Good for you, making decisions in keeping with your goals and values.
I am curious how you calculated the carbon emissions for that flight.
A search on Kayak for an arbitrary date about a month from now shows the cheapest flight from JFK-PVG is operated by China Eastern Airlines, which uses a Boeing 777-300ER for that flight. That aircraft has a fuel capacity of 47,890 gallons. Per the
US Energy Information Administration, jet fuel releases 9.57 kg of CO2 per gallon burned. That means if the plane fills its tanks completely before the flight and burns every drop of fuel, the flight will release a total of 458.3 metric tons of CO2 into the atmosphere each way.
The aircraft as configured for China Eastern holds
316 passengers, including six first-class seats and 52 in business class. If you apportion the CO2 equally across each passenger regardless of seat size and assume the CO2 is burned only for the benefit of the passengers (no other cargo being transported), that's 1.45 metric tons each way, or 2.9 for a round trip. Knock that number down a bit for coach travel, assume a bit of cargo on the plane, and assume the plane isn't burning every drop of fuel in a full tank, and you probably get the actual emissions pretty darn close to your two-ton annual budget.
2.0 (or even 2.9) is still quite a lot, but it's significantly less than 4.9.