climate change: the long view (on an immediate problem)

Joint Antarctic Research Institute - JARIJoint Antarctic Research Institute - JARI

Climate Change: The Long View (on an immediate problem)

Tim Naish

Antarctic Research Centre ,Victoria University of Wellington.& GNS Science, Lower Hutt


Understanding and attributing climate change

Source: IPCC, 2007


Medi

4

3

2

1

0

-1

800 1000 1200 1400 1600 1800 2000 2100

SRES

IPCC AR4 SRES Average

Global Temperature

Projection

= RCP 8.5

= RCP 6

= RCP 4.5

°C

550ppm

750ppm

1200ppm

365ppm

Future climate will be warmer than last 2000 years years as shown in the“IPCC hockey stick curve”

Medieval Warm

AnomalyLittle Ice Age

Source: IPCC, 2007

Joint Antarctic Research Institute - JARI

Future climate will be warmer than last 1 million years as shown in the “Antarctic ice core records”

Source: Nancy Bertler based on Vostok ice core

Source: IPCC, 2007

Joint Antarctic Research Institute - JARI Source: Zachos, 2001; Hansen et al., 2007; Beerlling & Royer 2011

Global average deep ocean temperature

Atmospheric carbon dioxide

Millions of years ago

Temp

erature °C

Co

nce

ntr

atio

n (

pp

m)

400ppm

+2-3°C

Plio

cen

e w

arm

per

iod

Ice sheet forms on Antarctic

Must go back 3 million years to find the last time carbon dioxide in the atmosphere was similar to today’s levels


The world does not warm evenly The polar regions are warming at 2 X the global average

“Polar amplification”

Source: IPCC (2007)


Polar amplification 3 million years agoGlobal average temperature ~2-3°C warmer

Source: Dowsett et al in prep.


20ka LGM Model/Data ~200ppm pCO2

3Ma Pliocene PRISM ~400ppm pCO2

Pre-industrial ~300ppm pCO2

Past polar temperature amplification

Source: PRISM, MARGO, WOA databases

5°C cooler

2-3°C warmer


Upper bound for sea-level rise of +59cm …”Larger values cannot be excluded, but understanding of these effects is too limited to assess their likelihood or provide a best estimate or an upper bound for sea level rise”, IPCC 2007

Could not estimate the contribution from ice sheet dynamics -

How will the ice sheets respond to future polar temperature amplification?

The answer to this question is presently the biggest impediment to constraining projections of sea level rise to 21st century and beyond


Rate = 3.3 mm/yr

Source: Nerem et al (2010), Cazenave and Llovel (2010).

Global mean sea-level variation 1992-2011 based on satellite altimeter

Global mean sea-level variation budget since the satellite era

Not bad agreement!

Present global sea-level rise & the global sea-level budget:

Do the observations = the sum of the contributions?


Sea-level observations and the estimates of the individual contributions have not always matched that well

Source: IPCC, 2007


Medi

4

3

2

1

0

-1

800 1000 1200 1400 1600 1800 2000 2100

SRES

°C

550ppm

750ppm

1200ppm

365ppm

Medieval Warm


Projections for 21st century sea-level rise

+2°C World: Using IPCC SRES B1 scenario = RCP-4.5 = ~550ppm CO2

• Semi-empirical projections = 75-110cm

• Projected from models without ice dynamics = 10-40cm

• Projected from models with ice dynamics = 20-120cm

• IPCC AR4 range = 18-59cm

Source: Vermeer & Rahmstorf (2100), Pfeffer et al., (2009), Pollard & DeConto (2009),

Katzman et al. (2011), Graversen et al. (2001), Mehl et al. (2007), Feltweis et al. (2008)


Medi

4

3

2

1

0

-1

800 1000 1200 1400 1600 1800 2000 2100

SRES

°C

550ppm

750ppm

1200ppm

365ppm

Medieval Warm


Projections for 21st century sea-level rise

+3°C World: Using IPCC SRES A1B scenario=RCP-6 = ~750ppm CO2

• Semi-empirical projections = 98-130cm

• Projected from models without ice dynamics = 20-50cm

• Projected from models with ice dynamics = 50-155cm

• IPCC AR4 range = 18-59cm

Source: Vermeer & Rahmstorf (2100), Pfeffer et al., (2009), Pollard & DeConto (2009),

Katzman et al. (2011), Graversen et al. (2001), Mehl et al. (2007), Feltweis et al. (2008)

SLR for 2100 = 1m ± 0.5m


Present contribution of polar ice sheets to global sea-level

• Polar ice sheets are

contributing between 1-1.6

mm per year to global sea-

level with Greenland and

West Antarctica about

equal.

• The rate of contribution

has doubled in the last 6

years and is now out-pacing

thermal expansion

• These systems are

capable of non-linear,

unpredictable behaviour

Sources listed in Bertler & Barrett (2010)


But sea-level does not rise evenly!

What 1 m of sea-level rise will look like

Source: Mitrovica (unpublished)

m

Joint Antarctic Research Institute - JARI Source: Zachos, 2001; Hansen et al., 2007; Beerlling & Royer 2011

Global average deep ocean temperature

Atmospheric carbon dioxide

Millions of years ago

Temp

erature °C

Co

nce

ntr

atio

n (

pp

m)

400ppm

+2-3°C

Plio

cen

e w

arm

per

iod

Ice sheet forms on Antarctic

What was the relationship between past climate and sea-level?

Joint Antarctic Research Institute - JARI Source: Modified from Alley et al. (2008)

What was the relationship between past climate and sea-level?

Joint Antarctic Research Institute - JARISources: Naish et al (2009), Pollard & DeConto (2009) Miller et al. (submitted), Dolan et al. (2011)

ANDRILL Program

• 400ppm atmospheric carbon dioxide

• +2-3°C warmer, polar amplification. +5°C in Ross Sea

• up to + 8m sea-level rise from Antarctica

• up to +7m sea-level rise from Greenland

• Geological reconstructions show global seal level ~+20m

Multiple collapses of the West Antarctic Ice sheet 3-5 million years ago

Global sea-level likely

to have been ~+ 20m


Global sea-level up to +9m higher during the lastInterglacial period 125,000 years ago!

“It is very likely (95%) that global sea-level peaked at

+6.6m…and likely (67%) global sea peaked at +8-9m”

Kopp et al. (2009), Nature


How fast can sea-level rise?Up to 4m per century when northern hemisphere ice sheets of the last ice age were

melting!

Gre

en

lan

d w

arm

ing


How fast can sea-level rise?

Models of present day ice sheets and geological data from the last interglacial suggest 30cm to 1m per century “most likely” and system potentially capable of up

2m per century

Sources: Kopp et al. (2009), Pfeffer et al. (2009) Blanchon et al. (2010), Pollard and DeConto (20090

Model of West Antarctic Ice Sheet – Pollard and DeConto, unpublished


• Paleoclimate models and geological records provide important

constraints on ice sheet response and sea-level rise for global

temperatures projected for coming centuries.

• Best estimate from models and observations is ~+1m±0.5 by

2100.

• Geological data and models suggest a “most likely” rate of 1m

per century

• The detailed trajectory of sea-level rise of the coming centuries

will be controlled by non-linear ice sheet dynamics – a major

modelling challenge

• The last time Earth had ~400ppm CO2 atmosphere, it had an

average surface temperature of 2-3°C and Greenland and West

Antarctic Ice Sheets melted!

Concluding remarks


There are three main ways to contribute to the AR5:

1. Get papers published in the peer-reviewed literature, before the cut-off date

that are relevant to the assessment of future climate projections.

2. Act as a contributing author, if requested.

3. Act as an expert reviewer, once a draft is made available.

For your research to be cited in the WG I Report, deadlines for papers are:

Submitted by 31 July 2012

Accepted by 15 March 2013

Material from the Southern Hemisphere is especially valuable, given the less

comprehensive nature of climate system studies south of the Equator,

compared to the north.

How to contribute to IPCC AR5


Chapter 5: Information from Paleoclimate Archives

Coordinating Lead Authors: Valérie Masson-Delmotte, Michael Schulz

Lead Authors: Ayako Abe-Ouchi, Juerg Beer, Andrey Ganopolski, Jesus Fidel

González Rouco , Eystein Jansen, Kurt Lambeck, Juerg Luterbacher, Tim

Naish, Timothy Osborn, Bette Otto-Bliesner, Terrence Quinn, Rengaswamy

Ramesh, Maisa Rojas, Xue Mei Shao, Axel Timmermann

Contributing Authors: Barbara Delmonte, Patrick de Deckker, Hubertus Fischer,

Claus Froehlich, Alan Haywood, Stefan Mulitza, Olga Solomina, Pavel

Tarasov, Dan Zwartz, Yusuke Yokoyama

Review Editors: Fatemeh Rahimzadeh, Dominique Raynaud, Heinz Wanner,

De`er Zhang

Date of Zero Order Draft: 18 March 2011


Earth surface temperature above 1000ppm CO2Average surface temperature +10-12°C warmer

3 million years ago

Present day

50 million years ago

Problem: modelled

and geological

temperatures don’t

match!

Source: Lunt et al. (in prep).


How is ice global sea-level measured?

© I Joughin, 2008

GRACE satellite

InSAR

How are the contributions to global sea-level estimated?

• globally averaged tide gauge and satellite altimetry

• Thermosteric (thermal expansion): Shipboard, XBTs, ARGO floating profilers and modelling

• Glaciers and Ice caps: Up-scaling direct glacier measurements, relationships between mass balance and local meteorological records

• Ice Sheets: Satellites, GRACE for mass and InSAR for flow

• Land water storage: Hydrological modelling and GRACE satellite

climate change: the long view (on an immediate problem)

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