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A severe drought hit the Greater Horn of Africa (GHA) in 2014, but it remains unclear whether this extreme event was attributable to anthropogenic climate change or part of longer‐term natural cycles. Precipitation patterns are known to be changing across the GHA, but trajectories in land surface variables are much less well known. We simulated the GHA land surface environment to assess the balance between natural cycles and human‐induced climate change. Using a new form of event attribution study where we focused on both climate variables and also directly simulated land surface variables, we combined publicly volunteered distributed computing with land surface simulations to quantify land surface responses. Uncertainty was quantified both for climate model and land surface model outputs. We identified two distinct "drought trajectories" in the GHA bimodal seasonality area during the March–May (Long Rains season) of 2014. Human‐induced climate change may have resulted in regions from Lake Nalubaale (Lake Victoria) to Northern Kenya receiving less precipitation in this season and having up to 20% higher probability of drought‐level evapotranspiration rates (increasing drought). In contrast, the simulated anthropogenic climate change signal for this season induced somewhat wetter conditions and up to 20% lower probability of drought‐level evapotranspiration in Eastern Ethiopia, Southern Somalia, and coastal Kenya (decreasing drought). Uncertainties in our modeling system varied by region and variable of focus, but broadly we found that land surface simulation uncertainty neither added significantly to climate model uncertainty nor significantly reduced it. Key Points: Precipitation patterns are known to be changing across the Horn of Africa, but trajectories in land surface variables are less well knownWe identify two distinct "drought trajectories" in the Horn of Africa: one of increasing drought and one of decreasing droughtChanges in water cycle impacts may best be assessed through attribution studies that include changes in land surface variables [ABSTRACT FROM AUTHOR]

The article examines the influence of meteorological drivers on the in the Greater Horn of Africa region in January to March 2014 using the probabilistic event attribution methods. Topics covered include the political and economic impact of the drought and the findings that anthropogenic influence increased greenhouse gas concentration and sea surface temperatures but did not affect the likelihood of reduced precipitation.