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similar teleconnection pattern as that derived from LMR2, so our discussion focuses on results from LMR2. b. CMIP5 and five model large ensembles To examine the effects of increasing anthropogenic forcing on global climate, we use two sets of multimodel ensemble means to reduce uncertainties in each model ( Deser et al. 2020 ). One is the ensemble mean of all 40 climate models provided in CMIP5 ( Taylor et al. 2012 ; Table 1 ) over the 1979–2017 period, combining model outputs from the 1979
similar teleconnection pattern as that derived from LMR2, so our discussion focuses on results from LMR2. b. CMIP5 and five model large ensembles To examine the effects of increasing anthropogenic forcing on global climate, we use two sets of multimodel ensemble means to reduce uncertainties in each model ( Deser et al. 2020 ). One is the ensemble mean of all 40 climate models provided in CMIP5 ( Taylor et al. 2012 ; Table 1 ) over the 1979–2017 period, combining model outputs from the 1979
thermosteric effects ( Purkey and Johnson 2010 ), while increases in glacial runoff have been shown to enhance sea level rise within the Southern Ocean ( Rye et al. 2014 ; van den Berk and Drijfhout 2014 ). AABW property and volume changes will likely alter the global overturning circulation. Current studies often refer to the role of AABW in the “bipolar seesaw.” Under such a scenario, reduced AABW transport enhances North Atlantic Deep Water (NADW) circulation (e.g., England 1993 ; Seidov et al. 2001
thermosteric effects ( Purkey and Johnson 2010 ), while increases in glacial runoff have been shown to enhance sea level rise within the Southern Ocean ( Rye et al. 2014 ; van den Berk and Drijfhout 2014 ). AABW property and volume changes will likely alter the global overturning circulation. Current studies often refer to the role of AABW in the “bipolar seesaw.” Under such a scenario, reduced AABW transport enhances North Atlantic Deep Water (NADW) circulation (e.g., England 1993 ; Seidov et al. 2001
variance at interannual and decadal time scales ( Yuan and Li 2008 ). ENSO’s impacts not only appear in the atmospheric circulation, surface climate, and sea ice, but also extend to the deep ocean and under ice shelves. McKee et al. (2011) detected ENSO signals from mooring temperature records at 4560 m below the surface south of South Orkney Island, where bottom water is exported out of the Weddell Sea. ENSO and SAM were mostly in phase from 1997 to 2002, which produced reinforced effects on surface
variance at interannual and decadal time scales ( Yuan and Li 2008 ). ENSO’s impacts not only appear in the atmospheric circulation, surface climate, and sea ice, but also extend to the deep ocean and under ice shelves. McKee et al. (2011) detected ENSO signals from mooring temperature records at 4560 m below the surface south of South Orkney Island, where bottom water is exported out of the Weddell Sea. ENSO and SAM were mostly in phase from 1997 to 2002, which produced reinforced effects on surface
Antarctica during winter and spring ( Steig et al. 2009 ; Ding et al. 2011 ; Schneider et al. 2012 ; Bromwich et al. 2013 ; Nicolas and Bromwich 2014 ). Apart from the warming on the northeast peninsula, the recent Antarctic Peninsula/West Antarctica climate trends lie within their respective ranges of internal variability and are likely tied to natural decadal variability in atmospheric circulation rather than anthropogenic forcing ( Jones et al. 2016a ; Turner et al. 2016 ). The western peninsula
Antarctica during winter and spring ( Steig et al. 2009 ; Ding et al. 2011 ; Schneider et al. 2012 ; Bromwich et al. 2013 ; Nicolas and Bromwich 2014 ). Apart from the warming on the northeast peninsula, the recent Antarctic Peninsula/West Antarctica climate trends lie within their respective ranges of internal variability and are likely tied to natural decadal variability in atmospheric circulation rather than anthropogenic forcing ( Jones et al. 2016a ; Turner et al. 2016 ). The western peninsula
since 1979 can be explained by interdecadal variability ( Fan et al. 2014 ; Gagné et al. 2015 ), particularly arising from the phase change of the interdecadal Pacific oscillation (IPO) to negative after the late 1990s ( Meehl et al. 2016a ), rather than by direct anthropogenic forcing. As such, it is pertinent to scrutinize the proposed causes of these trends. Here we further examine the concept that recent trends in tropical SST and tropical-to-extratropical teleconnections influenced the
since 1979 can be explained by interdecadal variability ( Fan et al. 2014 ; Gagné et al. 2015 ), particularly arising from the phase change of the interdecadal Pacific oscillation (IPO) to negative after the late 1990s ( Meehl et al. 2016a ), rather than by direct anthropogenic forcing. As such, it is pertinent to scrutinize the proposed causes of these trends. Here we further examine the concept that recent trends in tropical SST and tropical-to-extratropical teleconnections influenced the
with the strengthening of the circumpolar westerly winds primarily driven by anthropogenic forcing ( Marshall et al. 2006 ). Enhanced advection of warmer maritime air masses over the orographic barrier of the AP and the resulting foehn winds warm the cooler continental climate on the east side ( Orr et al. 2004 ; Marshall et al. 2006 ). Disintegration of ice shelves has progressed southward ( Scambos et al. 2004 ) from the northern tip as predicted by Mercer (1978) to occur in response to the
with the strengthening of the circumpolar westerly winds primarily driven by anthropogenic forcing ( Marshall et al. 2006 ). Enhanced advection of warmer maritime air masses over the orographic barrier of the AP and the resulting foehn winds warm the cooler continental climate on the east side ( Orr et al. 2004 ; Marshall et al. 2006 ). Disintegration of ice shelves has progressed southward ( Scambos et al. 2004 ) from the northern tip as predicted by Mercer (1978) to occur in response to the
radiative forcings [including greenhouse gasses (GHGs), natural and anthropogenic aerosols, solar variability, etc.] into a single category of “other” forcing. This is motivated by the fact that the direct impacts of these other radiative forcings (i.e., the components of the response not mediated by SSTs) have been previously found to be very small relative to the effects of ozone and SSTs (e.g., Deser and Phillips 2009 ; Polvani et al. 2011 ; Staten et al. 2012 ; Grise and Polvani 2014 ). Our
radiative forcings [including greenhouse gasses (GHGs), natural and anthropogenic aerosols, solar variability, etc.] into a single category of “other” forcing. This is motivated by the fact that the direct impacts of these other radiative forcings (i.e., the components of the response not mediated by SSTs) have been previously found to be very small relative to the effects of ozone and SSTs (e.g., Deser and Phillips 2009 ; Polvani et al. 2011 ; Staten et al. 2012 ; Grise and Polvani 2014 ). Our
