So how did 2011’s weather shake out in the grand scheme of things? First off, let’s make sure we are all on the same page regarding the difference between weather and climate.
Weather refers to the short term, while climate is about the long term. Weather can be what’s happening outside your window right now or what the past year has been like. Climate is the longer term, big picture view; it describes weather patterns across a number of years. Add all the weather together, and you get climate.
Let’s describe 2011’s weather and compare it with the climate for our region, beginning with snow. Many recall the winter of 2010-11, which, in terms of snow, began in December 2010. A whopping 68 inches of snow fell, making it the third snowiest winter in our 19 years of data collection at the Cary Institute. The winter of 1995-96 brought 92 inches of snow and the winter of 2002-03 brought 91 inches, so, although last winter was a humdinger, it wasn’t outstanding.
Our least snowy winter was 2001-02 with 19 inches. So far, this winter is turning out to be a calm one — with a total of 20.5 inches so far. This is despite a very unusual start, with a freak pre-Halloween snowstorm of 15 inches.
Total precipitation for 2011 tells us a different story. It was the wettest year in our 28-year precipitation data record, with 64.69 inches of rain and snow. Two big events associated with Tropical Storm Irene and then Tropical Storm Lee brought a total of 12.13 inches of rain in late August (Aug. 27-28) and early September (Sept. 5-8). These events resulted in major flooding in the region. While the total volume of precipitation we received did not break records, the already saturated soils and full lakes, ponds and wetlands caused the water to run off into streams and rivers, causing the major floods that we experienced. The long-term record of precipitation at the Cary Institute shows an increase in precipitation, which is consistent with climate change predictions.
How about temperature? While the average temperature in 2011 did not break records, it was the 19th year in a row with an average temperature above normal. Every month in 2011 except January had higher than normal temperatures. While the overall trend in temperature in our 24-year record shows only a slight increase over time, some other indicators show a definite warming trend over time.
The length of the growing season has increased in the last 24 years. That is, the number of frost-free days in the summer has gone up. The date of first autumn frost is coming later and later, but the date of the last frost in the spring isn’t changing.
Another measure of our changing climate can be seen in stream temperatures. Our 19-year record of average stream temperatures shows an increasing trend in the summer, but not the winter months.
While stream temperatures reflect overall air temperature to some extent, they can also be driven by water level and the temperature of water inputs to the stream among other factors. Lower water levels usually result in warmer stream temperatures in the summer.
Vicky Kelly manages the Environmental Monitoring Program for The Cary Institute in Millbrook.