New York City's Carbon Dioxide Story
When looking at carbon dioxide levels in New York City, there are three major players: trees, people, and wind. Were lucky, because two of these three factors (trees and wind) combine to keep carbon dioxide levels in our city significantly lower than other US cities. However, carbon dioxide levels in Manhattan this summer are approximately 5 % higher than the current global average.
By taking long term detailed measurements of carbon dioxide levels in Manhattan and in surrounding rural areas, we have shown that Manhattans elevated carbon levels extend at least 20 miles outside of the city, but the amount of elevation is not as bad as most US cities. Phoenix Arizona, for example, has a carbon dome that extends only a few miles from the city center, but carbon levels are about 15 years ahead of the global mean.
Wind, trees and people all have an effect on the depth and breadth of New York's carbon dome. There are no major mountain ranges nearby, and the Atlantic Ocean produces consistent winds, year round. The rural areas in the Catskill's Mountain area and New Jersey all provide a constant stream of low-carbon air for us.
We learned this by comparing concurrent atmospheric carbon dioxide measurements in Rockland County, in the forest near the Tappan Zee Bridge, with measurements taken on the Harlem Elementary School Future Leaders Institute on 122nd, and correlating that information with wind speed and direction, in order to show how and where the air is moving. Further proof of this theory comes from our understanding of tree physiology.
Trees are like humans, they breathe. During daylight hours, trees take carbon dioxide out of the air, and use it for photosynthesis. At night however, trees actually emit carbon dioxide, as they burn stored sugars to keep their systems running in the absence of light. Carbon dioxide levels in the air in rural environments clearly show this daily cycle. Manhattans carbon dioxide levels follow the same daily pattern, though slightly smaller and with a time lag. The time lag shows that wind from adjacent rural environments is a significant factor in cleaning Manhattan air. A good portion of Manhattan's air actually comes from New Jersey. The data can also help determine the amount of green coverage that is needed for urban environments to help control carbon dioxide levels.
Surprisingly, though, trees still have a greater influence upon New York Citys carbon dioxide trends than automobiles, as carbon behavior is still more in tune with the daily cyclical patterns of trees than cars. We can see a distinct morning rush hour spike in carbon dioxide levels, but its a lower spike than the daily swing due to trees. This is primarily because most New Yorkers dont commute by car, and as anyone who has tried to drive into Manhattan at rush hour knows, there are a very finite number of cars that can fit on the island. Mayor Bloomberg's commissioned paper documenting New Yorker's carbon dioxide consumption, reported that the per capita carbon consumption in the city is less than a third of the average American’s.
While New York is one of the most carbon-neutral cities in America, we still can and should strive to do better. We certainly hope that nothing we do begins to change local wind patterns, but we can ensure that we keep the forests outside of Manhattan in good condition, and keep what trees we have here safe and healthily, while encouraging developers to add trees to their designs. Reducing traffic congestion and increasing the availability of mass transit for both people and materials will further protect our air quality.