The numbers are in for 1999. According to climate researchers at the National Oceanic and Atmospheric Administration, last year was the 5th warmest year worldwide, on average, since record-keeping began around 1880. In fact, the 6 warmest years all occurred in the 1990s, easily making this past decade the warmest on record.

This begs the question: Is this recent warmth just natural variability, or are we causing the warming by adding greenhouse gases, such as carbon dioxide, to the air?

This issue of global warming is still controversial. But most climatologists agree that the observed warming is probably too large to be entirely natural. This issue won't go away anytime soon, so I'm sure I'll have more to report on future Franklin Facts.