Crozet Weather Almanac: December 2016

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December 2016

This year will go down as the sixth warmest year ever in Crozet/Charlottesville. We have 106 years of records with good enough data to count. The only other years that were warmer were, in order, 1953, 1998, 1991, 1941, and 1931. The coldest year ever was 1917 but close behind were a couple of recent years, 2003 and 2014.

This year wasn’t really that “hot.” Our heat wave index this summer was nowhere near the warmest ever. We just had a consistently warm spring, summer, and fall.

The catalyst for this year’s heat was a “Super el Niño” which peaked at the end of February. El Niño is an unusual but natural phenomena that causes a strong warming of the equatorial Pacific Ocean. The warm ocean usually lasts a year or so and comes back every few years, but this year it was exceptionally strong. The warm water changes the entire global atmospheric circulation pattern. Sometimes, we can forecast six or 12 months in advance with surprising accuracy based on the status of El Niño or the opposite, La Niña. However, in Virginia, the correlations are weak so long range forecasting remains elusive.

Globally, 2016 will rank as the “hottest ever” in most data sets. The earth was much warmer at times in the distant past but since thermometers became widespread in the 1880s, this will almost certainly be the warmest. Much will be made of this “hottest ever” tag at year-end, but global temperatures have cooled rapidly since El Niño faded and La Niña has slowly emerged this winter. The year 2017 will almost certainly be cooler than 2016 and the heat record this year will likely stand for a long time in a similar fashion to the 1998 El Niño year. The longer term warming trend since the start of the fossil fuel era (about 1950) remains about one degree of warming Fahrenheit every 40 years. Here in central Virginia, there has been no warming trend.

El Niño remains a mystery in many ways. Some studies have suggested that orbital pulls are highly correlated with El Niño and the occasional release of heat into the tropical Pacific provides just enough heat to keep us from slipping into another ice age. The earth slowly cools until a brief surge in El Niño heat comes every couple of years. Much research is being conducted now that we have better global data sets but much of what drives our climate remains a mystery.

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