Because
this large multidecadal variability is not random, but likely recurrent based on its past behavior, it has predictive value.
I disagree with: —
the large multidecadal oscillations (e.g NAO, PDO, AMO) being unforced.
Multi-decadal oscillations plus trend hypothesis: 20th century climate variability / change is explained by
the large multidecadal oscillations (e.g NAO, PDO, AMO) with a superimposed trend of external forcing (AGW warming).
This is because in the latter part of the time series there is a decrease in the total number of tropical cyclones, largely owing to
a large multidecadal cyclone in the WPAC (which comprises 40 % of the global tropical cyclones), see Fig 3 in Webster et al..
Not exact matches
The researchers next considered the influence of two
large weather patterns known to bring wetter conditions to the central United States — the El Niño - Southern Oscillation and the Atlantic
Multidecadal Oscillation.
Nonetheless, even if the substantial recent trend in the AO pattern is simply a product of natural
multidecadal variability in North Atlantic climate, it underscores the fact that western and southern Greenland is an extremely poor place to look, from a signal vs. noise point of view, for the
large - scale polar amplification signature of anthropogenic surface warming.
Finally, the El Niño - Southern Oscillation, Pacific Decadal Oscillation and Atlantic
Multidecadal Oscillation each contribute to
large variations in MHWs both regionally and globally.
Furthermore, since the end of the 19th century, we find an increasing variance in
multidecadal hydroclimatic winter and spring, and this coincides with an increase in the
multidecadal North Atlantic Oscillation (NAO) variability, suggesting a significant influence of
large - scale atmospheric circulation patterns.
In their paper Decadal Variations in the Global Atmospheric Land Temperatures, they find that the
largest contributor to global average temperature variability on short (2 - 5 year) timescales in not the El Nino - Southern Oscillation (ENSO)(as everyone else believes), but is actually the Atlantic
Multidecadal Oscillation (AMO).
The AWP
multidecadal variability coincides with the signal of the AMO; that is, the warm (cool) phases of the AMO are characterized by repeated
large (small) AWPs.
Patterns of variability that don't match the predicted fingerprints from the examined drivers (the «residuals») can be
large — especially on short - time scales, and look in most cases like the modes of internal variability that we've been used to; ENSO / PDO, the North Atlantic
multidecadal oscillation etc..
Nonetheless, even if the substantial recent trend in the AO pattern is simply a product of natural
multidecadal variability in North Atlantic climate, it underscores the fact that western and southern Greenland is an extremely poor place to look, from a signal vs. noise point of view, for the
large - scale polar amplification signature of anthropogenic surface warming.
In panel - b the magnitude of unforced variability is
large (wide range between the blue lines) and thus changes in the
multidecadal rate of warming could come about due to unforced variability.
There are, however, caveats: (1)
multidecadal fluctuations in Arctic — subarctic climate and sea ice appear most pronounced in the Atlantic sector, such that the pan-Arctic signal may be substantially smaller [e.g., Polyakov et al., 2003; Mahajan et al., 2011]; (2) the sea - ice records synthesized here represent primarily the cold season (winter — spring), whereas the satellite record clearly shows losses primarily in summer, suggesting that other processes and feedback are important; (3) observations show that while recent sea - ice losses in winter are most pronounced in the Greenland and Barents Seas, the
largest reductions in summer are remote from the Atlantic, e.g., Beaufort, Chukchi, and Siberian seas (National Snow and Ice Data Center, 2012, http://nsidc.org/Arcticseaicenews/); and (4) the recent reductions in sea ice should not be considered merely the latest in a sequence of AMOrelated
multidecadal fluctuations but rather the first one to be superposed upon an anthropogenic GHG warming background signal that is emerging strongly in the Arctic [Kaufmann et al., 2009; Serreze et al., 2009].
Our results suggest that the decadal AO and
multidecadal LFO drive
large amplitude natural variability in the Arctic making detection of possible long - term trends induced by greenhouse gas warming most difficult.
These net changes in OHC associated with ENSO are an order of magnitude
larger than the
multidecadal changes estimated for 1970 — 2012.
The results obtained from the five Coupled Global Climate Model, version 3, (CGCM3)- driven CRCM runs are similar, suggesting that the
multidecadal internal variability is not a
large source of uncertainty for the Peace River basin.
If a scientist and in particular climate scientists don't understand the wide swings that do occur in data over short
multidecadal time scales then how can they be trusted with understanding the
large climatic swings on longer millenia time scales or vise - versa.
Decadal variability is described via
large - scale patterns found in the atmosphere and ocean, which oscillate at decadal timescales and are concentrated in specific regions (e.g., Pacific Decadal Oscillation, Atlantic
Multidecadal Oscillation, Arctic and Antarctic Oscillations).
Given that the past 30 — 50 years is a relatively short period for evaluating long - term trends, the SST trends themselves could be viewed as a manifestation of
large - scale modes of
multidecadal Pacific variability (e.g. Zhang et al. 1997; Deser et al. 2004) or as part of the century scale positive SST trends associated with climate change (e.g. Deser et al. 2010); it is likely that both
multidecadal climate variability and climate change have contributed to the SST trend pattern evident in Fig. 9 and used to force the model.
What was done, was to take a
large number of models that could not reasonably simulate known patterns of natural behaviour (such as ENSO, the Pacific Decadal Oscillation, the Atlantic
Multidecadal Oscillation), claim that such models nonetheless accurately depicted natural internal climate variability, and use the fact that these models could not replicate the warming episode from the mid seventies through the mid nineties, to argue that forcing was necessary and that the forcing must have been due to man.
[Rob P]- The warming from 1910 - 1940, a time of weak anthropogenic (human - caused) forcing, matches the warm (positive) phase of the Interdecadal Pacific Oscillation (IPO)- the
largest natural
multidecadal oscillation in the climate system.
Similar decadal and
multidecadal cycles have being observed in numerous climatic proxy models for centuries and millennia, as documented in the references of my papers, although the proxy models need to be studied with great care because of the
large divergence from the temperature they may present.
The models heavily relied upon by the Intergovernmental Panel on Climate Change (IPCC) had not projected this
multidecadal stasis in «global warming»; nor (until trained ex post facto) the fall in TS from 1940 - 1975; nor 50 years» cooling in Antarctica (Doran et al., 2002) and the Arctic (Soon, 2005); nor the absence of ocean warming since 2003 (Lyman et al., 2006; Gouretski & Koltermann, 2007); nor the onset, duration, or intensity of the Madden - Julian intraseasonal oscillation, the Quasi-Biennial Oscillation in the tropical stratosphere, El Nino / La Nina oscillations, the Atlantic Multidecadal Oscillation, or the Pacific Decadal Oscillation that has recently transited from its warming to its cooling phase (oceanic oscillations which, on their own, may account for all of the observed warmings and coolings over the past half - century: Tsoniset al., 2007); nor the magnitude nor duration of multi-century events such as the Mediaeval Warm Period or the Little Ice Age; nor the cessation since 2000 of the previously - observed growth in atmospheric methane concentration (IPCC, 2007); nor the active 2004 hurricane season; nor the inactive subsequent seasons; nor the UK flooding of 2007 (the Met Office had forecast a summer of prolonged droughts only six weeks previously); nor the solar Grand Maximum of the past 70 years, during which the Sun was more active, for longer, than at almost any similar period in the past 11,400 years (Hathaway, 2004; Solankiet al., 2005); nor the consequent surface «global warming» on Mars, Jupiter, Neptune's largest moon, and even distant Pluto; nor the eerily - continuing 2006 solar minimum; nor the consequent, precipitate decline of ~ 0.8 °C in TS from January 2007 to May 2008 that has canceled out almost all of the observed warming of the 2
multidecadal stasis in «global warming»; nor (until trained ex post facto) the fall in TS from 1940 - 1975; nor 50 years» cooling in Antarctica (Doran et al., 2002) and the Arctic (Soon, 2005); nor the absence of ocean warming since 2003 (Lyman et al., 2006; Gouretski & Koltermann, 2007); nor the onset, duration, or intensity of the Madden - Julian intraseasonal oscillation, the Quasi-Biennial Oscillation in the tropical stratosphere, El Nino / La Nina oscillations, the Atlantic
Multidecadal Oscillation, or the Pacific Decadal Oscillation that has recently transited from its warming to its cooling phase (oceanic oscillations which, on their own, may account for all of the observed warmings and coolings over the past half - century: Tsoniset al., 2007); nor the magnitude nor duration of multi-century events such as the Mediaeval Warm Period or the Little Ice Age; nor the cessation since 2000 of the previously - observed growth in atmospheric methane concentration (IPCC, 2007); nor the active 2004 hurricane season; nor the inactive subsequent seasons; nor the UK flooding of 2007 (the Met Office had forecast a summer of prolonged droughts only six weeks previously); nor the solar Grand Maximum of the past 70 years, during which the Sun was more active, for longer, than at almost any similar period in the past 11,400 years (Hathaway, 2004; Solankiet al., 2005); nor the consequent surface «global warming» on Mars, Jupiter, Neptune's largest moon, and even distant Pluto; nor the eerily - continuing 2006 solar minimum; nor the consequent, precipitate decline of ~ 0.8 °C in TS from January 2007 to May 2008 that has canceled out almost all of the observed warming of the 2
Multidecadal Oscillation, or the Pacific Decadal Oscillation that has recently transited from its warming to its cooling phase (oceanic oscillations which, on their own, may account for all of the observed warmings and coolings over the past half - century: Tsoniset al., 2007); nor the magnitude nor duration of multi-century events such as the Mediaeval Warm Period or the Little Ice Age; nor the cessation since 2000 of the previously - observed growth in atmospheric methane concentration (IPCC, 2007); nor the active 2004 hurricane season; nor the inactive subsequent seasons; nor the UK flooding of 2007 (the Met Office had forecast a summer of prolonged droughts only six weeks previously); nor the solar Grand Maximum of the past 70 years, during which the Sun was more active, for longer, than at almost any similar period in the past 11,400 years (Hathaway, 2004; Solankiet al., 2005); nor the consequent surface «global warming» on Mars, Jupiter, Neptune's
largest moon, and even distant Pluto; nor the eerily - continuing 2006 solar minimum; nor the consequent, precipitate decline of ~ 0.8 °C in TS from January 2007 to May 2008 that has canceled out almost all of the observed warming of the 20th century.
Analyses of global climate from measurements dating back to the nineteenth century show an «Atlantic
Multidecadal Oscillation» (AMO) as a leading large - scale pattern of multidecadal variability in surface
Multidecadal Oscillation» (AMO) as a leading
large - scale pattern of
multidecadal variability in surface
multidecadal variability in surface temperature.
Never mind the fact that those same models were unable to reproduce
large scale natural climate variability such as the Pacific Decadal Oscillation, the Atlantic
Multidecadal Oscillation and ENSO.