NOAA/WDS Paleoclimatology - Anchukaitis - Firth River 1236 - PCGL - ITRDB AK132

Northwestern North America has one of the highest rates of recent temperature increase in the world, but the putative "divergence problem" in dendroclimatology potentially limits the ability of tree-ring proxy data at high latitudes to provide long-term context for current anthropogenic change. Here, summer temperatures are reconstructed from a Picea glauca maximum latewood density (MXD) chronology that shows a stable relationship to regional temperatures and spans most of the last millennium at the Firth River in northeastern Alaska. The warmest epoch in the last nine centuries is estimated to have occurred during the late twentieth century, with average temperatures over the last 30 yr of the reconstruction developed for this study [1973-2002 in the Common Era (CE)] approximately 1.3° ± 0.4°C warmer than the long-term preindustrial mean (1100-1850 CE), a change associated with rapid increases in greenhouse gases. Prior to the late twentieth century, multidecadal temperature fluctuations covary broadly with changes in natural radiative forcing. The findings presented here emphasize that tree-ring proxies can provide reliable indicators of temperature variability even in a rapidly warming climate.

北美西北部是全球近期升温速率最快的区域之一，但树木气候学（dendroclimatology）中所谓的“分异问题”，可能限制了高纬度地区树轮代用资料为当前人为气候变化提供长期背景的能力。本研究基于阿拉斯加东北部弗斯河地区的白云杉（Picea glauca）最大晚材密度（MXD）年表，重建了该区域的夏季温度序列；该年表与区域温度存在稳定的相关关系，且时间跨度覆盖了过去近千年的绝大多数时段。研究估算，过去9个世纪以来最暖的时段出现在20世纪后期；本研究重建序列的最后30年（公元1973-2002年）的平均温度，较长期工业化前平均水平（公元1100-1850年）偏高约1.3℃±0.4℃，这一温度变化与温室气体的快速增加密切相关。在20世纪后期之前，数十年尺度的温度波动与自然辐射强迫的变化总体上呈协同对应关系。本研究结果表明，即便在快速变暖的气候背景下，树轮代用资料仍可作为可靠的温度变化指示器。