US CLIVAR Decadal Predictability Working Group, 2011: Distinguishing the roles of natural and anthropogenically
forced decadal climate variability: Implications for prediction, Bull.
Not exact matches
Ice - sheet responses to
decadal - scale ocean
forcing appear to be less important, possibly indicating that the future response of the Antarctic Ice Sheet will be governed more by long - term anthropogenic warming combined with multi-centennial natural
variability than by annual or
decadal climate oscillations.»
Mike's work, like that of previous award winners, is diverse, and includes pioneering and highly cited work in time series analysis (an elegant use of Thomson's multitaper spectral analysis approach to detect spatiotemporal oscillations in the
climate record and methods for smoothing temporal data), decadal climate variability (the term «Atlantic Multidecadal Oscillation» or «AMO» was coined by Mike in an interview with Science's Richard Kerr about a paper he had published with Tom Delworth of GFDL showing evidence in both climate model simulations and observational data for a 50 - 70 year oscillation in the climate system; significantly Mike also published work with Kerry Emanuel in 2006 showing that the AMO concept has been overstated as regards its role in 20th century tropical Atlantic SST changes, a finding recently reaffirmed by a study published in Nature), in showing how changes in radiative forcing from volcanoes can affect ENSO, in examining the role of solar variations in explaining the pattern of the Medieval Climate Anomaly and Little Ice Age, the relationship between the climate changes of past centuries and phenomena such as Atlantic tropical cyclones and global sea level, and even a bit of work in atmospheric chemistry (an analysis of beryllium - 7 measure
climate record and methods for smoothing temporal data),
decadal climate variability (the term «Atlantic Multidecadal Oscillation» or «AMO» was coined by Mike in an interview with Science's Richard Kerr about a paper he had published with Tom Delworth of GFDL showing evidence in both climate model simulations and observational data for a 50 - 70 year oscillation in the climate system; significantly Mike also published work with Kerry Emanuel in 2006 showing that the AMO concept has been overstated as regards its role in 20th century tropical Atlantic SST changes, a finding recently reaffirmed by a study published in Nature), in showing how changes in radiative forcing from volcanoes can affect ENSO, in examining the role of solar variations in explaining the pattern of the Medieval Climate Anomaly and Little Ice Age, the relationship between the climate changes of past centuries and phenomena such as Atlantic tropical cyclones and global sea level, and even a bit of work in atmospheric chemistry (an analysis of beryllium - 7 measure
climate variability (the term «Atlantic Multidecadal Oscillation» or «AMO» was coined by Mike in an interview with Science's Richard Kerr about a paper he had published with Tom Delworth of GFDL showing evidence in both
climate model simulations and observational data for a 50 - 70 year oscillation in the climate system; significantly Mike also published work with Kerry Emanuel in 2006 showing that the AMO concept has been overstated as regards its role in 20th century tropical Atlantic SST changes, a finding recently reaffirmed by a study published in Nature), in showing how changes in radiative forcing from volcanoes can affect ENSO, in examining the role of solar variations in explaining the pattern of the Medieval Climate Anomaly and Little Ice Age, the relationship between the climate changes of past centuries and phenomena such as Atlantic tropical cyclones and global sea level, and even a bit of work in atmospheric chemistry (an analysis of beryllium - 7 measure
climate model simulations and observational data for a 50 - 70 year oscillation in the
climate system; significantly Mike also published work with Kerry Emanuel in 2006 showing that the AMO concept has been overstated as regards its role in 20th century tropical Atlantic SST changes, a finding recently reaffirmed by a study published in Nature), in showing how changes in radiative forcing from volcanoes can affect ENSO, in examining the role of solar variations in explaining the pattern of the Medieval Climate Anomaly and Little Ice Age, the relationship between the climate changes of past centuries and phenomena such as Atlantic tropical cyclones and global sea level, and even a bit of work in atmospheric chemistry (an analysis of beryllium - 7 measure
climate system; significantly Mike also published work with Kerry Emanuel in 2006 showing that the AMO concept has been overstated as regards its role in 20th century tropical Atlantic SST changes, a finding recently reaffirmed by a study published in Nature), in showing how changes in radiative
forcing from volcanoes can affect ENSO, in examining the role of solar variations in explaining the pattern of the Medieval
Climate Anomaly and Little Ice Age, the relationship between the climate changes of past centuries and phenomena such as Atlantic tropical cyclones and global sea level, and even a bit of work in atmospheric chemistry (an analysis of beryllium - 7 measure
Climate Anomaly and Little Ice Age, the relationship between the
climate changes of past centuries and phenomena such as Atlantic tropical cyclones and global sea level, and even a bit of work in atmospheric chemistry (an analysis of beryllium - 7 measure
climate changes of past centuries and phenomena such as Atlantic tropical cyclones and global sea level, and even a bit of work in atmospheric chemistry (an analysis of beryllium - 7 measurements).
[Response: The
forcings have been increasing since 1850 (see here), and taking the longest period possible minimises the influence of intrinsic
decadal variability in the
climate system.
But questions remained concerning the degree of
decadal variability, the length of the record and the balance in the models between aerosol
forcing and
climate sensitivity (which can't really be disentangled using this measure).
«Externally
Forced and Internally Generated
Decadal Climate Variability Associated with the Interdecadal Pacific Oscillation.»
Models all produce natural
variability, many of which show temperature flatlines over
decadal timescales, and given the wide importance of natural
variability over < 10 year time scales and uncertain
forcings, one can absolutely not claim that this is inconsistent with current thinking about
climate.
The IPCC treats natural internal
variability as «noise»; we argue that it is the fundamental
climate signal on
decadal to century time scales, with external
forcing projecting onto these modes.
The stadium wave holds promise in putting into perspective numerous observations of
climate behavior, such as regional patterns of
decadal variability in drought and hurricane activity, the researchers say, but a complete understanding of past
climate variability and projections of future
climate change requires integrating the stadium - wave signal with external
climate forcing from the sun, volcanoes and anthropogenic
forcing.
Causes of natural
variability include
forcings that are external to the
climate system (e.g., volcanic eruptions and aerosols and the 11 - year sunspot cycle) and internal fluctuations (weather phenomena, monsoons, El Niño / La Niña, and
decadal cycles).
According to IPCC AR5, the mismatch between models and observations during both 1984 - 1998 and 1998 - 2012 may be due to «internal
decadal climate variability, which sometimes enhances and sometimes counteracts the long - term externally
forced trend» (Chapter 9, p. 769).
Additional proxy records that cover the entire CE are needed to investigate
decadal - to centennial - scale responses of
climate to changes in radiative
forcing as well as internal
variability at these time scales.
Meehl, G. A., A. Hu, and B.D. Santer, 2008: The mid-1970s
climate shift in the Pacific and the relative roles of forced versus inherent decadal variability, J. Climate, in
climate shift in the Pacific and the relative roles of
forced versus inherent
decadal variability, J.
Climate, in
Climate, in press.
Now
forced to explain the warming hiatus, Trenberth has flipped flopped about the PDO's importance writing «One of the things emerging from several lines is that the IPCC has not paid enough attention to natural
variability, on several time scales,» «especially El Niños and La Niñas, the Pacific Ocean phenomena that are not yet captured by
climate models, and the longer term Pacific
Decadal Oscillation (PDO) and Atlantic Multidecadal Oscillation (AMO) which have cycle lengths of about 60 years.»
Unforced
variability of global temperature is great, as shown in Figure 4, but the global temperature trend on
decadal and longer time scales is now determined by the larger human - made
climate forcing.
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.
Meehl, G. A., Hu, A., Arblaster, J. M., Fasullo, J. T. & Trenberth, K. E. Externally
forced and internally generated
decadal climate variability associated with the Interdecadal Pacific Oscillation.
Meehl, G. A., Hu, A., Arblaster, J. M., Fasullo, J. Y. & Trenberth, K. E. Externally
forced and internally generated
decadal climate variability associated with the Interdecadal Pacific Oscillation.
«The figure clarifies that internal
climate variability over a short
decadal or 15 - year time scale is at least as important as the
forced climate changes arising from greenhouse gas emissions.»
9.3.1 Global Mean Response 9.3.1.1 1 % / yr CO2 increase (CMIP2) experiments 9.3.1.2 Projections of future
climate from forcing scenario experiments (IS92a) 9.3.1.3 Marker scenario experiments (SRES) 9.3.2 Patterns of Future Climate Change 9.3.2.1 Summary 9.3.3 Range of Temperature Response to SRES Emission Scenarios 9.3.3.1 Implications for temperature of stabilisation of greenhouse gases 9.3.4 Factors that Contribute to the Response 9.3.4.1 Climate sensitivity 9.3.4.2 The role of climate sensitivity and ocean heat uptake 9.3.4.3 Thermohaline circulation changes 9.3.4.4 Time - scales of response 9.3.5 Changes in Variability 9.3.5.1 Intra-seasonal variability 9.3.5.2 Interannual variability 9.3.5.3 Decadal and longer time - scale variability 9.3.5.4 Summary 9.3.6 Changes of Extreme Events 9.3.6.1 Temperature 9.3.6.2 Precipitation and convection 9.3.6.3 Extra-tropical storms 9.3.6.4 Tropical cyclones 9.3.6.5 Commentary on changes in extremes of weather and climate 9.3.6.6 Conc
climate from
forcing scenario experiments (IS92a) 9.3.1.3 Marker scenario experiments (SRES) 9.3.2 Patterns of Future
Climate Change 9.3.2.1 Summary 9.3.3 Range of Temperature Response to SRES Emission Scenarios 9.3.3.1 Implications for temperature of stabilisation of greenhouse gases 9.3.4 Factors that Contribute to the Response 9.3.4.1 Climate sensitivity 9.3.4.2 The role of climate sensitivity and ocean heat uptake 9.3.4.3 Thermohaline circulation changes 9.3.4.4 Time - scales of response 9.3.5 Changes in Variability 9.3.5.1 Intra-seasonal variability 9.3.5.2 Interannual variability 9.3.5.3 Decadal and longer time - scale variability 9.3.5.4 Summary 9.3.6 Changes of Extreme Events 9.3.6.1 Temperature 9.3.6.2 Precipitation and convection 9.3.6.3 Extra-tropical storms 9.3.6.4 Tropical cyclones 9.3.6.5 Commentary on changes in extremes of weather and climate 9.3.6.6 Conc
Climate Change 9.3.2.1 Summary 9.3.3 Range of Temperature Response to SRES Emission Scenarios 9.3.3.1 Implications for temperature of stabilisation of greenhouse gases 9.3.4 Factors that Contribute to the Response 9.3.4.1
Climate sensitivity 9.3.4.2 The role of climate sensitivity and ocean heat uptake 9.3.4.3 Thermohaline circulation changes 9.3.4.4 Time - scales of response 9.3.5 Changes in Variability 9.3.5.1 Intra-seasonal variability 9.3.5.2 Interannual variability 9.3.5.3 Decadal and longer time - scale variability 9.3.5.4 Summary 9.3.6 Changes of Extreme Events 9.3.6.1 Temperature 9.3.6.2 Precipitation and convection 9.3.6.3 Extra-tropical storms 9.3.6.4 Tropical cyclones 9.3.6.5 Commentary on changes in extremes of weather and climate 9.3.6.6 Conc
Climate sensitivity 9.3.4.2 The role of
climate sensitivity and ocean heat uptake 9.3.4.3 Thermohaline circulation changes 9.3.4.4 Time - scales of response 9.3.5 Changes in Variability 9.3.5.1 Intra-seasonal variability 9.3.5.2 Interannual variability 9.3.5.3 Decadal and longer time - scale variability 9.3.5.4 Summary 9.3.6 Changes of Extreme Events 9.3.6.1 Temperature 9.3.6.2 Precipitation and convection 9.3.6.3 Extra-tropical storms 9.3.6.4 Tropical cyclones 9.3.6.5 Commentary on changes in extremes of weather and climate 9.3.6.6 Conc
climate sensitivity and ocean heat uptake 9.3.4.3 Thermohaline circulation changes 9.3.4.4 Time - scales of response 9.3.5 Changes in
Variability 9.3.5.1 Intra-seasonal variability 9.3.5.2 Interannual variability 9.3.5.3 Decadal and longer time - scale variability 9.3.5.4 Summary 9.3.6 Changes of Extreme Events 9.3.6.1 Temperature 9.3.6.2 Precipitation and convection 9.3.6.3 Extra-tropical storms 9.3.6.4 Tropical cyclones 9.3.6.5 Commentary on changes in extremes of weather and climate 9.3.6.6
Variability 9.3.5.1 Intra-seasonal
variability 9.3.5.2 Interannual variability 9.3.5.3 Decadal and longer time - scale variability 9.3.5.4 Summary 9.3.6 Changes of Extreme Events 9.3.6.1 Temperature 9.3.6.2 Precipitation and convection 9.3.6.3 Extra-tropical storms 9.3.6.4 Tropical cyclones 9.3.6.5 Commentary on changes in extremes of weather and climate 9.3.6.6
variability 9.3.5.2 Interannual
variability 9.3.5.3 Decadal and longer time - scale variability 9.3.5.4 Summary 9.3.6 Changes of Extreme Events 9.3.6.1 Temperature 9.3.6.2 Precipitation and convection 9.3.6.3 Extra-tropical storms 9.3.6.4 Tropical cyclones 9.3.6.5 Commentary on changes in extremes of weather and climate 9.3.6.6
variability 9.3.5.3
Decadal and longer time - scale
variability 9.3.5.4 Summary 9.3.6 Changes of Extreme Events 9.3.6.1 Temperature 9.3.6.2 Precipitation and convection 9.3.6.3 Extra-tropical storms 9.3.6.4 Tropical cyclones 9.3.6.5 Commentary on changes in extremes of weather and climate 9.3.6.6
variability 9.3.5.4 Summary 9.3.6 Changes of Extreme Events 9.3.6.1 Temperature 9.3.6.2 Precipitation and convection 9.3.6.3 Extra-tropical storms 9.3.6.4 Tropical cyclones 9.3.6.5 Commentary on changes in extremes of weather and
climate 9.3.6.6 Conc
climate 9.3.6.6 Conclusions
Meehl, G. A., Hu, A., Arblaster, J., Fasullo, J. & Trenberth, K. E. Externally
forced and internally generated
decadal climate variability associated with the Interdecadal Pacific Oscillation.
This will include researchers involved in developing prediction systems, understanding mechanisms of
decadal and
forced climate variability, and assessing the needs of potential users.