Lisa Thalheimer, DPhil

Lisa Thalheimer, DPhil

Climate Change Attribution
Climate Econometrics
Modelling Climate Migration

Publications

L. Thalheimer; Schwarz, M.; and Pretis, F. (2023). Large weather and conflict effects on internal displacement in Somalia with little evidence of feedback onto conflict, Global Environmental Change, 79, 102641.

We analyze the effect of weather, drought and conflict on internal displacement in Somalia. We find that a 1°C temperature increase can cause a tenfold increase in displaced people. If average monthly rainfall declined from 100 mm to 50 mm, predicted numbers for internally displaced populations in Somalia doubled.

Abstract Extreme weather and conflict may drive forced displacement. However, their individual contribution to displacement is not fully understood due to challenges around isolating individual channels of causality. Here, we use novel disaggregated data on internal displacement in all of Somalia’s subregions from 2016 to 2018 broken down by reported reason of displacement and combine it with weather and conflict data. This allows us to isolate the effects of extreme weather and conflict on forced displacement, as well as the effects of displacement on conflict itself. We find large non-linear effects of weather on displacement where an increase in temperature anomalies from 1 °C to 2 °C (to approx. 1.5 standard deviations, SD) leads to a tenfold increase in displaced people, and a reduction in precipitation from 50 mm to 0 mm (approx. 1.5SD) leads to around a fourfold increase in displacement. We find significant effects of conflict events on displacement (which are masked when the data is aggregated) with a 1.5 standard deviation increase in conflict events increasing displacement 50-fold. We further show that displacement itself has little detectable effect on the occurrence of conflict events.

L. Thalheimer; Choquette-Levy, N.; and F. Garip (2022). Compound impacts from drought and structural vulnerability on human mobility, iScience, 25(12): 105491.

We analyze the impacts of compound risks (i.e. multiple climate and social factors that threaten livelihoods) on migration responses to drought in Madagascar, Mexico, and Nepal. We find that the net climate-migration relationship depends on social factors e.g. access to irrigation, accurate information, and social connections.

Abstract Extreme dry events already disrupt populations’ ability to migrate. In a warming climate, compound drought events could amplify vulnerability and drive forced migration. Here, we contribute the first multi-method research design on societal impacts from compound drought events. We show how mobility patterns are shaped by the intersection of drought and social vulnerability factors in three drought-prone countries – Madagascar, Nepal, and Mexico. We find that internal migration in agricultural communities in Mexico increased by 14 to 24 basis points from 1991 to 2018 and will prospectively increase by 2 to 15 basis points in Nepal in case of a compound drought event in 2025. We show that consecutive drought events exacerbate structural vulnerabilities, limiting migrants’ adaptation options, including long-range migration. We conclude that the additional social pre-conditions, e.g., social isolation and lack of accurate information, ultimately limit migration as an adaptation option for households vulnerable to compound drought events.

Otto, F.; Zachariah, M; Saeed, F.; Siddiqi, A.; Kamil, S.; Mushtaq, H.; Arulalan, T.; AchutaRao, K.; Chaithra, ST; Barnes, C.; Philip, S.; Kew, S.; Vautard, R.; Koren, G.; Pinto, I.; Wolski, P.; Vahlberg, M.; Singh, R.; Arrighi, J.; Van Aalst, M.; Thalheimer, L.; Raju, E.; Li, S.; Yang, W.; Harrington, L.; Clarke, B., Environmental Research: Climate, 2(2), 025001.

We attribute the extreme monsoon rainfall throughout the summer 2022 season in Pakistan to climate change. We find that across several models, climate change could have increased the rainfall intensity up to 50%.

Abstract 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.