Attribution of polar warming to human influence

Gillett, Nathan P.; Stone, Dáithí A.; Stott, Peter; Nozawa, Takashi; Karpechko, Alexey Yu.; Hegerl, Gabriele C.; Wehner, Michael; Jones, Phil

doi:10.1038/ngeo338

Cited by 229 publications

(166 citation statements)

References 25 publications

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“…9d), while solar forcing has reached a plateau. Gillett et al (2008) attributed overall twentieth-century temperature trends in the Arctic to anthropogenic forcing, and showed that only climate models that included anthropogenic forcing reproduced the twentieth-century temperature trends over Alaska.…”

Section: Resultsmentioning

confidence: 99%

Tree-Ring-Reconstructed Summer Temperatures from Northwestern North America during the Last Nine Centuries*

et al. 2013

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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 in the Common Era (CE)] approximately 1.38 6 0.48C 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.

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Section: Resultsmentioning

confidence: 99%

Tree-Ring-Reconstructed Summer Temperatures from Northwestern North America during the Last Nine Centuries*

et al. 2013

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“…Successive losses of ice shelves on the Antarctic Peninsula (Vaughan and Doake 1996;Shepherd et al 2003;Turner et al 2005;Cook et al 2005) may be among the dramatic impacts of the warming. Comparison with temperature variability simulated by climate models suggests the observed warming is at least partly anthropogenically-forced (Gillett et al 2008). Nevertheless, anthropogenic warming in the rest of the Southern Hemisphere high-latitudes has not been unambiguously detected, especially in the interior of Antarctica continent where both warming and cooling trends have been reported (Thompson and Solomon 2002;Turner et al 2006;Chapman and Walsh 2007;Steig et al 2009).…”

Section: Introductionmentioning

confidence: 99%

Why does the Antarctic Peninsula Warm in climate simulations?

Hall

Boé

2011

Clim Dyn

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The Antarctic Peninsula has warmed significantly since the 1950s. This pronounced and isolated warming trend is collectively captured by 29 twentiethcentury climate hindcasts participating in the version 3 Coupled Model Intercomparison Project. To understand the factors driving warming trends in the hindcasts, we examine trends in Peninsula region's atmospheric heat budget in every simulation. We find that atmospheric latent heat release increases in nearly all hindcasts. These increases are generally anthropogenic in origin, and account for about 60% of the ensemble-mean warming trend in the Peninsula. They are driven primarily by wellunderstood features of the anthropogenic intensification of global hydrological cycle. As sea surface temperature increases, moisture contained in atmospheric flows increases. When such flows are forced to ascend the Peninsula's topography, enhanced local latent heat release results. The mechanism driving the warming of the Antarctic Peninsula is therefore clear in the models. Evidence for a similar mechanism operating in the real world is seen in the increasing snow accumulation rates inferred from ice cores drilled in the Peninsula. However, the relative importance of this mechanism and other processes previously identified as potentially causing the observed warming, such as the recent sea ice retreat in the Bellingshausen Sea, is difficult to assess. Thus the relevance of the simulated warming mechanism to the observed warming is unclear, in spite of its robustness in the models.

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“…This is particularly significant with regards to the Southern Hemisphere westerly storm belt, which since the mid1970s, has undergone a significant intensification and southward shift (Gillett et al, 2008;Messié and Chavez, 2011). One measure of this change in atmospheric circulation is the Southern Annular Mode (SAM), described as the pressure difference between Antarctica (65 • S) and the latitude band at around 40 • S (Karpechko et al, 2009;Marshall, 2003).…”

Section: Introductionmentioning

confidence: 99%

A 250-year periodicity in Southern Hemisphere westerly winds over the last 2600 years

et al. 2016

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Abstract. Southern Hemisphere westerly airflow has a significant influence on the ocean-atmosphere system of the mid-to high latitudes with potentially global climate implications. Unfortunately, historic observations only extend back to the late 19th century, limiting our understanding of multi-decadal to centennial change. Here we present a highly resolved (30-year) record of past westerly wind strength from a Falkland Islands peat sequence spanning the last 2600 years. Situated within the core latitude of Southern Hemisphere westerly airflow (the so-called furious fifties), we identify highly variable changes in exotic pollen and charcoal derived from South America which can be used to inform on past westerly air strength. We find a period of high charcoal content between 2000 and 1000 cal. years BP, associated with increased burning in Patagonia, most probably as a result of higher temperatures and stronger westerly airflow. Spectral analysis of the charcoal record identifies a pervasive ca. 250-year periodicity that is coherent with radiocarbon production rates, suggesting that solar variability has a modulating influence on Southern Hemisphere westerly airflow. Our results have important implications for understanding global climate change through the late Holocene.

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Attribution of polar warming to human influence

Cited by 229 publications

References 25 publications

Tree-Ring-Reconstructed Summer Temperatures from Northwestern North America during the Last Nine Centuries*

Tree-Ring-Reconstructed Summer Temperatures from Northwestern North America during the Last Nine Centuries*

Why does the Antarctic Peninsula Warm in climate simulations?

A 250-year periodicity in Southern Hemisphere westerly winds over the last 2600 years

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