Do Longer Dry Spells Associated With Warmer Years Compound the Stress on Global Water Resources?
Increasingly frequent water crises and forest fires around the world, such as those that occurred in Australia and California between 2017 and 2019, highlight the catastrophic consequences of long periods without rain. As with the risks associated with intensified storm extremes, the lack of rain casts equally dire consequences to human life and safety (Vogel et al., 2019) . Preparing and maintaining adequate water reserves can mitigate water shortages such as those in Cape Town, South Africa
... aker, 2019) and Southern India in 2019 (Sharma, 2019). As we are faced with the prospect of a potentially warmer climate, the question we ask here is whether availability of water resources is mainly disrupted from changes in mean annual rain and droughts or do subtle changes in intra-season variability in rainfall in warmer climatic conditions also contribute to this threat. To answer this question, we first explore how the length of summer dry spells differ in warmer periods, specifically for warmer summers. We then assess the consequence of this change by investigating the impact on available water resources that is reflective of what we might expect as the global climate gets warmer. An important note is that here we define a dry spell as continuous days without rain. The majority of literature investigating intra-seasonal rainfall variability evaluates the frequency of wet/dry days (Dunstone et al., 2018; Greve et al., 2014; Groisman & Knight, 2008) , or uses longer timescales of average monthly or annual rainfall to define drought periods (Seneviratne et al., 2012) . Hence, these measures may be missing the impact of the length of continuous days without rain or "dry spells" as defined in this paper. This important distinction is critical to consider, as longer intra-seasonal dry spells will