This post is from the Spring 2012 edition of the Appalachian Mountain Club’s The Mountain Watcher newsletter:
Mount Washington Climate Trends
The long-term climate record for the Mount Washington summit (1914 m) and Pinkham Notch (612 m) in New Hampshire show that annual average temperatures are getting warmer over the span of 1935 to 2010. Pinkham Notch is warming by 0.10 °C per decade on an annual basis, while the summit is seeing a 0.08 °C per decade increase (see table). Spring average warming rates are even greater for both sites. The slower warming rates on the summit, compared to Pinkham Notch, are in part attributed to the top of the mountain being 1) frequently immersed in clouds, which can block heat coming in, and 2) often disconnected from the “mixed layer” of the atmosphere where the majority of heat is exchanged with the ground.
Warming trends are greatest in either winter or spring, as has been observed at the nearby the USFS Hubbard Brook Research Station (Campbell et al, 2010). The graph below shows Pinkham Notch spring-time average temperatures (black with dots) with its trend line (black line), and data from the Hubbard Brook site 6 (red), which began recording temperatures in 1961. These two sites are tracking well.
The trend analyses for the Mount Washington summit and Pinkham Notch, reported here, are an update from a joint project being conducted by the Appalachian Mountain Club, Mount Washington Observatory, and the University of New Hampshire (Seidel et al., 2007), adding 7 more years of data to that study for a total of a 76 year record. This additional data resulted in a stronger warming trend on the summit that is now “statistically significant”, a threshold that was not reached in the earlier study.
*This work has been funded in part, by the Waterman Fund, multiple NOAA grants (NA06OAR460029, NA06OAR4600180 and NA09OAR4590208), and The EnTrust Fund.
AMC’s science team has begun to analyze our plant “phenology” dataset to help us decipher what environmental queues best explain the timing of plant flowering and fruit set. We know that the day of year, as a proxy for the change in amount of sunlight, and air temperature are key drivers in plant flowering. However, a direct pairing of local temperature with plant development is needed to understand specific plant responses, and whether changes in temperature can impact flowering times.
This analysis began only after multiple years of on-site temperature data collection, because many years of data are needed to make sense of the natural variation in flowering from year to year. The initial work is currently limited to AMC’s alpine permanent plot data and only 3 alpine plant species. While only the starting point, this effort has shown us that we can predict the timing of flowering well for some species (see table), based on the day of year and the cumulative temperature (as growing degree days, a common index used in agriculture). The table above compares the actual average flowering day for the years 2008 to 2011 to the predicted flowering day, showing the best agreement for the earlier flowering species, Diapensia and Bigelow’s sedge.
Using the latest Mount Washington summit long-term temperature record (reported on above) we have also developed initial estimates of how flowering time has changed over the last 76 years in the NH Presidential Range alpine zone. All 3 alpine species show earlier average flowering times based on our models. The estimated average flowering times for Diapensia is shown in this graph with the trend line showing a shift to earlier flowering. Next steps will be to add more baseline years to strengthen the models, examine more plant species, and add citizen science observation datasets to conduct a broader spatial analysis.
Learn how you can help track flowering times in the eastern Appalachian region and contribute to this ongoing study of plant response to climate change.
*This work has been funded, in part, by the Waterman Fund, multiple NOAA grants (NA06OAR460029, NA06OAR4600180 and NA09OAR4590208), and The EnTrust Fund.