Klimaatverandering en broeikaseffect

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Klimaatverandering en broeikaseffect

HOVO Cursus Klimaat IMAU, 5 oktober 2009 Rob van Dorland, KNMI

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•  Climate change - various time scales

•  Global energy balance

•  Radiative forcing

•  Greenhouse effect

•  Climate sensitivity

•  Attribution of climate change

Outline

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Causes of Climate Change

  Natural factors

  Continental drift

  Earth’s orbital parameters

  Volcanism

  Solar activity

  El Niño - Southern Oscillation

  Human influence

  Greenhouse gases

  Aerosols

  Land use

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Greenhouse gases

•  Concentrations now far exceed pre-industrial values spanning many thousands of years

•  The increase of concentrations of CO₂, CH₄ and N₂O are primarily due to human activities

IPCC, 2007

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CO₂ emissions and increase

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CO₂ increase, O₂ and ¹³C decrease

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Detection: Ice Core Information

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Detection: CO₂ at Geological Time Scales

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Detection: Temperature at Geological Time Scales

Source:

Oerlemans, 2004

Long term cooling:

~11°C per 50 Myr

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A Millennium Perspective:

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Is er sprake van afkoeling?

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Radiative Balance of the Climate System

Incoming Solar Radiation 342 Wm^-2

Reflected Solar Radiation 102 Wm^-2 (about 30%)

Outgoing Infrared Radiation 240 Wm^-2

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Energy Balance Climate system

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Enhanced Greenhouse Effect

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Effective Temperature

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Change T_eff due to 2xCO₂

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Radiative Forcing

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Radiative forcing and climate response

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Feedbacks

Source: Soden & Held, 2006

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Bron: Hare en Meinshausen, 2004

How sensitive is the climate system?

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Bron: Hare en Meinshausen, 2004

How sensitive is the climate system?

Knutti & Hegerl, 2008

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Slow Feedbacks

Source: Hansen et al., 2008 Slow feedbacks point towards twice the IPCC estimated climate sensitivity, Largest uncertainty: aerosol forcing on various time scales

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Aardse temperatuur als

functie van het CO2 gehalte

Huidige toestand

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Greenhouse effect Earth, Venus and Mars

The greenhouse effect can be determined by using:

1) distance sun - planet 2) planetary albedo

3) composition atmosphere

4) surface pressure and gravity

5) temperature dependent processes Venus: ≈ 500 K

surface temperature = 733 K Mars: ≈ 3 K

surface temperature = 218 K For comparison:

Earth: ≈ 33 K

surface temperature = 288 K

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Water planet Earth

Water has important consequences:

•  Large heat capacity of oceans, resulting in:

1)  a delay between forcing and temperature response 2)  an attenuation of fast fluctuating forcings

•  Strong feedbacks due to 1)  water vapor

2)  clouds 3)  ice

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Frequency characteristics climate system

Climate model http://www.nat.vu.nl/envphysexp/

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Natural Climate Factors 20^th Century

1. Vulcanic eruptions

2. Solar activity

3. El Niño - Southern Oscillation

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Attribution of 20^th century global

temperature trend to natural causes

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Linear regression: fast fluctuations 1950-1998

  Natural climate factors selected:

volcanic activity, El Nino and solar activity

  Slow trends (e.g.

human influence,

Gleissberg cycle) are most uncertain 

  Linear regression on fast (2-20 yr) signals and observed

temperature

  Same scaling factors used for slow signals

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Attribution of 20^th century warming

Observed Temperature

trend

Human Influence?

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Global attribution

Most of the observed increase in globally averaged temperatures since the mid-20^th century is very likely due to observed increase in anthropogenic greenhouse gas concentrations.

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Figure 6.14

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Projections temperature

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