Christopher H. Trisos’s research while affiliated with University of Cape Town and other places

2023 was the hottest year in recorded history at the time of its recording ¹ and warmer than any in the past 125,000 years ² . Although the effects of this unprecedented year on human health, agriculture, and economies have been documented ³ , we know much less about its effects on global biodiversity, especially in poorly monitored regions. Here, we demonstrate a rapid climate bioassessment pipeline to pinpoint when and where species have recently been exposed to extreme weather. Applying this approach to > 33,000 terrestrial vertebrate species, we demonstrate that 2023 posed unprecedented levels of risk to biodiversity, with half of all species exposed to extreme temperatures somewhere in their geographic range and 1 in 10 exposed across > 25% of their range. We show that exposure to extreme weather has increased rapidly over the last decade and that many species now exist dangerously close to their historical niche limits. Consequently, although the global mean annual temperature in 2023 was only 0.2 o C warmer than the previous warmest year on record in 2016, species exposure doubled. Our 2023 vertebrate assessment provides a prototype for a highly flexible pipeline that can be extended to accommodate any pertinent weather data collected in real-time and can be customized for regional, taxonomic, or conservation-specific needs. Our pipeline can be used to direct management resources to those ecosystems and species, particularly in poorly monitored regions, that are at risk of unnoticed collapse, decline, or extinction following exposure to unprecedented conditions.

Despite widespread consensus that climate change poses a serious threat to global public health, very few studies have isolated the specific contributions of human-caused climate change to changes in morbidity and mortality. Here, we systematically review over 3,600 abstracts, and identify a dozen end-to-end impact attribution studies on human health outcomes published between 2016 and 2023. Based on these studies, we find that estimates of attributable mortality range from 10 to over 271,000 deaths, depending on timescale, spatial extent, climate hazard, and cause of death. We calculate that this loss of life amounts to up to US$ trillions in monetary value when using standard valuation approaches. So far, end-to-end attribution studies capture only a small fraction of the presumed global burden of climate change, with few studies addressing infectious and non-communicable diseases, and no subnational or event-specific studies focused on a location outside of Europe and the United States. However, the field of health impact attribution is poised to explode in the next decade, putting unprecedented pressure on policymakers to take action for human health.

Climate change is exposing marine species to unsuitable temperatures while also creating new thermally suitable habitats of varying persistence. However, understanding how these different dynamics will unfold over time remains limited. We use yearly sea surface temperature projections to estimate temporal dynamics of thermal exposure (when temperature exceeds realised species’ thermal limits) and opportunity (when temperature at a previously unsuitable site becomes suitable) for 21,696 marine species globally until 2100. Thermal opportunities are projected to arise earlier and accumulate gradually, especially in temperate and polar regions. Thermal exposure increases later and occurs more abruptly, mainly in the tropics. Assemblages tend to show either high exposure or high opportunity, but seldom both. Strong emissions reductions reduce exposure around 100-fold whereas reductions in opportunities are halved. Globally, opportunities are projected to emerge faster than exposure until mid-century when exposure increases more rapidly under a high emissions scenario. Moreover, across emissions and dispersal scenarios, 76%-97% of opportunities are projected to persist until 2100. These results indicate thermal opportunities could be a major source of marine biodiversity change, especially in the near- and mid-term. Our work provides a framework for predicting where and when thermal changes will occur to guide monitoring efforts.

Emerging infectious diseases are increasingly understood as a hallmark of the Anthropocene 1–3 . Most experts agree that anthropogenic ecosystem change and high-risk contact among people, livestock, and wildlife have contributed to the recent emergence of new zoonotic, vector-borne, and environmentally-transmitted pathogens 1,4–6 . However, the extent to which these factors also structure landscapes of human infection and outbreak risk is not well understood, beyond certain well-studied disease systems 7–9 . Here, we consolidate 58,319 unique records of outbreak events for 32 emerging infectious diseases worldwide, and systematically test the influence of 16 hypothesized social and environmental drivers on the geography of outbreak risk, while adjusting for multiple detection, reporting, and research biases. Across diseases, outbreak risks are widely associated with mosaic landscapes where people live alongside forests and fragmented ecosystems, and are commonly exacerbated by long-term decreases in precipitation. The combined effects of these drivers are particularly strong for vector-borne diseases (e.g., Lyme disease and dengue fever), underscoring that policy strategies to manage these emerging risks will need to address land use and climate change 10–12 . In contrast, we find little evidence that spillovers of directly-transmitted zoonotic diseases (e.g., Ebola virus disease and mpox) are consistently associated with these factors, or with other anthropogenic drivers such as deforestation and agricultural intensification ¹³ . Most importantly, we find that observed spatial outbreak intensity is primarily an artefact of the geography of healthcare access, indicating that existing disease surveillance systems remain insufficient for comprehensive monitoring and response: across diseases, outbreak reporting declined by a median of 32% (range 1.2%-96.7%) for each additional hour’s travel time from the nearest health facility. Our findings underscore that disease emergence is a multicausal feature of social-ecological systems, and that no one-size-fits-all global strategy can prevent epidemics and pandemics. Instead, ecosystem-based interventions should follow regional priorities and system-specific evidence, and be paired with investment in One Health surveillance and health system strengthening.

The escalating impacts of climate change on the movement and immobility of people, coupled with false but influential narratives of mobility, highlight an urgent need for nuanced and synthetic research around climate mobility. Synthesis of evidence and gaps across the Intergovernmental Panel on Climate Change (IPCC) Sixth Assessment Report highlight a need to clarify the understanding of what conditions make human mobility an effective adaptation option and its nuanced outcomes, including simultaneous losses, damages, and benefits. Priorities include integration of adaptation and development planning; involuntary immobility and vulnerability; gender; data for cities; risk from responses and maladaptation; public understanding of climate risk; transboundary, compound, and cascading risks; nature-based approaches; and planned retreat, relocation, and heritage. Cutting across these priorities, research modalities need to better position climate mobility as type of mobility, as process, and as praxis. Policies and practices need to reflect the diverse needs, priorities, and experiences of climate mobility, emphasizing capability, choice, and freedom of movement.

Impact attribution is an emerging transdisciplinary sub-discipline of detection and attribution, focused on the social, economic, and ecological impacts of climate change. Here, we provide an overview of common end-to-end frameworks in impact attribution, focusing on examples relating to the human health impacts of climate change. We propose a typology of study designs based on whether researchers choose to focus on long-term trends or specific events; whether they compare climate scenarios by estimating impact probabilities, or only focus on the difference in impact distributions; and whether they choose to split climate change attribution and impact estimation into separate analytical steps (and often, separate studies). We map four common study designs onto this typology, and discuss their relative strengths in terms of both inferential rigor and science communication potential. We conclude by discussing a handful of related and emerging approaches, and discuss how methodological innovations in impact attribution are continuing to advance our understanding of the climate crisis.

Assessing the potential impacts and tipping points of temperature overshoot requires acknowledging that the journey of the overshoot is just as important as the final global warming level.

This policy brief on targets (both thematic and dimensional) of the global goal on adaptation framework of the UNFCCC was prepared by independent authors who participated in the IPCC AR6 WGII. This policy brief helped the global goal on adaptation negotiations of the UNFCCC during the COP 28 in Dubai. It provides global goal on adaptation targets that are informed by science.

Cattle farming is a major source of global food production and livelihoods that is being impacted by climate change. However, despite numerous studies reporting local-scale heat impacts, quantifying the global risk of heat stress to cattle from climate change remains challenging. We conducted a global synthesis of documented heat stress for cattle using 164 records to identify temperature-humidity conditions associated with decreased production and increased mortality, then projected how future greenhouse gas emissions and land-use decisions will limit or exacerbate heat stress, and mapped this globally. The median threshold for the onset of negative impacts on cattle was a temperature-humidity index of 68.8 (95% C.I.: 67.3-70.7). Currently, almost 80% of cattle globally are exposed to conditions exceeding this threshold for at least 30 days a year. For global warming above 4 • C, heat stress of over 180 days per year emerges in temperate regions, and year-round heat stress expands across all tropical regions by 2100. Limiting global warming to 2 • C, limits expansion of 180 days of heat stress to subtropical regions. In all scenarios, severity of heat stress increases most in tropical regions, reducing global milk yields. Future land-use decisions are an important driver of risk. Under a low environmental protection scenario (SSP3-RCP7.0), the greatest expansion of cattle farming is projected for tropical regions (especially Amazon, Congo Basin, and India), where heat stress is projected to increase the most. This would expose over 500 million more cattle in these regions to severe heat risk by 2090 compared to 2010. A less resource-intensive and higher environmental protection scenario (SSP1-RCP2.6) reduces heat risk for cattle by at least 50% in Asia, 63% in South America, and 84% in Africa. These results highlight how societal choices that expand cattle production in tropical forest regions are unsustainable, both worsening climate change and exposing hundreds of millions more cattle to large increases in severe, year-round heat stress.