The current warm spell that we're experiencing can be attributed to El Nino, but the larger context for that and other changes is global warming. According to the article,
The computer models reviewed in the “Metropolitan East Coast Climate Assessment”—a 50-year prediction of New York’s changing climate, developed by nasa and Columbia University—suggest that the city will continue to heat up by as much as one degree by 2010, two degrees by 2020, and accelerate on a gentle curve until we reach as much as nine degrees warmer than now in 2100.
I remember back in the warm winter of '97 that people said "it's El Nino, not global warming," but climatologists argue that it's not an "either/or" explanation. We'll continue to have more el ninos because of global warming.
Has anyone else noticed how people keep saying hopefully, "it's really going to cool down this weekend!" and then if you look at the forecasts, it says it will be in the high forties? Sheesh, it's December and I still have time to plant hollyhocks for next year. I was already delaying Fall bulb planting by a month to fit the real temperatures, and it looks like I'm not alone.