2016 Evaluation of Fair Plan 3: Outlook for Global Temperature Change throughout the 21^st Century

Abstract

In 2013, the author and colleagues made a projection of temperature departures (from the 1961-1990 average) throughout the remainder of the 21st century due both to Humanity and Nature. Two scenarios of human-caused emissions of greenhouse gases and aerosol precursors were examined: (1) A reference scenario with no emissions reductions, and (2) our Fair Plan to Safeguard Earth’s Climate which zeroes emissions from 2020 through 2100. Human-caused temperature changes from 1756 were calculated using an engineering-type Simple Climate Model. Temperature changes due to Nature were projected from our analyses of the observed temperature departures from 1850 through 2012. These natural changes were due to: (1) Three quasi-periodic oscillations (QPOs), each of which we fit with a sine wave to project into the future on a year-by-year basis; (2) Other QPOs that are too irregular to predict yearly, and (3) stochastic noise. We projected natural variations (2) and (3) by the 90% confidence interval of a Normal (Gaussian) probability density function, with zero mean and standard deviation of 0.08°C. Here we add four more years of observed temperature departures to compare with our projections made in 2013. Each of the additional four temperature departure observations for 2013, 2014, 2015 and 2016 fits within the 90% envelop of temperature departures, thereby rendering our projection accurate to date. Most of the temperature changes during the 2012-2016 period were due to the annually unpredictable natural variability. This evaluation will be repeated quadrennially for the remainder of the author’s life.