Tag: sea level rise

A Historic Perspective on the Greenland Ice Sheet and its Contribution to Global Sea Level

One of the most feared of all model-based projections of CO2-induced global warming is that temperatures will rise enough to cause a disastrous melting/destabilization of the Greenland Ice Sheet (GrIS), which would raise global sea level by several meters. But how likely is this scenario to occur? And is there any way to prove such melting is caused by human activities?

The answer to this two-part question involves some extremely complex and precise data collection and understanding of the processes involved with glacial growth and decay. Most assuredly, however, it also involves a scientifically accurate assessment of the past history of the GrIS, which is needed to provide a benchmark for evaluating its current and future state. To this end, a recent review paper by Vasskog et al. (2015) provides a fairly good summary of what is (and is not) presently known about the history of the GrIS over the previous glacial-interglacial cycle. And it yields some intriguing findings.

Probably the most relevant information is Vasskog et al.’s investigation of the GrIS during the last interglacial period (130-116 ka BP). During this period, global temperatures were 1.5-2.0°C warmer than the peak warmth of the present interglacial, or Holocene, in which we are now living. As a result of that warmth, significant portions of the GrIS melted away. Quantitatively, Vasskog et al. estimate that during this time (the prior interglacial) the GrIS was “probably between ~7 and 60% smaller than at present,” and that that melting contributed to a rise in global sea level of “between 0.5 and 4.2 m.” Thus, in comparing the present interglacial to the past interglacial, atmospheric CO2 concentrations are currently 30% higher, global temperatures are 1.5-2°C cooler, GrIS volume is from 7-67% larger, and global sea level is at least 0.5-4.2 m lower, none of which signal catastrophe for the present.

Clearly, therefore, there is nothing unusual, unnatural or unprecedented about the current interglacial, including the present state of the GrIS. Its estimated ice volume and contribution to mean global sea level reside well within their ranges of natural variability, and from the current looks of things, they are not likely to depart from those ranges any time soon.

 

References

Reyes, A.V., Carlson, A.E., Beard, B.L., Hatfield, R.G., Stoner, J.S., Winsor, K., Welke, B. and Ullman, D.J. 2014. South Greenland ice-sheet collapse during Marine Isotope Stage 11. Nature 510: 525–528.

Vasskog, K., Langebroek, P.M., Andrews, J.T., Nilsen, J.E.Ø. and Nesje, A. 2015. The Greenland Ice Sheet during the last glacial cycle: Current ice loss and contribution to sea-level rise from a palaeoclimatic perspective. Earth-Science Reviews 150: 45-67.

On the Bright Side: A Deceleration of Sea Level Rise Along the Indian Coastline

Parker and Ollier (2015) set the tone for their new paper on sea level change along the coastline of India in the very first sentence of their abstract: “global mean sea level (GMSL) changes derived from modelling do not match actual measurements of sea level and should not be trusted” (emphasis added). In contrast, it is their position that “much more reliable information” can be obtained from analyses of individual tide gauges of sufficient quality and length. Thus, they set out to obtain such “reliable information” for the coast of India, a neglected region in many sea level studies, due in large measure to its lack of stations with continuous data of sufficient quality.

A total of eleven stations were selected by Parker and Ollier for their analysis, eight of which are archived in the PSMSL database (PSMSL, 2014) and ten in a NOAA sea level database (NOAA, 2012). The average record length of the eight PSMSL stations was 54 years, quite similar to the average record length of 53 years for the eleven NOAA stations.

Results indicated an average relative rate of sea level rise of 1.07 mm/year for all eleven Indian stations, with an average record length of 51 years. However, the two Australian researchers report this value is likely “overrated because of the short record length and the multi-decadal and interannual oscillations” of several of the stations comprising their Indian database. Indeed, as they further report, “the phase of the 60-year oscillation found in the tide gauge records is such that sea level in the North Atlantic, western North Pacific, Indian Ocean and western South Pacific has been increasing since 1985-1990,” which increase most certainly skews the rate trend of the shorter records over the most recent period of record above the actual rate of rise.

The Spin Cycle: Accelerating Sea Level Rise

The Spin Cycle is a reoccurring feature based upon just how much the latest weather or climate story, policy pronouncement, or simply poo-bah blather spins the truth. Statements are given a rating between 1-5 spin cycles, with less cycles meaning less spin. For a more in-depth description, visit the inaugural edition.

A popular media story of the week was that sea level rise was accelerating and that this was worse than we thought. The stories were based on a new paper published in the journal Nature Climate Change by an author team led by the University of Tasmania’s Christopher Watson.

Watson and colleagues re-examined the satellite-based observations of sea level rise (available since the early 1990s) using a new methodology that supposedly better accounts for changes in the orbital altitude of the satellites—obviously a key factor when assessing sea levels by determining the height difference between the ocean’s surface and the satellites, the basic idea behind altimetry-based sea level measurements.

So far so good.

Their research produced two major findings, 1) their new adjusted measurements produced a lower rate of sea level rise than the old measurements (for the period 1993 to mid-2014), but 2) the rate of sea level rise was accelerating.

It was the latter that got all of the press.

But, it turns out, that in neither case, were the findings statistically significant at even the most basic levels used in scientific studies. Generally speaking, scientists report a findings as being “significant” if there is a less than 1-in-20 chance that the same result could have been produced by random (i.e., unexplained) processes. In some fields, the bar is set even higher (like 1 in 3.5 million). We can’t think of any scientific field that accepts a lower than a 1-in-20 threshold (although occasional individual papers do try to get away with applying a slightly lower standard).

You Ought to Have a Look: Science Round Up—Less Warming, Little Ice Melt, Lack of Imagination

You Ought to Have a Look is a feature from the Center for the Study of Science posted by Patrick J. Michaels and Paul C. (“Chip”) Knappenberger. While this section will feature all of the areas of interest that we are emphasizing, the prominence of the climate issue is driving a tremendous amount of web traffic. Here we post a few of the best in recent days, along with our color commentary.

As Pope Francis, this week, focused on examining the moral issues of climate change (and largely ignoring the bigger moral issues that accompany fossil fuel restrictions), he pretty much took as a given that climate change is “a scientific reality” that requires “decisive mitigation.” Concurrently, unfolding scientific events during the week were revealing a different story.

First and foremost, Roy Spencer, John Christy and William Braswell of the University of Alabama-Huntsville (UAH)—developers and curators of the original satellite-derived compilation of the temperature history of the earth’s atmosphere—released a new and improved version of their iconic data set. Bottom line: the temperature trend in the lower atmosphere from the start of the data (1979) through the present came in as 0.114°C/decade (compared with 0.14°C in the previous data version). The new warming trend is less than half what climate models run with increasing atmospheric carbon dioxide emissions project to have occurred.

While the discrepancy between real world observations and climate model projections of temperature rise in the lower atmosphere has been recognized for a number of years, the question has remained as to whether the “problem” lies within the climate models or the observations. With this new data release, the trend in the UAH data now matches very closely with the trend through an independent compilation of the satellite-temperature observations maintained by a team of researchers at Remote Sensing Systems (RSS). The convergence of the observed data sets is an indication the climate models are the odd man out.

As with most long-term, real-world observations, the data are covered in warts. The challenge posed to Spencer et al. was how to splice together remotely sensed data collected from a variety of instruments carried aboard a variety of satellites in unstable orbits—and produce a product robust enough for use in climate studies. The details as to how they did it are explained as clearly as possible in this post over at Spencer’s website (although still quite a technical post). The post provides good insight as to why raw data sets need to be “adjusted”—a lesson that should be kept in mind when considering the surface temperature compilations as well. In most cases, using raw data “as is” is an inherently improper thing to do, and the types of adjustments that are applied may vary based upon the objective.

Here is a summary of the new data set and what was involved in producing it:

Version 6 of the UAH MSU/AMSU global satellite temperature data set is by far the most extensive revision of the procedures and computer code we have ever produced in over 25 years of global temperature monitoring. The two most significant changes from an end-user perspective are (1) a decrease in the global-average lower tropospheric (LT) temperature trend from +0.140 C/decade to +0.114 C/decade (Dec. ’78 through Mar. ’15); and (2) the geographic distribution of the LT trends, including higher spatial resolution. We describe the major changes in processing strategy, including a new method for monthly gridpoint averaging; a new multi-channel (rather than multi-angle) method for computing the lower tropospheric (LT) temperature product; and a new empirical method for diurnal drift correction… The 0.026 C/decade reduction in the global LT trend is due to lesser sensitivity of the new LT to land surface skin temperature (est. 0.010 C/decade), with the remainder of the reduction (0.016 C/decade) due to the new diurnal drift adjustment, the more robust method of LT calculation, and other changes in processing procedures.

Figure 1 shows a comparison of the data using the new procedures with that derived from the old procedures. Notice that in the new dataset, the temperature anomalies since about 2003 are less than those from the previous version. This has the overall effect of reducing the trend when computed over the entirety of the record.

Figure 1. Monthly global-average temperature anomalies for the lower troposphere from Jan. 1979 through March, 2015 for both the old and new versions of LT (source: www.drroyspencer.com)

 

Figure 1. Monthly global-average temperature anomalies for the lower troposphere from Jan. 1979 through March 2015 for both the old and new versions of LT. (Source: www.drroyspencer.com)

While this new version, admittedly, is not perfect, Spencer, Christy, and Braswell see it as an improvement over the old version. Note that this is not the official release, but rather a version the authors have released for researchers to examine and see if they can find anything that looks irregular that may raise questions as to the procedures employed. Spencer et al. expect a scientific paper on the new data version to be published sometime in 2016.

But unless something major comes up, the new satellite data are further evidence the earth is not warming as expected.  That means that, before rushing into “moral obligations” to attempt to alter the climate’s future course by restricting energy production, we perhaps ought to spend more time trying to better understand what it is we should be expecting in the first place.

One of the things we are told by the more alarmist crowd that we should expect from our fossil fuel burning is a large and rapid sea level rise, primarily a result of a melting of the ice sheets that rest atop Greenland and Antarctica. All too frequently we see news stories telling tales of how the melting in these locations is “worse than we expected.” Some soothsayers even attack the United Nations’ Intergovernmental Panel on Climate Change (IPCC) for being too conservative (of all things) when it comes to projecting future sea level rise. While the IPCC projects a sea level rise of about 18–20 inches from its mid-range emissions scenario over the course of this century, a vocal minority clamor that the rise will be upwards of 3 feet and quite possibly (or probably) greater. All the while, the sea level rise over the past quarter-century has been about 3 inches.

But as recent observations do little to dissuade the hardcore believers, perhaps model results (which they are seemingly more comfortable with) will be more convincing.

A new study available this week in the journal Geophysical Research Letters is described by author Miren Vizcaino and colleagues as “a first step towards fully-coupled higher resolution simulations with more advanced physics”—basically, a detailed ice sheet model coupled with a global climate model.

They ran this model combination with the standard IPCC emissions scenarios to assess Greenland’s contribution to future sea level rise. Here’s what they found:

The [Greenland ice sheet] volume change at year 2100 with respect to year 2000 is equivalent to 27 mm (RCP 2.6), 34 mm (RCP 4.5) and 58 mm (RCP 8.5) of global mean SLR.

Translating millimeters (mm) into inches give this answer: a projected 21st century sea level rise of 1.1 in. (for the low emissions scenario; RCP 2.6), 1.3 in. (for the low/mid scenario; RCP 4.5), and 2.3 in (for the IPCC’s high-end emission scenario). Some disaster.

As with any study, the authors attach some caveats:

The study presented here must be regarded as a necessary first step towards more advanced coupling of ice sheet and climate models at higher resolution, for instance with improved surface-atmosphere coupling (e.g., explicit representation of snow albedo evolution), less simplified ice sheet flow dynamics, and the inclusion of ocean forcing to Greenland outlet glaciers.

Even if they are off by 3–4 times, Greenland ice loss doesn’t seem to be much of a threat. Seems like it’s time to close the book on this imagined scare scenario.

And while imagination runs wild when it comes to linking carbon dioxide emissions to calamitous climate changes and extreme weather events (or even war and earthquakes),  imagination runs dry when it comes to explaining non-events (except when non-events string together to produce some sort of negative outcome [e.g., drought]).

Case in point, a new study looking into the record-long absence of major hurricane (category 3 or higher) strikes on the U.S. mainland—an absence that exceeds nine years (the last major hurricane to hit the U.S was Hurricane Wilma in late-October 2005). The authors of the study, Timothy Hall of NASA’s Goddard Institute for Space Studies and Kelly Hereid from ACE Tempest Reinsurance, concluded that while a streak this long is rare, their results suggest “there is nothing unusual underlying the current hurricane drought. There’s no extraordinary lack of hurricane activity.” Basically they concluded that it’s “a case of good luck” rather than “any shift in hurricane climate.”

That is all well and good, and almost certainly the case. Of course, the same was true a decade ago when the United States was hit by seven major hurricanes over the course of two hurricane seasons (2004 and 2005)—an occurrence that spawned several prominent papers and endless discussion pointing the finger squarely at anthropogenic climate change. And the same is true for every hurricane that hits the United States, although this doesn’t stop someone, somewhere, from speculating to the media that the storm’s occurrence was “consistent with” expectations from a changing climate.

What struck us as odd about the Hall and Hereid paper is the lack of speculation as to how the ongoing record “drought” of major hurricane landfalls in the United States could be tied in with anthropogenic climate change. You can rest assured—and history will confirm—that if we had been experiencing a record run of hurricane landfalls, researchers would be falling all over themselves to draw a connection to human-caused global warming.

But the lack of anything bad happening? No way anyone wants to suggest that is “consistent with” expectations. According to Hall and Hereid:

A hurricane-climate shift protecting the US during active years, even while ravaging nearby Caribbean nations, would require creativity to formulate. We conclude instead that the admittedly unusual 9-year US Cat3+ landfall drought is a matter of luck. [emphasis added]

Right! A good string of weather is “a matter of luck” while bad weather is “consistent with” climate change.

It’s not like it’s very hard, or (despite the authors’ claim) it requires much “creativity” to come up with ways to construe a lack of major hurricane strikes on U.S. soil to be “consistent with” anthropogenic climate change. In fact, there are loads of material in the scientific literature that could be used to construct an argument that under global warming, the United States should experience fewer hurricane landfalls. For a rundown of them, see p. 30 of our comments on the government’s National Assessment on Climate Change, or check out our piece titled, “Global Savings: Billion-Dollar Weather Events Averted by Global Warming.”

It is not for lack of material, but rather, for lack of desire, that keeps folks from wanting to draw a potential link between human-caused climate change and good things occurring in the world.

References:

Hall, T., and K. Hereid. 2015. “The Frequency and Duration of US Hurricane Droughts.” Geophysical Research Letters, doi:10.1002/2015GL063652

Vizcaino, M. et al. 2015. “Coupled Simulations of Greenland Ice Sheet and Climate Change up to AD 2300.” Geophysical Research Letters, doi: 10.1002/2014GL061142

Repeating News Story: Eroding Shorelines and Imperiled Coastal Villages in Alaska

U.S. Secretary of the Interior Sally Jewell was in Alaska last week at the invite of the Alaska Federation of Natives to discuss climate change and other issues. During her visit, she made a side trip to the 400 or so person town of Kivalina, located on a low-lying barrier island along Alaska’s northwest coast. The settlement sprung up about a century ago when the Interior Department decided to erect a school there under a program to promote the “education of natives in Alaska.” The same program established schools in other coastal location such as Golovin, Shishmaref, and Barrow.

Now these locations are in the news (see this week’s Washington Post story for example) because they are being threatened by coastal erosion coming at the hands of global warming—and are discussing relocating and who should be responsible for the footing the bill (incidentally, the courts have ruled out the energy industry).

With or without human-caused climate change, bluffs and barrier islands along the coast of northwestern Alaska are inherently unstable and not particularly good places to establish permanent towns. This is probably one of the reasons the natives were largely nomadic.

“Were,” we say, because ironically, as pointed out by the Post’s Chris Mooney, research indicates that the abandonment of the nomadic ways was encouraged/hastened by the establishment of government schools!

Evidenced-based Sea Level Rise Projections Remain Low

Global Science Report is a feature from the Center for the Study of Science, where we highlight one or two important new items in the scientific literature or the popular media. For broader and more technical perspectives, consult our monthly “Current Wisdom.”

When it comes right down to it, the biggest potential threat from a warming climate is a large and rapid sea level rise. Everything else that a changing climate may bring we’ve seen before (or at least the likes of it), recovered from, and are better off for it (i.e., gained experience, learned lessons, developed new technologies, etc.). In fact, the more often extreme weather occurs, the more adaptive is our response (see for example, decreasing mortality in heat waves). So in that sense, climate change may hasten our adaptive response and reduce our overall vulnerability to it.

A large and rapid sea level rise is a bit of a different story—although perhaps not entirely so.

While we do have a large amount of infrastructure (e.g., big cities) in low-lying coastal regions, it is completely wrong to show them underwater in the future—a typical device used by climate activists. What will happen is that we will act to protect the most valued portions of that infrastructure, as shown in a recent report from leading experts (including from the U.S. Environmental Protection Agency) on sea level rise and response.

But, while targeted action will save our big cities, there is still a lot of real estate that will be lost if sea level rises a large amount in a short amount of time (say, by more than a meter [a little more than 3 feet] by the end of the 21st century).

We therefore keep a vigilant eye on sea level rise research. And what we’ve concluded is that sea level rise by the year 2100 is very likely to be quite modest, say about 15 inches—an amount that should allay concerns of a catastrophe. We’ve detailed literature in support of our conclusions here, there, and elsewhere.

This week, a new paper has come to our attention that further supports our synthesis.

Some Perspective on the Headlining Antarctic Ice Loss Trends

The mainstream media has lit up the past few days with headlines of “alarming” news coming out of Antarctica highlighting new research on a more rapid than expected loss of ice from glaciers there.

But, as typical with blame-it-on-humans climate change stories, the coverage lacks detail, depth, and implication as well as being curiously timed.

We explain.

The research, by a team led by University of Cal-Irvine doctoral candidate Tyler Sutterley, first appeared online at the journal Geophysical Research Letters on November 15th, about two weeks before Thanksgiving. So why is it making headlines now? Probably because the National Aeronautics and Space Administration issued a press release on the new paper on December 2nd. Why wait so long? Because on December 1st, the United Nations kicked off its annual climate confab and the Obama administration is keen on orchestrating its release of scary-sounding climate stories so as to attempt to generate support for its executively commanded (i.e., avoiding Congress) carbon dioxide reduction initiatives that will be on display there. This also explains the recent National Oceanic and Atmospheric Administration speculation that 2014 is going to be the “warmest year on record”—another headline grabber—two months before all the data will be collected and analyzed.

This is all predictable—and will essentially be unsuccessful.

Missing from the hype are the broader facts.

The new Sutterley research finds that glaciers in the Amundsen Sea Embayment region along the coast of West Antarctica are speeding up and losing ice. This is potentially important because the ice loss contributes to global sea level rise. The press coverage is aimed to make this sound alarming—“This West Antarctic region sheds a Mount Everest-sized amount of ice every two years, study says” screamed the Washington Post.

Wow! That sounds like a lot. Turns out, it isn’t.