Chaotic climate response to long-term solar forcing variability

Abstract. A key issue of climate change is to identify the forcings and their relative contributions. Solar-climate relationship is currently the matter of a fierce debate. We address here the need for high quality observations and adequate statistical approach. A recent work by Le Mouël et al. (2010) and its companion paper by Kossobokov et al. (2010) show spectacular correlations between solar activity and meteorological parameters. We question both the data and the method used in these works. We stress 1) that correlation with solar forcing alone is meaningless unless other forcings are properly accounted and that sunspot counting is a poor indicator of solar irradiance, 2) that long series of temperature require homogenization to remove historical artefacts that affect long term variability, 3) that incorrect application of statistical tests leads to interpret as significant a signal which arises from pure random fluctuations. As a consequence, we reject the results and the conclusions of Le Mouël et al. (2010) and Kossobokov et al. (2010). We believe that our contribution bears some general interest in removing confusion from the scientific debate.

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Solar cycles or random processes? Evaluating solar variability in Holocene climate records

Scientific Reports ◽

10.1038/srep23961 ◽

2016 ◽

Vol 6 (1) ◽

Cited By ~ 15

Author(s):

T. Edward Turner ◽

Graeme T. Swindles ◽

Dan J. Charman ◽

Peter G. Langdon ◽

Paul J. Morris ◽

...

Keyword(s):

Solar Variability ◽

Solar Cycles ◽

Climate Data ◽

Critical Approach ◽

Solar Forcing ◽

Holocene Climate ◽

Proxy Records ◽

Wide Range ◽

Solar Type

Abstract Many studies have reported evidence for solar-forcing of Holocene climate change across a range of archives. These studies have compared proxy-climate data with records of solar variability (e.g. 14C or 10Be), or have used time series analysis to test for the presence of solar-type cycles. This has led to some climate sceptics misrepresenting this literature to argue strongly that solar variability drove the rapid global temperature increase of the twentieth century. As proxy records underpin our understanding of the long-term processes governing climate, they need to be evaluated thoroughly. The peatland archive has become a prominent line of evidence for solar forcing of climate. Here we examine high-resolution peatland proxy climate data to determine whether solar signals are present. We find a wide range of significant periodicities similar to those in records of solar variability: periods between 40–100 years, and 120–140 years are particularly common. However, periodicities similar to those in the data are commonly found in random-walk simulations. Our results demonstrate that solar-type signals can be the product of random variations alone, and that a more critical approach is required for their robust interpretation.

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Experiments based on blue intensity for reconstructing North Pacific temperatures along the Gulf of Alaska

Climate of the Past ◽

10.5194/cp-13-1007-2017 ◽

2017 ◽

Vol 13 (8) ◽

pp. 1007-1022 ◽

Cited By ~ 13

Author(s):

Rob Wilson ◽

Rosanne D'Arrigo ◽

Laia Andreu-Hayles ◽

Rose Oelkers ◽

Greg Wiles ◽

...

Keyword(s):

Tree Ring ◽

North Pacific ◽

Ring Width ◽

Gulf Of Alaska ◽

Climate Response ◽

Cool Period ◽

Climate Signal ◽

Latewood Density ◽

Blue Intensity

Abstract. Ring-width (RW) records from the Gulf of Alaska (GOA) have yielded a valuable long-term perspective for North Pacific changes on decadal to longer timescales in prior studies but contain a broad winter to late summer seasonal climate response. Similar to the highly climate-sensitive maximum latewood density (MXD) proxy, the blue intensity (BI) parameter has recently been shown to correlate well with year-to-year warm-season temperatures for a number of sites at northern latitudes. Since BI records are much less labour intensive and expensive to generate than MXD, such data hold great potential value for future tree-ring studies in the GOA and other regions in mid- to high latitudes. Here we explore the potential for improving tree-ring-based reconstructions using combinations of RW- and BI-related parameters (latewood BI and delta BI) from an experimental subset of samples at eight mountain hemlock (Tsuga mertensiana) sites along the GOA. This is the first study for the hemlock genus using BI data. We find that using either inverted latewood BI (LWBinv) or delta BI (DB) can improve the amount of explained temperature variance by > 10 % compared to RW alone, although the optimal target season shrinks to June–September, which may have implications for studying ocean–atmosphere variability in the region. One challenge in building these BI records is that resin extraction did not remove colour differences between the heartwood and sapwood; thus, long term trend biases, expressed as relatively warm temperatures in the 18th century, were noted when using the LWBinv data. Using DB appeared to overcome these trend biases, resulting in a reconstruction expressing 18th–19th century temperatures ca. 0.5 °C cooler than the 20th–21st centuries. This cool period agrees well with previous dendroclimatic studies and the glacial advance record in the region. Continuing BI measurement in the GOA region must focus on sampling and measuring more trees per site (> 20) and compiling more sites to overcome site-specific factors affecting climate response and using subfossil material to extend the record. Although LWBinv captures the inter-annual climate signal more strongly than DB, DB appears to better capture long-term secular trends that agree with other proxy archives in the region. Great care is needed, however, when implementing different detrending options and more experimentation is necessary to assess the utility of DB for different conifer species around the Northern Hemisphere.

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The significance of climate and solar variability on historical European grain prices

10.5194/egusphere-egu2020-11257 ◽

2020 ◽

Author(s):

Fredrik Charpentier Ljungqvist ◽

Peter Thejll ◽

Bo Christiansen ◽

Andrea Seim ◽

Claudia Hartl ◽

...

Keyword(s):

Early Modern ◽

Tree Ring ◽

Early Modern Europe ◽

Solar Forcing ◽

Time And Space ◽

Climate Signal ◽

Temperature Reconstructions ◽

Modern Europe ◽

Grain Prices

Grain was the most important food source for a majority of the population in early modern Europe (c. 1500&#8211;1800). The price level and volatility had huge societal effects: high prices tended to increase mortality, decrease fertility as well as affect overall consumption patterns. To what extent climate variability influenced the long-term grain price evolution in early modern Europe has for a long time been a matter of debate. Recent advances in high-resolution palaeoclimatology and historical climatology have made it possible to reassess the grain price&#8211;climate relationship in time and space with unprecedented detail (Esper et al. 2017). We analyse the climate signal in 56 multi-centennial long series of annual prices of barley, oat, rye, and wheat across Europe. The grain price&#8211;climate relationship in regional clusters of grain price data is analysed using both tree-ring based temperature reconstructions, documentary-based temperature reconstructions, tree-ring based drought reconstructions, and early temperature and precipitation instrumental data, considering possible different climate responses in each grain type and different seasonal targets. In addition, we systematically investigate whether, and to what extent, the imprints of variations in solar forcing, including possible lag effects, can be detected in the grain prices.We find a highly significant and persistent negative temperature&#8211;price relationship (i.e., cold = high prices and vice versa) across all of Europe and for all four grain types using both temperature reconstructions and instrumental temperature data. Excluding the Thirty Years&#8217; War (1618&#8211;1648) and the period following the French Revolution (1789), this relationship is as strong as r = &#8211;0.41 between the annual average of all the 56 included European grain price series and the reconstructed June&#8211;August temperature for the previous year. The correlations to drought and precipitation are, on the other hand, mainly insignificant and inconsistent in time and space. The evidence for the existence of the effect of solar forcing variations on early modern European grain prices is not strong, although we can detect statistically significant grain price&#8211;solar forcing relationships for certain regions. In conclusion, we find much stronger evidence than hitherto reported for long-term temperature imprints on historical grain prices in Europe, implying that temperature variability and change have been a more important factor in European economic history, even in southern Europe, than commonly acknowledged.&#160;Reference:Esper J., et al., 2017. Environmental drivers of historical grain price variations in Europe. Clim. Res. 72: 39&#8211;52.

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Simulated long-term climate response to idealized solar geoengineering

Geophysical Research Letters ◽

10.1002/2016gl068079 ◽

2016 ◽

Vol 43 (5) ◽

pp. 2209-2217 ◽

Cited By ~ 10

Author(s):

Long Cao ◽

Lei Duan ◽

Govindasamy Bala ◽

Ken Caldeira

Keyword(s):

Climate Response ◽

Solar Geoengineering

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North Atlantic Climate Response to Lake Agassiz Drainage at Coarse and Ocean Eddy-Permitting Resolutions

Journal of Climate ◽

10.1175/jcli-d-11-00683.1 ◽

2013 ◽

Vol 26 (8) ◽

pp. 2651-2667 ◽

Cited By ~ 14

Author(s):

Paul Spence ◽

Oleg A. Saenko ◽

Willem Sijp ◽

Matthew H. England

Keyword(s):

North Atlantic ◽

Meridional Overturning Circulation ◽

Climate Response ◽

Model Resolution ◽

Lake Agassiz ◽

The North ◽

Freshwater Forcing ◽

North Atlantic Climate ◽

The North Atlantic

Abstract The North Atlantic climate response to the catastrophic drainage of proglacial Lake Agassiz into the Labrador Sea is analyzed with coarse and ocean eddy-permitting versions of a global coupled climate model. The North Atlantic climate response is qualitatively consistent in that a large-scale cooling is simulated regardless of the model resolution or region of freshwater discharge. However, the magnitude and duration of the North Atlantic climate response is found to be sensitive to model resolution and the location of freshwater forcing. In particular, the long-term entrainment of freshwater along the boundary at higher resolution and its gradual, partially eddy-driven escape into the interior leads to low-salinity anomalies persisting in the subpolar Atlantic for decades longer. As a result, the maximum decline of the Atlantic meridional overturning circulation (AMOC) and the ocean meridional heat transport (MHT) is amplified by about a factor of 2 at ocean eddy-permitting resolution, and the recovery is delayed relative to the coarse grid model. This, in turn, increases the long-term cooling in the high-resolution simulations. A decomposition of the MHT response reveals an increased role for transients and the horizontal mean component of MHT at higher resolution. With fixed wind stress curl, it is a stronger response of bottom pressure torque to the freshwater forcing at higher resolution that leads to a larger anomaly of the depth-integrated circulation.

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