In the target article, Van Lange et al. go beyond the documentation of interesting temperature-aggression effects and try to explain such findings with their theoretical model. However, there are some critical points for further consideration. First, the CLASH model focuses only on “hot” (i.e., reactive) aggression and does not try to explain “cold” aggression, the kind of calculated, planful aggression that takes a degree of self-control and future orientation to execute. A parsimonious model of the role of climate-related variables in aggression and violence should explain both types of aggression. Would “cooler” aggressive behaviors be more likely to occur in cooler climates and/or those with more seasonal variation in temperature? How does their model address such types of aggression?

Second, and worthy of further elaboration, the CLASH model does not account for the research finding that warmer temperatures (and the concept of warmth more generally) are also associated with increased prosocial behaviors and that both hot and cold temperatures have been found to reduce self-control (Gailliot Reference Gailliot2014). These results, at first glance, seem to contradict the CLASH model; however, it may be possible for the authors to revise it to encompass this broader set of findings.

There are significantly more publications examining how temperature and climate-related factors are associated with aggressive outcomes, rather than prosocial outcomes (see target article). However, one can also make a case for the role of temperature in promoting prosocial outcomes. Future researchers should add to this literature and revise their theoretical models to include a fuller picture of climatological effects that include prosocial outcomes.

Starting in the realm of everyday language use and metaphor, people commonly talk about their “warm feelings” toward loved ones or shunning by way of giving the “cold shoulder.” Images of warmth and coldness are thus central to discussions of relationship closeness and connection, similar to the importance of images of heat when discussing anger and aggression (e.g., “red hot” anger or “fiery temper”). Social psychologists have long been aware that the concepts of psychological warmth (vs. coldness) are of central importance to people's judgments about others (Asch Reference Asch1946; Fiske et al. Reference Fiske, Cuddy and Glick2007; Kelley Reference Kelley1950). Indeed, scholars have suggested that noticing others' potential warmth could provide a survival advantage by helping to identify trustworthy partners (Fiske et al. Reference Fiske, Cuddy and Glick2007). Attachment theorists link physical warmth to early experiences of parental bonding and care (e.g., Bowlby Reference Bowlby1969). These lines of research all place the concept of warmth (whether psychological or physical) as fundamental to bonding and social regulation. Metaphorical links between physical and psychological warmth have substantive implications for behavior (for a discussion see Bargh & Shalev [Reference Bargh and Shalev2012]).

Indeed, not only has some laboratory research found that high temperatures can actually inhibit aggressive behavior (e.g., Baron Reference Baron1972), but also other studies have found that they promote prosocial behaviors. Warmer temperatures can enhance relational mindsets (IJzerman & Semin Reference IJzerman and Semin2009) and affiliative motivation (Fay & Maner Reference Fay and Maner2012), but also making people see others as interpersonally warmer and closer to the self. For example, participants who were holding a warm object (such as a hot coffee), compared with those holding a cold object, felt closer to a loved one (IJzerman & Semin Reference IJzerman and Semin2009) and judged others as being friendlier (Williams & Bargh Reference Williams and Bargh2008). Warmer temperatures can also affect prosocial behaviors, making people more likely to give a gift (Williams & Bargh Reference Williams and Bargh2008) or share money with others (Kang et al. Reference Kang, Williams, Clark, Gray and Bargh2010; Storey & Workman Reference Storey and Workman2013). The effects of warm temperature on prosocial behavior seem to be especially pronounced for those who have a secure attachment style (IJzerman et al. Reference IJzerman, Karremans, Thomsen and Schubert2015b).

Of course, laboratory experiments on the effects of temperature on prosocial outcomes may not translate to the role of broader climatological variables. Thus, field studies on how weather variations are associated with behaviors are also informative. Although these studies do indicate a role for temperature in promoting prosocial behaviors, they find that other climatological factors are also important (Cunningham Reference Cunningham1979; Guéguen & Lamy Reference Guéguen and Lamy2013; Lagacé-Séguin & d'Entremont Reference Lagacé-Séguin and d'Entremont2005). For example, studies find that sunshine is associated with increased positive moods, more helping behaviors, and less aggression (Cunningham Reference Cunningham1979; Guéguen & Lamy Reference Guéguen and Lamy2013; Lagacé-Séguin & d'Entremont Reference Lagacé-Séguin and d'Entremont2005), with one study finding that the effects of sunshine are stronger than temperature itself (Cunningham Reference Cunningham1979). In addition, studies have pointed to the role of humidity, rather than temperature itself, in predicting increased aggression and decreased prosocial behavior in children (Ciucci et al. Reference Ciucci, Calussi, Menesini, Mattei, Petralli and Orlandini2011; Lagacé-Séguin & d'Entremont Reference Lagacé-Séguin and d'Entremont2005), suggesting that Van Lange et al. also need to disentangle temperature from humidity effects.

To date there have been limited cross-national studies examining how climate-related variables are associated with prosocial outcomes. Using data from the World Values Survey, one study found that people from cultures with demanding hot or cold climates (represented as deviations from a comfortable 22°C), especially those from the richest cultures, held more cooperative values (Van de Vliert et al. Reference Van de Vliert, Van der Vegt and Janssen2009). People from poorer cultures with demanding climates held more egoistic values (Van de Vliert et al. Reference Van de Vliert, Van der Vegt and Janssen2009). Another study by the same authors finds similarly complex relationships between climate, wealth, and prosocial behavior (Van de Vliert et al. Reference Van de Vliert, Huang and Parker2004). Although these studies did not report main effects of average annual climatological variables such as temperature and sunshine, they suggest another lens of analysis for Van Lange et al.

There is some evidence that increases in temperature can lead to both increased aggression, as the target article suggests, and increased prosocial outcomes, although this is based on a smaller literature. Thus, a theory on climate and social behavior must allow for both positive and negative emotional and behavioral responses to warmer temperatures. There may be evidence for a more general argument, namely, that warmer temperatures influence emotional reactivity in general – both positivity and negativity. Future theories and research studies must address why some people react with more hostility and aggression in warmer temperatures, whereas others react more prosocially with similar situational triggers. Moreover, this future work should go beyond temperature itself and consider the psychological and behavioral implications of other climate-related variables.