 The Hiatus Controversy. Global mean near-surface temperature increased significantly during the 1990s but then showed little increase between the late 1990s and the early 2010s. By the mid-2000s, contrarians began to claim that global warming had stopped and that climate models (and climate science) were thus fundamentally flawed, since they had projected more warming. Part of the problem here was communication: graphs shared with policymakers and the public often highlighted the average of climate model projections, which smoothed out the significant variability seen in individual simulations and suggested a relatively steady warming; in fact, the observed rate of warming was not so different from that seen in some of the model projections (see Schmidt 2012; Risbey et al. 2014). Moreover, significant variations in temperature on decadal time scales, akin to that seen in the observations, were not entirely unexpected, given internal variability in the climate system (Easterling &amp; Wehner 2009). Nevertheless, by the early 2010s, pressure was mounting for climate scientists to give a detailed explanation of the apparent slowdown in surface warming, by then referred to as the “hiatus” or “pause”, and to explain why most models projected more warming. A preliminary analysis was given in the IPCC Fifth Assessment Report (see Flato et al. 2013: Box 9.2). A host of potential explanatory factors were identified—related to external forcing, internal variability, ocean heat uptake and errors in observational data—which contrarians portrayed as excuses. Subsequent investigation found evidence for actual contributions from most of the hypothesized factors, though discussion of their relative importance continues (see Medhaug et al. 2017 for an overview; a large literature on the topic has emerged). In the meantime, since 2014, global mean temperature has once again shown a sharp increase, in part due to a strong El Niño event in 2015/16.