Challenging the Bleak Climate Forecast for Georgian Bay (Updated)

‘State of the Bay’ is an initiative of the Georgian Bay Biosphere Reserve (GBBR) which has forecast that water temperatures in Georgian Bay Ontario “are warming” and could rise by “10°C this century within coastal ecosystems”, and warns of “catastrophic events”. These claims are evaluated herein from year-round government records at 11 weather stations surrounding Georgian Bay, and June-October records at the two moored buoys in the water. [Note: Since this paper was first published in 2020 some GBBR claims have been moderated but claims of ‘warming’ have been retained. Air and water temperatures in this study are now updated to include 2020.]From the mid-1940s, Georgian Bay waterfront towns have followed a cycle of cooling to about 1980, warming to the mid-2000s, and then cooling in the last 15-20 years. A rough estimate of cooling rates of air temperatures is -0.20°C/decade since 2005 and -0.40°C/decade since 2010. Surface water in northern Georgian Bay has cooled at -0.10°C/decade since 2005. In the south, cooling was -0.24°C/decade since 2004-2006, cooling in June - July, warming in August - September, and constant in October. ‘Extreme highs’ and ‘extreme lows’ in Wiarton show cooling of -0.31°C/decade and -0.36°C/decade for 2000-2020, and extreme temperatures in Collingwood and Parry Sound have cooled since 2000 and 2005 respectively.There is no sign of warming of air or water over the last 15 years. Forecasts are inherently difficult for natural rhythms, and are critically flawed when linear trends through non-linear cyclical data are extrapolated into the future.