Global warming is about a long-term tendency, which might temporarily be reversed in individual places, or in individual years. But it is the long-term tendency that should be watched.
Difference in opinions hath cost many millions of lives: for instance, whether flesh be bread, or bread be flesh; whether whistling be a vice or a virtue; whether it be better to kiss a post, or throw it into the fire... (from Gulliver's Travels)