The Earth is warming up. That's a fact. Denialists will deny (and no doubt will amp up the noise in the comments below) but the truth is the Earth has warmed on average over a degree Fahrenheit in the past century or so, and the past decade, 2000 - 2009, was the warmest on record.

NASA is not taking this lightly. Our space agency has a fleet of satellites in orbit which examine the Earth, taking its temperature and measuring the effects of this global rise in heat. They have a website called A Warming World, which does a really good job discussing the reality of global warming, and debunking some of the bigger claims of the denialists. A video they put online discusses things like how changing solar input might affect the Earth, how much of this energy from the Sun is reflected, and how much is trapped. It's done simply, elegantly, and with excellent graphics that show just how the Earth is warming up. They've also put online a devastating series of images depicting what's happening on our warming world. Here's one of the Bering Glacier, taken by Landsat 7 in 2002:

In the past century, rising temperatures have caused this glacier's terminus to retreat 12 km (7+ miles), and the ice has thinned by several hundred meters. They have many other images there as well showing what's going on. If I were to say what the biggest problem we have with all this, it's that, ironically, while the warming is happening rapidly on a geological timescale, and too rapidly for us to wait much longer to take action, the changes are happening too slowly to shake people out of their complacence. I'm certainly not wishing the effects were accelerated! But it's far too easy for political maneuvering and loud noise-making to distract people from a very real and very serious issue. I have a lot of confidence in humans. We're smart, and even better, we're clever. There are solutions to global warming, and a lot of them are engineering and technology-driven -- I think we can advance technology greatly while actually fighting the climate change. But we also have to change our behavior, and part of that is facing reality and accepting that this really is happening, and that we have to get off our fat cans and do something about it. The noise machine will rattle cages and distract and sling mud and do a grave disservice to everyone. But I'll be here to fight them along with thousands and thousands of other scientists. And you know what? I have a hope: if we must battle over this for the next hundred years, we'll have a nice, cool world in which to do it. Credit: NASA/Goddard Space Flight Center