National climate projections are specialized regional climate projections, typically produced for and by individual countries. What distinguishes national climate projections from other climate projections is that they are officially signed-off by the national government, thereby being the relevant national basis for adaptation planning. Climate projections are commonly produced over several years by countries' national meteorological services or academic institutions working on climate change. Typically distributed as a single product, climate projections condense information from multiple climate models, using multiple greenhouse gas emission pathways to characterize different yet coherent climate futures. Such a product highlights plausible climatic changes through the use of narratives, graphs, maps, and perhaps raw data. Climate projections are often publicly available for policy-makers, public and private decision makers, as well as researchers to undertake further climate impact studies, risk assessments, and climate change adaptation research. The projections are updated every few years, in order to incorporate new scientific insights and improved climate models.
Aims
National climate projections illustrate plausible changes to a country's climate in the future. By using multiple emission scenarios, these projections highlight the impact different global mitigation efforts have on variables, including temperature, precipitation, and sunshine hours. Climate scientists strongly recommend the use of multiple emission scenarios in order to ensure that decisions are robust to a range of climatic changes. National climate projections form the basis of national climate adaptation and climate resilience plans, which are reported to UNFCCC and used in IPCC assessments.
Design
To explore a wide range of plausible climatic outcomes and to enhance confidence in the projections, national climate change projections are often generated from multiple general circulation models. Such climate ensembles can take the form of perturbed physics ensembles, multi-model ensembles, or initial condition ensembles. As the spatial resolution of the underlying GCMs is typically quite coarse, the projections are often downscaled, either dynamically using regional climate models, or statistically. Some projections include data from areas which are larger than the national boundaries, e.g. to more fully evaluate catchment areas of transboundary rivers. Some countries have also produced more localized projections for smaller administrative areas, e.g. States in the United States, and Länder in Germany. Various countries have produced their national climate projections with feedback and/or interaction with stakeholders. Such engagement efforts have helped tailoring the climate information to the stakeholders' needs, including the provision of sector-specific climate indicators such as degree-heating days. In the past, engagement formats have included surveys, interviews, presentations, workshops, and use-cases. While such interactions helped not only to enhance the usability of the climate information, it also fostered discussions on how to use climate information in adaptation projects. Interestingly, a comparison of the British, Dutch, and Swiss climate projections revealed distinct national preferences in the way stakeholders were engaged, as well as how the climate model outputs were condensed and communicated.
For countries which lack adequate resources to develop their own climate change projections, organisations such as UNDP or FAO have sponsored development of projections and national adaptation programmes.
Applications
National climate projections are widely used to predict climate change impacts in a wide range of economic sectors, and also to inform climate change adaptation studies and decisions. Some examples include:
