand flourishing of the earliest human

civilizations.


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(K) scale. x °C = (273.15 + x) K

KEY QUESTIONS

How may climate cha!ge afect the9ates o9 +hi!ese a!cie!t dy!asties"

Is a glaciatio! overde" +old earlycivili:atio!s already have alteredclimate"


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(K) scale. x °C = (273.15 + x) K

t/s tal0 a,ot a 2ro3y for rainfall

)emember that !ot all water #H;O$ is the same. Some H

;O is

heavier tha! other H;O 1roto!s a!d >!etro!s i! its !cles

?t a small @ #abot A.;@$ has> 1roto!s a!d BA !etro!s

That heavier H;B>O does!Ct eva1orate as easily as thelighter H;

BDO. So rai!water is actally lighter tha! the

seawater 9rom which it comes.Similarly4 the rst water to 9all ot o9 the clod has a

larger @ o9 heavier o=yge! tha! water that 9alls ot later.


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(K) scale. x °C = (273.15 + x) K

+&'E 2E,OSITS #ST&(&-%ITES &N2ST&(&+TITES$ &S & +(I%&TE &)+HI'E


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(K) scale. x °C = (273.15 + x) K

INTO THE 2&)K TO SHE2 SO%E(I-HTS ON )E+ENT +(I%&TE

%i!eralFlade! rai!water 1asses

throgh soil a!d rocG cracGs4 a!ddri1s o!to the cave oor. The waterthe! eva1orates. +alcite #+a+O/$ is

the mi!eral le9t behi!d. It 9ormsstalagmites that rise 9rom the oor o9

the cave.

htt1wiGi1ediacommo!s(echgillaJ+aveJ,earlsia!J-l9.1g

+ave de1osits #stalagmites a!d

stalactites$ ca! be a very se9lclimate archive. &!d 1ast climatecha!ge ca! be recorded throgh thecha!ges o! the ratio o9 B>OBDO i! thecalcim carbo!ates.O!e o9 the sig!ica!t adva!tages tose stalagmite to reco!strct 1ast

climate is that they ca! be dated1recisely by si!g the radioactivedecay o9 ra!im #here ;/0U$ tothorim #here ;/A Th$ i! thecarbo!ates. The less ra!im a!d the

more thorim4 the older the sam1le.

-eochemists at EOS&SE se a masss1ectrometer to measre the atoms

o9 ra!im a!d thorim4 a!d the!


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(K) scale. x °C = (273.15 + x) K

+&'E 2E,OSITS #ST&(&-%ITES &N2ST&(&+TITES$ &S & +(I%&TE &)+HI'E

9o# the ratio of 13 to1&3 is a climate proy#

and can record the

'ea,ening and

strengthening of theEast Asian monsoon.

7etBs loo, at a cave at


18/248ha!g et al ;AA> H

e a v i e r H

; O

( i g h t e r

H ;

O


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The Ha!g+hao U1risi!go9 the >LAs a!d>>As was 9eledby a droght4whe! locstsswarmed thela!d4 a!d led to

the e!d o9 the Ta!g 2y!asty.

2ri!g the Norther! So!gStro!g %o!soo! ,eriod4 the+hi!ese 1o1latio! more

tha! tri1led. )ice becamethe sta1le o9 the +hi!ese

Ha!g+hao

)iver sce!e at Qi!gmi!g 9estival

8h Ya!:ha!g4

Bst %i!gem1eror

&t the e!d o9 the Ya!2y!asty4 there were a serieso9 droghts a!d a 1easa!t1risi!g. I! B/D>4 8h

Ya!:ha!g4 the leader o9 the

1risi!g4 tooG ?eii!g. His1are!ts a!d older brother all

The +ho!g:he!2roght4 at the e!d o9the %i!g 2y!asty#BD/LFBD0/$4 is G!ow!as o!e o9 the most

severe i! +hi!esehistory. It afectedmore tha! ;A 1rovi!cesi! N a!d S +hi!a. The1rolo!ged droghthel1ed (i 8iche!gorga!i:e a 1o1lar1risi!g a!d overthrow+ho!g:he! i! BD00.

(i 8iche!g


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(K) scale. x °C = (273.15 + x) K

+(I%&TE &N2 +I'I(I8&TION

500

51 15Cear (A/

multiyear droughtsi!s o9 a 'iGi!g bar! i! -ree!la!d

9everal ma:or civilization collapses coincide 'ithperiods of intense droughts# or etremely cold climate.

Abandoned in ~14

th

and 15th centuries

Dariations in climate can +e dangerous to societies and civilizations. 3ther

factors can also play a role4 political sta+ility ('ar# overeploitation of soiland resources# food and 'ater securities

Maya, ucatan

(Zhang et al. 2008, Science)


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(K) scale. x °C = (273.15 + x) K

2I2 E&)(Y *&)%E)S &(TE) +(I%&TE"

Eventually# the relationship +et'een humans and their environment

+egan to change. nstead of +eing passive players# human +egan toactively influence their environment and EarthBs climate.

*y clearing of forests# slashing and +urning agriculture# and other practices# evenfarmers 'ith 'ooden plo's could alter the atmosphere. The modern man,ind 'illfurther mess up the planetBs thermostat. %%%


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(K) scale. x °C = (273.15 + x) K

IS & -(&+I&TION O'E)2UE"

(Kump, Kasting and Crane, 2010, The Earth System; Petit et al., 1999, Nature)

!emperature stability

in last 1",""" years

B. & sawtooth 9eatre o9 the glacialFi!terglacial cycle the tra!sitio!9rom glacial 1eriods to i!terglacial 1eriods is characteri:ed by a!abr1t warmi!g4 a!d the! relatively4 it cools gradally i!toglacials.;. I!terglacial co!ditio!s o!ly 1revailed abot BA@ o9 the,leistoce!e glaciatio!. However4 the climate i! the 1ast MBA4AAA

years is !sally commo!. It a11ears to be the lo!gest stableclimate i! the 1ast 0AA4AAA years.


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(K) scale. x °C = (273.15 + x) K

E&)(Y &NTH)O,O-ENI+ HY,OTHESIS

(Ruddiman, 2014, Earth’s Climate: Past and

1. “Wrong-way trend”: during the current

interglaciation (Holocene), greenhouse-gas

(here, CH4) concentration did not track the

.H. su!!er insolation change, "ut instead

started to rise at #$,%%% years ago.

&. 'ast $ interglacial CH4 records ro! ntarctic ice

cores. CH4 concentration rose during the later *art o

Holocene, "ut continuously ell during *re+ious

interglaciations.


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(K) scale. x °C = (273.15 + x) K

E&)(Y &NTH)O,O-ENI+ HY,OTHESIS

(R ddi 2014 E h’ Cli P d

1. ice was irst culti+ated in China. y 4,%%%

years ago, archeological sites (red) show that

rice irrigation was *resent across !ost o

China, where rice is !ainly grown in its south

today ("lue).

&. ince $,%%% years ago, rice irrigation has

e/*anded ra*idly into other countries inoutheast sia and 0ast sia

. e+eral hu!an

acti+ities can generate

CH4, including irrigatingields, "urning "io!ass

(weeds and cro*

residues), tending

li+estock, and *roduction

o organic wastes.

0arly rice ar!ing

and ano!alous

!ethane (CH4) trend

8.Humans and Climate

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