Climate change refers to long-term shifts in temperature and weather patterns, which can be natural, but human activities are thought to be the main driver of climate change beginning in the 1800s. According to Sharon’s Municipal Vulnerability Preparedness (MVP) Plan, the top climate change hazards facing the Town are flooding, severe storms, and drought, followed by extreme temperatures. “Across the northeast, precipitation during heavy events increased by more than 70% between 1958-2010. This change in precipitation patterns can lead to increased riverine and stormwater flooding. These conditions are expected to continue to worsen with an anticipated 8% increase in extreme precipitation events by midcentury, and a 13% increase by 2100.
More Intense Rainfall and Runoff Climate change impacts weather and rainfall patterns, leading to alternating periods of drought and intense storms. This can cause more nutrient runoff into waterbodies, feeding cyanobacteria blooms. It is likely that the numerous 2021 beach and lake closures due to E. coli and cyanobacteria were due to the heavy rainfalls which occurred during the month of July, with 11.6 inches rainfall, and August-October, which continued to experience well above average rainfall. According to the Blue Hill Observatory & Science Center data, average rainfall 2017-2021 was nearly 12 inches higher than average rainfall 2012-1016.
Extreme Heat Cyanobacteria usually bloom during the warm summer season or when water temperatures are warmer than usual, due to several factors:
Cyanobacteria prefer warmer water.
Warmer temperatures prevent water from mixing, allowing cyanobacteria to grow faster.
In warmer water, cyanobacteria move faster, and float to the surface faster.
Cyanobacteria blooms absorb sunlight, making water even warmer, further promoting the bloom.
Average air temperature in 2021 was 3 degrees higher than the 1891-2020 mean, with every month higher than the mean except July (with heavy rain). Warmer air results in warmer water temperatures.