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So what is a GCM?. GCMs. General Circulation Models Atmospheric GCMs Ocean Representations Specified Sea Surface Temperatures (SSTs) Simple Ocean Models (Slab) Coupled Ocean-Atmos GCMs. GCMs. Global Climate Models Qflux Mixed-Layer Oceans Coupled Dynamic Oceans Sea Ice

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GCMs

  • General Circulation Models

  • Atmospheric GCMs

  • Ocean Representations

  • Specified Sea Surface Temperatures (SSTs)

  • Simple Ocean Models (Slab)

  • Coupled Ocean-Atmos GCMs


GCMs

  • Global Climate Models

    • Qflux Mixed-Layer Oceans

  • Coupled Dynamic Oceans

  • Sea Ice

  • Vegetation (physical)

  • Ground Hydrology (buckets)

  • Middle and Upper Atmosphere

  • Passive Tracer Transports


GCMs

  • Earth System Models

  • Coupled and Dynamic Everything

  • Physiological Vegetation

    • Dynamic Ice Sheets

    • Carbon Cycle Modeling


GCMs

  • Off-Line or Nested Models

  • Regional Climate Models

  • Crop Models

  • Economic Models

  • Sediment Transport Models

  • Watershed Models

  • .

  • .

  • .



Unix Scripts

FORTRAN Code

SnowballEarth_Sim2.R Model II 8/24/2000Owner: Dr. Mark Chandler, chandler@giss.nasa.govGroup: Paleoclimate GroupThis experiment simulates a time period approximately 600 million years ago.Object modules:MainC9DiagC9RadC9FFTC9UTILC9Data input files:7=G8X10_600Ma9=NOV1910.rsf_snowball15=O8X10_600Ma17=25=Modern_OceanTransports19=CD8X10_600Ma23=V8X10_600Ma26=Z8X101_600Ma21=RTAU.G25L1522=RPLK2529=Snowball_Earth_RegionsLabel and Namelist:Snowball_sim2 (Snowball Earth Experiment: 600 million years ago) &INPUTZ TAUI=10176.,IYEAR=1900, KOCEAN=1, SRCOR=.95485638151, S0X=1.,CO2=.31746031746031, USET=0.,TAUE=35040., USESLP=-12., ISTART=3,KCOPY=2,NDPRNT=-1,TAUE=10177.,TAUP=95616., &END

C**** INITIALIZE SOME ARRAYS AT THE BEGINNING OF SPECIFIED DAYS 82.

fName = './prt/'//JMNTH0(1:3)//CYEAR//'.prt'//LABEL1(1:LLAB1)

IF(JDAY.NE.32) GO TO 294

c ** END (CHANGED)

JEQ=1+JM/2 83.01

DO 292 J=JEQ,JM 83.02

DO 292 I=1,IM 83.03

292 TSFREZ(I,J,1)=JDAY 83.04

JEQM1=JEQ-1 83.05

DO 293 J=1,JEQM1 83.06

DO 293 I=1,IM 83.07

293 TSFREZ(I,J,2)=JDAY 83.08

GO TO 296 83.09

294 IF(JDAY.NE.213) GO TO 296 83.1

JEQM1=JM/2 83.11

DO 295 J=1,JEQM1 83.12

DO 295 I=1,IM 83.13

295 TSFREZ(I,J,1)=JDAY 83.14

C**** INITIALIZE SOME ARRAYS AT THE BEGINNING OF EACH DAY 83.4

296 DO 297 J=1,JM 83.5

DO 297 I=1,IM 83.51

TDIURN(I,J,1)=1000. 83.511

TDIURN(I,J,2)=-1000. 83.512

TDIURN(I,J,3)=1000. 83.513

TDIURN(I,J,4)=-1000. 83.514

TDIURN(I,J,5)=0. 83.52

TDIURN(I,J,6)=-1000. 83.521

PEARTH=FDATA(I,J,2)*(1.-FDATA(I,J,3)) 83.53

IF(PEARTH.GT.0.) GO TO 297 83.54

TSFREZ(I,J,1)=365. 83.55

TSFREZ(I,J,2)=365. 83.56

297 CONTINUE 83.57

C**** 84.

C**** INTEGRATE DYNAMIC TERMS 85.

C**** 86.

300 MODD5D=MOD(NSTEP,NDA5D) 87.

IF(MODD5D.EQ.0) CALL DIAG5A (2,0) 88.


Atmosphere

Oceans

Ice Sheets

Sea Ice

Vegetation

A Computer Simulation of the Earth System


Cartesian grid general circulation models

The NASA/GISS Family of GCMs:

Cartesian Grid General Circulation Models

(Henderson-Sellers, 1985)

(Hansen et al., 1983)


Primitive equations in a gcm
Primitive Equations in a GCM

Conservation Equations Conservation of Energy Conservation of Mass Conservation of Moisture Conservation of MomentumEquation of State


Key state variables in a gcm handled by primitive equations
Key State Variables in a GCMhandled by primitive equations

  • T, TemperatureP, PressureQ, Specific Humidity (Atm. Water Vapor)U, East-West WindsV, North-South Winds



Linking parameterizations and primitive equations
Linking Parameterizations andPrimitive Equations


8°X 10°

4°X 5°

1980’s

1990’s

2°X 2.5°

2000’s

Atmospheric

Global Climate Model

Grid Resolutions


The gcm family tree

Paul N. Edwards

Univ. of Michigan, ca. 2000

The GCM Family Tree

GFDL

NCAR

GISS


Relevant to Science

Why use GCMs?

Relevant to Society


The “Keeling Curve”: CO2 rise during the 20th Century

380

360

340

Carbon Dioxide (parts per million)

320

300

Mauna Loa Observatory

280

1960

1970

1980

1990

2000

Year

Image Credit: NASA Earth Observatory


20th Century Trend of the

Dow Jones Industrials Average

Source: Yahoo!, Inc.


CAUSE

EFFECT

PROCESS

PROCESS

PROCESS

PROCESS

PROCESS

PROCESS


CAUSE

EFFECT

Recent Climate Change:

Observed Forcings and Observed Results.

Verification of models and

Analyze processes


21 st century global warming
21st Century Global Warming

Climate Simulations for IPCC 2007 Report

►Climate Model Sensitivity 2.0-5.0ºC for 2xCO2

(consistent with paleoclimate data & other models)

►Simulations Consistent with 1880-2003 Observations

Source: Hansen et al., to be submitted to J. Geophys. Res.



CAUSE

EFFECT

Future Climate Change:

Observed and Estimated Forcings

Unknown Results


Instantaneous

Doubling of CO2

Transient

Doubling of CO2



2050sChange in Surface Air Temperature

+2.33 °C


CAUSE

EFFECT

Past Climate Change:

Observed Results

Unknown Forcings


CO2 Through Earth History

Pliocene, 3mya


Middle Pliocene Sea Level Rise

B)

A)

Modern Shoreline

Pliocene Shoreline

A) Based upon marine stable isotope records, sequence stratigraphy, and ancient

shorelines, mid Pliocene sea level is estimated to be +25 m relative to today.

B) This image shows a section of the Orangeburg Scarp in Georgia, dated at 3.5-3.0 Ma.

The Orangeburg Scarp suggests a sea level 35±17m relative to today.


Pliocene temperature change 3 mya
Pliocene Temperature Change: 3 MYA

+2.13 °C

2050s

+2.33 °C


3 mya

2050s




Global Warming with Altered Ocean Circulation

CO2 Increase

+

0.8 OHT

Latitude

20% OHT Decrease

CO2 Increase

+

1 OHT

Latitude

0% OHT Change

CO2 Increase

+

1.2 OHT

Latitude

20% OHT Increase


Has it happened before?

The warming of the 1930s was more similar to a warming caused by

altered ocean heat transports than to greenhouse gas increases.

5-Year Running Mean

90N

3.0

60N

1.4

0.7

30N

0.3

0.1

°C

0.0

0 EQ

-0.1

-0.3

30S

-0.7

-1.4

60S

-3.0

90S

1880

1895

1910

1925

1940

1955

1970

1985

Year


Could it

happen again?

If the oceans respond in a manner similar to the mid-Pliocene warming then estimates of global warming would be altered significantly in some regions.

Regional changes in temperature associated with altered ocean circulation scenarios


Climate@Home

Simulation

Distribution

Simulation

Results Collection

Scientific

Community

GSFC

GISS

Langley

Personal

Computers

School

Labs

University

Clusters

DOE

NASA

NSF

EdGCM

Model E

EdGCM

Model E

EdGCM

Model E

GISS

Model E

GISS

Model E

GISS

Model E

Desktop Client Computing Resources

National Lab Supercomputing Resources

Primary Server

Perturbed Physics Ensembles

NASA MAP Climate Scientists


The Democratization of Global Climate Modeling

The EdGCM Cooperative Project

Columbia University and the University of Wisconsin-Madison

Support provided by:

NSF Paleoclimate Program and NASA High-Performance Computing Program



Responsibility for co 2 emissions and climate change
Responsibility for CO2 Emissions and Climate Change


Metrics for “Dangerous” Change

Extermination of Animal & Plant Species

1. Extinction of Polar and Alpine Species

2. Unsustainable Migration Rates

Ice Sheet Disintegration: Global Sea Level

1. Long-Term Change from Paleoclimate Data

2. Ice Sheet Response Time

Regional Climate Change

1. General Statement

2. Droughts/Floods


Status of CO2

Pre-industrial Amount: 280 ppm

Present Amount: 382 ppm

Maximum Allowable ≤ 450 ppm

Rate of Change: +2 ppm/year (and growing)

 Maximum Will Be Exceeded!

 ‘Geoengineering’ Probably Needed


Methods to Reduce CO2 Emissions

1.Energy Efficiency & Conservation

More Efficient Technology

Life Style Changes

2.Renewable & CO2-Free Energy

Hydro

Solar, Wind, Geothermal

Nuclear

3.CO2 Capture & Sequestration

 No Silver Bullet

 All Three are Essential


Gcm initial condition data sets

DEC

DEC

JAN

SST

JAN

SEA-ICE

GCM Initial Condition Data Sets

TOPO-

GRAPHY

SEA

LEVEL

VEG

ATMOSPHERE:

TEMPERATURE

PRESSURE

WATER VAPOR


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