T I N Y B U B B L E S Dr. Ed Brook, Oregon State University US Ice Drilling Program Greenhouse gases and climate information from polar ice cores
Three Messages • Humans have radically altered the amount of atmospheric greenhouse gases. • Greenhouse gases and climate are linked tightly in the record from ice cores. • We should expect warming, and sea level change, as greenhouse gas levels rise in the future.
Greenhouse Effect • Greenhouse gases are like a dam on a river. They increase the amount of heat in the atmosphere. • Major ones are water vapor, carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). • Without them earth would be -18˚C (0˚F) • The greenhouse effect is well understood. It was articulated in the early 1800’s by Joseph Fourier, but influenced by earlier work. C O O
The Changing Atmosphere“The Keeling Curve” • Modern measurement network is sophisticated and accurate http://www.esrl.noaa.gov/gmd/index.html • Systematic, direct measurements of greenhouse gases since the 1950’s at best. • What happened before that?
Polar Ice Cores WAIS Divide
Gas Extraction and Analysis Dry Extraction Crushing under vacuum Analysis by gas chromatography, laser spectroscopy, mass spectrometry Wet Extraction Melting under vacuum Analysis by gas chromatography, laser spectroscopy, mass spectrometry
Other Climate Information from Ice Cores Snowfall rate from layer thickness Temperature from stable isotopes (18O/16O, or 2H/1H) of ice Dust and aerosol content of atmosphere from chemical measurements Ice sheet elevation from total air content Pre-ice sheet history from basal material
WAIS Divide Camp, Antarctica http://www.waisdivide.unh.edu
The Human Impact: CO2 Industrial Revolution 40% Increase since 1700s
The Human Impact: Methane 240% Increase since 1700s
The Long View Dome C Ice Core - Antarctica Preindustrial Carbon Dioxide Preindustrial Methane Antarctic Temperature *Greenhouse Gases and Climate Change Together in Natural Cycles *No Precedent for Modern Greenhouse Gas Levels in last 800,0000 years
What Do These Data Tell us About Climate Change? • The modern atmosphere is very different than the previous 800,000 years. • Can’t explain the warm periods of the past without greenhouse gases. Gases always higher during warm periods. • The climate system works the way we think it does. In detail there are puzzles we spend lots of time on, but we understand that greenhouse gases cause warming. That warming is happening now, and will continue.
Global Temperatures and Sea Level • ~1˚C of warming since 1850. Likely that ~ 50% due to human activity • ~ 20 cm sea level change in the same time period • Decreases in snow cover and sea ice, and increases in drought
What about the Future? • Need models. They are good, but not perfect. • Models predict the last century pretty well. • Models respond to greenhouse gases in ways that are similar to what we see in the past. • Models don’t predict small-scale regional climate that well yet, but things are getting better.
What about the Future? • To predict the future we need to know how greenhouse gases will change. • How much will they increase?. A lot in the short run, but the range of “a lot” matters for prediction of climate. • Warming by 2100 is about 2-4˚C (4-7 ˚F) by most predictions. • Ice age to present warming was about 5˚C (9˚F). • Sea level is rising, and will continue to rise. The future amount is uncertain because how ice sheets behave is not known well. More than a meter by 2100 is possible.
Science Communication Lessons • You have to know the science! Really well! • You have to know the science! Really well! • Believe it or not, journalists, and politicians, and the public, are often really smart. Really. They can, and will, ask very hard questions, and expect answers. • Even when the questions are hard, they expect clear, simple, non-waffling answers. Practice these. • Know what your message is, and stick with it. Know your audience – figure them out beforehand. • Not everything scientists do is interesting to the public. In fact, most of what we think is cool is not interesting. That’s OK.
Science Communication Lessons • Is it OK to advocate for policy when talking about science of climate change?