Summer
Many of our favorite summer activities in the Burlington area rely on our climate. Burlington summers are usually not too hot or too cold, with enough precipitation to keep things interesting - though, of course, they vary a great deal from year to year.
Climate helps guide our gardening activities, and draws tourists here to hike and camp. How might climate change affect our summertime activities?
Heating Up
There's an old saying: "If you don't like the weather in New England, wait a minute." The unpredictable weather can make it hard to notice slow changes in climate. So, what are the long-term trends?
What Scientists Know (And Don't Know)
That 1.8 degree rise in the Northeast is an average across very different places. Scientists can give us a range of possible future temperatures, but local factors like elevation will also be important.
A weather station at the Burlington Airport has detected a significant temperature rise over the past 50 years. That's just one spot - what about the broader region?
Temperatures across the Northeast are going up. The average temperature in the Northeast rose 1.8 degrees Farenheit since 1899. The number of very hot days - days above 90 degrees - also increased.
Summer heat waves can threaten our health and worsten air pollution. What will our summers be like as the climate changes?
The chart on the right is one possible future projection for Vermont. It comes from a report by the Union of Concerned Scientists. It shows possible future changes in summer heat index - how hot it actually feels outside due to heat and humidity.
The 
yellow arrows show changes in heat index if we strongly cut back our greenhouse gas emissions. The 
red arrows show changes without strong cuts.
For more, read this Vermont report from the Union of Concerned Scientists, and explore the Nature Conservancy's Climate Wizard to see how Vermont's temperature will change. This chart's citation is below.
Rain and Drought
What About Snow?
How will climate change affect winter precipitation? To read about winter snowfall, visit the Winter page.
Since 1950, the Burlington Airport weather station has detected an increase in annual precipitation. The whole Northeast has seen an average increase in precipitation in the past century, as well as an increase in extreme, damaging rainstorms.
What's in store for the future? Unfortunately, precipitation is more difficult to predict than other climate factors. It works at a small scale, and it varies a lot from season to season.
Many scientists say that there will be more heavy rainfall events as the climate changes, especially if we don't make significant cuts to our greenhouse gas emissions. They also project that higher summer temperatures will create more droughts in Vermont. This might seem like a strange mix, but it's not uncommon for flooding and drought to happen one after the other; in 1998-1999, for example, drought came after statewide flooding.
Explore the Northeast regional reports located here and produced by the Union of Concerned Scientists. Also, read Drought Follows the Deluge in Vermont by state climatologist Lesley-Ann Dupigny-Giroux.
How Will Your Garden Grow?
What is the Growing Season?
It's the number of days between the last spring frost and the first winter frost, when garden plants (including agricultural crops) grow best.
Since 1900, the growing season in the Northeast has increased by more than a week. Scientists predict that the growing season will keep lengthening as the climate changes.
What does this mean for gardeners? This longer growing season is a mixed blessing.
On the one hand, it means that gardeners can grow plants that need a warmer climate. They can plant earlier and keep harvesting later. Farmers who have the resources can try planting exciting new crops.
On the other hand, it means unpredictacle changes. Many invasive weeds seem to respond better than native plants to climate change. Also, the most competitive crops in the Northeast (like apples) prefer a cooler climate, so farmers will have to decide if switching to new crops will be economically smart.
We need to consider: do the possible benefits of climate change outweigh the drawbacks of unpredictably changing the world we know?
Gardeners, check out the Gardener's Guide to Global Warming from the National Wildlife Federation. Also, read this study about climate change and invasive species in Massachusetts.
Poison Ivy and Ragweed
Some plants will handle climate change better than others. Here are two unwelcome climate "winners" that will affect our summertime hikes.
Researchers at the Duke University Forest raised the levels of CO2 - an important greenhouse gas - and studied what happened to forest plants. They found that as CO2 increased, poison ivy grew more than most other woody plants. It also became more toxic!
In late summer, ragweed allergies can turn picnics into sneeze-a-thons. Researchers have found that higher levels of atmospheric CO2 can help ragweed grow, and can even make its pollen more allergenic.
Today's climate change isn't just about warming. It's about unusual changes to our familiar outdoor spaces.
Click here to read the poison ivy study by Mohan et al., and read a Newsweek article about climate and allergies.
The image of "migrating" heat index was used with permission from: Frumhoff, P.C., J.J. McCarthy, J.M. Melillo, S.C. Moser, and D.J. Wuebbles. 2007. Confronting Climate Change in the U.S. Northeast: Science, Impacts, and Solutions. Synthesis report of the Northeast Climate Impacts Assessment (NECIA). Cambridge, MA: Union of Concerned Scientists (UCS).
