CE 401 Climate Change Science and Engineering modeling of climate change predictions from models 10 February 2011 team selection and project topic proposal (paragraph): due electronically exam on first half of class: new on website: IPCC chapter on models HW 7 due next Thursday now on the website

where are we in the syllabus: latest version always on website  

we have finished our discussion of the observations of climate – any questions?

POLICY MAKERS ARE INTERESTED IN THE FUTURE What will happen and what is the cause? Models are used to predict future climate How well do these models predict the past? Can we trust models to predict the future? Decisions are based on the models!

“this is a difficult subject; by long tradition the happy hunting ground for robust speculation, it suffers much because so few can separate fact from fancy” G.S. Callendar, 1961, climate modeler

 take a look at this climate model that you can run

source: IPCC 2007 The Climate System - very complicated

NASA Global Temperature Record source: GISS, 2010

temp anomaly relative to 1981 – 2010 average satellite based temperature anomaly, lower atmosphere 

factors that influence the radiative equilibrium of the Earth system average solar input: 342 w/m 2 what analysis did this cartoon come from ?

Model Testing and Evaluation atmosphere temperature radiation balance moisture and precipitation GHG and trace gases that drive chemistry ocean mean temp and salinity circulation features sea ice land surface snow cover land hydrology surface fluxes carbon variability – various meteorological and oceanic variables pacific decadal variability atlantic multidecadal variability’ El Nino Southern oscillation Madden-Julian Oscillation Quasi biennial oscillation monsoon variability

Figure 10.1

19 th century development of climate thoughts 1820 – Joseph Fourier – atmosphere retains heat radiation – got 255K, not 288K – GH effect Tyndall 1862 – H 2 O and CO 2 are opaque to heat rays (IR radiation) – shined light of different wavelengths through a glass cylinder and measured the transmission Arrhenius – 1896 – studied how changes in CO2 affect climate energy budget added up solar energy received, absorbed, and reflected idea of feedbacks – could not calculate crude physics  x2 [CO 2 ]  5 - 6°C temp change

What Goes into Atmospheric Climate Models mathematical equations to describe air motion and processes

physical process and parameters in an atmospheric model

What Goes into Atmospheric Climate Models mathematical equations to describe air motion and processes solar flux and its changes in time - Earth energy balance clouds - largest source of uncertainty in the models 61% of the globe on average is covered with clouds clouds both reflect energy (cooling) - feedbacks and serve as thermal blankets (warming) - feedbacks

schematic of physical processes associated with clouds clouds

Cloud radiation feedback

clouds reflect radiation back to space (albedo effect) - SW component trap IR radiation emitted by surface and lower trop (GHG effect) - LW component balance between these two components of cloud RF depends on macrophysical and microphysical cloud properties cloud feedbacks are the largest source of uncertainty in climate sensitivity in current models, clouds exert a net cooling effect (global RF < 0) > ~ half predict this, but not very convincing understanding physical processes in cloud feedbacks many types - lower boundary layer to deep convective clouds climate changes affect cloud types and radiative properties and radiative budgets

Model Estimates of Cloud Radiative Forcing with CO 2 Doubling

Global average change in T °C Houghton, 2001

What Goes into Atmospheric Climate Models mathematical equations to describe air motion and processes solar flux and its changes in time - Earth energy balance clouds - largest source of uncertainty in the models 61% of the globe on average is covered with clouds clouds both reflect energy (cooling) - feedbacks and serve as thermal blankets (warming) - feedbacks Earth reflectivity (land, sea/water, ice, snow, vegetation, etc.) thermodynamics of water and radiation chemistry and carbon cycle (atmosphere, oceans, biosphere) anthropogenic contributions (e.g. CO 2 increases with time, biomass burning, land use changes, etc.) aerosols which cool the atmosphere (natural and anthropogenic)

The atmospheric models must be coupled to: cryosphere biosphere oceans hydrosphere

Figure 4.1 components of the cryosphere and their time scales

cryosphere in terms of heat capacity, cryosphere is 2nd largest component of climate system physical properties affecting climate albedo (snow ~ 80-95%) latent heat associated with phase changes 75% of fresh water on Earth 10% of earth surface permanently covered with ice 7% of oceans on average covered with ice ice sheets of Greenland and Antarctica are main reservoirs capable of affecting sea level (Greenland 7.3 m, Antarctica 56.6 m) observations hampered before 1970 due to lack of satellite coverage glacier records go back to the 1600’s general retreat started around 1800 most important feedback is an increase in absorbed solar radiation as ice decreases first speculation (Brooks, 1925) for a polar melt feedback through albedo - was dismissed a “preposterous”

The atmospheric models must be coupled to: cryosphere biosphere oceans hydrosphere

Coupled atmosphere / ocean climate model Radiation Atmosphere: Density Motion Water Heat Exchange of: Momentum Water Ocean: Density (inc. Salinity) Motion Sea Ice Land example for ocean coupling

The atmospheric models must be coupled to: cryosphere biosphere oceans hydrosphere all on a high resolution global spatial grid of latitude and longitude and altitude as a function of time and incorporating the many feedback mechanisms that control atmospheric processes This is a huge job that requires experts from many fields and a large computer! There are a number of groups around the world working on this problem.

geographical grid for a model

19 levels in atmosphere 20 levels in ocean 2.5 lat 3.75 long km -5km Hadley Center model in England grid sizes

far = first assessment report IPCC, …, AR4 = assessment report 4 IPCC