Regional reconstructions of air temperature over the past millennium provide critical context for ongoing climate change, but they are temporally limited in the recent period or absent for many parts of the world. We demonstrate the use of latewood blue intensity (LWB) to reconstruct current-year growing (warm) season maximum temperatures (T_max) in the low-to-mid latitudes (30°-50°N) of western North America. We present a new tree ring network comprised of 26 LWB chronologies developed from living, high-elevation Engelmann spruce (Picea engelmannii Parry ex Engelm.) sampled across the western United States. The LWB parameter shows strong, positive (r = 0.65–0.73), and temporally-stable correlations with growing season T_max. From this network we present 4 regional T_max reconstructions, which characterize regional temperature histories across western North America from northern Mexico to southern British Columbia over the past 4 centuries. Our comparison of these 4 temperature reconstructions highlights the spatial patterns of regional temperature trends throughout time. These reconstructions provide important updates and increased data point density to the tree ring temperature proxy network of the Northern Hemisphere. We highlight the use of blue intensity methods at both low- and mid-latitude upper tree line locations to increase the presence of strongly temperature-sensitive records at increasingly lower latitudes of the Northern Hemisphere.

过去千年的区域气温重建为持续的气候变化提供了关键背景，但在最近一段时间内，它们在时间上受到限制，或者在世界许多地方都不存在。我们展示了使用晚材蓝色强度 (LWB) 来重建北美西部中低纬度 (30°-50°N) 的当年生长（暖）季节最高温度 (T _max )。我们提出了一个新的树轮网络，由 26 个 LWB 年表组成，这些年表是从美国西部采样的活的、高海拔的恩格尔曼云杉 ( Picea engelmannii Parry ex Engelm.)发展而来的。LWB 参数显示出 与生长季节 T _{max 的}强、正 ( r = 0.65–0.73) 和时间稳定的相关性. 从这个网络中，我们提出了 4 个区域 T _max重建，它们表征了过去 4 个世纪从墨西哥北部到不列颠哥伦比亚省南部的北美西部区域温度历史。我们对这 4 次温度重建的比较突出了区域温度随时间变化趋势的空间模式。这些重建为北半球的树木年轮温度代理网络提供了重要的更新和增加的数据点密度。我们强调在低纬度和中纬度上树线位置使用蓝色强度方法，以增加北半球越来越低纬度地区强烈温度敏感记录的存在。