In our world of information overload, we get used to hearing of records being broken. Even so, some moments stand out: Usain Bolt smashing the 100-meter dash record in Beijing, despite easing up before the finish. In 1998, Mark McGuire hitting 70 home runs to crush Roger Maris' nearly forty-year-old record of 61 in a season. We remember these moments because breaking the record seemed to signal the beginning of a new era. You could tell something had really changed.
In 2007, the scientists who make their living studying Arctic ice were stunned. That year the sea ice plummeted to a new record - 23% less than the previous low point. The bottom had fallen out of earlier projections of the speed and extent of Arctic sea ice loss. That 2007 record was one of the key global warnings that catapulted climate change into the public imagination. It was a game changer.
Three weeks ago scientists and climate-watchers were buzzing again with news: the startling 2007 record had itself been broken. I wrote about it then. But at that time, we only knew that a game-changing record had been broken. We didn't know whether the new record itself would be game-changing. Now we do.
Since the 2007 record was surpassed in late August, Arctic ice levels have been dropping, and dropping and dropping. Due to a combination of warmer water, warmer air and strong winds, Arctic sea levels dropped almost another 20% in 20 days. This is an area the size of Texas - lost in three weeks. When the U.S. National Snow and Ice Data Center (NSIDC) finally determined that we'd reached bottom for this year, sea ice levels were 50% below the average from 1979-2000.
As in 2007, this new record demonstrates a significant shift in our expectations for the speed at which the Arctic is disappearing. As NSIDC Director Mark Serreze said, "We are now in uncharted territory." Just a few years ago scientists were projecting summer sea ice would remain in the Arctic through mid-century or even until 2100. Now some scientists are saying the Arctic could be ice-free in the summer within two or three years.
The disappearing sea ice not only has major implications for the Arctic ecosystem itself, but scientists now believe that these changes influence weather throughout the Northern Hemisphere. The strength and trajectory of the jet stream is affected by the temperature difference between the Arctic, north of the jet stream, and the areas south of it. The greater the temperature difference, the stronger the jet stream. As that difference decreases, thanks to a warming Arctic, the jet stream tends to weaken and to wobble, introducing more north-south waves into the usual east-west trajectory of the stream. A weaker and wobblier jet stream means that weather systems tend to linger, producing more extreme events like droughts, heat waves and floods. And a winter wobble can also produce unusually heavy snow storms in unusual places, such as Washington DC's so-called "snowmageddon" in 2010.
So when we look closer, many of the record-breaking weather events we've witnessed in recent years - from heat waves to droughts to the disappearing Arctic sea ice - are not isolated, but connected. And in this new era of extremes, we aren't just breaking records. By continuing to pour carbon pollution into the atmosphere we are rewriting the rulebook for the future of life on Earth.