Thursday, August 11, 2016

Sea Level's Increase Is Accelerating

John Fasullo and colleagues predict that satellites will detect accelerating sea level rise within the next decade.  I've written (a lot) about the rise in sea levels.  And now there's some indication that these levels are increasing nonlinearly.

As humans emit greenhouse gases, it’s causing the Earth to warm. That’s indisputable and proven. We can actually measure the amount of extra heat. Since most of it ends up in the oceans, we can also measure other changes in the oceans.
For instance, the oceans are rising. We know that’s indisputable. Measurements taken from physical gauges and from satellites confirm sea level rise. The cause of the rise is more complex. 
A very recent paper published in Nature has evaluated the history of sea level rise, and what they find is really interesting. The lead author (John Fasullo from the National Center for Atmospheric Research) and his colleagues tried to determine if the rate of sea level rise is changing. That is, are the water levels rising linearly, the same amount each year? Or, is the rate increasing (faster and faster each year)?
Using satellite data, the authors found little evidence of an acceleration. However, they show that this is because the satellites began measuring in 1993, right after a large volcanic eruption (Mount Pinatubo). This eruption temporarily reduced global warming because particles from the eruption blocked sunlight. Just by coincidence, the timing of the satellites and the eruption has affected the water rise so that it appears to be linear. Had the eruption not occurred, the rate would have increased.
This allows the scientists to make a prediction:
barring another major volcanic eruption, a detectable acceleration is likely to emerge from the noise of internal climate variability in the coming decade.
 This implies a nonlinear increase in sea level.  It will be scarcely noticeable at first, and then suddenly our shores will be awash.