Several changes have been made to GCAM since the last release version (v4.4). The key updates are:
The sections below provide short summaries of all changes.
GCAM5.1 represents demand for water by sector and technology, including both water withdrawals and water consumption.
GCAM5.1 switches land use regions from climatically defined agro-ecological zones (AEZs) developed by the GTAP group to water basin-defined geographic land units (GLUs), developed in house.
GCAM5.1 endogenizes yields and fertilizer application rates, making these levels each a function of crop prices, production costs, and other contributors to modeled land profit rates. This is achieved by nesting four different crop technologies within the logit structure (irrigated/hi fertilizer, irrigated/lo fertilizer, rainfed/hi fertilizer, rainfed/lo fertilizer).
GCAM5.1 includes the ability to model five alternative Shared Socioeconomic Pathways, as described in Calvin et al. (2017).
GCAM5.1 includes Hector v2.0, which (1) adds a better representation of oceanic heat uptake, (2) simulates the temperature response from volcanic forcings in the historical period, and (3) addresses odd results found in the impulse response experiments.
GCAM converts the system for processing GCAM inputs into an R package using clean, consistent, well-documented code. The data system is available on github.
GCAM5.1 updates the land use and land cover history to use outputs from Moirai.