A large-ensemble climate simulation database, which is known as the database for policy decision-making for future climate changes (d4PDF), was designed for climate change risk assessments. Since the completion of the first set of climate simulations in 2015, the database has been growing continuously. It contains the results of ensemble simulations conducted over a total of thousands years respectively for past and future climates using high-resolution global (60 km horizontal mesh) and regional (20 km mesh) atmospheric models. Several sets of future climate simulations are available, in which global mean surface air temperatures are forced to be higher by 4 K, 2 K, and 1.5 K relative to preindustrial levels. Nonwarming past climate simulations are incorporated in d4PDF along with the past climate simulations. The total data volume is approximately 2 petabytes. The atmospheric models satisfactorily simulate the past climate in terms of climatology, natural variations, and extreme events such as heavy precipitation and tropical cyclones. In addition, data users can obtain statistically significant changes in mean states or weather and climate extremes of interest between the past and future climates via a simple arithmetic computation without any statistical assumptions. The database is helpful in understanding future changes in climate states and in attributing past climate events to global warming. Impact assessment studies for climate changes have concurrently been performed in various research areas such as natural hazard, hydrology, civil engineering, agriculture, health, and insurance. The database has now become essential for promoting climate and risk assessment studies and for devising climate adaptation policies. Moreover, it has helped in establishing an interdisciplinary research community on global warming across Japan.

专为气候变化风险评估而设计的大型综合气候模拟数据库，即用于未来气候变化的政策决策数据库（d4PDF）。自2015年完成第一组气候模拟以来，数据库一直在不断增长。它包含使用高分辨率的全球（60公里水平网格）和区域（20公里网格）大气模型分别针对过去和未来气候进行了总计数千年的合集模拟的结果。有几套未来的气候模拟可用，其中全球平均地表温度被迫相对于工业化前的水平升高4 K，2 K和1.5K。d4PDF中结合了过去的气候模拟，将过去的非气候模拟与过去的气候模拟结合在一起。总数据量约为2 PB。大气模型在气候，自然变化和极端事件（如强降水和热带气旋）方面令人满意地模拟了过去的气候。此外，数据用户可以通过简单的算术计算获得任何过去和未来气候之间的平均状态或感兴趣的极端天气和极端气候的统计显着变化，而无需任何统计假设。该数据库有助于理解气候状态的未来变化，并将过去的气候事件归因于全球变暖。在自然灾害，水文学，土木工程，农业，健康和保险等多个研究领域中，同时进行了气候变化影响评估研究。现在，该数据库对于促进气候和风险评估研究以及制定气候适应政策至关重要。此外，它还帮助建立了一个有关日本全球变暖的跨学科研究社区。