Many things have changed in Concord between when Thoreau walked the woods near Walden Pond, and today. Thoreau was used to far more open land and agriculture, and fewer beavers and deer. Today agriculture in Concord has declined, and the land is much more heavily forested. Another major change is the average temperature in Concord. As a result of warming resulting from the urban heat island from Boston and from anthropogenic climate change, the average temperatures in Concord today are much warmer than during Thoreau's time.
The graph below shows changes in mean March and April temperature over time between 1853 and 2012. 2010 and 2012 were record warm years. On average the mean spring temperature in Concord has increased by 2.5 degrees C between the 1850s and today. These data were recorded by the Blue Hills Meteorological Observatory.
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| This graph shows the extremely variable spring weather (mean March and April temperature) in Eastern Massachusetts between 1853 and 2012. These data were recorded at the Blue Hills Meteorological Observatory. |
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