Communicating (Paleo)climate Science Kim Cobb EAS, Georgia Inst. of Technology Acknowledgements Lab...

Communicating (Paleo)climate ScienceKim CobbEAS, Georgia Inst. of Technology

AcknowledgementsLab members:Intan Suci NurhatiJulien Emile-GeayLaura ZaunbrecherJames HerrinHussein SayaniEAS undergrads

with special thanks to:Norwegian Cruise LinesPalmyra Research ConsortiumSarawak Department of Forestry, MalaysiaNOAA, NSF

Which of the following are scientific statements?

1) Reducing CO2 emissions would hurt the economy.

2) Improved technology is the best way to slow globalwarming.

3) A warming of 1ºC over the next 50yrs is “dangerous”.

4) Global temperatures were 5ºC colder during the LastGlacial Maximum.

5) Hurricane Katrina was caused by global warming.

Why do 99.999% of climate scientists believe that CO2 is warming the planet?

1. Theory predicts that increasing atmospheric CO2 should warm the planet.

2. Geologic evidence links CO2 and temperature in the past.

3. The warming is unprecedented in the most recent centuries (dwarfs natural variability).

4. Climate models show that rising CO2 is necessary to simulate20th century temperature trends (solar and volcanic minor players).

Ice core climate and CO2 records

tiny gas bubbles in the ice trapancient air samples

Atmospheric CO2 and temperature over the past 650 thousand years

CO2 and temperatureare closely linkedon geologic timescales

#2

To understand how climate has changed in the past, we need to use records of climate preserved in ice cores, ancient tree rings, coral bands, and other “paleoclimatic” sources:

key is to CALIBRATE to temperature records

The “Hockey Stick”

Key Points:error bars increase as you go back in timenatural variability accounts for <0.5ºC over the last millenniumlate 20th century temperature trend is unprecedentedin 1,000 years

#3

IntergovernmentalPanel onClimate Change(IPCC) 2001

#4

Solar and volcanic only anthropogenic only

natural & anthropogenic

The uncertain climate futureRange of scenarios:Strict international agreements CO2 at 600ppm by 2100 *390ppm todayMid-ground 850ppm by 2100 280ppm 1800Business as usual 1200ppm by 2100

IPCC AR4, 2007

but we need to know about regional climate changes, and specifically

about regional precipitation changes

white = models disagreecolor = models mostly agreestippled = models agree

IPCC AR4, 2007

Research Goal: constrain tropical Pacific response to anthropogenic global warming

Approach: reconstruct tropical Pacific climate at high-resolution forthe last millennium

Dai and Wigley, 2000

El Niño Temperature

El Niño Precipitation

WHY?

“El Niño-Southern Oscillation” (ENSO)

ENSO is a climate pattern in thetropical Pacific which arisesfrom coupled interactions betweenthe atmosphere and ocean

ENSO impacts global climate every2-7 years (huge impact on rainfall)

Research Questions

How has the tropical Pacific climate system responded to CO2 forcing?

What aspects of present tropical Pacific climate are unprecedented?

compare last several decades to recent centuries

Fanning2005-?

Palmyra1997-?

Christmas1998-?

Corals: The geologic record of El Niño

CORALS from the tropical Pacific record El Niño’s in the geochemistry of their skeletons

Living Porites corals provide recordsfor the last 200 years

Fossil Porites corals enable us to extend the record back many centuries

SS

T A

nom

oly

(°C

)

3

2

1

0

-1

-2

18 O

(‰

)

-0.6

-0.4

-0.2

0.0

0.2

NIÑO3.4 SSTPalmyra coral

Year (A.D.)

1900 1920 1940 1960 1980 2000

SS

T A

nom

oly

(°C

) 1

0

-1

-2

-0.3

-0.2

-0.1

0.0

0.1

0.2

0.3

R = -0.66

R = -0.84

18 O

(‰

)

Palmyra coral oxygen isotopes vs. tropical Pacific SST

Overlapping fossil corals: ancient El Niño events

Good reproducibility between coral geochemical recordsincreases confidence in coral climate reconstructions.

A millennium-long reconstruction of tropical Pacific temperature

Key climate observations:1) late 20th century warming is unprecedented in the last millennium2) no cooling during the Northern Hemisphere’s “Little Ice Age”3) significant cooling implied during the NH’s “Medieval Warm Period”

THIS IS THE END OF MY SCIENCE PRESENTATION

Reflections of a (Paleo)climatologist

Paleoclimate data havestrong visual, intuitiveappeal.

Their dismissal by a large fraction of the climatescience communityhasn’t helped cementtheir contributions, norutilize their full potential.

But this is changing …

Is anthropogenic CO2 warming the planet? yes or no?

The Pyramid of Climate Consensus


What are the impacts of AGW?(what? how much? by when?)




What are the impacts of AGW?(what? how much? by when?)

What should be done about it?

How climate scientists can help

1)Appreciate the differences between climate science and climate policy.

climatescientist

policyadvocate

??



2)Denounce sloppy science from both extremes of the climate science debate. (climate skeptics, IPCC WG2)

climatescientist

policyadvocate

??




3)Publish data in data repositories with new standards for climate metadata.

climatescientist

policyadvocate

??





4) Engage public, policymakers, skeptics in science of climatechange, with the pyramid of consensus always in mind.

climatescientist

policyadvocate

??





4) Engage public, policymakers, skeptics in science of climatechange, with the pyramid of consensus always in mind.

5) Remove existing structural impediments to outreach, considercreating new structures to aid outreach. (Beyond RC?)

climatescientist

policyadvocate

??

Some thoughts on the IPCC

As the IPCC turns 22, needs to address the question:“What do I want to be when I grow up?”

from Judy Curry

Communicating (Paleo)climate Science Kim Cobb EAS, Georgia Inst. of Technology Acknowledgements Lab...

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