Climatide

flyzipper / flickr

You’ve heard about hockey sticks, right? No, not the actual wood and carbon-fiber things you use to push a puck around on the ice, although those are perfectly nice. What I’m referring to are graphs of the history of various climate factors that are shaped roughly like a hockey stick – a long, relatively flat line that suddenly takes a sharp upward turn around the turn of the 20th century.

The original hockey stick graph was one of global average temperatures over the past 1,000 years. The graph was popularized by Al Gore in his film An Inconvenient Truth, then demonized – along with one of its primary creators, Dr. Michael Mann – by the 2009 ClimateGate email affair. Since then, the hockey stick meme has stayed pretty dormant … until now.

A few weeks ago, Peter Sinclair, producer of Climate Crock of the Week, declared sea level rise “an emerging hockey stick.”

And now we can add ocean acidification to the list of hockey stick graphs. A new study published in this week’s issue of Nature Climate Change concludes that the rate of acidification brought about by human-produced carbon dioxide emissions in the last 200 years is one hundred times greater than anything seen since the last ice age 17,000 years ago.

“When Earth started to warm 17,000 years ago, terminating the last glacial period, atmospheric CO₂ levels rose from 190 parts per million (ppm) to 280 ppm over 6,000 years. Marine ecosystems had ample time to adjust,” says lead author Tobias Friedrich. “Now, for a similar rise in CO₂ concentration to the present level of 392 ppm, the adjustment time is reduced to only 100 – 200 years.”

Nature Climate Change

As carbon dioxide levels rise, acidity increases. One major reason that’s of concern is because acidity limits the availability of aragonite, a mineral that is the essential building block for the calcified skeletons of corals, among others. The new study simulated aragonite availability over the past 21,000 years and found a precipitous drop (at right) starting about 100 years ago and continuing through at least 2100, when the authors ended their simulation. The hockey stick nature of the graph is pretty self-evident.

But if you’d like to look at the data a different way, they’ve also created an animation.