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The science of climate change
Barry Lefer
University of Houston Department of Earth and Atmospheric Sciences
28 August 2013
UH Law Center
ANTCI, 2005
The science of climate change
ANTCI, 2005
I. Basics of Earth System Science
II. Climate change on geologic and historical time scales
III. Natural and anthropogenic causes of climate change
IV. Consequences of future climate change
All climate scientists agree that:
1) Earth’s average surface temperature has warmed by 0.7°C
since 1900, a conclusion based on direct measurements.
2) concentrations of CO2, CH4, N2O, and other greenhouse
gases have built up in the atmosphere over the last 100
years due to human activities.
The issue at the heart of the greenhouse debate is not whether
rising greenhouse gas levels have contributed to the
warming, but rather the magnitude of the amplification of
the warming by various feedbacks.
Climate change debate
Lefer 3 – i. basics
Climate vs. weather
Weather Climate
Shorter-term fluctuations Longer-Term Changes
Current atmospheric conditions Broad composite of average (or mean)
(e.g., temp, press, ws, wdir, condition of a region (e.g., temp, rain,
rainfall, etc.) snowfall, ice cover, winds)
Hours, Days, Weeks Years (and longer), Typically 30 yr ave.
Specific location for specific time Mean state of a specific region
(e.g., continent, ocean, or entire planet)
Lefer 4 – i. basics
What is a greenhouse gas?
globalwarmingart.com Lefer 5 – i. basics
Greenhouse gas warming
Earth’s Ave. Temperature = 15ºC
Natural GH Effect = 31ºC Warming
Ruddiman, 2008 Lefer 6 – i. basics
Greenhouse gas warming
Dessler, 2012 Lefer 6 – i. basics
Tone _ layer =476
5.67 ´10-84 = 302.7K
P
a= sT 4 = 476W m2 = Eout
Greenhouse gas warming
Lefer 6 – i. basics Dessler, 2012
Tone _ layer =714
5.67 ´10-84 = 335K = 62 Ctwo_layers
Some basic “reactions”
C6H12O6 + O2 → CO2 + H2O + heat
H2O + CO2 + sunlight → C6H12O6+ O2
C6H12O6 + O2 → CO2 + H2O + heat + NO + SO2
NO → NO2 → HNO3
SO2 → H2SO4 → sulfate aerosol
NOX + VOCs + sunlight → O3
CO2 + H2O = HCO3- + H2CO3
Lefer 7 – i. basics
Where does atmospheric CO2 go?
Ruddiman, 2008 Lefer 8 – i. basics
Geochemical reservoir and fluxes
At Steady-State Input = Output
Residence time = Reservoir size / Flux rate in (or out)
Ruddiman, 2008
Global Carbon Cycle
Lefer 10b – i. basics GLOBE, 2007
8.3 Pg C
2011
How long is CO2 in the atmosphere?
http://www.globalwarmingart.com/images/4/48/Carbon_Dioxide_Residence_Time.png Lefer 9 – i. basics
CO2 lifetime in the atm-ocean system
http://www.globalwarmingart.com/images/4/48/Carbon_Dioxide_Residence_Time.png Lefer 10 – i. basics
Climate system response
Ruddiman, 2008 Lefer 11 – i. basics
Response times of climate system components
Ruddiman, 2008 Lefer 12 – i. basics
Ruddiman, 2008 Lefer 13 – i. basics
Albedo-temperature feedback
Source: NASA Lefer 14 – i. basics
Albedo-temperature feedback
Albedo-temperature feedback
Source: NASA Lefer 15 – i. basics
Another positive feedback
Ruddiman, 2008 Lefer 16 – i. basics
Positive and negative feedbacks
Ruddiman, 2008 Lefer 17 – i. basics
Time scales of climate change
Ruddiman, 2008 Lefer 18 – ii. past climates
Ocean sediment core record
GlobalWarming Art (t), Ruddiman, 2008 (b) Lefer 19 – ii. past climates
Coring Earth’s ice sheets
Lefer 20 – ii. past climates Twickler – GISP2 SMO (1994)
Bubbles trapped in ice core
EPICA (2004) Lefer 20 – ii. past climates
Ice core proxy T, CO2, dust record
GlobalWarmingArt.com Lefer 21 – ii. past climates
Atmospheric CO2 measurement record
Lefer 23 – iii. natural & anthro cc
Anthropogenic CO2
Ruddiman, 2008 Lefer 24 – iii. natural & anthro cc
GlobalWarmingArt Lefer 25 – iii. natural & anthro cc
Anthropogenic CO2
Global Temperature Anomaly
Lefer 26 – iii. natural & anthro cc NASA GISS
Global Temperature Anomaly
Lefer 26 – iii. natural & anthro cc NASA GISS
Lefer 27 – iii. natural & anthro cc NASA GISS
Lefer 28 – iii. natural & anthro cc NASA GISS
Global Temperature Anomaly - April 2013
Volcanic cooling and El Niño warming
Ruddiman, 2001 Lefer 29 – iii. natural & anthro cc
Natural warming and greenhouse effects
Ruddiman, 2008 Lefer 31 – iii. natural & anthro cc
Modeling climate change attribution
Lefer 32 – iii. natural & anthro cc http://www.globalwarmingart.com/
Lefer 33 – iii. natural & anthro cc
Natural temperature changes
(<0.07 ˚ C)
Ruddiman, 2008
Natural interannual variability
Lefer 34 – iii. natural & anthro cc Science, 2010
Apple Stock Price – June 2013
Lefer 34 – iii. natural & anthro cc NASADAQ, 2013
Apple Stock Price – today
Lefer 34 – iii. natural & anthro cc NASDAQ, 2013
Apple Stock Price – Past Year
Lefer 34 – iii. natural & anthro cc NASDAQ, 2013
Apple Stock Price ~ 30 years
Lefer 34 – iii. natural & anthro cc NASDAQ, 2013
150 0.0450.012 100 0.0740.018
50 0.1280.026
25 0.1770.052 Period Rate
Years /decade
Kevin Trenberth, 2008
Rate of global temperature rise
Lefer 35 – iv. future cc
Radiative forcing of recent warming
Ruddiman, 2008 Lefer 36
Ruddiman, 2008 Lefer 37 – iv. future cc
Response to abrupt CO2 and SO2 emissions?
Ruddiman, 2008 Lefer 38 – iv. future cc
Response to abrupt CO2 and SO2 emissions?
Response to abrupt CO2 and SO2 emissions?
Ruddiman, 2008 Lefer 39 – iv. future cc
A future global temperature forecast
Science, 2010 Lefer 40 – iv. future cc
http://www.globalwarmingart.com/ Lefer 41 – iv. future cc
Another future global temperature forecast
Projected impacts of climate change
IPCC, 2007 Lefer42 – iv. future cc
Questions? Thank you.
Beals, 2008 Barry Lefer University of Houston
Department of Earth and Atmospheric Sciences [email protected]
