The Global Change Assessment Model (GCAM)
JAE EDMONDS FOR THE GCAM TEAM

Asia Integrated Modeling Meeting
Tsukuba, Japan
23 January 2015

GCAM evolution has always been
PROBLEM DRIVEN and linked to Energy
AND Earth System Science.
GCAM is evolving toaddress a new set ofproblems: climate impacts
on the interconnected energy,
water and land system in aworld that may or may not be
simultaneously mitigating
GHG emissions, at temporal,
spatial, and sectoral scales
appropriate to science anddecision-support problems.
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GCAM Is Evolving Rapidly
Tackling new problems such as climate impacts on theenergy-water-land nexus means that GCAM has evolved to:

Produce output products, at appropriate space, time,sectoral, and technological resolutions.
New problems are emerging that require tools that produce outputs
at time scales ranging from days to decades.
Spatial scales ranging from global to local

Employ high-resolution data inputs as well as those with
global coverage;
Reconcile and transform data to appropriate analyticalscales,Employ interoperable modules and models to facilitate
research at problem-appropriate scales.
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GCAM TODAY

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The Core Element of the Global
Change Assessment Model (GCAM)
GCAM is a global integrated assessment
model, with regional and localresolutions

EnergyGCAM links Economic, Energy, Landuse, Water and Climate systems

LandClimate

WaterEconomy

Technology-rich model
Emissions of 16 greenhouse gases andshort-lived species: CO2, CH4, N2O,
halocarbons, carbonaceous aerosols,reactive gases, sulfur dioxide. At global,regional and 0.5° resolution.
Land use, land use change, and land
cover. At global, regional and 0.5°resolution.

Runs through 2100 in 5-year time-steps.

GCAM’s Adaptive Spatial Resolution50-State Energy
Economy Regions
32 Energy
EconomyRegions

283 LandRegions
Grid-Level Water,Energy, Land, andEmissions

233 Water
BasinsGCAM is a community model
GCAM has a large and growing community of users.
GCAM annual meeting brings users together to collaborate and network.

http://www.globalchange.umd.edu/models/gcam/download/‎

418 people hadreceived copies ofGCAM (@258
institutions, in 58
countries, on 7continents)

GCAM documentation: wiki.umd.edu/gcam/‎Recent Development: The First Version of a
New Community Climate Emulator-Hector• Fast-executing newly developed globalclimate and carbon cycle model• Open source and community oriented• Capable of replicating some outputs ofmore complex models• Being expanded to facilitate research onenergy-water-land interactions andintegrated impacts within GCAM

HECTORgraphicalinterface
User

Modular, opensource C++
codebase. Central
coupler enforces
message passingand unit checking.

Model or otherprogram

HECTOR
command-line
wrapperGCAM(or something else)

HECTOR
computational
core

Fast, flexible emulation CMIP5
global to biome-scale outputs

Adding sub-national detail to GCAM facilitates
coupling with sector models
To facilitate coupling with detailed sector
models, we have added subnational detail
to GCAM (version name: GCAM-USA):

Stand-alone GCAM with 32 Global
Geopolitical Regions

50-state (+DC) climate-dependentbuilding energy
50-state (+DC) electricity generation
mix
Increased spatial and technologicalresolution for agriculture and land use

Water supply and demand at majorwatershed scale
The rest of the model operates normally,
thus providing global constraints andcontext (i.e., GCAM-USA is GCAM)

GCAM-USA: Subnational Detail 9

GCAM-USA Electricity: Results
2050 Electricity supply mix in Gulf Coast states

The carbon policy has the largest
influence on electricity mix

Future GDP has alarge effect on total
supply/demand
Trade also importantin certain states

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Coupling to Other Models, e.g. the BEND Model,
allows research at finer space and time scales
The Building Energy Demand (BEND)
simulates climate-dependent building energy
demand at high spatial, temporal, andtechnological resolution
Combines‎DOE’s‎EnergyPlus model (forindividual buildings) with a geostatisticalanalysis of regional climate, population,and building types and technologies
Resolution as fine as 1/8 degree (~12 km);results can be aggregated to any geographicregion (e.g., utility zone)

Climate similar regions in the Eastern Interconnection

Uses GCAM input (population-driven floor
space growth, technology turnover) to drive
future building stock changes
Uses RESM or other hourly weather/climate
input (9 variables!) to simulate changes inbuilding energy demand
Can also be used to model demand response,
smart charging, etc.

Sample BEND output/validation for a single utility zone
11Electricity Operations Model (EOM)
Hourly Unit Commitment with zonal transmission constraints
Unique capability: Hourly climate-dependent capacity rating(can account for air temperature and cooling water availability)
Open source; Validated against PROMOD
Validation for Eastern Interconnection

Good agreement with PROMOD(Simulation: 1/4/2004-1/10/2004)

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Recent developments in representing land systems and processes

AGRICULTURE AND LAND USE

13Core GCAM land regions
While core GCAM has 283 AEZs, many problems require finer spatial
resolution

283 AEZ LandRegions
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GCAM land cover decisions occur at 283 region
resolution, but results are available at 0.05° resolution
Economic decisions about
land are made at a 283
region resolution globally (9regions in the USA).
However, land cover data isoutput at 0.05° x 0.05°
resolution.
Transition from economic
regions to spatial scaleconsiders factors likeproximity to existing
agricultural areas andconversion types.
We are expanding thismodeling to include land
suitability and protected
lands.

9 AgLU Economic Regions in the USA

Cropland area in 2005 at a 0.05° Resolution

Source: Tristram O. West, Yannick Le Page, Maoyi Huang, Julie Wolf, and Allison M. Thomson. 2014. Downscaling Global Land
Cover Projections from an Integrated Assessment Model for Use in Regional Analyses: Results and Evaluation for the US from2005 to 2095. Accepted for Publication in Environmental Research Letters.

As we develop and incorporate newcapability, we are evaluating its performance.
Correlation between crop PFT land cover in the native 2010 MODIS
land cover and the 2010 land GCAM RCP 4.5 was r2=0.98.
Correlation between the cropland difference maps representing only
those grid cells that changed, was r2=0.83.
Cropland
ChangeMODIS 2005MODIS 2010

Cropland
ChangeMODIS 2005GCAM 2010R2 = 0.83

Source: Tristram O. West, Yannick Le Page, Maoyi Huang, Julie Wolf, and Allison M. Thomson. 2014. Downscaling Global Land CoverProjections from an Integrated Assessment Model for Use in Regional Analyses: Results and Evaluation for the US from 2005 to 2095.
Accepted for Publication in Environmental Research Letters.

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GCAM has evolved to include intensificationand irrigation (a major fresh water demand)
Allocation between irrigated & rainfed depends on economics.
Profit rate for each will depend on yield, cost of production, and carbon price(if applicable)
Yields are higher for irrigated crops.
Costs are higher for irrigated crops.
Carbon implications are lower for irrigated crops.
Change in Cropland Area
from Reference

Change in Water Withdrawals
from Reference

2050

2050
00%

IRR
RFD%

−25

−50

−50
−75−100
Land
January 19,Expensive
2015

Expensive Water

Expensive Land

Expensive Water

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Hydrology using climate model outputs to assess stream-flow, river
routing, and river management to assess energy system impacts

GCAM NOW INCLUDES WATER

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GCAM Global Water Supplies
1. Renewable 233 basins global
 Macro-scale hydrologic model
emulates runoff and stream flow(1901-2100)
 Requires climate information fromGCMs as inputs

2. Non-renewable (fossil)
groundwater Depletable resources Supply curves by GCAM region
 Cost of groundwater pumping
increases with depth following theDesalination
work of Zhu et al., (2007)
water source

3. Desalinated water Constant cost per unit water

Sea
BrackishRiverWaste water
Pure
Brine
SUM

GlobalUS
Share Cost Share Cost(%) ($/m3) (%) ($/m3)
56%
17%
124%
0.6 51%
0.69%
0.6 26%0.66%
0.69%
0.65%0.6
7%0.60%0%
100% 0.824 100% 0.628

Gleick (1993)

Wangnick/GWI (2005)
Zhou & Tol (2005)

GCAM Global Water Demands
Technologically detailed
representation of water
demand sectors

(5)
(1)

(2,3)

(4)

Tracks water demands
for several sectors,
subsectors, andtechnologies
Tracks water demands
at various spatial scales(regions, state, agroecological zones)
Tracks both annual
withdrawal andconsumptive water use
Endogenously
incorporated in GCAM

(1) Hejazi et al. (2013). Hydrological Sciences Journal.
(2) Kyle et al. (2013). International Journal of Greenhouse Gas Control.
(3) Davies et al. (2013). Advances in Water Resources.
(4) Chaturvedi et al. (2013). Mitigation and Adaptation Strategies for Global Change.
(5) Hejazi et al. (2014). Technological Forecasting and Social Change

14 GCAM
Regions

151 AEZ
scale

US(50-state)Climate change will affect hydropower
generation
Application using HadCM3
Hydropower potential

Latin America

Positive values mean an increase in electricity
generation when impacts are considered21

Humans play a larger role in water scarcity
in 93% of the basins (89% of total land)
No policy (8.8 W/m2 by year 2100)

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Water demands and availability are now
reconciled in GCAM, i.e. Limits in water
availability have consequences.

Water Scarcity - 200523

Agricultural demands are most affected byscarcity when GCAM uses a shadow price

January 19, 201524

2050: Regional Changes in ECONOMICALLYEFFICIENT Crop Production with Water Limits by AEZ

CornRice

Wheat

Sugar Crops
January 19, 201525

FUTURE DIRECTIONS

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Looking to the Future
GCAM development will continue to be PROBLEM
DRIVEN—E.g. climate impacts on the energy-water-land nexus.

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Looking to the Future
GCAM development will continue to be PROBLEM
DRIVEN—E.g. climate impacts on the energy-water-land nexus.
High-resolution input data
Multiple sources
Reconciled data products
Multiple scales (appropriate to theproblem at hand)

GCAM model modules
Interoperable (appropriate to theproblem at hand)
Utilization of GCAM’s telescopic design
to examine problems at a variety ofresolutions—Space, Time, Sectors,
Technologies
Connection to infrastructure models
Energy, water, land physical andeconomic system closure.

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Looking to the Future
GCAM development will continue to be PROBLEM
DRIVEN—E.g. climate impacts on the energy-water-land nexus.
High-resolution input data
Multiple sources
Reconciled data products
Multiple scales (appropriate to theproblem at hand)

GCAM model modules
Interoperable (appropriate to theproblem at hand)
Utilization of GCAM’s telescopic design
to examine problems at a variety ofresolutions—Space, Time, Sectors,Technologies
Connection to infrastructure models
Energy, water, land physical andeconomic system closure.

GCAM’s unique contribution remains INTEGRATION—theprovision of insights from interactions between human andbiogeophysical systems that would not otherwise be available
from traditional independent disciplinary research alone.

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DISCUSSION

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