1. IPCC Climate Change Report
Moving Towards Consensus
Based on real world data

2. IPCC Consensus process is Conservative by Nature

3. The most Recent (2013) IPCC report is, by far
The most Recent (2013) IPCC report is, by far. The most comprehensive compared to the previous 4
Climate Change 2013
FAR 1990
11 Chapters
SAR 1995
11 Chapters
TAR 2001
14 Chapters
AR4 2007
11 Chapters
AR5 2013
14 Chapters     
observations  
paleoclimate    
sea level 
clouds  
carbon cycle   
regional change

4. A Key Observation

5. Warming since 1850
c/o Gian-Kasper Plattner,

6. Preponderance of Evidence

7. Climate Modeling Evolution
We have the Sun, some Rain and some CO2 pollution, that’s it

8. Climate Modeling Evolution
Now we add in Clouds, the land surface, and ice reflectivity

9. Climate Modeling Evolution
In the First Assessment Report (FAR – 1990) the Ocean as CO2 sink was now added in

10. Climate Modeling Evolution
By the mid 1990s sulfur emissions from volcanoes and/or industry were added as cooling agents (this is because of Pinatubo)) and the role of surface ocean current transport was more strongly considered

11. Pinatubo Ash Eruption

12. Climate Modeling Evolution
By 2001 aerosol scattering (very complicated) is now incorporated as is deep ocean transport, the actual carbon cycle and the role that rivers play in the hydrological cycle

13. Climate Modeling Evolution
Finally atmospheric chemistry is considered in the 2007 report along with reflectivity changes on the Earth due to changing vegetation patterns

14. Much better grid resolution for climate data is also achieved in this process, but its still not fine enough to even include CLOUDS!

15. Data-Model Comparisons
Models constructed to simulate Modern circulation
Changes based on Earth History inserted in model
Climate output compared with observations

16. One-Dimensional Models
Simplified representation of of entire planet
Model driven by global mean incoming solar radiation and albedo
Single vertical column of air divided into layers
Each layer contains important constituents (dust, greenhouse gases, etc)
Layers exchange only vertically

17. Two-Dimensional Models
Multi-layered atmosphere coupled with Earth’s physical properties averaged by latitude
Allows simulations of climatic processes that vary with latitude
Angle of incoming solar radiation
Albedo of Earth’s surface
Heat capacity changes

18. Three-Dimensional Models - GCM
3-D representation of Earth’s surface and atmosphere
Most sophisticated attempt to simulate the climate system
3-D model based on fundamental laws of physics:
Conservation of energy
Conservation of momentum
Conservation of mass
Ideal Gas Law

19. Model Resolution
Can’t image New Zealand, for example – (2° lat x 3° long) – this deficiency matters!

20. Steady State Tub
If flux of tracer into and out of reservoir are equal, the system is at steady state

21. Residence Time Time it takes for tracer to pass through tub
Residence time = reservoir size/flux
Residence time of tracer typically > mixing time of the ocean (1500 y)
In this way, the oceans are an enormous buffer (on short time scales)

22. Basic Approach double CO2 and model planetary response

23. Convolution of positive and negative forcings are what we observe.
GHG produces the net positive here

24. An Inconvenient Coincidence

25. Equilibrium Temperature
Planet radiates as a blackbody in TE with incoming solar radiation:
A = Albedo; L = 1370 watts per sq meter
T = 278(1-A)4
T = 255K for A=0.32
This is not the right answer compared to observations

26. The Role of the Atmosphere
Fo = incident flux
Ts = transmission % incoming
Tt = transmission % outgoing
Fg = Flux from ground
Fa = Flux from the atmosphere.
Fo = Fa + TtFg top of atmosphere equilibrium
Let Fa = Fo –TtFg
Fg = Fa + TsFo outgoing ground equilibrium
Fg = Fo