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1. Increased risk of malaria transmission with warming temperature in the Ethiopian Highlands

   https://doi.org/10.1088/1748-9326/ab7520  

   Endo, Noriko ; Eltahir, Elfatih A. B. ( April 2020 , Environmental Research Letters)

   The heavily populated highlands of Ethiopia are currently at low risk for malaria transmission, but global warming may change the risk level significantly. The inhabitants of the Ethiopian Highlands are highly vulnerable to this potential hazard due to their lack of immunity. Here, we identify hotspots within the Highlands where projected warming towards the end of the 21st century will increase the risk of malaria transmission significantly. Based on projected temperature changes, we conclude that about a third of the region’s population and roughly 14% of its land area will become at high risk for malaria transmission within a century under the high-emissions-no-mitigation baseline scenario for future climate change. Our analysis combines dynamically down-scaled regional climate projections, high resolution satellite observations of temperature, and a village-scale malaria transmission model that was developed based on climatic, environmental, entomological, and medical data collected by our group in comprehensive multi-year field surveys of villages in this region. The projected impacts of global warming on malaria transmission in Africa have been controversial. We propose a framework that reconciles seemingly contradictory conclusions, and informs strategies for climate adaptation not only over the Ethiopian Highlands but broadly over Africa, where more than 90% of malariamore »deaths occur every year.

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2. Today’s 100 year droughts in Australia may become the norm by the end of the century

   https://doi.org/10.1088/1748-9326/ac58ac  

   Araujo, Diogo S. A. ; Marra, Francesco ; Merow, Cory ; Nikolopoulos, Efthymios I. ( March 2022 , Environmental Research Letters)

   Accumulating evidence on the impact of climate change on droughts, highlights the necessity for developing effective adaptation and mitigation strategies. Changes in future drought risk and severity in Australia are quantified by analyzing nine Coupled Model Intercomparison Project Phase 6 climate models. Historic conditions (1981–2014) and projections for mid-century (2015–2050) and end-century (2051–2100) from four shared socioeconomic pathways (SSP1-2.6, SSP2-4.5, SSP3-7.0 and SSP5-8.5) are examined. Drought events are identified using both the standardized precipitation index and the standardized precipitation evapotranspiration index. The spatial-temporal evolution of droughts is addressed by quantifying the areal extent of regions under moderate, severe and extreme drought from historic to end-century periods. Drought characteristics derived from the models are used to develop severity–duration–frequency curves using an extreme value analysis method based on ordinary events. Under SSP5-8.5, a tenfold increase in the area subject to extreme droughts is projected by the end of the century, while a twofold increase is projected under SSP1-2.6. Increase in extreme droughts frequency is found to be more pronounced in the southern and western regions of Australia. For example, frequency analysis of 12 month duration droughts for the state of South Australia indicates that, under SSP5-8.5, drought severities currently expected tomore »happen on average only once in 100 years could happen as often as once in 3 years by the end of the century, with a 33 times higher risk (from 1% to 33%), while under SSP1-2.6, the increase is fivefold (1%–5%). The significant difference in the increase of drought risk between the two extreme scenarios highlights the urge to reduce greenhouse gases emission in order to avoid extreme drought conditions to become the norm by the end of the century.

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3. Large humidity effects on urban heat exposure and cooling challenges under climate change

   https://doi.org/10.1088/1748-9326/acc475  

   Yang, Joyce ; Zhao, Lei ; Oleson, Keith ( March 2023 , Environmental Research Letters)

   Many urban climates are characterized by increased temperature and decreased relative humidity, under climate change and compared to surrounding rural landscapes. The two trends have contrasting effects on human-perceived heat stress. However, their combined impact on urban humid heat and adaptation has remained largely unclear. Here, we use simulations from an earth system model to investigate how urbanization coupled with climate change affects urban humid heat stress, exposure, and adaptation. Our results show that urban humid heat will increase substantially across the globe by 3.1 °C by the end of the century under a high emission scenario. This projected trend is largely attributed to climate change-driven increases in specific humidity (1.8 °C), followed by air temperature (1.4 °C)—with urbanization impacts varying by location and of a smaller magnitude. Urban humid heat stress is projected to be concentrated in coastal, equatorial areas. At least 44% of the projected urban population in 2100, the equivalent of over 3 billion people worldwide, is projected to be living in an urban area with high humid heat stress. We show a critical, climate-driven dilemma between cooling efficacy and water limitation of urban greenery-based heat adaptation. Insights from our study emphasize the importance of usingmore »urban-explicit humid heat measures for more accurate assessments of urban heat exposure and invite careful evaluation of the feasibility of green infrastructure as a long-term cooling strategy.

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4. Projected Changes in Future Extreme Precipitation over the Northeast United States in the NA-CORDEX Ensemble

   https://doi.org/10.1175/JAMC-D-22-0008.1  

   Nazarian, Robert H. ; Vizzard, James V. ; Agostino, Carissa P. ; Lutsko, Nicholas J. ( November 2022 , Journal of Applied Meteorology and Climatology)

   The northeastern United States (NEUS) is a densely populated region with a number of major cities along the climatological storm track. Despite its economic and social importance, as well as the area’s vulnerability to flooding, there is significant uncertainty around future trends in extreme precipitation over the region. Here, we undertake a regional study of the projected changes in extreme precipitation over the NEUS through the end of the twenty-first century using an ensemble of high-resolution, dynamically downscaled simulations from the North American Coordinated Regional Climate Downscaling Experiment (NA-CORDEX) project. We find that extreme precipitation increases throughout the region, with the largest changes in coastal regions and smaller changes inland. These increases are seen throughout the year, although the smallest changes in extreme precipitation are seen in the summer, in contrast to earlier studies. The frequency of heavy precipitation also increases such that there are relatively fewer days with moderate precipitation and relatively more days with either no or strong precipitation. Averaged over the region, extreme precipitation increases by +3%–5% °C⁻¹of local warming, with the largest fractional increases in southern and inland regions and occurring during the winter and spring seasons. This is lower than the +7% °C⁻¹rate expectedmore »from thermodynamic considerations alone and suggests that dynamical changes damp the increases in extreme precipitation. These changes are qualitatively robust across ensemble members, although there is notable intermodel spread associated with models’ climate sensitivity and with changes in mean precipitation. Together, the NA-CORDEX simulations suggest that this densely populated region may require significant adaptation strategies to cope with the increase in extreme precipitation expected at the end of the next century.

   Observations show that the northeastern United States has already experienced increases in extreme precipitation, and prior modeling studies suggest that this trend is expected to continue through the end of the century. Using high-resolution climate model simulations, we find that coastal regions will experience large increases in extreme precipitation (+6.0–7.5 mm day⁻¹), although there is significant intermodel spread in the trends’ spatial distribution and in their seasonality. Regionally averaged, extreme precipitation will increase at a rate of ∼2% decade⁻¹. Our results also suggest that the frequency of extreme precipitation will increase, with the strongest storms doubling in frequency per degree of warming. These results, taken with earlier studies, provide guidance to aid in resiliency preparation and planning by regional stakeholders.

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5. Understanding perceived climate risks to household water supply and their implications for adaptation: evidence from California

   https://doi.org/10.1007/s10584-023-03517-0  

   Dobbin, Kristin B. ; Fencl, Amanda L. ; Pierce, Gregory ; Beresford, Melissa ; Gonzalez, Silvia ; Jepson, Wendy ( April 2023 , Climatic Change)

   Rapid adaptation is necessary to maintain, let alone expand, access to reliable, safe drinking water in the face of climate change. Existing research focuses largely on the role, priorities, and incentives of local managers to pursue adaptation strategies while mostly neglecting the role of the broader public, despite the strong public support required to fund and implement many climate adaptation plans. In this paper, we interrogate the relationship between personal experiences of household water supply impacts from extreme weather events and hazard exposure with individual concern about future supply reliability among a statewide representative sample of California households. We find that more than one-third of Californians report experiencing impacts of climate change on their household water supplies and show that these reported impacts differently influence residents’ concern about future water supply reliability, depending on the type of event experienced. In contrast, residents’ concern about future water supplies is not significantly associated with hazard exposure. These findings emphasize the importance of local managers’ attending to not only how climate change is projected to affect their water resources, but how, and whether, residents perceive these risks. The critical role of personal experience in increasing concern highlights that post-extreme events with watermore »supply impacts may offer a critical window to advance solutions. Managers should not assume, however, that all extreme events will promote concern in the same way or to the same degree.

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