It's only going to get hotter.

It's damn hot outside -- heat index is hovering around 100 degrees Fahrenheit, humidity is near 60% (actually kind of low for East TN). And no doubt someone somewhere has attributed the current heatwave to climate change. It's unseasonably hot, so isn't that evidence of global warming? Not necessarily. Nor would a cold day in July signal that global warming is a myth. Claims like these make a category mistake -- they confuse "climate" and "weather."

Weather is highly variable, subject to daily changes that are notoriously difficult to predict. Climate, on the other hand, refers to long-term weather patterns and averages over time. When scientists talk about climate change and global warming, they are talking about average global temperatures rising over time -- this doesn't mean they necessarily rise in all locations equally. In fact, temperatures may rise dramatically in some areas while falling in others.

There's some speculation that a rise in average global temperature would cause ice melts in the North Atlantic that would cool the temperature of the ocean and disturb the "normal" circulation of the Gulf Stream. The Gulf Stream is largely responsible for the temperate climate currently enjoyed by Ireland, Britain, and Europe. If the GS ceases to function as it currently does, these nations could suddenly find themselves much, much colder. While this claim is somewhat controversial, it does show how global warming could, in theory, lead to serious drops in temperature for certain parts of the world. So, when thinking of climate change or global warming, think big -- in terms of averages over time, not specific daily temperatures, heatwaves, or cold snaps.

The Union of Concerned Scientists has a great section on climate change at their website.

The UCS is also featuring an article on some hardline hold-outs on the global warming issue (guess who?)-- despite the fact that scientific consensus continues to grow behind the theory that current global warming trends are directly related to human activity. This despite the fact that:

In June 2005, the national scientific academies of 11 nations issued a joint statement that reads, “The scientific understanding of climate change is now sufficiently clear to justify nations taking prompt action” to reduce global warming emissions. And at the G8 Summit in July 2005, President Bush himself acknowledged that he accepts the overwhelming evidence that human activity contributes significantly to global warming.

Geez.