title: Solar cycles or random processes? Evaluating solar variability in Holocene climate records.
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. (14)C or (10)Be), 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.
authors.affiliation: School of Geography, University of Leeds, LS2 9JT, UK.
authors.forename: T Edward
authors.initials: TE
authors.lastname: Turner
authors.affiliation: School of Geography, University of Leeds, LS2 9JT, UK.
authors.forename: Graeme T
authors.initials: GT
authors.lastname: Swindles
authors.affiliation: Department of Geography, University of Exeter, EX4 4RJ, UK.
authors.forename: Dan J
authors.initials: DJ
authors.lastname: Charman
authors.affiliation: Geography and Environment, University of Southampton, Southampton, SO17 1BJ, UK.
authors.forename: Peter G
authors.initials: PG
authors.lastname: Langdon
authors.affiliation: School of Geography, University of Leeds, LS2 9JT, UK.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Morris
authors.affiliation: Earth &Environmental Sciences, Lehigh University, Bethlehem, PA18015-3001, USA.
authors.forename: Robert K
authors.initials: RK
authors.lastname: Booth
authors.affiliation: School of Interdisciplinary Studies, University of Glasgow, DG1 4ZL, UK.
authors.forename: Lauren E
authors.initials: LE
authors.lastname: Parry
authors.affiliation: Lamont-Doherty Earth Observatory at Columbia University, Palisades, NY 10964, USA.
authors.forename: Jonathan E
authors.initials: JE
authors.lastname: Nichols