The report oil companies are worried about: Climate attribution science

石油公司担忧的报告：气候归因科学

Climate change is being driven largely by the greenhouse gases we’ve pumped into the atmosphere, which trap more of the Sun’s energy there. That added energy increases the odds of extreme events: longer, more intense heat waves and droughts, interspersed with excessive precipitation. 气候变化在很大程度上是由我们排放到大气中的温室气体所驱动的，这些气体将更多的太阳能量困在大气层中。这种增加的能量提高了极端事件发生的几率：更长、更强烈的热浪和干旱，以及伴随而来的极端降水。

But these sorts of events have happened in the past—how can we tell if any given weather disaster has been made more likely by the climate? It’s a question with implications for everything from building codes to disaster preparedness. And there’s some good news: According to a report released by the US National Academies of Science on Thursday, the field of climate attribution is growing increasingly mature and can answer some questions for us with far greater confidence than it could just a decade ago. 但这类事件在过去也曾发生过——我们如何判断某次特定的气象灾害是否因气候变化而变得更有可能发生？这个问题影响深远，从建筑规范到防灾准备都与之相关。好消息是：根据美国国家科学院周四发布的一份报告，气候归因领域正日益成熟，与十年前相比，它现在能以更高的置信度回答我们的某些问题。

The report also notes that there are still important limits and suggests steps to address them. Overall, this makes it clear that climate attribution is normal, mainstream science. And the fossil fuel industry views that as a problem, as it could make it easier to hold companies liable for damages. This has triggered a backlash that has Republicans in Congress and state governments threatening the National Academies’ funding. 报告还指出，该领域仍存在重要的局限性，并提出了解决这些问题的步骤。总的来说，这表明气候归因已成为正常的主流科学。而化石燃料行业将其视为一个问题，因为它可能使追究公司损害赔偿责任变得更容易。这引发了强烈抵制，国会和州政府中的共和党人甚至威胁要削减国家科学院的经费。

A decade of progress

十年的进步

Heat waves, excessive precipitation, and other extreme weather events have been happening throughout Earth’s history. The relatively stable climate humanity has enjoyed since the end of the last glacial period has meant that historic extremes typically fall within a relatively narrow range. But we’ve been exiting the stable climate humanity has been familiar with, so we should expect events that fall outside the normal range of variability we’re accustomed to. 热浪、极端降水和其他极端天气事件在地球历史上一直存在。自上一个冰河时代结束以来，人类所享受的相对稳定的气候意味着历史上的极端事件通常处于一个相对狭窄的范围内。但我们正在脱离人类所熟悉的那种稳定气候，因此我们应该预见到那些超出我们习惯的正常变率范围的事件。

Can we recognize them when they happen? That question is linked to a query that has accompanied many weather disasters—the public wants to know if it was the outcome of the global warming we’ve been warned about. Attribution science has been developed to try to answer these questions. At its simplest, it identifies the major atmospheric features associated with a weather event and then asks how often they occur in climate models under two scenarios: one with our present conditions and one without humanity’s greenhouse gas emissions. 当这些事件发生时，我们能识别它们吗？这个问题与许多气象灾害伴随的疑问相关——公众想知道这是否是我们一直被警告的全球变暖的结果。归因科学的发展正是为了尝试回答这些问题。简单来说，它识别与天气事件相关的主要大气特征，然后在两种情景下询问它们在气候模型中发生的频率：一种是基于我们当前的条件，另一种是不考虑人类温室气体排放的条件。

The difference in frequency within these two scenarios provides a measure of the influence of climate change. This approach has been through peer review and has since been used to examine a wide variety of weather events, many of which show the fingerprint (or, in some cases, the fist print) of climate change. There have also been some instances where the methods don’t provide a clear picture. 这两种情景下频率的差异提供了衡量气候变化影响的尺度。这种方法已经过同行评审，并已被用于检查各种各样的天气事件，其中许多事件显示了气候变化的“指纹”（在某些情况下甚至是“拳印”）。当然，也有一些情况下，这些方法无法提供清晰的结论。

Degrees of difficulty

难度等级

The report provides a great overview of how attribution analysis works, where it succeeds, and what challenges keep it from being effective in some circumstances. But one of the first things it makes clear is that the field has gotten better since the NAS last checked in. 该报告对归因分析的工作原理、其成功之处以及在某些情况下阻碍其有效性的挑战进行了很好的概述。但它首先明确的一点是，自美国国家科学院上次评估以来，该领域已经取得了进步。

“Over the past decade, advances in physical understanding—through accumulating observational and modeling evidence supporting long-standing theoretical expectations—together with improved and more sophisticated numerical models, expanded observational datasets, and advanced statistical and machine-learning techniques, have strengthened the foundation for extreme event attribution,” the report’s authors write. “This progress has led to more robust assessments and an increased ability to examine a broader range of extreme event types.” 报告作者写道：“在过去十年中，物理理解的进步——通过积累支持长期理论预期的观测和模拟证据——加上改进且更复杂的数值模型、扩展的观测数据集以及先进的统计和机器学习技术，加强了极端事件归因的基础。这些进展带来了更稳健的评估，并提高了检查更广泛极端事件类型的能力。”

While there have been (and continue to be) new approaches developed for answering questions, the report says that most of the work is being done within one of two frameworks. The first is called “probabilistic,” which focuses on how climate change has altered the odds of a similar event occurring. The second is termed “storyline,” and is more focused on the specifics of the weather event (to give one example, the frequency of large hailstones) as well as the atmospheric conditions that make them possible. 虽然回答问题的新方法一直在开发中，但报告称，大部分工作是在两个框架之一内完成的。第一个被称为“概率法”，侧重于气候变化如何改变了类似事件发生的几率。第二个被称为“故事线法”，更侧重于天气事件的具体细节（例如大冰雹的频率）以及使其成为可能的大气条件。