Although Pacific decadal variability is often described in terms of processes operating separately in the tropics and North Pacific, interactions between these two regions are also potentially important but are not well understood. Using 60 years of monthly sea surface temperature and height reanalysis data, here we investigate a dynamical mode with a spatial pattern extending from the Northeast Pacific to the Central equatorial Pacific, the “North Pacific-Central Pacific” mode. We show that this mode accounts for a large fraction of decadal variance in both tropical and North Pacific regions and appears to encapsulate tropical-North Pacific coupled dynamics. We also show that the unprecedented intensity and duration of Northeast Pacific marine heatwaves in recent decades was primarily associated with enhanced variability of this mode, while sea surface temperature variations at interannual timescales in the equatorial Pacific did not play any significant role. Increased understanding of this mode may improve assessments of decadal predictability and aid prediction of Northeast Pacific marine heatwaves. The North Pacific - Central Pacific climate mode accounts for a large fraction of decadal variance in both tropical and North Pacific regions, according to analysis of sea surface temperature and height data.

Cooling energy demand in buildings is rapidly increasing as climate warms. Current methods of estimating and predicting residential cooling demand are primarily based on daily temperature, which neglects intraday temperature variations. To determine whether large-scale cooling demand is substantially affected by intraday temperature variations, we conduct a thorough comparison between variable degree days (VDDs) derived from daily temperature data with variable degree hours (VDHs) derived from hourly temperature data during the summer seasons in the United States. The results imply that incorporating intraday variations in temperature will have substantial impacts on cooling estimation and prediction. A comparison of the historical (1990–2014) VDD and VDH calculated from ERA5 temperature data reveals that US summer cooling demand estimated from hourly temperature is 29%–45% higher than those estimated from daily temperature, with differences exceeding 60% when hourly solar radiation is considered. This occurs because the hourly calculations captures the ‘hot hours’ of the mild days. Future scenario analysis, using the NASA Earth Exchange Global Daily Downscaled Projections, indicates that under the medium greenhouse gas emissions pathway (SSP2-45), US summer VDH and VDD are expected to increase by approximately 45% and 100% by the late century (2081–2100). This suggests that, daily-based predictions generally project cooling demand growth at twice the rate of hourly-based predictions, as the daily method accounts for increases in both high and low temperatures regardless of whether they exceed the baseline, while the hourly method, with its finer temporal resolution, includes only temperatures that surpass the baseline. Such effects are seen across most areas of the US. Our analysis underscores the significance of incorporating temperature data at higher temporal resolution in estimating and predicting cooling demand, which is essential for effectively implementing various measures to achieve energy conservation and climate goals.

Sulfate burden over the North Atlantic Ocean (NATL) exhibits strong seasonality despite no seasonality in anthropogenic sulfur dioxide (SO2) emissions. However, the seasonality of sulfate aerosols over NATL has decreased since 1970, likely due to a reduction in the United States (US) SO2 emissions following the Clean Air Act of 1970. We performed atmospheric chemistry and transport simulations to assess the impact of changing US SO2 emissions between 1970 and 2010 on NATL sulfate burden and radiative forcing. United States SO2 emission reductions weakened the seasonality in NATL sulfate burden by similar to 17%, primarily due to a decrease in chemical production and transport in summer. These emission reductions caused a summertime radiative forcing (similar to 2 W m(-2)) twice as large as the wintertime forcing. Our findings highlight the complex, season-dependent responses of sulfate burden and radiative effects to regional emission changes.

This study analyzes future changes in population-weighted degree-days in 48 states over the contiguous U.S. Using temperature data from the NASA Earth Exchange Global Daily Downscaled Projects and population data from NASA Socioeconomic Data and Applications Center, we computed population-weighted degree-days (PHDD and PCDD) and EDD (energy degree-days, PHDD + PCDD) over the 21st century, under a business-as-usual scenario. Results show that although the rising temperature is the primary driver, population distribution and projection play undeniable roles in estimating state-level heating and cooling demand. Throughout the 21st century, the U.S. is projected to experience a heating-to-cooling shift in energy demand, with the number of heating-dominant states dropping from 37 to 17 and the length of cooling seasons extending by 2 months (indicating a corresponding reduction in heating seasons) in all states by late-century. Meanwhile, a more homogenous EDD pattern is expected due to the increasing PCDD and decreasing PHDD, and the peak EDD month will switch from winter to summer in 15 out of 48 states. Our study provides a more nuanced understanding of future heating and cooling demand by examining both annual and monthly variations in the demands and how their relative dominance in a single framework may evolve over time. The study’s state-level perspective can provide valuable insights for policymakers, energy providers, and other stakeholders regarding the forthcoming shift in demand patterns and related building operations and energy consumption at both state and regional levels.

The modes of Pacific decadal-scale variability (PDV), traditionally defined as statistical patterns of variance, reflect to first order the ocean's integration (i.e., reddening) of atmospheric forcing that arises from both a shift and a change in strength of the climatological (time-mean) atmospheric circulation. While these patterns concisely describe PDV, they do not distinguish among the key dynamical processes driving the evolution of PDV anomalies, including atmospheric and ocean teleconnections and coupled feedbacks with similar spatial structures that operate on different timescales. In this review, we synthesize past analysis using an empirical dynamical model constructed from monthly ocean surface anomalies drawn from several reanalysis products, showing that the PDV modes of variance result from two fundamental low-frequency dynamical eigenmodes: the North Pacific-central Pacific (NP-CP) and Kuroshio-Oyashio Extension (KOE) modes. Both eigenmodes highlight how two-way tropical-extratropical teleconnection dynamics are the primary mechanisms energizing and synchronizing the basin-scale footprint of PDV. While the NP-CP mode captures interannual- to decadal-scale variability, the KOE mode is linked to the basin-scale expression of PDV on decadal to multidecadal timescales, including contributions from the South Pacific.

A cyclostationary Linear Inverse Model (CSLIM) is used to investigate the seasonal growth of tropical Pacific El Niño / Southern Oscillation (ENSO) events with canonical, Central Pacific (CP), or Eastern Pacific (EP) sea surface temperature (SST) characteristics. Analysis shows that all types of ENSO events experience maximum growth toward final states occurring in November and December. ENSO events with EP characteristics also experience growth into May and June, but CP events do not. A single dominant “ENSO-mode”, growing from an equatorial heat content anomaly into a characteristic ENSO-type SST pattern in about 9 months (consistent with the delayed / recharge oscillator model of ENSO), is essential for the predictable development of all ENSO events. Notably, its seasonality is responsible for the late calendar year maximum in ENSO amplification. However, this ENSO-mode alone does not capture the observed growth and evolution of diverse ENSO events, which additionally involve the seasonal evolution of other non-orthogonal Floquet modes. EP event growth occurs when the ENSO-mode is initially “covered up” in combination with other Floquet modes. The ENSO-mode’s slow seasonal evolution allows it to emerge while the other modes rapidly evolve and / or decay, leading to strongly amplifying and more predictable EP events. CP events develop when the initial state has a substantial contribution from Floquet modes with meridional mode-like SST structures. Thus, while nearly all ENSO events involve the seasonally-varying ENSO-mode dynamics, the diversity and predictability of ENSO events cannot be understood without identifying contributions from the remaining Floquet modes.

The Pacific cold tongue annual cycle in sea surface temperature is presumed to be driven by Earth’s axial tilt1–5 (tilt effect), and thus its phasing should be fixed relative to the calendar. However, its phase and amplitude change dramatically and consistently under various configurations of orbital precession in several Earth System models. Here, we show that the cold tongue possesses another annual cycle driven by the variation in Earth–Sun distance (distance effect) from orbital eccentricity. As the two cycles possess slightly different periodicities6, their interference results in a complex evolution of the net seasonality over a precession cycle. The amplitude from the distance effect increases linearly with eccentricity and is comparable to the amplitude from the tilt effect for the largest eccentricity values over the last million years (e value approximately 0.05)7. Mechanistically, the distance effect on the cold tongue arises through a seasonal longitudinal shift in the Walker circulation and subsequent annual wind forcing on the tropical Pacific dynamic ocean–atmosphere system. The finding calls for reassessment of current understanding of the Pacific cold tongue annual cycle and re-evaluation of tropical Pacific palaeoclimate records for annual cycle phase changes. The Pacific cold tongue is shown to possess two distinct annual cycles with complex interference effects, calling for a reassessment of its seasonal dynamics and re-evaluation of tropical Pacific palaeoclimate records of annual cycle phase changes.

Climatic design conditions are widely used by the building community as environmental parameters informing the size and energy requirements for heating, ventilation and air conditioning systems, along with other building design characteristics. Climatic design conditions are calculated by the American Society of Heating, Refrigerating and Air-conditioning Engineers using historical climate data. Our work advances methods for projecting future climate design conditions based on data from global climate models. These models do not typically archive the hourly data required for climate design condition calculations, and they often exhibit large biases in extreme conditions, daily minimum temperatures and daily maximum temperatures needed for climatic design conditions. We present a method for rescaling historical hourly data under future climatic states to estimate the impact of climate change on future building climatic design conditions. This rescaling method is then used to calculate future climatic design conditions in Madison, Wisconsin, throughout the 21st century for two future greenhouse gas emissions scenarios. The results are consistent with a warming climate and show increases in heating, cooling, humidification and dehumidification design conditions, suggesting less extreme cold conditions and more extreme hot and humid conditions in Madison. The design conditions used for estimating energy demand, degree days, show that under a business-as-usual scenario, by the mid-century, building heating and cooling in Madison (climate zone 5A) will be similar to the current heating demand in Chicago, IL (climate zone 5A) and cooling demand in Baltimore, MD (climate zone 4A); by the late-century, building heating and cooling in Madison will resemble the current heating demand in St Louis, MO (climate zone 4A) and cooling demand in Augusta, GA (climate zone 3A). Given the rapid pace of climate change in the 21st century, our work suggests that historical design conditions may become obsolete during even the initial stages of a building’s expected life span. Changes in climatic design conditions in Madison highlight the importance of considering future climatic changes in building design to ensure that buildings built today meet the performance needs of the future.

The Asian tiger mosquito, Aedes albopictus (Skuse), is a public health threat because it can potentially transmit multiple pathogenic arboviruses, exhibits aggressive diurnal biting, and is highly invasive. As Ae. albopictus moved northward into the United States, the limits of expansion were predicted as locations with a mean January temperature warmer than -2.5°C. We postulated that the range of Ae. albopictus could exceed these temperature limits if eggs in diapause overwinter in tires that provide an insulating effect from extreme temperatures. Fifteen tires with Ae. albopictus and Aedes triseriatus (Say) eggs, a native cold hardy species, were placed outside at five locations along a latitudinal gradient in Wisconsin and Illinois during the winter of 2018-2019; notably, in January 2019, a regional arctic air event brought the lowest temperatures recorded in over 20 yr. External and internal tire temperatures were recorded at 3 hr intervals, and egg survival was recorded after six months. Aedes albopictus eggs survived only from tires at northernmost locations. The mean internal January temperature of tires that supported survival was -1.8°C, while externally the mean temperature was -5.3°C, indicating that tires provided an average of +3.5°C of insulation. Tires that supported egg survival also had over 100 mm of snow cover during January. In the absence of snow cover, tires across the study area provided an average +0.79°C [95% CI 0.34-1.11] insulation. This work provides strong argument for the inclusion of microhabitats in models of dispersal and establishment of Ae. albopictus and other vector species.

Climate variability in the tropical Pacific affects global climate on a wide range of time scales. On interannual time scales, the tropical Pacific is home to the El Niño–Southern Oscillation (ENSO). Decadal variations and changes in the tropical Pacific, referred to here collectively as tropical Pacific decadal variability (TPDV), also profoundly affect the climate system. Here, we use TPDV to refer to any form of decadal climate variability or change that occurs in the atmosphere, the ocean, and over land within the tropical Pacific. “Decadal,” which we use in a broad sense to encompass multiyear through multidecadal time scales, includes variability about the mean state on decadal time scales, externally forced mean-state changes that unfold on decadal time scales, and decadal variations in the behavior of higher-frequency modes like ENSO.

The Pacific-North American (PNA) teleconnection pattern has been linked both to tropical phenomena, including the Madden-Julian oscillation (MJO) and El Nino-Southern Oscillation (ENSO), and to internal extratropical processes, including interactions with the zonally varying basic state and synoptic eddies. Many questions remain, however, concerning how these various relationships act, both separately and together, to yield observed PNA variability. Using linear inverse modeling (LIM), this study finds that the development and amplification of PNA anomalies largely results from the interference of modes strongly coupled to sea surface temperatures (SST), such as ENSO, and modes internal to the atmosphere, including the MJO. These SST-coupled and "internal atmospheric'' modes form subspaces that are not orthogonal, and PNA growth is shown to occur via non-normal interactions. An internal atmospheric space LIM is developed to examine growth beyond this interference by removing the SST-coupled modes, effectively removing ENSO and retaining MJO variability. Optimal PNA growth in the internal atmospheric space LIM is driven by MJO heating, particularly over the Indian Ocean, and a retrograding northeast Pacific streamfunction anomaly. Additionally, the individual contributions of tropical heating and the extratropical circulation on PNA growth are investigated. The non-normal PNA growth is an important result, demonstrating the difficulty in partitioning PNA variance into contributions from different phenomena. This cautionary result is likely applicable to many geophysical phenomena and should be considered in attribution studies.

Atmospheric blocking is associated with sensible weather impacts such as anomalous precipitation and flooding, cold air outbreaks, and heat waves. Given the asymmetry in the persistence characteristics of anticyclones and cyclones, many studies have emphasized the role of nonlinearities in blocking onset and maintenance. However, previous studies have demonstrated that both linear and nonlinear dynamics can amplify blocks. In this paper the structure and evolution of North Pacific blocking on weekly time scales is investigated using two methods: statistical analysis not requiring linearity, and a linear inverse model (LIM) composed of tropical outgoing longwave radiation and extratropical streamfunction, which relies on purely linear (and linearly parameterized) dynamics. Both approaches produce a similar evolution of North Pacific blocking. Using the LIM, the optimal precursors to blocking are determined, which at a 14-day lead time include an upper-level east Pacific anticyclone and suppressed convection over the central tropical Pacific. The tropics and extratropics both contribute to the deterministic evolution of blocking, with the tropics acting on longer time scales but imposing a weaker response than that contributed by the extratropics. The tropical contribution was driven by La Niña–like conditions that produce a hemispheric anticyclonic anomaly, while the extratropical initial conditions produce an equivalent barotropic, wavelike pattern. The LIM’s ability to reproduce the observed blocking evolution suggests the predictable evolution of blocking on weekly time scales can be modeled in a linear framework, and that subseasonal forecasting of North Pacific blocking needs to consider both tropical and extratropical conditions.

大气和上层海洋状态的实地观测网和再分析产品,显示了明确的从季节到年代际耦合气候变率的大尺度特征.我们通过观测分析、用各种复杂程度的非耦合和耦合大气和海洋模式进行试验及从理论发展视角,总结了这些现象及其物理含义.我们从讨论赤道热带太平洋和大西洋季节循环开始,它无疑受到了大气和海洋之间耦合的影响.之后,我们讨论仅仅因为大气和海洋之间耦合而存在的热带现象:太平洋和大西洋经向模态,太平洋上的厄尔尼诺-南方涛动(ENSO),以及大西洋类似ENSO的现象.对于ENSO,我们进一步讨论ENSO冷暖阶段之间的不规则和不对称的来源,以及ENSO对强迫的响应.北半球中纬度所有尺度变率的基础,首先是不依赖于海洋、陆地或海冰分布状态的任何变化而存在的非耦合大气变率.这些特征包括北大西洋涛动(NAO)、北太平洋涛动(NPO)和太平样北美/阿留申低压(PNA)分布;它们大多在冬季最活跃,时间谱近似于白噪声.NPO、PNA和NAO的随机变率通过湍流交换和Ekman传输在从天到年际时间尺度上驱动海洋,在年代际和更长时间尺度上通过风应力驱动.PNA是导致太平洋年代际涛动的部分原因;NAO是北大西洋类似副极地海洋涡旋现象的成因.模式方面,NAO的随机强迫还使得大西洋经向翻转环流(AMOC)的强度变率增加,它是被称为大西洋多年代涛动(AMO)的北大西洋气候多年代际距平的部分原因;充分确定AMO物理机制的观测尚不存在.我们评述过去50年里我们在认识这些现象中取得的每一个进步,以及惠及的短期(季节到年际)气候预测.最后,简要讨论将要实现的进展暂时性措施和期盼中的进展.

Sustained ocean observations benefit many users and societal goals but could benefit many more. Such information is critical for using ocean resources responsibly and sustainably as the ocean becomes increasingly important to society. The contributions of many nations cooperating to develop the Global Ocean Observing System has resulted in a strong base of global and regional ocean observing networks. However, enhancement of the existing observation system has been constrained by flat funding and limited cooperation among present and potential users. At the same time, a variety of actors are seeking new deployments in remote and newly ice-free regions and new observing capabilities, including biological and biogeochemical sensors. Can these new needs be met? In this paper, a vision for how to sustain ocean observing in the future is presented. A key evolution will be to grow the pool of users, engaging end users across society. Users with shared values need to be brought together with commitment to sustainable use of the ocean in the broadest sense. Present planning for sustained observations builds on the development of the Global Ocean Observing System which has primarily targeted increased scientific understanding of ocean processes and of the ocean's role in climate. We must build on that foundation to develop an Ocean Partnership for Sustained Observing that will incorporate the growing needs of a broad constituency of users beyond climate and make the case for new resources. To be most effective this new Partnership should incorporate the principles of a collective impact organization, enabling closer engagement with the private sector, philanthropies, governments, NGOs, and other groups. Steps toward achieving this new Partnership are outlined in this paper, with the intent of establishing it early in the UN Decade of Ocean Science.