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

IPCC Consensus process is Conservative by Nature

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

A Key Observation

Warming since 1850 c/o Gian-Kasper Plattner, 10-8-13

Preponderance of Evidence

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

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

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

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

Pinatubo Ash Eruption

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

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

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

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

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

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

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

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

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

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)

Basic Approach double CO2 and model planetary response

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

An Inconvenient Coincidence

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

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 https://www.youtube.com/watch?v=otRPf3rRwZk Fg = Fo