A stretched Polar Vortex and North American and Eastern Asian Cold-Air Events during January/February 2025

During mid-January through February 2025 the low-level stratospheric polar vortex (LSPV) at 100 mb extended from North America across the pole to east-central Asia, a stretched pattern, coinciding with a period of extended cold weather on both continents. The LSPV, and its associated tropospheric blocking projections, were a main organizing feature. Weather events were mostly contained in the tropospheric west-east wave guide. For the United States (US), cold conditions occurred in a corridor that includes Illinois, through Mississippi and Virginia. During the second half of January, a 500 mb ridge-trough was set up off the west coast of California, driving cold temperatures into the southeastern US, with record snow in New Orleans. During early February there were cold events in Korea and Eastern Asia; an intermediate timing between cold air outbreaks in the US. The end of February saw a second US cold air outbreak. Although the stretched LSPV at 100 mb had a one and a half month duration extending over the subarctic, mid-tropospheric weather events were of shorter duration in both the US and Eastern Asia. The troughing at 100 mb in the stretched LSPV pattern coincided with event-based barotropic atmospheric troughing response at lower levels. Tropospheric weather events can coexist with the LSPV and thus contribute to sub-seasonal forecasting.

Rise in heat related mortality in the United States

Over the past century, extreme heat events (EHEs) have become more frequent and intense, resulting in significant health impacts and economic challenges worldwide. In the United States, extreme heat is the leading weather-related cause of death, claiming more lives annually than hurricanes, floods, and tornadoes combined. However, the characteristics of extreme heat events can vary widely across events and over time. Even events perceived as similarly severe can result in vastly different health and societal outcomes—differences that remain largely understudied. In this paper, we explore regional trends in heat severity and mortality rates across the conterminous United States from 1981-2022 and provide a regional examination of how specific EHE characteristics impact heat mortality. We find that the number of extreme heat days has the strongest influence on heat related mortality. We observe increasing trends in heat-related mortality in every climate region throughout the U.S., except for the Western North Central region. These increases—likely tied to rising counts of annual EHE days—signal a structural shift to a new, elevated baseline of heat-related mortality in the U.S. Further, in the Southwest and Southeast regions, heat-related mortality is increasing at a higher rate than heat severity, suggesting potential for modification by community and individual level social vulnerability. Future heat mortality models should be holistic in their approach, incorporating not only multiple characteristics of heat but also measures of vulnerability to fully capture the complex dynamics of risk and exposure.

Systematic anomalies in the recent global atmospheric CO2 concentration

Atmospheric CO2 is the major contributor to climate change and ocean acidification resulting from human activities. Over recent decades of improving measurement precision of CO2, of its isotopic composition and of air mass history, highly systematic variation has emerged in data selected for minimal exposure to regional air–surface exchange and maximum spatial representation. Between 2009 and 2015, anomalous behaviour is observed in air samples collected in baseline conditions from globally distributed sites. It is evident in atmospheric CO2 amount, in its stable carbon isotope ratio, in individual sample data and in annually averaged data, and in the interhemispheric difference between primary baseline sites. The behaviour is also anomalous with respect to the wide-spread CO2 response to El Niño-Southern Oscillation. It is clearly observed as a residual from either the 10-year running mean or smooth exponential curves that describe the CO2 increase, and isotopic decrease, due to anthropogenic emissions. In Southern Hemisphere annual data there is uniformity throughout 71° of extratropical latitudes, and the isotopic data exclude an ocean-atmosphere contribution. The 2009–2015 anomaly is globally apparent in our data, but not previously reported in conventional global carbon budget studies using CO2 growth rate changes where it is less evident. It is preceded by the Global Financial Crisis and bracketed by unprecedented activity in interhemispheric exchange indices. The robust and precise anomaly in Southern Hemisphere baseline data provides an unusual opportunity to calibrate causal studies with conventional CO2 transport models used to verify anthropogenic CO2 emission estimates and air-surface exchange.

Nunakut naguatun atugluu/Co-stewardship: Co-production’ through the lens of the Study of Environmental Arctic Change’s Human Wellbeing Team

This paper explores the concept of co-stewardship in the Arctic through the lens of the Study of Environmental Arctic Change’s Human Wellbeing (HWB) team. Rooted in Indigenous knowledge and collaborative science, our work prioritizes equity in decision-making, recognizing multiple knowledge systems as equally valuable. Through intentional team-building, trust, and reciprocity, we examine successes, challenges, and opportunities in co-stewardship. Key successes include fostering meaningful relationships, integrating Indigenous perspectives into scientific and policy discussions, and uplifting innovative knowledge-sharing tools such as oral histories and visual storytelling. However, structural challenges persist, including colonial policy frameworks, inadequate funding models, and a lack of institutional mechanisms to support Indigenous leadership in co-stewardship initiatives. We propose policy shifts, long-term funding commitments, and greater Indigenous representation in decision-making as steps toward meaningful change. This work underscores the importance of Indigenous-led stewardship in addressing Arctic environmental and social challenges, offering a model for collaborative governance rooted in respect and reciprocity.

Exploring implementation of disaster risk management strategies by public housing authorities: A national survey

The United States is experiencing an affordable housing crisis. Simultaneously, disasters are increasing in frequency and intensity partly due to anthropogenic climate change. Disasters exacerbate adverse impacts on extremely low-income renters living in federally-subsidized housing units managed by Public Housing Authorities (PHAs). To date, there is an overall lack of knowledge around what disaster risk management (DRM) strategies are being implemented by PHAs, as well as factors that influence PHA DRM implementation. A national survey was administered to PHAs to assess their implementation of DRM strategies. Survey results, along with secondary data, were analyzed using descriptive statistics. Fisher’s exact test of independence was used to calculate the association between each binary DRM strategy variable (“Yes” versus “No”) and each PHA characteristic. Findings suggest that PHA Moving To Work (MTW) status, PHA size, urban classification, state-level political affiliation, and perceived hazard risk influence PHA DRM implementation.

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Political ideology and views toward solar geoengineering in the United States

Political polarization remains a significant barrier to effective climate action in the United States. Conservatives often express skepticism toward climate change policies emphasizing government intervention, while liberals are generally more supportive of these efforts. Solar geoengineering (SG), an emerging technology proposed to cool the Earth’s atmosphere, offers a climate intervention that may transcend entrenched ideological divides. SG remains relatively unknown to the public and has not yet been widely framed in partisan terms. Moreover, its perceived nature as a technological solution could appeal to conservatives resistant to traditional climate measures. This study investigates the relationship between political ideology and public attitudes toward SG, conditional on respondents’ familiarity with the technology. Using a nationally representative sample of 2,109 American voters and applying linear probability and multinomial logistic regression models, we find that greater familiarity with SG is associated with reduced political polarization regarding SG’s perceived effectiveness, associated risks, and preferred climate strategies. Our findings suggest that increasing public awareness of SG could foster bipartisan engagement with climate policy, helping bridge the ideological divide.

Enhancing the understanding of the contribution of anthropogenic land system management to the achievement of climate neutrality