"Global Warming" could be called climate destabilization, or climate polarization, instead. People made the same stupid argument as you have, when it was discovered that the Pacific current, that runs down the coast of California, is getting cooler. Only later did the reason become obvious - the arctic ice cap is melting.
So, yeah, the effects of pouring tons of pollution into the air, don't always lead to warmer weather, but it is foolish to conclude that, therefore, there is no issue.
