climate literacy session: causes peter coombe august 5, 2015
TRANSCRIPT
Climate Literacy
Session: Causes
Peter CoombeAugust 5, 2015
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Causes: Anthropogenic Climate Change
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The “Keeling Curve”
1. Energy from the Sun – Radiation2. Albedo – How Much Reflectivity3. Atmospheric Composition
SUN
Mercury Venus MarsEarth
What Factors Influence Climate?
1. Energy from the Sun – Radiation2. Albedo – How Much Reflectivity3. Atmospheric Composition
Mercury Venus MarsEarth
What Factors Influence Climate?
Equilibrium T (°F)
Actual Surface T (°F)
324
35614
847-2
59
-67-45
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IceOceanLand
Sub-surface Earth
Atmosphere
Heat fromSurface
About 31%reflected into space
69% absorbed at surface
Solarradiation
Earth’s Climate System
Greenhouse Gases
59°F
Sun
Land
Sub-surface
AtmosphereHeat fromSurface
Extract and burn fossil fuelsadd CO2 to atmosphere
More greenhouse gases, more radiation absorbed
Additional heat retained, higher surface temperatures
Earth’s Climate SystemEnhanced Greenhouse Effect
“Anthropogenic Climate Change”
Ocean Ice
More greenhouse gases, more
radiation absorbed
Compound
Formula
ContributionApprox. (%)
Water vapor and Clouds H2O
50% Water Vapor 25% Clouds
Carbon dioxide CO2 20%
Methane CH4 4% Other GHGs 1%
When ranked by their direct contribution to the greenhouse effect, the most
important GHGs are:
More greenhouse gases, more
radiation absorbed
Compound
Formula
Global Warming Potential- (GWP)
Carbon dioxide CO2 1
Methane CH4 25
Nitrous oxide N2O 298
Chlorofluorocarbons (CFCs) 1,000- 10,000s
Greenhouse GasesAnthropogenic Sources:
GWP is used to calculate Carbon Dioxide Equivalents [CO2e] for emissions reporting
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Changes in GHG Concentrations
Image created by Robert A. Rohde
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CO2 Changes since the Industrial Revolution
Image created by Robert A. Rohde
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Visualization of the history of CO2
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So we’ve reached 400 ppm.… Now what happens?
https://scripps.ucsd.edu/programs/keelingcurve/
Carbon Dioxide (CO2)
Absorption
Emission
Greenhouse Gases trap heat because they absorb radiation in the infrared range, according to specific bond geometries and vibrational modes (ex CO2 below)
IPCC(2007)
Warming from increasesin greenhouse gases
www.ncdc.noaa.gov
What do models tell us?
Meehl et al. (2004)
The dominant mechanisms (to which recent climate change has been attributed) are anthropogenic:
• Increasing atmospheric concentrations of greenhouse gases• Global changes to land surface, such as deforestation• Increasing atmospheric concentrations of aerosols
What about natural mechanisms?
• Changes in solar activity • Volcanic activity
What do models tell us?
Meehl et al. (2004)
Global Temperature and CO2 CO2 level
today > 400 ppm
Take Home Points
• A basic physical understanding of the climate system: greenhouse gas concentrations have increased and their warming properties are well-established.
• Historical estimates of past climate changes suggest that the recent changes in global surface temperature are unusual.
• Computer-based climate models are unable to replicate the observed warming unless human greenhouse gas emissions are included.