Department of Earth System Science, Stanford University, Stanford, CA 94305;
Department of Earth System Science, Stanford University, Stanford, CA 94305.
Proc Natl Acad Sci U S A. 2021 Jan 26;118(4). doi: 10.1073/pnas.2017524118.
Precipitation extremes have increased across many regions of the United States, with further increases anticipated in response to additional global warming. Quantifying the impact of these precipitation changes on flood damages is necessary to estimate the costs of climate change. However, there is little empirical evidence linking changes in precipitation to the historically observed increase in flood losses. We use >6,600 reports of state-level flood damage to quantify the historical relationship between precipitation and flood damages in the United States. Our results show a significant, positive effect of both monthly and 5-d state-level precipitation on state-level flood damages. In addition, we find that historical precipitation changes have contributed approximately one-third of cumulative flood damages over 1988 to 2017 (primary estimate 36%; 95% CI 20 to 46%), with the cumulative impact of precipitation change totaling $73 billion (95% CI 39 to $91 billion). Further, climate models show that anthropogenic climate forcing has increased the probability of exceeding precipitation thresholds at the extremely wet quantiles that are responsible for most flood damages. Climate models project continued intensification of wet conditions over the next three decades, although a trajectory consistent with UN Paris Agreement goals significantly curbs that intensification. Taken together, our results quantify the contribution of precipitation trends to recent increases in flood damages, advance estimates of the costs associated with historical greenhouse gas emissions, and provide further evidence that lower levels of future warming are very likely to reduce financial losses relative to the current global warming trajectory.
在美国的许多地区，降水极值都有所增加，预计随着全球变暖的进一步加剧，这种情况还会进一步增加。量化这些降水变化对洪水灾害的影响对于估计气候变化的成本是必要的。然而，几乎没有经验证据将降水变化与历史上观察到的洪水损失增加联系起来。我们使用超过 6600 份州级洪水灾害报告，定量分析了美国降水变化与洪水灾害之间的历史关系。研究结果表明，月降水和 5 日降水对州级洪水灾害都有显著的正向影响。此外，我们发现历史降水变化导致了 1988 年至 2017 年期间累计洪水灾害损失的约三分之一（主要估计值为 36%；95%置信区间为 20%至 46%），历史降水变化的累计影响总计为 730 亿美元（95%置信区间为 390 亿至 910 亿美元）。此外，气候模型表明，人为气候强迫增加了在极湿润分位数上超过降水阈值的可能性，而这些分位数正是造成大部分洪水灾害的原因。气候模型预测，在未来三十年，湿润条件将继续加剧，尽管符合联合国巴黎协定目标的轨迹将显著遏制这种加剧趋势。总的来说，我们的研究结果量化了降水趋势对近期洪水灾害损失增加的贡献，推进了对与历史温室气体排放相关成本的估计，并进一步证明，未来较低的变暖水平很可能会降低与当前全球变暖轨迹相关的经济损失。
