Weather Watch

This winter's record-high temperatures are a man-made trend

A cherry tree blooms in Los Osos in January.
A cherry tree blooms in Los Osos in January.

Two Saturdays ago, I drove to the North County to take photographs of water releases from Lake Nacimiento and San Antonio. As I drove along Lake Nacimiento Drive, a few miles northwest of Paso Robles, I noticed the light-pink blooms of a cherry tree.

Over the years, I’ve gotten used to the appearance of pink blossoms in early winter throughout the coastal regions of San Luis Obispo County where winter temperatures are warmer, but I was amazed to see January cherry blooms in the North County.

So what caused this North County tree to blossom in January? Probably the abnormally warm temperatures we’ve experienced. In fact, this January was the warmest on record.

Normally the Paso Robles average high temperature is 59.5 degrees Fahrenheit. This January, it was a balmy 71.9 degrees — more than 10 degrees warmer than normal.

Due to the lack of storm systems, skies were frequently clear, which allowed the atmosphere’s heat to propagate toward space that produced cooler mornings. The average low temperature in Paso Robles was 33. 6 degrees, normally it is 34.9 degrees.

Overall, the mean Paso Robles temperature for January was 52.8 degrees, breaking the previous record of 51.6 degrees setback in 2007.

At the San Luis Obispo County Regional Airport, the maximum average temperature was 75.7 degrees or over 12 degrees warmer than normal. Due to the persistent night and morning Santa Lucia — offshore winds — and the compressional heating they give, the morning low temperatures at the airport averaged 43.2 degrees. Stretching across the decades, it’s normally 40.7 degrees.

On Jan. 16, the San Luis Obispo Airport hit 91 degrees, while Cal Poly (home of climatology for San Luis Obispo) reported 89 degrees, breaking the historical all-time record for the month of January of 88 degrees. Like the North County, San Luis Obispo experienced its warmest January on record with a mean temperature of nearly 60 degrees.

Not only did San Luis Obispo County experience record warm January temperatures, but many regions in California also did. San Francisco reported an average maximum temperature of 64.0 degrees breaking the previous record of 62.6 degrees set back in 2003. Sacramento’s average maximum temperature was 65.9 degrees smashing the previous record 60.5 degrees recorded in 2012.

Even though most of these atmospheric databases stretched back more than a century, you may have noticed that most of the previous record-breaking temperatures have occurred in just the last decade. And that’s accurate observation.

You see, average temperatures have increased over the last century. According to long-term temperature data from the Cal Poly, and the airports in San Luis Obispo and Paso Robles, the median temperature has increased about two degrees Fahrenheit since 1950.

From year-to-year there is a natural variation in temperature, some years cooler and others warmer, but overall the long-term temperature trend continues to rise. The overwhelming majority — about 97 percent-of peer-reviewed papers on this trend — blame the ever increasing amounts of manmade carbon dioxide in the atmosphere.

PG&E is now accepting applications for the Bright Minds Scholarship program. PG&E is awarding scholarships ranging from $2,000 to $20,000 to 100 deserving students in Northern and Central California. This scholarship is open to high school seniors, current college students, veterans and adults returning to school. All majors are encouraged to apply. Apply by Feb. 28, 2014.