Sea level rise is a topic that we frequently focus on because of all the gross environmental alterations which may result from anthropogenic greenhouse gas emissions, it is perhaps the only one which could lead to conditions unexperienced by modern societies. A swift (or accelerating) sea level rise sustained for multiple decades and/or centuries would pose challenges for many coastal locations, including major cities around the world—challenges that would have to be met in some manner to avoid inundation of valuable assets. However, as we often point out, observational evidence on the rate of sea level rise is reassuring, because the current rate of sea level rise from global warming lies far beneath the rates associated with catastrophe. While some alarmists project sea level rise of between 1 to 6 meters (3 to 20 feet) by the end of this century, currently sea level is only inching up at a rate of about 20 to 30 centimeters per hundred years (or about 7 to 11 inches of additional rise by the year 2100)—a rate some 3-4 times below the low end of the alarmist spectrum, and a whopping 20 to 30 times beneath the high end.
September 10, 2012
June 29, 2012
Last week, the National Academies of Sciences’ National Research Council (NRC) released a report Sea-Level Rise for the Coasts of California, Oregon, and Washington: Past, Present, and Future. The apparent intent of the report was to raise global warming alarm by projecting rapidly rising seas—some 2-3 times higher than recent IPCC estimates—along the California coast and elsewhere. Based on the news coverage, the NRC was successful.
Successfully handling the media does not equate to successfully handling the science, if scientific success is judged by scientific accuracy.
The NRC was quite adept at sidestepping the inconvenient scientific literature which would have tempered their conclusions and which would have replaced alarm with prudent vigilance. Sure, global sea level will continue to rise, but the rate of future rise will likely be closer to the rise observed during the 20th century, about 8-12 inches—a rate to which coastal residents have easily adapted—than to the NRC’s upper bound which approaches some 4-5 feet by the year 2100.
June 24, 2011
A recent study has attempted to use a long-term (~2,100 years), local (coastal North Carolina), determination of sea level derived from the build-up of salt marsh sediments to better characterize the behavior of global sea level (and by proxy, global temperatures) over the same multi-millennial time period. Based upon the results of this investigation, the research team led by Andrew Kemp from the University of Pennsylvania, concludes that there were four rather distinct periods of sea level rise over the past 2,100 years. Here is how they describe the first three:
Sea level was stable from at least BC 100 until AD 950. Sea level then increased for 400 y at a rate of 0.6 mm/y, followed by a further period of stable, or slightly falling, sea level that persisted until the late 19th century.
And then, and here’s the kicker (and why this paper received all the press coverage that it did, with headlines such as “Fastest Sea-Level Rise in 2,000 Years Linked to Increasing Global Temperatures“):
Since then, sea level has risen at an average rate of 2.1 mm/y, representing the steepest century-scale increase of the past two millennia. This rate was initiated between AD 1865 and 1892. Using an extended semiempirical modeling approach, we show that these sea-level changes are consistent with global temperature for at least the past millennium.
But can a paleo-record of sea level rise from basically one locality (e.g., coastal North Carolina) provide a good indication of the long-term history of global sea level rise? Obviously, the authors think so, but others are not so sure.
May 2, 2011
We dedicated our last World Climate Report post to the findings from our just-published (and quite popular) paper in which we attempted a reconstruction of the warm season ice melt extent that has taken place across Greenland each year since 1784. Our goal was to develop a larger context in which to place the direct observations of ice melt across Greenland (available only since 1979) and to better be able to judge the reports of record high ice melt in recent years.
Our general conclusions were:
• several recent years (in particular 2007 and from preliminary observations 2010) likely had a historically high degree of surface ice melt across the Greenland ice sheet,
• on a decadal scale, there were several 10-yr periods during the 1930s through the early 1960s during which the average annual ice melt extent across Greenland was likely greater than the most recent 10 years of available data in our study (2000-2009),
• that the ice melt across Greenland was particularly low at the start of the era of satellite observations (which began in 1979), such that a sizeable portion of increasing ice melt observed by satellite-borne instruments since then could potentially be part of the natural variability about the mean state,
• that, for the next several decades at least, Greenland’s contribution to global sea level rise was likely to be modest.
But not everyone was enamored with our findings.
Last week, the most popular article from among those recently published in the American Geophysical Union’s (AGU) Journal of Geophysical Research-Atmospheres was one which presents a 225-yr reconstruction of the extent of ice melt across Greenland. We are happy to say that your obedient servants here at World Climate Report were part of the research team of this oft-downloaded paper.
The full citation (for those who may want to check it out) is:
Frauenfeld, O.W., P.C. Knappenberger, and P.J. Michaels, 2011. A reconstruction of annual Greenland ice melt extent, 1785-2009. Journal of Geophysical Research, 116, D08104, doi: 10.1029/2010JD014918.
April 7, 2011
Back in the summer of 2009, we ran a piece titled “Sea Level Rise: An Update Shows a Slowdown” in which we showed that the much ballyhooed “faster rate of sea level rise during the satellite era” was actually slowing down.
We suggested that this observation would help the IPCC to adjudicate an issue that it raised in its 2007 Fourth Assessment Report:
“Whether the faster rate [of sea level rise] for 1993 to 2003 reflects decadal variability or an increase in the longer term trend is unclear.”
February 16, 2011
One word that comes up over and over in the global warming issue is “uncertainty”. The alarmists tend to minimize the discussion of uncertainties while the so-called skeptics seem to harp on how uncertain we are on so many fronts. Two articles have appeared in the literature during the past year highlighting amazing uncertainties dealing with ice loss from glaciers and water mass in the world’s oceans.
February 3, 2011
If you haven’t heard the news, global warming is causing sea level to rise and causing storms to become more severe, and the net result is shoreline erosion throughout the world. This pillar of the apocalypse is particularly easy to sell—gather up some pictures of shoreline erosion, throw in some images of turtle nest destruction, and you are on your way to winning a Nobel Prize for putting all the pieces together.
A recent issue of Global and Planetary Change contains an article on this subject written by two scientists with the School of Earth and Environmental Sciences at James Cook University in Townsville, Queensland; funding was provided by the Environmental Protection Agency-Queensland. Dawson and Smithers focused on Raine Island located on the northern portion of the Great Barrier Reef, and if you don’t know, Raine Island is “a globally significant turtle rookery.” So it’s all here—an island on the Great Barrier Reef, turtles, sea level rise, relatively frequent tropical cyclones, sand beaches easily eroded—we are sure the global warming alarmists cannot wait to see how bad things have become at this sacred location.
But, alas, the results from Raine Island are about to rain on their parade of pity.
August 9, 2010
We are sure you’ve heard that sea level is rising? We conducted a web search on “Global Warming and Sea Level” and nearly 3.5 million websites are immediately located. And before you conduct the search yourself, you already know what you will find. The earth is getting warmer due to the buildup of greenhouse gases, the warmer sea water expands causing sea level to rise, and most of all, you will read all about the ice melting throughout the world pouring fresh water into ocean basins causing sea level to rise far more. Alarmists insist that the worst is just around the corner, and the sea level rise will accelerate or even quickly jump to a new level given some catastrophic collapse of large sheets of ice near the fringes of the polar areas. Coastlines will be inundated, the human misery will be on a Biblical scale, ecosystems will be destroyed … this goes on for millions of websites!
But things aren’t really so simple.
February 9, 2010
The Technical Summary of the most recent IPCC reports states that “Over the 1961 to 2003 period, the average rate of global mean sea level rise is estimated from tide gauge data to be 1.8 ± 0.5 mm yr–1.” “The average thermal expansion contribution to sea level rise for this period was 0.42 ± 0.12 mm yr–1, with significant decadal variations, while the contribution from glaciers, ice caps and ice sheets is estimated to have been 0.7 ± 0.5 mm yr–1. The sum of these estimated climate-related contributions for about the past four decades thus amounts to 1.1 ± 0.5 mm yr–1, which is less than the best estimate from the tide gauge observations. Therefore, the sea level budget for 1961 to 2003 has not been closed satisfactorily.”
That is indeed very interesting – the average rate of sea level is around 1.8 mm per year, and the IPCC can account for only 60% of the increase. This uncertainty is compound considering IPCC’s statements that “The global average rate of sea level rise measured by TOPEX/Poseidon satellite altimetry during 1993 to 2003 is 3.1 ± 0.7 mm yr–1. This observed rate for the recent period is close to the estimated total of 2.8 ± 0.7 mm yr–1 for the climate-related contributions due to thermal expansion (1.6 ± 0.5 mm yr–1) and changes in land ice (1.2 ± 0.4 mm yr–1). Hence, the understanding of the budget has improved significantly for this recent period, with the climate contributions constituting the main factors in the sea level budget (which is closed to within known errors). Whether the faster rate for 1993 to 2003 compared to 1961 to 2003 reflects decadal variability or an increase in the longer-term trend is unclear”.
As you might guess, there is much to be done to improve our understanding of sea level rise.