"Climate change, once considered an issue for a distant future, has moved firmly into the present."

That's the takeaway line from Tuesday's National Climate Assessment, a sweeping new U.S. government report on how climate change is already affecting the country. The report teems with evidence of those effects, but the mere timing of its release also highlights how wildly things are changing: In April 2014, the air around Hawaii's Mauna Loa Observatory averaged more than 400 parts per million of carbon dioxide for a full month, the first time that's happened in human history.

Putting it that way doesn't really do justice to the scale of our CO2 problem, though. Earth's recent foray into 400 ppm isn't just unprecedented in 200,000 years of human history; it hasn't happened in at least 800,000 years, and possibly not in several million. If you're wondering why the U.S. — and much of the world — has recently experienced historic droughts, storms, heat waves and rising seas, just look up at those extra few CO2 molecules steadily squeezing into every million molecules of air.

Since CO2 is invisible, though, our increasingly dangerous surplus can be easy to ignore. We've all seen those "hockey stick" charts that show CO2 and temperatures soaring in recent decades, yet static graphs are a relatively subtle way to convey an already-abstract concept to non-scientists.

To truly appreciate how much we've already changed Earth's atmosphere — and how much we're on pace to change it even more — it helps to have a better grasp of the timing involved. And as the video below proves, a simple animation of CO2 graphs can make a world of difference. Newly released after April's 400 ppm milestone, the video turns seemingly dry data into a concise, compelling story about our species' relationship with our planet. Be sure to watch all the way to the end for the full effect:

The rise to 400 ppm of CO2 may seem slow to creatures who rarely live longer than a century, but it has been explosive by geological standards. And remixing the sky is only where the trouble begins.

The animation above — produced by the Cooperative Institute for Research in Environmental Sciences at the University of Colorado-Boulder — provides some valuable context for why Earth seems to be growing moodier. For a closer look at how those mood swings are already affecting life on the surface, check out this selection of images from the new National Climate Assessment:

These images may not hit you over the head quite like an animation would, but each one follows an important thread in the big, sprawling story of climate change. And this is just a sample of what's available in the enormous 2014 National Climate Assessment. Check out the full report online for more visuals, interactive tools and other dynamic explanations of what's happening to our planet.

Russell McLendon is science editor at MNN. Follow him on Twitter and Google+.

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