In tests of the rigor of the Steffen/Wong statement that “not only is the OHC increasing, it is increasing faster“, we previously used a linear regression model including natural cycles. The question was raised about the confounding of an upward trend with part of the quadratic terms representing ‘acceleration’. This risk is increased by the short run of data (only 54 years) and also because the phase of the periodic terms is a free variable. The periodic is free because both sin() and cos() are used.
The phase can be bound easily by the simplification below. I introduce 1976 as a start date for the sin() periodic, the date of the Great Pacific Climate Shift, a widely recognized change in ocean and atmospheric phenomena. The code for obtaining the probability that the model is improved by a quadratic term is then:
The results below for existing data and data with an appended low value for 2009 show little change. The p values are 0.07 and 0.12 respectively, indicating no improvement in the model by adding a quadratic term. With the suggested alterations, we again find no empirical justification for the Senator and her advisor’s statement, when we include natural cycles in the model, i.e. for OHC to be increasing faster we have to exclude natural cycles as a possible explanation.
Previous result with free phase:
The change in OHC from peak to trough is 2*2.7 or 5.4 x1022 joules, while the linear increase in heat over the same period is 0.33*54 or 17.8X1022 joules. The coefficients of the linear regression suggest periodic oceanographic phenomena could account for 30% of the increase in OHC since 1958.
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