Analysis of the temperature records in Lake Tahoe has shown that the lake warmed (between 1969 and 2002) at an average rate of 0.027 °F (0.015 °C) per year. The warming is caused primarily by increasing air temperatures, and secondarily by increasing downward long-wave radiation. The warming trend is reducing the frequency of deep mixing in the lake, and may have important effects on water clarity and nutrient cycling.