Detecting the human fingerprint in the summer 2022 western-central European soil drought

In the 2022 summer, western-central Europe and several other regions in the northern extratropics experienced substantial soil moisture deficits in the wake of precipitation shortages and elevated temperatures. Much of Europe has not witnessed a more severe soil drought since at least the mid-20th century, raising the question whether this is a manifestation of our warming climate. Here, we employ a well-established statistical approach to attribute the low 2022 summer soil moisture to human-induced climate change using observation-driven soil moisture estimates and climate models. We find that in western-central Europe, a June-August root zone soil moisture drought such as in 2022 is expected to occur once in 20 years in the present climate but would have occurred only about once per century during preindustrial times. The entire northern extratropics show an even stronger global warming imprint with a 20-fold soil drought probability increase or higher, but we note that the underlying uncertainty is large. Reasons are manifold but include the lack of direct soil moisture observations at the required spatiotemporal scales, the limitations of remotely sensed estimates, and the resulting need to simulate soil moisture with land surface models driven by meteorological data. Nevertheless, observation-based products indicate long-term declining summer soil moisture for both regions, and this tendency is likely fueled by regional warming, while no clear trends emerge for precipitation. Finally, our climate model analysis suggests that under 2C global warming, 2022-like soil drought conditions would become twice as likely for western-central Europe compared to today and would take place nearly every year across the northern extratropics.</p

Climate change increased extreme monsoon rainfall, flooding highly vulnerable communities in Pakistan

As a direct consequence of extreme monsoon rainfall throughout the summer 2022 season Pakistan experienced the worst flooding in its history. We employ a probabilistic event attribution methodology as well as a detailed assessment of the dynamics to understand the role of climate change in this event. Many of the available state-of-the-art climate models struggle to simulate these rainfall characteristics. Those that pass our evaluation test generally show a much smaller change in likelihood and intensity of extreme rainfall than the trend we found in the observations. This discrepancy suggests that long-term variability, or processes that our evaluation may not capture, can play an important role, rendering it infeasible to quantify the overall role of human-induced climate change. However, the majority of models and observations we have analysed show that intense rainfall has become heavier as Pakistan has warmed. Some of these models suggest climate change could have increased the rainfall intensity up to 50%. The devastating impacts were also driven by the proximity of human settlements, infrastructure (homes, buildings, bridges), and agricultural land to flood plains, inadequate infrastructure, limited ex-ante risk reduction capacity, an outdated river management system, underlying vulnerabilities driven by high poverty rates and socioeconomic factors (e.g. gender, age, income, and education), and ongoing political and economic instability. Both current conditions and the potential further increase in extreme peaks in rainfall over Pakistan in light of anthropogenic climate change, highlight the urgent need to reduce vulnerability to extreme weather in Pakistan

Interplay between climate change and climate variability: the 2022 drought in Central South America

Since 2019, Central South America (CSA) has been reeling under drought conditions, with the last 4 months of 2022 receiving only 44% of the average total precipitation. Simultaneously to the drought, a series of record-breaking heat waves has affected the region. The rainfall deficit during October–November-December (OND) is highly correlated with the Niño3.4 index, indicating that the OND 2022 rainfall deficit is partly driven by La Niña, as observed in previous droughts in this region. To identify whether human-induced climate change was also a driver of the OND 2022 rainfall deficit, we analysed precipitation over the most impacted region. Our findings revealed a pattern of decreased rainfall over the past 40 years, although we cannot definitively conclude whether this trend exceeds what would be expected from natural variations. To clarify if this trend can be attributed to climate change, we looked at 1-in-20-year low rainfall events over the same region in climate models. The models show that the severity of low rainfall events decreases (i.e. they become wetter, the opposite of the trend observed in most weather records), although this trend is again not significant and is compatible with natural variability. Therefore, we cannot attribute the low rainfall to climate change. Moreover, our analysis of effective precipitation potential (evapotranspiration minus rainfall) shows that, in climate models, the increase in temperature does partly compensate for the increase in rainfall but only to offset the wetting, and does not lead to a significant climate change signal in effective precipitation. However, higher temperatures in the region, which have been attributed to climate change, decreased water availability in the models in late 2022, indicating that climate change probably reduced water availability over this period also in the observations, increasing agricultural drought, although this study did not quantify this effect. This means that even though the reduced rainfall is within the natural variability, the consequences of drought are becoming more severe due to the strong increase in extreme heat. The case of the OND 2022 rainfall deficit and the ongoing drought in CSA is a clear example of the interplay between climate variability and human-induced climate change. This shows the importance of considering not only those aspects associated with climate change but also climate variability in order to understand and attribute particular events or trends at the regional level

The role of climate change in extreme rainfall associated with Cyclone Gabrielle over Aotearoa New Zealand’s East Coast

Aotearoa is a country with good channels for communicating forecasts of extreme rainfall. Significant warning was able to be given for Cyclone Gabrielle of expected heavy rainfall and the potential for rapidly rising rivers, which may have reduced impacts. Still, the significant damage, economic cost, and loss of life can be linked to factors such as a reliance on flood protection systems and infrastructure that are not built to withstand such extreme flood events, settlements in highly flood-prone regions, and social vulnerability factors that can reduce coping capacity such as higher rates of disability and unemployment amongst Māori communities. Land use changes that reduced soil stability, combined with deforestation and forestry slashing likely also contributed to the impacts. Future efforts to reduce vulnerability should focus on addressing shortcomings such as updating infrastructure to be built to the “new normal”, and strengthening early-warning systems for impacts, social connectedness, knowledge, skills and awareness of natural hazards which can improve risk perception and increase self-protective action based on a forecast or warning. Adaptation efforts must be inclusive of a variety of stakeholder viewpoints, especially Indigenous cultural values that may differ from Pākehā views of flood risk management

Early warning early action (EWEA) in secondary cities in South Asia : guidance note

Ministry of Foreign Affairs of the Netherland

2022 early-summer heatwave in Southern South America: 60 times more likely due to climate change

A large area including the central-northern part of Argentina, southern Bolivia, central Chile, and most of Paraguay and Uruguay, experienced record-breaking temperatures during two consecutive heatwaves in late November and early December 2022. During the second heatwave, nine locations in northern Argentina registered their highest maximum temperature of December since at least 1961. Our analysis based on observational and reanalysis datasets indicate that South America, like the rest of the world, has experienced heatwaves increasingly frequently in recent years. The December 2022 heatwave has an estimated return time of 1 in 20 years in the current climate, meaning it has about a 5% chance of happening each year. To estimate how human-caused climate change has influenced the likelihood and intensity of the observed heatwave, we combined climate models with the observation-based data. We found that human-caused climate change made the event about 60 times more likely. A heatwave with a return period of 20 years would be about 1.4 °C less hot in a world without anthropogenic global warming. Heatwaves this early in the summer season pose a substantial risk to human health and are potentially lethal. This risk is aggravated by climate change, but also by other factors such as an aging population, urbanisation and the built environment, and individual behavior and susceptibility to the heat. This highlights the importance of attribution studies in a region already threatened and vulnerable to climate change