October 2015 Archives

Forget 2100

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What will the world look like in the year 2100? If we can avoid nuclear winter, robot overlords, or some unforeseen apocalypse, then the question is really about climate change. The answers, of which there are many, have to do with global temperatures, sea level rise, ocean acidification, species extinction or collapse, drought, and storm intensity--just to name a few. These predictions don't always agree, but one commonality is that the time frame is on the scale of 50-100 years. A lot of the projections look something like this:


Well, the graphs that you see might look a little more technical that this one, but the basic idea is to figure out the trend line. That is: how will the average conditions change over a long period of time?

These calculations are useful, and scientists can often make them with reasonably high certainty. But this type of graph makes a particular imprint in our minds of what climate change looks like. As a consequence, we often focus on that distant horizon--the year 2100. You often hear about acting on climate change for the benefit of our children or grandchildren.

The problem with that smooth, gradual line is that it misses all of the bumps and wiggles along the way. Those ups and downs are the variance around the line, and they look something like this:


Along the way to those unsettling 2100 conditions are sharp increases (and decreases) that occur over short time periods. This is the climate change that we'll have to deal with, and it will come much sooner than 2100.

Bouts of rapid warming will occur in different places at different times, and we're already starting to see some of them popping up.  The rapid warming in the Gulf of Maine is an instructive case. Warming of ocean temperatures in this location over the past decade has been almost 10 times as fast as the background warming rate and faster than 99.9% of the rest of the ocean. It's a rate of warming that has been extremely rare among marine ecosystems. This coastal sea has essentially gone through one of those big bumps/wiggles on its way to 2100 conditions. 

The rapid warming has turned the ecosystem on its head. From seahorses in lobster traps to dense swarms of jellyfish, unusual species have become the norm. For many commercial species, the temperature change was too quick for management to keep pace, leading to unforeseen collapses of once reliable stocks, such as Atlantic cod and northern shrimp. The recent paper in Science referenced above reports that the additional unpredicted mortality to cod correlates remarkably well with the fast year-to-year warming. Meanwhile, along the coast, new visitors like the invasive green crab are physically reengineering the system.

The Gulf of Maine may be one of the first to go through a bump/wiggle like this, but it won't be the last. In many places around the world, we'll find that the road to 2100 conditions is not a gradual slope, but a roller coaster ride. For those who are thinking about ways to prepare for and adapt to changing climate, take your eyes off the year 2100. Rapid changes that occur over ~10 year time scales will arrive much sooner, and that is what we'll be forced to respond to. 

Again, assuming we can avoid the robot overlords.

Nick Record, signing off

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