New Climate Report: Sea Level Up Again After Sharp Decline

By Tom Yulsman | August 6, 2013 7:13 pm

This map, based on satellite data, shows where sea level was higher than normal in 2012 (blue areas), and lower than normal (brown areas). Overall, global average sea level was 1.4 inches higher than the 1993-2010 average. (Map: NOAA)

The State of the Climate in 2012 report came out today, and I’ve been going through it to find some newsworthy nuggets that may not have been widely reported already. (Check out Climate.gov for highlights; download the full report here.)

The peer-reviewed report, compiled by 384 scientists from 52 countries, was published as a supplement to the August 2013 issue of the Bulletin of the American Meteorological Society. It goes into detail on things you may have heard already. For example, 2012 ranked among the warmest 10 years on record, and Arctic sea ice continued to decline in extent (but Antarctic sea ice expanded).

But here’s something I had not heard and maybe you missed it too: It turns out that in 2012, sea level rose to its highest value seen in the satellite record (which began in 1993).

I think it’s newsworthy because sea level actually declined sharply in 2011 — a point that climate change skeptics didn’t hesitate to emphasize. In fact, at least one accused scientists of trying to hide the decline.

Now it looks like the decline (yes, we knew about it because it obviously wasn’t hidden) was linked to La Niña — which has since transitioned into neutral conditions in the Pacific. (For more on La Niña, go here.) The seas responded in 2012, according to the report, rising 1.4 inches above the 1993-2010 global average.

If that doesn’t seem terribly significant, consider this from Climate.gov’s highlights section on sea level rise:

In the United States alone, just under 40 percent of the population lives in coastal areas, where sea level plays a role in flooding and storm hazards, shoreline erosion, and even city water supplies (where seawater seeps into aquifers). Globally, 44 percent of the people on Earth live within 150 kilometers of the shore, and 8 of the 10 largest cities in the world are near the coast, according to the U.N. Atlas of the Oceans.

The map at the top of this post, from NOAA’s Environmental Visualization Laboratory (and included in the report), uses data from the Jason-2 satellite mission and others to show how sea surface heights for 2012 varied from the long-term average. Blue areas are where sea level was higher than the 1993-2012 average. Sea level was lower in the brown areas.

Here’s what the overall trend in sea level looks like:

The trend in sea level through 2012, compared to the 1993-2010 average. (Graph: Climate.gov)

Sea level is rising as heat accumulates in the ocean, causing it to expand, and as meltwater from glaciers and ice sheets flows into the seas. Since 2005, the latter factor has accounted for more than twice the sea level rise as thermal expansion of the oceans.

Another nugget of news that caught my attention involves that heat. A snippet about this from Climate.gov’s highlights: “Heat content in the upper 2,300 feet, or a little less than one-half mile, of the ocean remained near record high levels in 2012.”

More about that in the next day or so.

  • http://blogs.discovermagazine.com Claus Mohr

    What these pseudo scientists totally forget is that a higher ocean temperature also causes more significant evaporation to compensate for the melting of ice. Global warming will cause more rain and warmer temperatures, a major benefit to most of the planet. It’s only 1000 years ago that the Vikings were farming grain and cattle in Greenland, (no polluting cars) when it was warmer than now. The ocean level, based on any available information was not higher than now, remnants of farm structures are still there for the Al Gores to look at if they don’t believe me. This planet has had temperature changes at all times, how else do you explain ice ages? We are lucky to probably live in a period between ice ages. Enjoy it.

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ImaGeo

ImaGeo is a visual blog focusing on the intersection of imagery, imagination and Earth. It focuses on spectacular visuals related to the science of our planet, with an emphasis (although not an exclusive one) on the unfolding Anthropocene Epoch.

About Tom Yulsman

Tom Yulsman is Director of the Center for Environmental Journalism and a Professor of Journalism at the University of Colorado, Boulder. He also continues to work as a science and environmental journalist with more than 30 years of experience producing content for major publications. His work has appeared in the New York Times, Washington Post, Audubon, Climate Central, Columbia Journalism Review, Discover, Nieman Reports, and many other publications. He has held a variety of editorial positions over the years, including a stint as editor-in-chief of Earth magazine. Yulsman has written one book: Origins: the Quest for Our Cosmic Roots, published by the Institute of Physics in 2003.

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