Hurricanes deposit a layer of sediment in inland areas that get buried and can remain undisturbed for thousands of years. By taking core samples it is possible to identify storms, date them and even determine how strong they were. In this way, the researchers were able to identify 23 events during that time span, each more powerful than anything that has occurred in recorded history. That is an average of one major storm every 40 years. These storms would all be classified as category 3 or 4 hurricanes today. To put that in perspective, there have been only three category 2 hurricanes in that area since the 1600s. The last was Hurricane Bob in 1991. There have been no storms stronger than category 2 to strike New England in that time period.
What has changed? Ocean temperature. Hurricanes require warm water to provide the massive amounts of energy they consume. Ocean temperature in this region of the Atlantic has been cooler for the last 850 years, but not anymore. Today, ocean temperatures are warmer than they were between 250 and 1150. Take a look at this plot:
|Source: Climate Reanalyzer|
Does this mean New England can expect a category 3 or 4 hurricane every 40 years on average? No, not by itself. There are many factors involved with the development of hurricanes and their paths. Without more detailed data we cannot reach an absolute conclusion that New England will get hit by big storms. But, it certainly means the risk is greater than we thought.