Extended Data Fig. 2: Northern Hemisphere LTG at three temporal scales.
From: Mid-latitude net precipitation decreased with Arctic warming during the Holocene
a–c, Changes in LTG slope over (a) the instrumental period (twentieth century), (b) the past two millennia, and (c) Holocene (black) compared with Holocene annual latitudinal insolation gradient (red), and past two millennia LTGs binned to the same resolution as the Holocene data (dark blue). Gradients were calculated using linear regression across five 20° latitudinal composites as illustrated in Extended Data Fig. 8. Twentieth-century LTGs were calculated from CRU TS4.01 data15, last two millennia LTGs rely on the PAGES 2k network16, and Holocene-long LTGs use the new dataset presented in this study. Shading represents the one- and two-standard deviation bootstrapped confidence intervals over 500 iterations. Age and proxy temperature uncertainties included in the Holocene error estimations (Methods) smooth the error envelope with respect to the last two millennia, for which there is less age uncertainty16. The Holocene latitudinal insolation gradient uses data from ref. 14. The historical trend in a towards weaker gradients (less negative slopes) characterizes recent Arctic amplification.
