Scientific consensus on climate changeThere is a strong scientific consensus that the Earth is warming and that this warming is mainly caused by human activities. This consensus is supported by various studies of scientists' opinions and by position statements of scientific organizations, many of which explicitly agree with the Intergovernmental Panel on Climate Change (IPCC) synthesis reports. Nearly all actively publishing climate scientists say humans are causing climate change. Surveys of the scientific literature are another way to measure scientific consensus.
General circulation modelA general circulation model (GCM) is a type of climate model. It employs a mathematical model of the general circulation of a planetary atmosphere or ocean. It uses the Navier–Stokes equations on a rotating sphere with thermodynamic terms for various energy sources (radiation, latent heat). These equations are the basis for computer programs used to simulate the Earth's atmosphere or oceans. Atmospheric and oceanic GCMs (AGCM and OGCM) are key components along with sea ice and land-surface components.
Climate modelNumerical climate models use quantitative methods to simulate the interactions of the important drivers of climate, including atmosphere, oceans, land surface and ice. They are used for a variety of purposes from study of the dynamics of the climate system to projections of future climate. Climate models may also be qualitative (i.e. not numerical) models and also narratives, largely descriptive, of possible futures.
Ice–albedo feedbackIce–albedo feedback is a positive feedback climate process where a change in the area of ice caps, glaciers, and sea ice alters the albedo and surface temperature of a planet. Ice is very reflective, therefore it reflects far more solar energy back to space than the other types of land area or open water. Ice–albedo feedback plays an important role in global climate change. For instance, at higher latitudes, warmer temperatures melt the ice sheets.
Climate justiceClimate justice is a concept that addresses the just division, fair sharing, and equitable distribution of the burdens of climate change and its mitigation and responsibilities to deal with climate change. It has been described as encompassing "a set of rights and obligations, which corporations, individuals and governments have towards those vulnerable people who will be in a way significantly disproportionately affected by climate change.
Climate riskClimate risk refers to risk assessments based on formal analysis of the consequences, likelihoods and responses to the impacts of climate change and how societal constraints shape adaptation options. Common approaches to risk assessment and risk management strategies based on natural hazards have been applied to climate change impacts although there are distinct differences. Based on a climate system that is no longer staying within a stationary range of extremes, climate change impacts are anticipated to increase for the coming decades despite mitigation efforts.
Coupled Model Intercomparison ProjectIn climatology, the Coupled Model Intercomparison Project (CMIP) is a collaborative framework designed to improve knowledge of climate change. It was organized in 1995 by the Working Group on Coupled Modelling (WGCM) of the World Climate Research Programme (WCRP). It is developed in phases to foster the climate model improvements but also to support national and international assessments of climate change. A related project is the Atmospheric Model Intercomparison Project (AMIP) for global coupled ocean-atmosphere general circulation models (GCMs).
Arctic methane emissionsArctic methane release is the release of methane from seas and soils in permafrost regions of the Arctic. While it is a long-term natural process, methane release is exacerbated by global warming. This results in a positive feedback cycle, as methane is itself a powerful greenhouse gas. The Arctic region is one of the many natural sources of the greenhouse gas methane. Global warming could potentially accelerate its release, due to both release of methane from existing stores, and from methanogenesis in rotting biomass.
Economic impacts of climate changeThe economic impacts of climate change vary geographically and are difficult to forecast exactly. Researchers have warned that current economic forecasts may seriously underestimate the effects of climate change, and point to the need for new models that give a more accurate picture of potential damages. Nevertheless, one 2018 study found that potential global economic gains if countries implement mitigation strategies to comply with the 2 °C target set at the Paris Agreement are in the vicinity of US$17 trillion per year up to 2100 compared to a very high emission scenario.
United Nations Environment ProgrammeThe United Nations Environment Programme (UNEP) is responsible for coordinating responses to environmental issues within the United Nations system. It was established by Maurice Strong, its first director, after the United Nations Conference on the Human Environment in Stockholm in June 1972. Its mandate is to provide leadership, deliver science and develop solutions on a wide range of issues, including climate change, the management of marine and terrestrial ecosystems, and green economic development.
