Climate Fact: Lake Warming in California and Nevada
Air temperatures are fickle – they fluctuate significantly from day to day, from season to season and from year to year. The temperature of a water body fluctuates as well, but is much more constant than the surrounding air temperature. Water has a higher heat capacity than air, which means it takes far more energy to raise the temperature of a given volume of water than a given volume of air. It also means that once warmed, the water must lose lots of energy to fall in temperature. This higher heat capacity causes seasonal changes in water temperature to “lag” behind the ambient air temperature. This phenomenon is easily observable. The air temperature can remain below freezing for weeks before ice cover begins to form on lakes. The higher heat capacity of water means that temperature fluctuations on multi-annual time scales in lake water as a whole are much smoother than temperature fluctuations in the atmosphere, making lakes effective indicators of longer term warming or cooling trends. Records from satellite imaging systems that collect nighttime infrared emissions show that several large lakes in the Sierra Nevada region (Tahoe, Mono, Pyramid, Almanor and Clear Lake) have collectively been warming at a rate of 0.2 degrees Fahrenheit per year since 1992. This trend may have implications for the life in these lakes that has adapted to the traditionally cold high-altitude temperatures.
Seasons: Winter, Spring, Summer and Fall
Source: Schneider, P et al. “Satellite observations indicate rapid warming trend for lakes in California and Nevada.” Geophysical Research Letters 36 (2009): L22402.
