1

climate change

2007

Joachim CurtiusInstitut für Physik der Atmosphäre

Universität Mainz

CO

2 (p

pm)

Contents1. Summary

2. Background

3. Climate change: observations

4. CO2

5. Other Greenhouse Gases (GHGs)

6. Aerosols and Clouds

7. Solar variability

8. Future climate change

9. Paleo-climate

10. Climate protection

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global mean radiation balance

kurzwellig

langwellig

4 4

4 4

4

2 0

0,7 04

0,7 04

A B

KA B

KA

T T

IT T

IT

σ σ

σ σ

σ

− + =

− + =

− + =

simple (perfect) greenhouse model:

area A:

area B:

net:

results:TA= -18°C, TB= 30°C

TA corresponds to Teff,Erde

Model:Ø Atmosphere = one planeØ surface has albedo of 30% Ø no other energy transport→ natural greenhouse effect qualitative

[Kraus, 2004]

3

4 42 0A A A BT Tε σ ε σ− + =

Extension of the simple greenhouse model:

plane A:

plane B:

results:for TB= 288 K à TA= 242 K

and εA=0,78

for TB= 289 K à TA= 243 Kand εA=0,79

Model:Ø Atmosphere = one planeØ Earth surface has albedo agØ no other energy transportØ longwave "window" with the hep of εA→ demonstrates the effect of additional GHGs

( )4 4 1 04K

A A B g

IT T aε σ σ− + − =

[Kraus, 2004]

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[IPCC,2001]

radiative forcing ∆F:

"change of the radiative budget at the tropopause, caused by disturbancesof the energy fluxes in the sub system surface-atmosphere "(definition after Schönwiese, IPCC-Def. more complex).

negative radiative forcing: coolingpositive radiative forcing: warming

semi-empirical connection between temperature and climate forcing:

F Tλ∆ = ∆

dc F T

dtλ

∆Τ= ∆ − ∆

in long-term steady-state:

time-delayedclimate response radiative

forcing parameter:sensitivity(feedbacks etc.)

change ofsurface temperature

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Contents1. Summary

2. Background

3. Climate change: observations

4. CO2

5. Other Greenhouse Gases (GHGs)

6. Aerosols and Clouds

7. Solar variability

8. Future climate change

9. Paleo-climate

10. Climate protection

anthropogenic sources of climate change:

two components:

A) detection

B) attribution of causes

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Questions:

Ø By how much has Earth warmed?

Ø Is that unusual?

Ø Have water vapor and precipitationchanged?

Ø Increase of wether extremes?

Ø Are the observations of climate change consistentwith each other?

3. observed climate changeØ records of temperatures at surface: "Hockeystick"

Ø records of temperatures for stratosphere and ocean, etc.Ø changes in sea ice content, snow cover and glaciers

Ø changes in precipitation

Ø regional development, urban climate

Ø changes in extreme events:

Ø tropical storms

Ø heat waves

Ø flooding

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Network for ground-based atmospheric measurements

[Schönwiese, 2003]

[IPCC,2001]Ø past decade most likely the warmest in the past 1000 years.

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[IPCC, 2001]

temperature reconstruction for NH after Mann et al.,1999, from Multi-Proxy-Analysis of: tree rings, coral reefs, ice cores, bore holes, etc.

further reconstructions

[IPCC, 2001]

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comparison:simulations by von Storch et al., Science, 2004,with reconstructions by Mann, Bradley, Hughs, Nature, 1998 (MBH)

MBH-reconstructions: are long-termvariabilityincluded correctly?

Global mean temperatures are rising faster with time

100 0.074±0.01850 0.128±0.026

Warmest 12 years:1998,2005,2003,2002,2004,2006, 2001,1997,1995,1999,1990,2000

Period Rate

Years ° /decade

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temperature reconstruction from bore holes 1500-2000

a) methodb) 862 reconstructions

world-widec) averaged reconstruction

and comparison withdirect measurements

a)

c)

b)

temperature trends 1901-2000 in three time intervals

[IPCC,2001]

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temperature trends 1976-2000 by seasons

[IPCC,2001]

heat content and temperatures of the oceans

left: observed (dot-dashed line, Levitus et al., Science, 2000) und modelled(full line, Barnett et al., Science, 2001) increase in the heat contents of the oceans(upper 3000 m).

right: increase in temperature of the ocean temperatures , modelled, (Barnett et al., Science, 2001), 1.5e22 J corresponds to 1 W yr m -2

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Ø currently: non-equilibrium of the energy budget

Ø Earth takes up ~0.85 W/m2 more than what is deposited to space

Ø Temperatures of the atmosphere will increase further(+0.6°C), even if atmospheric concentrations of GHGs do not increase further.

heat content change of the oceansHansen et al., Science 2005

Trend in the changes of the diurnal-temperature-range:

daytime maximum temperatures have risen more strongly than thenighttime minimum temperatures.

[IPCC,2001]

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Maximum temperature changes between city centerand surrounding rural areas.

Average urban heat island effect: 0.5-1.5°C[Schönwiese, 2003]

temperature-change in thestratosphere:

causes: ...

ozone depletion

troposphericwater vapouris enhanced.

[Schönwiese, 2003]

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temperature change in the upper stratosphere: 50 km

trend: minus 3-6°C within 20 years

[Shindell]

increase of water vapour at the ground.

[IPCC, 2001]

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increase of watervapour in thestratosphere

causes:manyfold, methaneH2O-transport

regional changes of precipitation over the past century

Ø increase of precipitaion by 0.5 - 1%/decadeover land in mid-latitudes .

[IPCC, 2001]