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Tahoe Nugget #172 Tahoe Climate Change The combination of Earth Day and a record-breaking heat wave in California and western Nevada flashed global warming into media headlines again. No matter that last week Truckee reported the lowest temperature in the lower 48 states at about 18 degrees during a January-like cold snap. Or that when the heat wave broke, I had to fight congested traffic over Donner Pass the day after Earth Day due to snow. It's spring after all and wild weather swings are to be expected as the atmosphere over the northern hemisphere adjusts from winter to summer. Earth Day often brings out the best in people. Individuals and families make a point of joining the collective effort to clean our local communities and vow to protect the planet. It's a festive, hopeful event, but it is also a call for action and a plea to reduce our individual carbon footprints and hopefully avert rapid climate change. Convincing everyone that human activities are causing climate change is far from a done deal. A recent poll indicated that only 34 percent of Americans believe that global warming is caused by human activities. This skepticism is surprising considering that a recent survey among more than 3,100 scientists revealed that about 80 percent agreed with the statement "Human activity is a significant contributing factor in changing mean global temperatures." An interesting caveat to those results is that only 64 percent of meteorologists surveyed agreed with that statement. Environmentalists and many governments have said that humans are pumping too much greenhouse gas into the atmosphere, while others point out that the Earth has always fluctuated between warm and cool periods, based on climactic change, sunspot activity, oceanic oscillations, and even the axis tilt of the planet. One thing is for sure — it's getting warmer at Lake Tahoe. Over the past century air temperatures at lake level have increased by about 2 degrees Fahrenheit for the daily maximum and more than 4 degrees for the daily minimum. This warming has also changed the ratio of snow and rainfall in the basin. In the past 100 years, snow has declined as a fraction of total annual precipitation from 52 percent to 34 percent. In other words, in the "old days" more than half of our annual precipitation at lake level came as snow. Today it's just about one third. More remarkable has been the warming of Lake Tahoe's water. The average July surface water temperature has increased dramatically, almost 5 degrees, from 62.9 degrees to 67.8 degrees, in less than a decade. On July 26, 2006, the lake's surface water was a tropical 78 degrees! It appears that some of the warming at Lake Tahoe can be blamed on earlier snowmelt. In the past 50 years, peak stream flow from snowmelt has shifted earlier by two-and-a-half weeks, indicating a quicker melting of the snowpack than before. There are more data to confirm the warming trends, but I'll end here. It's easy to get bogged down in the argument of what should be done about climate change and its causes. The point is that most people do support efforts to improve air quality that will save thousands of lives a year in the U.S. alone and help reduce respiratory illnesses like asthma. Businesses lose huge amounts of money every year due to employee sick days related to air pollution. Reducing air pollution will help us now, today. But it's important to remember that no matter what we do to reduce greenhouse gas emissions, the climate may change anyway. It always has. Tahoe Nuggets are now archived at www.thestormking.com Photo #1: Snow in Carnelian Bay on April 23, 2009.
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