Paleoclimate record points toward potential rapid climate changes agu fall meeting dec 6 2011
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James Hansen
Director, NASA’s Goddard Institute for Space Studies, New York, New York, USA PowerPoint PPT Presentation


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Paleoclimate Record Points Toward Potential Rapid Climate Changes AGU Fall Meeting Dec. 6, 2011. James Hansen
Director, NASA’s Goddard Institute for Space Studies, New York, New York, USA

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James Hansen
Director, NASA’s Goddard Institute for Space Studies, New York, New York, USA

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Paleoclimate record points toward potential rapid climate changes agu fall meeting dec 6 2011

Paleoclimate Record Points Toward Potential Rapid Climate ChangesAGU Fall Meeting Dec. 6, 2011

James Hansen
Director, NASA’s Goddard Institute for Space Studies, New York, New York, USA

EelcoRohling
Professor of Ocean and Climate Change, Southampton University, Southampton, United Kingdom


Ken Caldeira
Senior Scientist, Department of Global Ecology Carnegie Institutution of Washington, Stanford University, Stanford, California, USA


James hansen director nasa s goddard institute for space studies new york new york usa

Basis of Understanding

1. Earth’s Paleoclimate History

2. On-Going Global Observations

3. Climate Models/Theory


James hansen director nasa s goddard institute for space studies new york new york usa

50 million years ago (50 MYA) Earth was ice-free.

Atmospheric CO2 amount was of the order of 1000 ppm 50 MYA.

Atmospheric CO2 imbalance due to plate tectonics ~ 10-4 ppm per year.


James hansen director nasa s goddard institute for space studies new york new york usa

Cenozoic Era

End of Cretaceous (65 My BP)

Present Day


James hansen director nasa s goddard institute for space studies new york new york usa

Climate Change over Cenozoic Era

1. Dominant Forcing: Natural ΔCO2

- Rate ~100 ppm/My (0.0001 ppm/year)

- Human-made rate today: ~2 ppm/year

Humans Now Overwhelm Slow Geologic Changes


James hansen director nasa s goddard institute for space studies new york new york usa

Climate Sensitivity

1. Depends on Climate Forcing

- Usually 2XCO2 (4W/m2 forcing)

2. Depends on Climate State

- Usually today’s climate

3. Depends on Time Scale

- Usually “Equilibrium” for Fast Feedbacks (Ice Sheets fixed, Methane Hydrates fixed)


James hansen director nasa s goddard institute for space studies new york new york usa

Global deep ocean

temperature.

Past 5,300,000 years.

Past 500,000 years.


James hansen director nasa s goddard institute for space studies new york new york usa

Climate forcings during ice age 20 ky BP, relative to the present (pre-industrial) interglacial period.


James hansen director nasa s goddard institute for space studies new york new york usa

Figure 2. Global temperature relative to peak Holocene temperature

(Hansen and Sato, 2011).


James hansen director nasa s goddard institute for space studies new york new york usa

Fig. 3. (A) Decay of instantaneous injection or extraction of atmospheric CO2, (B) CO2 amount if fossil fuel emissions are terminated at the end of 2010, 2030, or 2050.


James hansen director nasa s goddard institute for space studies new york new york usa

Fig. 6. CO2 emissions by fossil fuels (1 ppm CO2 ~ 2.12 GtC). Estimated reserves and potentially recoverable resources are from EIA (2011) and GAC (2011).


Ice sheet and sea level response

Ice Sheet and Sea Level Response

EelcoRohling

Professor of Ocean and Climate Change, Southampton University, Southampton, United Kingdom


James hansen director nasa s goddard institute for space studies new york new york usa

Sea level and GHG forcing – geological context

40 Million

years

10 Million years

W/m2

500,000 years

In natural context, the ‘equilibrium’ sea level for current anthropogenic forcingis 25 ±3m higher than today.

This is a measure of the climate disequilibrium.

Full adjustment takes time (likely millennia)

Large disequilibrium creates increased likelihood of abrupt adjustments

Unpublished with G. Foster


James hansen director nasa s goddard institute for space studies new york new york usa

How fast did rises occur above the present, in recent geological past? Last Interglacial

Structure of two main & one minor peak, separated by lowstands, corroborated by stratigraphic reef sequences (Bruggemann et al., 2004)

3

2

1

2

1

3

Rohling et al. Nature Geoscience 1, 2008

A modelled “best estimate” Eemian Greenland ice sheet (Cuffey and Marshall, 2000)

  • world max. 1 °C warmer than today and Greenland up to 3-5 °C warmer

  • meansea-level highstand4-6 m above present

  • up to half due to Greenland reduction

    • but not all, so Antarctica was involved!

  • we find rates of rise above 0m of 1 to 2.5 m/century

  • similar rates reported since (esp. near lower end)

  • RATES


    James hansen director nasa s goddard institute for space studies new york new york usa

    Climate sensitivity overview paper (in progress; Paleosens working group)

    T increase for CO2 doubling

    (°F , °C)

    Climate sensitivity in °C per W/m2

    13.3

    7.4

    10.1

    5.6

    4.8

    8.6

    6.7

    3.7

    2.6

    4.7

    3.4

    1.9

    0.0

    0.0

    Individual study or compilation

    • Differences stem from different definitions, different reference systems, and different time-periods considered between studies.

    • Schmittner et al. (Science) based on LGM is № 18.

    • Rohling et al. (J. Clim in press) based on last 500,000 years is №s 9 and 10.

    • Deep time warm climate values are №s 11 to 16.


    Radiative forcing and climate r esponse from paleoclimate to future

    Radiativeforcing and climate responsefrom paleoclimateto future

    Ken Caldeira

    6 Dec 2011

    [email protected]


    There is no one number that is climate sensitivity

    There is no one number that is climate sensitivity

    • Scientists estimate how much climate will change under conditions where some factors are allowed to vary and others are held constant.

      The answer depends on which factors are held constant and which vary

      • Greenhouse gas concentrations

      • Aerosol concentrations

      • Ice sheets

      • Land-cover change / Ecosystem distributions

      • Atmosphere and ocean circulation

      • Clouds

      • Etc


    James hansen director nasa s goddard institute for space studies new york new york usa

    Event 55 million years ago (PETM) suggests, with long-term

    feedbacks, 5.5 - 8 ⁰C ( 10 - 14 ⁰ F) per CO2-doubling

    Pagani et al 2006


    James hansen director nasa s goddard institute for space studies new york new york usa

    (m)

    Antarctica = 61.1 m

    Greenland = 7.2 m

    Caldeira, ICDC meeting, 2005


    James hansen director nasa s goddard institute for space studies new york new york usa

    Fleming et al. 1998, Fleming 2000, Milne et al. 2005


    James hansen director nasa s goddard institute for space studies new york new york usa

    Climatically important amounts of carbon dioxidewill remain in the atmosphere for thousands of years

    3

    Number of CO2-doublings

    2

    1

    0

    Archer et al 2009


    James hansen director nasa s goddard institute for space studies new york new york usa

    Morality

    Science

    Values

    Facts


    James hansen director nasa s goddard institute for space studies new york new york usa

    Morality

    Science

    Values

    Facts

    Good

    Policy


    James hansen director nasa s goddard institute for space studies new york new york usa

    For more information:

    http://www.giss.nasa.gov/research/briefs/hansen_15/

    http://pubs.giss.nasa.gov/abs/ha05510d.html

    For press inquiries:

    Patrick Lynch

    [email protected]

    757-897-2047


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