Scaling regimes and linear/nonlinear responses of last millennium climate to volcanic and solar forcings
At scales much longer than the deterministic predictability limits (about 10 days), the statistics of the atmosphere undergoes a drastic transition, the high-frequency weather acts as a random forcing on the lower-frequency macroweather. In addition, up to decadal and centennial scales the equivalen...
| Main Authors: | , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2016-02-01
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| Series: | Earth System Dynamics |
| Online Access: | http://www.earth-syst-dynam.net/7/133/2016/esd-7-133-2016.pdf |
| _version_ | 1811219464510767104 |
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| author | S. Lovejoy C. Varotsos |
| author_facet | S. Lovejoy C. Varotsos |
| author_sort | S. Lovejoy |
| collection | DOAJ |
| description | At scales much longer than the deterministic predictability limits
(about 10 days), the statistics of the atmosphere undergoes a drastic
transition, the high-frequency weather acts as a random forcing on the lower-frequency macroweather. In addition, up to decadal and centennial scales the
equivalent radiative forcings of solar, volcanic and anthropogenic
perturbations are small compared to the mean incoming solar flux. This
justifies the common practice of reducing forcings to radiative equivalents
(which are assumed to combine linearly), as well as the development of
linear stochastic models, including for forecasting at monthly to decadal scales.
<br><br>
In order to clarify the validity of the linearity assumption and determine
its scale range, we use last millennium simulations, with both the
simplified Zebiak–Cane (ZC) model and the NASA GISS E2-R fully coupled GCM.
We systematically compare the statistical properties of solar-only, volcanic-only and combined solar and volcanic forcings over the range of timescales
from 1 to 1000 years. We also compare the statistics to multiproxy
temperature reconstructions. The main findings are (a) that the variability
in the ZC and GCM models is too weak at centennial and longer scales;
(b) for longer than ≈ 50 years, the solar and volcanic forcings combine
subadditively (nonlinearly) compounding the weakness of the response; and (c) the
models display another nonlinear effect at shorter timescales: their
sensitivities are much higher for weak forcing than for strong forcing
(their intermittencies are different) and we quantify this with statistical
scaling exponents. |
| first_indexed | 2024-04-12T07:26:26Z |
| format | Article |
| id | doaj.art-b97a46758ccf4f4b8f821a64a91c1b72 |
| institution | Directory Open Access Journal |
| issn | 2190-4979 2190-4987 |
| language | English |
| last_indexed | 2024-04-12T07:26:26Z |
| publishDate | 2016-02-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Earth System Dynamics |
| spelling | doaj.art-b97a46758ccf4f4b8f821a64a91c1b722022-12-22T03:42:11ZengCopernicus PublicationsEarth System Dynamics2190-49792190-49872016-02-017113315010.5194/esd-7-133-2016Scaling regimes and linear/nonlinear responses of last millennium climate to volcanic and solar forcingsS. Lovejoy0C. Varotsos1Physics, McGill University, 3600 University St., Montreal, Quebec, CanadaClimate Research Group, Division of Environmental Physics and Meteorology, Faculty of Physics, University of Athens, University Campus Bldg. Phys. V, 15784 Athens, GreeceAt scales much longer than the deterministic predictability limits (about 10 days), the statistics of the atmosphere undergoes a drastic transition, the high-frequency weather acts as a random forcing on the lower-frequency macroweather. In addition, up to decadal and centennial scales the equivalent radiative forcings of solar, volcanic and anthropogenic perturbations are small compared to the mean incoming solar flux. This justifies the common practice of reducing forcings to radiative equivalents (which are assumed to combine linearly), as well as the development of linear stochastic models, including for forecasting at monthly to decadal scales. <br><br> In order to clarify the validity of the linearity assumption and determine its scale range, we use last millennium simulations, with both the simplified Zebiak–Cane (ZC) model and the NASA GISS E2-R fully coupled GCM. We systematically compare the statistical properties of solar-only, volcanic-only and combined solar and volcanic forcings over the range of timescales from 1 to 1000 years. We also compare the statistics to multiproxy temperature reconstructions. The main findings are (a) that the variability in the ZC and GCM models is too weak at centennial and longer scales; (b) for longer than ≈ 50 years, the solar and volcanic forcings combine subadditively (nonlinearly) compounding the weakness of the response; and (c) the models display another nonlinear effect at shorter timescales: their sensitivities are much higher for weak forcing than for strong forcing (their intermittencies are different) and we quantify this with statistical scaling exponents.http://www.earth-syst-dynam.net/7/133/2016/esd-7-133-2016.pdf |
| spellingShingle | S. Lovejoy C. Varotsos Scaling regimes and linear/nonlinear responses of last millennium climate to volcanic and solar forcings Earth System Dynamics |
| title | Scaling regimes and linear/nonlinear responses of last millennium climate to volcanic and solar forcings |
| title_full | Scaling regimes and linear/nonlinear responses of last millennium climate to volcanic and solar forcings |
| title_fullStr | Scaling regimes and linear/nonlinear responses of last millennium climate to volcanic and solar forcings |
| title_full_unstemmed | Scaling regimes and linear/nonlinear responses of last millennium climate to volcanic and solar forcings |
| title_short | Scaling regimes and linear/nonlinear responses of last millennium climate to volcanic and solar forcings |
| title_sort | scaling regimes and linear nonlinear responses of last millennium climate to volcanic and solar forcings |
| url | http://www.earth-syst-dynam.net/7/133/2016/esd-7-133-2016.pdf |
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