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 % of climate scientists believe that CO 2 is warming the planet? 1.Theory predicts that increasing atmospheric CO 2 should warm the planet. 2.Geologic evidence links CO 2 and temperature in the past. 3.The warming is unprecedented in the most recent centuries (dwarfs natural variability). 4.Climate models show that rising CO 2 is necessary to simulate 20 th century temperature trends (solar and volcanic minor players).

Ice core climate and CO 2 records tiny gas bubbles in the ice trap ancient air samples

Atmospheric CO 2 and temperature over the past 650 thousand years CO 2 and temperature are closely linked on 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 time natural variability accounts for <0.5ºC over the last millennium late 20 th century temperature trend is unprecedentedin 1,000 years #3

Intergovernmental Panel on Climate Change (IPCC) 2001 #4 Solar and volcanic only anthropogenic only natural & anthropogenic

The uncertain climate future Range of scenarios: Strict international agreements  CO 2 at 600ppm by 2100*390ppm today Mid-ground  850ppm by ppm 1800 Business 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 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 Dai and Wigley, 2000 El Niño Temperature El Niño Precipitation 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 ENSO impacts global climate every 2-7 years (huge impact on rainfall)

Research Questions How has the tropical Pacific climate system responded to CO 2 forcing? What aspects of present tropical Pacific climate are unprecedented? compare last several decades to recent centuries Fanning 2005-? Palmyra 1997-? Christmas 1998-?

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 records for the last 200 years Fossil Porites corals enable us to extend the record back many centuries

Palmyra coral oxygen isotopes vs. tropical Pacific SST

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 20 th 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 …

Is anthropogenic CO 2 warming the planet? yes or no? The Pyramid of Climate Consensus

Is anthropogenic CO 2 warming the planet? yes or no? What are the impacts of AGW? (what? how much? by when?) The Pyramid of Climate Consensus

The Pyramid of Climate Consensus Is anthropogenic CO 2 warming the planet? yes or no? 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. climate scientist policy advocate ??

How climate scientists can help 1)Appreciate the differences between climate science and climate policy. 2)Denounce sloppy science from both extremes of the climate science debate. (climate skeptics, IPCC WG2) climate scientist policy advocate ??

How climate scientists can help 1)Appreciate the differences between climate science and climate policy. 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. climate scientist policy advocate ??

How climate scientists can help 1)Appreciate the differences between climate science and climate policy. 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. climate scientist policy advocate ??

How climate scientists can help 1)Appreciate the differences between climate science and climate policy. 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?) climate scientist policy advocate ??

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