Discussion on common errors in analyzing sea level accelerations, solar trends and global warming
Regular Research Article
13 May 2013
Active Cavity Radiometer Irradiance Monitor (ACRIM) Lab, Coronado, CA 92118, USA
Duke University, Durham, NC 27708, USA
Abstract. Herein I discuss common errors in applying regression models and wavelet filters used to analyze geophysical signals. I demonstrate that: (1) multidecadal natural oscillations (e.g. the quasi 60 yr Multidecadal Atlantic Oscillation (AMO), North Atlantic Oscillation (NAO) and Pacific Decadal Oscillation (PDO)) need to be taken into account for properly quantifying anomalous background accelerations in tide gauge records such as in New York City; (2) uncertainties and multicollinearity among climate forcing functions also prevent a proper evaluation of the solar contribution to the 20th century global surface temperature warming using overloaded linear regression models during the 1900–2000 period alone; (3) when periodic wavelet filters, which require that a record is pre-processed with a reflection methodology, are improperly applied to decompose non-stationary solar and climatic time series, Gibbs boundary artifacts emerge yielding misleading physical interpretations. By correcting these errors and using optimized regression models that reduce multicollinearity artifacts, I found the following results: (1) the relative sea level in New York City is not accelerating in an alarming way, and may increase by about 350 ± 30 mm from 2000 to 2100 instead of the previously projected values varying from 1130 ± 480 mm to 1550 ± 400 mm estimated using the methods proposed, e.g., by Sallenger Jr. et al. (2012) and Boon (2012), respectively; (2) the solar activity increase during the 20th century contributed at least about 50% of the 0.8 °C global warming observed during the 20th century instead of only 7–10% (e.g.: IPCC, 2007; Benestad and Schmidt, 2009; Lean and Rind, 2009; Rohde et al., 2013). The first result was obtained by using a quadratic polynomial function plus a 60 yr harmonic to fit a required 110 yr-long sea level record. The second result was obtained by using solar, volcano, greenhouse gases and aerosol constructors to fit modern paleoclimatic temperature reconstructions (e.g.: Moberg et al., 2005; Mann et al., 2008; Christiansen and Ljungqvist, 2012) since the Medieval Warm Period, which show a large millennial cycle that is well correlated to the millennial solar cycle (e.g.: Kirkby, 2007; Scafetta and West, 2007; Scafetta, 2012c). These findings stress the importance of natural oscillations and of the sun to properly interpret climatic changes.