Josh Willis on Sea Level Rise

November 9, 2011

Above, a conversation between Andy Revkin and Josh Willis, an ocean and climate researcher at NASA’s Jet Propulsion Laboratory, and advisor to this series. Below, the recent summary on sea level from JPL.

NASA Jet Propulsion Lab:

Like mercury in a thermometer, ocean waters expand as they warm. This, along with melting glaciers and ice sheets in Greenland and Antarctica, drives sea levels higher over the long term. For the past 18 years, the U.S./French Jason-1, Jason-2 and Topex/Poseidon spacecraft have been monitoring the gradual rise of the world’s ocean in response to global warming.

While the rise of the global ocean has been remarkably steady for most of this time, every once in a while, sea level rise hits a speed bump. This past year, it’s been more like a pothole: between last summer and this one, global sea level actually fell by about a quarter of an inch, or half a centimeter.

So what’s up with the down seas, and what does it mean? Climate scientist Josh Willis of NASA’s Jet Propulsion Laboratory, Pasadena, Calif., says you can blame it on the cycle of El Niño and La Niña in the Pacific.

Willis said that while 2010 began with a sizable El Niño, by year’s end, it was replaced by one of the strongest La Niñas in recent memory. This sudden shift in the Pacific changed rainfall patterns all across the globe, bringing massive floods to places like Australia and the Amazon basin, and drought to the southern United States.

Data from the NASA/German Aerospace Center’s twin Gravity Recovery and Climate Experiment (Grace) spacecraft provide a clear picture of how this extra rain piled onto the continents in the early parts of 2011. “By detecting where water is on the continents, Grace shows us how water moves around the planet,” says Steve Nerem, a sea level scientist at the University of Colorado in Boulder.

So where does all that extra water in Brazil and Australia come from? You guessed it–the ocean. Each year, huge amounts of water are evaporated from the ocean. While most of it falls right back into the ocean as rain, some of it falls over land. “This year, the continents got an extra dose of rain, so much so that global sea levels actually fell over most of the last year,” says Carmen Boening, a JPL oceanographer and climate scientist. Boening and colleagues presented these results recently at the annual Grace Science Team Meeting in Austin, Texas.

But for those who might argue that these data show us entering a long-term period of decline in global sea level, Willis cautions that sea level drops such as this one cannot last, and over the long-run, the trend remains solidly up. Water flows downhill, and the extra rain will eventually find its way back to the sea. When it does, global sea level will rise again.

“We’re heating up the planet, and in the end that means more sea level rise,” says Willis. “But El Niño and La Niña always take us on a rainfall rollercoaster, and in years like this they give us sea-level whiplash.”

Willis restates what the overwhelming body of evidence says.  The armchair oceanographers of the climate denial fringe will continue to tapdance and armwave, but knowledgeable pros who are reading the data are telling us that a business as usual approach is going to give a much higher sea level rise than was thought just a few years ago.

Below, listen to US Navy Chief Oceanographer Admiral David Titley, who, after years as a stubborn skeptic of climate change, finally was overwhelmed by the evidence. He told his boss  “Sir, look at 3 to 6 feet” in the coming century.

Starts at about 3:50, if you’re rushed.


6 Responses to “Josh Willis on Sea Level Rise”

  1. Martin_Lack Says:

    Clearly, neither Andy nor Josh has read James Hansen’s 2008 paper Target CO2 where should humanity aim or, indeed, anything James Hnasen has written in the last 10 years!

  2. A long reader comment from the Lone Star State:

    Rice University professor, John Anderson, is retracting his scientific report about various environmental challenges facing Galveston Bay. His scientific opinion was commissioned by the Texas Commission on Environmental Quality. He pushed back because TCEQ deleted references linking sea level rise to global warming.

    John Anderson (reason for retraction): “It’s one thing to have an administration with its head in the sand. It’s altogether another thing to have an administration that tries to put all our heads in the sand.”

    Governor Perry appointee, TCEQ Chairman Bryan Shaw (confirmation hearing): “I don’t believe [AGW] it’s fully vetted. It warrants a critical process of looking forward because the implications of moving forward based on the assumption that man-made contribution is the primary driver of climate change may close windows of opportunity for us with regard to the environmental good that we’re trying to achieve.”

    Andy Saenz, TCEQ spokesman (justifying TCEQ’s decision to edit report): “It is not censorship to correctly state our agency’s position in a report that carries our name on it. We are paying for this report, and the assertions and statements will be attributable to the TCEQ. So why would we include questionable information we don’t agree with?. Our intent with this report is to give an accurate portrayal of the state of Galveston Bay and not act as a forum for debate and discussion about global warming.”

    This is the edited report – with change tracking enabled.

    John Anderson’s red blooded Texas persona hardly matches the caricature of a radical left wing tree hugger….

    Rice University supports his stance.

  3. Alteredstory Says:

    I have to say – if things keep warming (which it looks like they will for a few hundred years at this point), we’d better HOPE the sea level keeps rising.

    I mean, seriously – if you’re religious, pray to your gods like you’ve never prayed before.

    If sea levels keep falling as it gets warmer, that means that they’re evaporating into the atmosphere, and we’ve started on the absolute worst-case scenario – a feedback loop that evaporates the oceans and broils the planet till no life can survive.

  4. Hansen sees a 5 meter rise by 2090- non linear response to warming.

  5. michiganken Says:

    The recent drop in sea level shown in the graph of sea level since 1992 suggests there has been a real ‘change of state’ in the Earth’s climate. The explanation for the recent fall in sea level is that great amounts of rain have fallen on the land in the past year, thus lowering the level of the oceans. Well, let’s suppose there was a change of state in the weather leading to considerably greater precipitation on the land. After some time a new equilibrium would be established where the amount of water that flows back to the oceans from the land would be equal (on average) to the amount that falls onto the land. So the sea level would resume its rise at a steady rate consistent with increasing ocean temperatures and the melting of ice sheets and glaciers. The change of state is indicated by a transition between two sections of the graph that rise linearly with about the same slope.
    That may be what the recent drop in sea level is indicating…. a significant long-term change in the precipitation patterns on the planet. If the trend in future data matches the trend before the drop, then the graph would not provide evidence for such a change in state. But if the current dip is the start of a discontinuity separating two linear trends, then a change of state may be what’s happening. There is certainly much other evidence for it.

    • Martin_Lack Says:

      I beg your pardon, did I just read that right? A supposed “…recent drop in sea level..” is due to your belief that it rained a lot last year? You cannot be serious? I think you would find it particlularly hard to convince people in places like the Eastern half of Africa, where they have not seen much of your rain for several years now.

      Meanwhile, I have an alternaitve hypothesis for you to consider, which goes something lke this: Given the large volume of water involved, the oceans take a very long time to warm-up. Similarly, large masses of ice take a long time to melt even when held at temperatures above freezing. Such things are often referred to using terms like inertia, specific heat capacity, and latent heat. Therefore, even though the average global temperature of the Earth has warmed by at least 1 Celsius in the last 200 years, it is only now that we are beginning to see the accelerating effects of this warming. Furthermore, this pattern of behaviour was predicted many decades ago, has been confirmed by studying palaeoclimate data for the last million years, and has been validated by computer modelling.

      Thus, there is no remaining uncertainty: Just as 1 + 1 = 2, increasing temperatures + melting ice = sea level rise. I think you need to get used to this concept; it’s called reality.

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