Carter Amanda W, Fleming J Morgan
Northern Arizona University, Department of Biological Sciences; 617 S Beaver St. Flagstaff, AZ 86011, United States.
University of Tennessee, Department of Ecology and Evolutionary Biology; 1416 Circle Drive, Knoxville, Tennessee, 37920, United States.
Integr Comp Biol. 2025 Aug 13. doi: 10.1093/icb/icaf146.
Global temperatures are shifting in complex ways due to climate change. While early research focused on rising mean temperatures and its effect on biological outcomes, recent work has shifted toward understanding the influence of temperature variability. In particular, many studies investigate temperature variation by symmetrically expanding daily temperature ranges around a fixed mean or by increasing daytime maximums. Although these approaches isolate specific aspects of temperature change, they often fail to capture how climate change is actually reshaping daily temperature cycles. In this perspective paper, we use climate data across three geographic scales to illustrate a striking and consistent pattern: daily minimum temperatures are rising faster than daily maximums, effectively reducing daily temperature range. A global analysis reveals that nighttime minimum temperatures are increasing more rapidly than daytime maximums across most land areas worldwide, especially at higher latitudes and elevations. At the continental scale, North American climate data show that asymmetric warming occurs year-round, with the strongest effects in winter. Regional patterns reveal especially strong nighttime warming in mountainous regions like the Rocky and Pacific Mountain systems. Locally, hourly data from Paradise, Nevada show nighttime temperatures have risen by over 4°C since the 1950s, while daytime highs remained stable, reducing daily temperature range by more than 4°C. We then synthesize findings from 84 studies that directly investigated biological responses to nighttime warming. Nearly half (47%) of the orders studied were plants, highlighting major taxonomic gaps in animal and microbial systems. Most studies (57%) were in organismal biology, yet few were hypothesis driven. Across taxa, asymmetric warming alters energetics, increases metabolic costs, and affects both thermal performance traits (e.g., metabolism, activity) and threshold-dependent traits (e.g., phenology, sex determination). We highlight evidence that nighttime warming may enhance or inhibit cellular recovery from heat stress (Heat Stress Recovery Hypotheses), shift species interactions, disrupt pollination networks, and reshape community structure. We conclude with a call for broader research across taxa, life stages, and ecological contexts, and recommend experimental, field-based, and modeling approaches tailored to disentangle the unique effects of asymmetric warming. Understanding asymmetric warming is not just a research gap-it's a pressing ecological imperative essential for predicting and mitigating climate change impacts on biodiversity.
由于气候变化，全球气温正以复杂的方式发生变化。早期研究聚焦于平均气温上升及其对生物结果的影响，而近期的工作已转向理解温度变异性的影响。特别是，许多研究通过围绕固定均值对称扩展每日温度范围或提高日间最高温度来研究温度变化。尽管这些方法分离出了温度变化的特定方面，但它们往往无法捕捉到气候变化实际上是如何重塑每日温度周期的。在这篇观点论文中，我们使用跨越三个地理尺度的气候数据来说明一个显著且一致的模式：日最低气温的上升速度快于日最高气温，有效地缩小了每日温度范围。一项全球分析表明，在全球大多数陆地区域，夜间最低气温的上升速度快于日间最高气温，尤其是在高纬度和高海拔地区。在大陆尺度上，北美气候数据显示全年都存在不对称变暖现象，冬季的影响最为强烈。区域模式显示，在落基山脉和太平洋山脉系统等山区，夜间变暖尤为明显。在局部地区，内华达州天堂市的每小时数据显示，自20世纪50年代以来，夜间气温上升了超过4°C，而日间高温保持稳定，每日温度范围缩小了超过4°C。然后，我们综合了84项直接研究生物对夜间变暖反应的研究结果。所研究的目近一半（47%）是植物，这凸显了动物和微生物系统中主要的分类学空白。大多数研究（57%）属于生物有机体生物学领域，但很少有研究是由假设驱动的。在各个分类群中，不对称变暖会改变能量学、增加代谢成本，并影响热性能特征（如新陈代谢、活动）和阈值依赖性特征（如物候、性别决定）。我们强调有证据表明夜间变暖可能会增强或抑制细胞从热应激中恢复（热应激恢复假说）、改变物种相互作用、破坏授粉网络并重塑群落结构。我们呼吁开展跨分类群、生命阶段和生态背景的更广泛研究，并推荐采用实验性、基于实地和建模方法，以厘清不对称变暖的独特影响。理解不对称变暖不仅是一个研究空白——它是预测和减轻气候变化对生物多样性影响所必需的紧迫生态要务。
