Implicaciones metodológicas e inconsistencias de la Tercera Comunicación Nacional sobre Cambio Climático de Colombia

The National Communications on Climate Change (NCCC) are a mechanism for countries to report on their progress in mitigation and adaptation, and are a basis for climate change policy at the national level. Colombia has issued three NCCCs. The third CNCC presents a scenario that considers projections from various models included in the fifth phase of the Coupled Model Comparison Project (CMIP). This scenario is estimated as the average of the projections corresponding to the four Representative Concentration Pathways (RCPs) presented in the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. Each of these RCPs represents a greenhouse gas (GHG) concentration trajectory for a particular scenario of population, economic and technological growth, leading to a possible trajectory of climate system evolution. Our article compares the projections presented in the Third CNCC with those obtained directly from the models used. Our results show that by using an average CPR, alternative scenarios that could be important in considering different possible futures are lost, negating the usefulness of proposing different GHG emission trajectories. Moreover, a comparison between the Second and Third CNCC shows opposite precipitation projections for different regions of the country. This is particularly important because the climate change scenario proposed in the Third CNCC is a reference scenario for climate change decision-making at the national level.