Quantifying the contribution of forcing and three prominent modes of variability to historical climate
<p>Climate models can produce accurate representations of the most important modes of climate variability, but they cannot be expected to follow their observed time evolution. This makes direct comparison of simulated and observed variability difficult and creates uncertainty in estimates of f...
| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2023-05-01
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| Series: | Climate of the Past |
| Online Access: | https://cp.copernicus.org/articles/19/943/2023/cp-19-943-2023.pdf |
| _version_ | 1797830465737981952 |
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| author | A. P. Schurer G. C. Hegerl H. Goosse M. A. Bollasina M. H. England M. J. Mineter D. M. Smith S. F. B. Tett |
| author_facet | A. P. Schurer G. C. Hegerl H. Goosse M. A. Bollasina M. H. England M. J. Mineter D. M. Smith S. F. B. Tett |
| author_sort | A. P. Schurer |
| collection | DOAJ |
| description | <p>Climate models can produce accurate representations of the most important
modes of climate variability, but they cannot be expected to follow their
observed time evolution. This makes direct comparison of simulated and
observed variability difficult and creates uncertainty in estimates of
forced change. We investigate the role of three modes of climate
variability, the North Atlantic Oscillation, El Niño–Southern
Oscillation and the Southern Annular Mode, as pacemakers of climate
variability since 1781, evaluating where their evolution masks or enhances
forced climate trends. We use particle filter data assimilation to constrain the observed variability in a global climate model without nudging, producing a near-free-running model simulation with the time evolution of these modes similar to those observed. Since the climate model also contains external forcings, these simulations, in combination with model experiments with identical forcing but no assimilation, can be used to compare the forced response to the effect of the three modes assimilated and evaluate the extent to which these are confounded with the forced response. The assimilated model is significantly closer than the “forcing only” simulations to annual temperature and precipitation observations over many regions, in particular the tropics, the North Atlantic and Europe. The results indicate where initialised simulations that track these modes could be expected to show additional skill. Assimilating the three modes cannot explain the large discrepancy previously found between observed and modelled variability in the southern extra-tropics but constraining the El Niño–Southern Oscillation reconciles simulated global cooling with that observed after volcanic eruptions.</p> |
| first_indexed | 2024-04-09T13:36:31Z |
| format | Article |
| id | doaj.art-cbf15d32aef142bdab4b0888604aac43 |
| institution | Directory Open Access Journal |
| issn | 1814-9324 1814-9332 |
| language | English |
| last_indexed | 2024-04-09T13:36:31Z |
| publishDate | 2023-05-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Climate of the Past |
| spelling | doaj.art-cbf15d32aef142bdab4b0888604aac432023-05-09T09:09:14ZengCopernicus PublicationsClimate of the Past1814-93241814-93322023-05-011994395710.5194/cp-19-943-2023Quantifying the contribution of forcing and three prominent modes of variability to historical climateA. P. Schurer0G. C. Hegerl1H. Goosse2M. A. Bollasina3M. H. England4M. J. Mineter5D. M. Smith6S. F. B. Tett7School of GeoSciences, University of Edinburgh, Edinburgh, EH9 3JW, United KingdomSchool of GeoSciences, University of Edinburgh, Edinburgh, EH9 3JW, United KingdomEarth and Life Institute, Université Catholique de Louvain, Louvain-La-Neuve, 1348, BelgiumSchool of GeoSciences, University of Edinburgh, Edinburgh, EH9 3JW, United KingdomClimate Change Research Centre, ARC Centre for Excellence in Antarctic Science, University of New South Wales, New South Wales, 2052, AustraliaSchool of GeoSciences, University of Edinburgh, Edinburgh, EH9 3JW, United KingdomMet Office Hadley Centre, Exeter, EX1 3PB, United KingdomSchool of GeoSciences, University of Edinburgh, Edinburgh, EH9 3JW, United Kingdom<p>Climate models can produce accurate representations of the most important modes of climate variability, but they cannot be expected to follow their observed time evolution. This makes direct comparison of simulated and observed variability difficult and creates uncertainty in estimates of forced change. We investigate the role of three modes of climate variability, the North Atlantic Oscillation, El Niño–Southern Oscillation and the Southern Annular Mode, as pacemakers of climate variability since 1781, evaluating where their evolution masks or enhances forced climate trends. We use particle filter data assimilation to constrain the observed variability in a global climate model without nudging, producing a near-free-running model simulation with the time evolution of these modes similar to those observed. Since the climate model also contains external forcings, these simulations, in combination with model experiments with identical forcing but no assimilation, can be used to compare the forced response to the effect of the three modes assimilated and evaluate the extent to which these are confounded with the forced response. The assimilated model is significantly closer than the “forcing only” simulations to annual temperature and precipitation observations over many regions, in particular the tropics, the North Atlantic and Europe. The results indicate where initialised simulations that track these modes could be expected to show additional skill. Assimilating the three modes cannot explain the large discrepancy previously found between observed and modelled variability in the southern extra-tropics but constraining the El Niño–Southern Oscillation reconciles simulated global cooling with that observed after volcanic eruptions.</p>https://cp.copernicus.org/articles/19/943/2023/cp-19-943-2023.pdf |
| spellingShingle | A. P. Schurer G. C. Hegerl H. Goosse M. A. Bollasina M. H. England M. J. Mineter D. M. Smith S. F. B. Tett Quantifying the contribution of forcing and three prominent modes of variability to historical climate Climate of the Past |
| title | Quantifying the contribution of forcing and three prominent modes of variability to historical climate |
| title_full | Quantifying the contribution of forcing and three prominent modes of variability to historical climate |
| title_fullStr | Quantifying the contribution of forcing and three prominent modes of variability to historical climate |
| title_full_unstemmed | Quantifying the contribution of forcing and three prominent modes of variability to historical climate |
| title_short | Quantifying the contribution of forcing and three prominent modes of variability to historical climate |
| title_sort | quantifying the contribution of forcing and three prominent modes of variability to historical climate |
| url | https://cp.copernicus.org/articles/19/943/2023/cp-19-943-2023.pdf |
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