Deterministic signals in European fish catches, wine harvests, and sea‐level, and further experiments

Abstract

Abstract Maximum entropy spectrum analysis of six fish catch series, seven series giving dates of wine harvest, and forty four height of sea‐level records from Europe yields evidence for two peaks with periods 18–19 and 10–11 years, the same terms recently reported in European tree‐ring chronologies. For each series the two wavetrains are obtained by bandpass filters, summed, superimposed on the trend‐like components of the raw data, and plotted against the raw data. The contribution, on average, of the waves to total variance in the raw data varies from a high of 50 per cent for fish catches to a low of 14 per cent for dates of wine harvest (the mean contribution for height of sea‐level is 18 per cent). The peaks are identified as the 18·6‐year luni‐solar, M n , and 10–11‐year solar cycle, S c , signals, which also have been reported recently in other climate variables, such as air temperature, air pressure, in rain‐gauge and tree‐ring data from North and South America, South Africa, Tasmania, and New Zealand; and in sea‐surface temperature as well as in American crop yield and other economic data. Further experiments show that with 110 years, or more, of data the Yule‐Walker method of spectrum analysis has sufficient resolution to resolve both signals. It is also shown that failure to apply a properly designed digital high‐pass filter to climate records prior to spectrum analysis usually leads to failure in detecting the terms.