HOT STUFF: CLIMATE CHANGE - Chapter 6: A Task for the Whole World.

S

TEFAN

R

AHMSTORF IS

P

ROFESSOR OF

P

HYSICS OF THE

O

CEANS AT

P

OTSDAM

U

NIVERSITY AND HEAD OF

E

ARTH

S

YSTEM

A

NALYSIS AT THE

P

OTSDAM

I

NSTITUTE FOR

C

LIMATE

I

MPACT

R

ESEARCH.

H

IS RESEARCH FOCUSES ON THE ROLE OF THE OCEANS IN

CLIMATE CHANGE.

T

HE RESEARCH SHIP

S

TANLEY

R

IGGS IS IN

R

OANOKE

S

OUND BY THE

O

UTER

B

ANKS NEAR

N

AG‘S

H

EAD,

N

ORTH

C

AROLINA,

USA

H

UMANITY IS RESPONSIBLE FOR THE GLOBAL TEMPERATURE RISE WE ARE EXPERIENCING TODAY.

F

IRSTLY AS A RESULT OF THE USE OF FOSSIL FUELS; SECONDLY AS A RESULT OF

DEFORESTATION.

T

HERE IS A SCIENTIFIC CONSENSUS ON THE BASIC FACTS

AND FIGURES ABOUT HUMAN-INDUCED CLIMATE CHANGE; BY NOW IT IS ALSO ACCEPTED AT ALL

POLITICAL LEVELS.

S

TEFAN IS TAKING SOIL SAMPLES FROM A LAYER OF PEAT SEVERAL METRES THICK TO STUDY HOW THE SEA LEVEL HAS CHANGED OVER THE PAST

MILLENNIA.

W

HEN THERE IS NO HUMAN INTERFERENCE, THE *CARBON CYCLE IS IN EQUILIBRIUM.

H

^OWEVER,

OUR USE OF FOSSIL FUELS IS INCREASING THE AMOUNT OF

ATMOSPHERIC CARBON BY 5 GIGATONNES A YEAR.

T

HE CONCENTRATION OF

CO

2 IN THE ATMOSPHERE HAS INCREASED RAPIDLY SINCE CA. 1850, FROM 280 PPM (A TYPICAL VALUE FOR WARM INTERGLACIAL PERIODS) TO OVER 390 PPM.

CO

2 IS A RADIATIVE FORCING GAS: THE HIGHER ITS CONCENTRATION IN THE ATMOSPHERE, THE MORE THE SURFACE TEMPERATURES RISE.

I

^{F THE}

CO

CONTENT IN THE AIR DOUBLES, THE AVERAGE GLOBAL TEMPERATURE RISES BY 2-4°

C

S

UNLIGHT SHINES ON THE

E

ARTH.

A

THIRD OF IT IS REFLECTED, THE REST IS CONVERTED INTO HEAT IN THE ATMOSPHERE AND ON THE

E

ARTH’S SURFACE.

T

E

ARTH CAN ONLY GET RID OF HEAT BY RADIATING IT BACK OUT

INTO SPACE.

H

OWEVER, GREENHOUSE GASES PREVENT THE ATMOSPHERE FROM

LETTING LONG-WAVE THERMAL RADIATION THROUGH.

A

^{LOT OF}

THE RADIATION EMITTED FROM THE SURFACE IS ABSORBED AND

RERADIATED BACK DOWN.

G

LOBAL ENERGY FLOWS AND GREENHOUSE-GAS EFFECT, DATA IN

W

ATTS/M²

CARBON (C) FLOWS IN GIGATONNES (GT) PER ANNUM (BOLD TYPE: TOTAL AMOUNTS OF STORED

CARBON IN GT)

FOSSILE FUELS

> 12 000

*SEDIMENTATION 0,1 MARINE SEDIMENTS 30 MILLION

MEDIUM AND GREAT DEPTHS

37 000

REFLECTED S^OLAR RADIATION

INCOMING SOLAR

RADIATION ESCAPING

LONG-W

VAPO-RATION RADIATION BY

THE SURFACE ABSORBED BY THE SURFACE OF VEGETATION

Source: WBGU 2012

I

F WE DO NOT CHANGE OUR WAYS SOON, WE EXPECT TEMPERATURES

TO INCREASE BY AN AVERAGE OF 4-7°

C

OVER THE NEXT 100 YEARS.

B

Y TAKING RESOLUTE MEASURES TO PROTECT THE CLIMATE, WE COULD LIMIT WARMING TO 2°

C

, BUT ONLY IF WE START TAKING ACTION STRAIGHT AWAY.

B

Y WAY OF COMPARISON, THE LAST GREAT GLOBAL WARMING TOOK PLACE AT THE END OF THE LAST

I

A

GE APPROXIMATELY 15,000 YEARS AGO.

O

VER A PERIOD OF 5,000 YEARS THE GLOBAL TEMPERATURE ROSE BY APPROXIMATELY 5°

C

A

N UNLIMITED MAN-MADE GLOBAL WARMING COULD REACH SUCH A SCALE IN A FRACTION OF

THAT TIME – AND IT’S STARTING FROM A CLIMATE THAT’S ALREADY WARM.

I

CE-COVERED REGIONS DURING THE

P

LEISTOCENE GLOBAL MEAN TEMPERATURE

WARMING RELATIVE TO PRE-INDUSTRIAL PERIOD (°C)

SUCCESSFUL CLIMATE PROTECTION BUSINESS AS USUAL

Source: Nature 2009

8 7 6 5 4 3 2 1 0

1900 2000 2100 2200 2300

T

HE EXACT COORDINATES AND ELEVATION OF THE SITE ARE

DETERMINED USING

GPS

AND LASERS.

T

HE GLOBAL TEMPERATURE IS RELATIVELY EASY TO PREDICT, BUT IT’S MUCH MORE DIFFICULT TO PREDICT THE EFFECTS OF WARMING ON THE ICE MASSES, THE SEA LEVEL OR VEGETATION.

R

EGIONAL DIFFERENCES IN WARMING, ASSUMING A MEAN GLOBAL WARMING OF ABOUT 4°

C

UP UNTIL THE END OF THE CENTURY.

T

HE CONTINENTS AND POLAR REGIONS ARE THE MOST SERIOUSLY AFFECTED.

T

HE EVIDENCE FOR THE IMPACT OF OUR GREENHOUSE-GAS EMISSIONS ON THE CLIMATE IS BASED ON DECADES OF RESEARCH

WORK AND THOUSANDS OF STUDIES.

I

^T‘S

PRACTICALLY INCONCEIVABLE THAT THIS COULD ALL BE SUDDENLY OVERTURNED BY NEW

RESULTS.

Source: IPCC 2007 0 2 4 6 8

°C

S

TEFAN COMES ON BOARD TO TAKE SEDIMENT CORES IN THE LAGOON.

A

ND THE *TIPPING ELEMENTS MAKE LIFE EVEN MORE DIFFICULT FOR US: CERTAIN REGIONS OR PROCESSES REACT PARTICULARLY SENSITIVELY AND ACT AS SELF-REINFORCING ELEMENTS IN THE SYSTEM.

W

HEN THE HIGHLY REFLECTIVE ICE SURFACES MELT, THIS REVEALS THE DARK OCEAN, WHICH ABSORBS MUCH MORE SOLAR HEAT AND FURTHER

ACCELERATES THE MELTING.

O

THER TIPPING ELEMENTS ARE IMPOSSIBLE TO CALCULATE.

F

OR EXAMPLE, WHEN THE *PERMAFROST IN

S

IBERIA THAWS, IT RELEASES METHANE, WHICH IS A MUCH MORE AGGRESSIVE GREENHOUSE GAS

THAN

CO

2 – BUT NO ONE YET KNOWS TO WHAT EXTENT AND WITH WHAT CONSEQUENCES.

J

UST ONE EXAMPLE: HALF OF THE SUMMER SEA-ICE COVER ON THE

A

^RCTIC

O

CEAN HAS ALREADY DISAPPEARED.

COMPARISON OF THE EXTENT OF THE ARCTIC SEA ICE IN 1979 AND 2012

A

ND THE GLACIERS

ARE ALSO DISAPPEARING RAPIDLY ALL OVER

THE WORLD.

Y

OU CAN READ HOW SEA LEVELS HAVE CHANGED FROM PEAT DEPOSITS IN

COASTAL SALT MARSHES.

A

COLLEAGUE WINCHES THE CORE SAMPLES OUT OF THE WATER.

MISSISSIPPI

ANGES-BRAHMAPUTRA JANGTSEKIANG

COASTAL DELTAS MOST SERIOUSLY THREATENED

M

ANY OF TODAY’S MEGACITIES ARE SITUATED IN ESTUARIES, MAKING THEM PARTICULARLY VULNERABLE TO SEA-LEVEL RISE.

I

N SOME WAYS, THE EFFECTS OF CLIMATE CHANGE ARE COMING FASTER THAN EXPECTED.

F

OR EXAMPLE, THE MELTING

OF SEA ICE AND ICE SHEETS WAS UNDERESTIMATED, AS WAS THE RISE IN THE

SEA LEVEL.

T

M

UELLER

G

LACIER IN

N

Z

EALAND.

T

HE LINE SHOWS THE EXPANSE OF THE GLACIER 100 YEARS AGO.

Source: IPCC 2007

SEA LEVEL OVER 2000 YEARS

0 + 0,6 - 0,1

0 500 1000 1500 2000

+ 2,1

SEA LEVEL (METRES)

SEA LEVEL RISE (MM/YEAR)

E

VEN IF WE MANAGE TO GREATLY REDUCE GREENHOUSE-GAS EMISSIONS AND LIMIT GLOBAL WARMING TO 2°

C

, THE SEA LEVEL

IS LIKELY TO RISE MORE THAN 1 METRE OVER THE NEXT TWO OR

THREE CENTURIES.

D

URING THE

M

EDIEVAL

W

ARM

P

ERIOD, THE SEA LEVEL ROSE SLOWLY BETWEEN THE YEARS 1000 AND 1400.

T

HEN IT WAS STABLE FOR SEVERAL CENTURIES, UNTIL THE END OF

THE 19TH CENTURY; SINCE THEN THERE HAS BEEN THIS STEEP RISE IN RESPONSE TO THE

CURRENT GLOBAL WARMING.

0,2

0,0

-0,2

T

HIS PUTS COASTAL CITIES AND LOW-LYING ISLANDS AT RISK.

H

URRICANES LIKE

S

ANDY, WHICH HIT

N

^EW

Y

^{ORK IN}

O

^CTOBER

2012 – CAUSING DEVASTATING DAMAGE, FLOODED ROADS AND SUBWAYS, POWER FAILURES AND MANY DEATHS – HIGHLIGHT THE URGENCY OF THE PROBLEM.

B

ECAUSE COASTAL FLOODING FROM HURRICANES WILL GET WORSE AS THE SEA LEVEL RISES.

T

HE RISK OF EXTREME WEATHER EVENTS IS ALSO INCREASING.

T

HE NUMBER OF FLOODS, DROUGHTS AND FOREST FIRES

WILL INCREASE WORLDWIDE.

S

TEFAN ON HIS WAY TO A WORKSHOP ON COASTAL PROTECTION IN

N

AG’S

H

EAD.

F

OREST FIRES IN

S

PAIN 2012

F

LOODING IN SOUTHERN

R

USSIA 2012

A

ND OF COURSE, THIS HAS AN EFFECT ON THE WATER SUPPLY AND FOOD SECURITY.

B

OTH THE MODELS AND THE DATA SHOW AN INCREASE IN THE

STRENGTH, AND POSSIBLY ALSO IN THE FREQUENCY, OF HURRICANES AS

A RESULT OF HIGHER SEA SURFACE TEMPERATURES.

E

XTREME DROUGHT IN THE

USA

2012

H

URRICANE

K

ATRINA IN THE

USA

IN 2005

N

AG’S

H

EAD

A

LTHOUGH GLOBAL AGRICULTURAL PRODUCTION DOES NOT NECESSARILY HAVE TO DECLINE IN WARMER CLIMATIC CONDITIONS, SOME HARVESTS WILL BE LOST IN POORER AND WARMER COUNTRIES

AS A RESULT OF WATER SCARCITY AND

WEATHER EXTREMES.

T

HE WATER SUPPLY IN

L

IMA IS HIGHLY DEPENDENT ON THE

A

NDEAN GLACIERS.

W

HILE THE POPULATION IS GROWING, THE GLACIERS ARE MELTING, AND NO ONE

CAN STOP THEM.

I

F THE MOUNTAIN GLACIERS DISAPPEAR,

THIS WILL THREATEN WATER SUPPLIES TO MAJOR CITIES LIKE

L

IMA.

T

ODAY AT 9 AM,

S

TAKEHOLDER

W

^ORKSHOP

S

Im Dokument Chapter 6: A Task for the Whole World. (Seite 38-48)