Ratcheting of climate pledges needed to limit peak global warming – Nature.com

by | Nov 10, 2022 | Climate Change

The Global Change Analysis ModelGCAM is an open-source model developed and maintained at the Pacific Northwest National Laboratory’s Joint Global Change Research Institute. In this study, we use the version of the GCAM (v.5.3) used in ref. 5 and available in a public repository55. The full documentation of the model is available at the GCAM documentation page (http://jgcri.github.io/gcam-doc/) and the description here is a summary of the online documentation and based on refs. 5,56,57,58,59.GCAM includes representations of five systems: economy, energy, agriculture and land-use, water and climate in 32 geopolitical regions across the globe and the associated land allocation, water use and agriculture production across 384 land subregions and 235 water basins. GCAM operates in 5-year time-steps from 2015 (calibration year) to 2100 by solving for the equilibrium prices and quantities of various energy, agricultural, water, land-use and GHG markets in each time period and in each region. GCAM is a dynamic recursive model. Hence, solutions for each modelling period only depend on conditions in the last modelling period. Outcomes of GCAM are driven by exogenous assumptions about population growth, labour participation rates and labour productivity in the 32 geopolitical regions, along with representations of resources, technologies and policy. GCAM tracks emissions of 24 gases, including GHGs, short-lived species and ozone precursors, endogenously based on the resulting energy, agriculture and land-use systems as discussed in the following subsections.The GCAM energy system contains representations of fossil resources (coal, oil and gas), uranium and renewable sources (wind, solar, geothermal, hydro and biomass and traditional biomass) along with processes that transform these resources to final energy carriers (electricity generation, refining, hydrogen production, gas processing and district heat), which are ultimately used to deliver goods and services demanded by end-use sectors (residential buildings, commercial buildings, transportation and industry). Each of the sectors in GCAM include technological detail. For example, the electricity generation sector includes several different technology options to convert coal to electricity such as pulverized coal with and without carbon capture and storage (CCS) and coal integrated gasification combined cycle (IGCC) with and without CCS. In every sector within GCAM, individual technologies compete for market share on the basis of the levelized cost of a technology. The cost of a technology in any period depends on (1) its exogenously specified non-energy cost, (2) its endogenously calculated fuel cost and (3) any cost of emissions, as determined by the climate policy. The first term, non-energy cost, represents capital, fixed and variable operation and maintenance costs incurred over the lifetime of the equipment (except for fuel or electricity costs), expressed per unit of output. For example, the non-energy cost of coal-fired power plant is calculated as the sum of overnight capital cost (amortized using a capital recovery factor and converted to dollars per unit of energy output by applying a capacity factor), fixed and variable operations and maintenance costs. The second term, fuel or electricity cost, depends on the specified efficiency of the technolog …

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