Transcript Document

Communicating (Paleo)climate Science
Kim Cobb
EAS, Georgia Inst. of Technology
Acknowledgements
Lab members:
Intan Suci Nurhati
Julien Emile-Geay
Laura Zaunbrecher
James Herrin
Hussein Sayani
EAS undergrads
with special thanks to:
Norwegian Cruise Lines
Palmyra Research Consortium
Sarawak Department of Forestry, Malaysia
NOAA, 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 global
warming.
3) A warming of 1ºC over the next 50yrs is “dangerous”.
4) Global temperatures were 5ºC colder during the Last
Glacial Maximum.
5) Hurricane Katrina was caused by global warming.
Which of the following are scientific statements?
1) Reducing CO2 emissions would hurt the economy.
2) Improved technology is the best way to slow global
warming.
3) A warming of 1ºC over the next 50yrs is “dangerous”.
4) Global temperatures were 5ºC colder during the Last
Glacial 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 simulate
20th century temperature trends (solar and volcanic minor
players).
Ice core climate and CO2 records
tiny gas bubbles
in the ice trap
ancient air samples
#2
Atmospheric CO2 and temperature over
the past 650 thousand years
CO2 and temperature
are closely linked
on geologic timescales
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
#3
The “Hockey Stick”
Key Points:
error bars increase as you go back in time
natural variability accounts for <0.5ºC over the last millennium
late 20th century temperature trend is unprecedentedin 1,000 years
#4
Solar and volcanic only
anthropogenic only
Intergovernmental
Panel on
Climate Change
(IPCC) 2001
natural & anthropogenic
The uncertain climate future
Range of scenarios:
Strict international agreements  CO2 at 600ppm by 2100
Mid-ground  850ppm by 2100
Business as usual  1200ppm by 2100
*390ppm today
280ppm 1800
IPCC AR4, 2007
but we need to know about
regional climate changes, and specifically
about regional precipitation changes
white = models disagree
color = models mostly agree
stippled = models agree
IPCC AR4, 2007
Research Goal: constrain tropical Pacific response to anthropogenic
global warming
Approach: reconstruct tropical Pacific climate at high-resolution for
the last millennium
El Niño Temperature
WHY?
“El Niño-Southern Oscillation”
(ENSO)
ENSO is a climate pattern in the
tropical Pacific which arises
from coupled interactions between
the atmosphere and ocean
El Niño Precipitation
ENSO impacts global climate every
2-7 years (huge impact on rainfall)
Dai and Wigley, 2000
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
Palmyra
1997-?
Fanning
2005-?
Christmas
1998-?
Corals: The geologic record of El Niño
Living Porites corals provide records
for the last 200 years
Fossil Porites corals enable us to
extend the record back many centuries
CORALS from the tropical Pacific
record El Niño’s in the geochemistry
of their skeletons
Palmyra coral oxygen isotopes vs. tropical Pacific SST
3
R = -0 .6 6
S T A n o m o ly (°C )
2
1
0
-1
Overlapping fossil corals: ancient El Niño events
Good reproducibility between coral geochemical records
increases 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 millennium
2) 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 have
strong visual, intuitive
appeal.
Their dismissal by a
large fraction of the climate
science community
hasn’t helped cement
their contributions, nor
utilize their full potential.
But this is changing …
The Pyramid of
Climate Consensus
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?)
Is anthropogenic CO2 warming the planet?
yes or no?
The Pyramid of
Climate Consensus
What should
be done about it?
What are the impacts of AGW?
(what? how much? by when?)
Is anthropogenic CO2 warming the planet?
yes or no?
How climate scientists can help
1)Appreciate the differences between climate science and
climate policy.
climate
scientist
??
policy
advocate
How climate scientists can help
1)Appreciate the differences between climate science and
climate policy.
climate
policy
??
scientist
advocate
2)Denounce sloppy science from both extremes of the
climate science debate. (climate skeptics, IPCC WG2)
How climate scientists can help
1)Appreciate the differences between climate science and
climate policy.
climate
policy
??
scientist
advocate
2)Denounce sloppy science from both extremes of the
climate science debate. (climate skeptics, IPCC WG2)
3)Publish data in data repositories with new standards for
climate metadata.
How climate scientists can help
1) Appreciate the differences between climate science and
climate policy.
climate
policy
??
scientist
advocate
2) Denounce sloppy science from both extremes of the
climate science debate. (climate skeptics, IPCC WG2)
3) Publish data in data repositories with new standards for
climate metadata.
4) Engage public, policymakers, skeptics in science of climate
change, with the pyramid of consensus always in mind.
How climate scientists can help
1) Appreciate the differences between climate science and
climate policy.
climate
policy
??
scientist
advocate
2) Denounce sloppy science from both extremes of the
climate science debate. (climate skeptics, IPCC WG2)
3) Publish data in data repositories with new standards for
climate metadata.
4) Engage public, policymakers, skeptics in science of climate
change, with the pyramid of consensus always in mind.
5) Remove existing structural impediments to outreach, consider
creating new structures to aid outreach. (Beyond RC?)
Some thoughts on the IPCC
from Judy Curry
As the IPCC turns 22, needs to address the question:
“What do I want to be when I grow up?”