What, Again? Sea Level Will Continue Rising for Centuries

Summary: This series of three posts tabulates important findings from the six Assessment Reports (ARs) that the United Nations Intergovernmental Panel on Climate Change (IPCC) has released since 1990.  The first post, “What, Again? Greenhouse Gases Accumulate in the Atmosphere, presents past greenhouse gas (GHG) emission rates and future emission scenarios in the ARs, and presents principles in the ARs to keep accumulated GHG levels to as low a level as possible.

The second post, “What, Again? Global Warming Continues Unabated” summarizes the effects of higher GHGs on past and future projected global temperatures, and reiterates the need conveyed in the ARs to constrain GHG emissions by decarbonizing the energy economy. 

This third post reviews specifically the effects of warming on our water environment: melting ice domains and rising seas, and extremes of precipitation or droughts. The six ARs warn humanity to bring future GHG emissions to near zero; but sea level rise (SLR) is distinguished because melting of ice has passed a threshold of irreversibility: SLR will continue for centuries or longer.

Some may feel this series repeats refrains, looping like broken records; such people may suffer from “climate fatigue”.  Humanity, however, has not responded to the worsening climate documented in the AR series. The critical, dire climate projections summarized in these posts provide powerful incentives finally to take meaningful action at this time.

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The United Nations Intergovernmental Panel on Climate Change (IPCC) released the first of the three parts of its Sixth Assessment Report (AR6) in August 2021.  ARs have been issued at intervals of 6-7 years since 1990. They document the history of the annual rate of global emissions of the principal GHGs, arising from human activity, and of the total amount of GHGs accumulated in the atmosphere since the industrial revolution began.  Using climate models and a range of scenarios of GHG emission rates from relaxed to stringent they present projections for each scenario of future climate characteristics and effects to the end of this century.  They also discuss general goals (but not specific actions) for limiting future emission rates.

The results and projections presented in ARs 1-6 are broadly consistent with each other across the AR series, but have greater specificity and stronger assessments of likelihood as the series progresses.  All the ARs have stated the need to limit further accumulation of GHGs in the atmosphere in order to minimize the effects of global warming on Earth’s climate.  The faster that emission rates are reduced toward zero, the lower will be the total accumulation of GHGs in the atmosphere.  The cartoon below of two cars traveling down the GHG highway captures this message.

Two cars travelled down the GHG Highway.  Each applied brakes at the same point. On the red trip the brakes were applied gently (a metaphor for moderate GHG mitigation measures), so the car travelled far down the highway before stopping, leading to more GHG emissions accumulating in the atmosphere. (Stopping is a metaphor for ceasing to emit any more GHGs.) On the green trip the brakes were applied hard (a metaphor for intensive, aggressive mitigation measures), so the car traveled only a short distance down the highway before stopping, leading to less accumulated GHG emissions.

 

The topics selected for this post, tabulated below in the Details section, are Past Sea Level Rise (SLR) and precipitation (column 2), Projected Sea Level Rise and precipitation (column 3), and Recommended Actions (column 4).  Column 2 in the table documents the greater severity (and the greater detail of the data) of melting of glaciers and ice sheets feeding SLR, as well as extreme precipitation events in the later ARs, across the 30 years that the ARs have been issued. Column 3 details projections for future SLR, which are projected to continue for centuries or millennia regardless of mitigation measures that may be applied in the future.  SLR has two contributions (first mentioned in column 3 of the table for the AR2 entry), the expansion of water of the oceans as its temperature rises, and addition of new water to the oceans as glaciers and ice sheets continue to melt. 

The second factor, melting of ice, has reached the stage of being irreversible because the Earth has warmed sufficiently.  A model for melting glaciers or ice sheets is presented in the graphic below:

The melting point of ice is 0°C.  At or below this temperature an ice cube in your refrigerator is stable, and does not melt.  Even a little above this melting point, say at 1°C, the ice cube begins to melt slowly and forms a small puddle as shown.  At 2°C the model shows even more melting, yielding a smaller ice cube and a larger puddle.  Now suppose the refrigerator cools back down to less than 0°C.  The water in the puddles is not magically restored to the remaining mass of the ice cube, but freezes in place.

 

Extending the above model and its description to nature, the melted water flows away and ultimately drains into the ocean.  The glacier or ice sheet will be restored only if the year-round average temperature is less than 0°C and there is new precipitation as ice or snow.  But enough GHGs have already entered Earth’s atmosphere to warm the air over glaciers and ice sheets, tilting the balance toward net melting, assessed year-round.  This is why climate projections in column 3 of the table below foresee continued SLR for hundreds or thousands of years even if a way is ultimately found to remove accumulated GHGs from the atmosphere. For melting ice sheets and glaciers the “tipping point” has already been reached, and is irreversible on time scales of interest to humans.

The Recommended Actions summarized in column 4 of the table emphasize the need for significant lowering of the rate of emissions of GHGs, coupled with adaptation measures to address aspects of warming that cannot be remedied by mitigation.  This need was presented already in AR1 (1990), saying that immediate 60% reductions in emission rates …would stabilize atmospheric GHGs at the then current level.  In one way or another analogous remedies were presented in the succeeding ARs.  By AR6 (2021) the table’s summary urges substantial emissions reductions over the next few decades to reduce longer term climate risks.  Even so the AR warns with high confidence that warming by 2100 will lead to a high risk of severe, widespread and irreversible impacts, including flooding, droughts and continued SLR.

Whereas the need to reduce emissions was expressed as early as AR1 and extends up to the present in AR6, the strength of climate science underpinning those conclusions has increased dramatically over time.  The capabilities of gathering data and using more powerful computers to analyze them, and to develop more refined, detailed climate models have all increased dramatically.  (Incidentally the Nobel Prize in Physics, awarded October 5, 2021, recognized the development of early climate models.  These have served as the foundation for today’s highly refined models.)

Recent ARs reflect this enhancement in data gathering and climate modeling.  For example  the current first part of AR6 was compiled by 234 climate scientists chosen from the nations of the IPCC.  They reviewed over 14,000 research articles published since AR5.  Drafts of the chapters in AR6 were reviewed by other scientists as well as by national governments and revised accordingly.  We can feel assured that the final text represents scientific and political consensus views.

Conclusion

Column 4, “Recommended Actions” in the table shown in the Details section summarizes the increasing urgency of acting to reduce annual emission rates to near zero as the AR series progresses.

Indeed, actual extreme weather and climate events have become the subjects of frequent current headlines, documenting actual heat waves and droughts, famine, uncontrolled wildfires, intense precipitation events and flooding, and melting of glaciers and ice sheets leading to sea level rise, effects that were only predicted in the early ARs.  Also, by AR6 the science of attribution of extreme climate events has progressed dramatically, and permits ascribing the severity, if not the actual occurrence or not, of events to the effects of human-induced global warming.

Early action such as recommended in earlier ARs could have been taken at moderate levels of effort and expense (“Gentle Braking” in the first graphic above) to avert future, if not yet apparent, climate hazards.  But policymakers around the globe did not seize these opportunities to anywhere near the needed extent.  By 2021 such extreme events are now current, requiring immediate action.  Necessarily these current actions must be far more aggressive, pervasive and costly (“Hard Braking” in the graphic) in order to deal with a warming Earth approaching criticality.  They also require fundamental and comprehensive changes in social and cultural approaches to adapt to the consequences of warming.

Unequivocally we must encourage our political, corporate and civic leaders to embark on bold, comprehensive actions without further delay.

Details

This writer collated the entries in the following table from either the Summary for Policymakers, a “Headline” document or a press release, all issued by the IPCC in conjunction with each AR.  The entries are necessarily selective rather than comprehensive, and have been edited for brevity.

EVALUATIONS OF SEA LEVEL RISE AND PRECIPITATION IN IPCC ASSESSMENT REPORTS

© 2021 Henry Auer

A Denier Clouds Reality by Misrepresentations and False Accusations

Summary.  This writer recently attended a presentation by a global warming denier.  The speaker accused the climate scientists of the world, asserting that they lie, have an agenda, and conspire together while preparing global warming reports.  He also misrepresented factual findings related to global warming in a way that would cast doubt on the reality of the phenomenon.

This post refutes the positions taken by the denier.  The harms caused by global warming require knowledgeable, reasoned assessment of scientific observations, not maligning of the scientists involved in studying this subject.  It is not appropriate to shoot the messenger if one doesn’t agree with the message.  Likewise, misrepresenting scientific findings in a way intended to generate doubts about global warming cannot be tolerated.

The processes used to generate major reports and communicate to policymakers are rigorous and free of prejudice.  The reality of global warming is supported with virtually complete certainty by the full panoply of data available.

Introduction.  The most recent post published by this writer, “Denying Global Warming Has No Scientific Basis”, was intended as a one-time response to an email from a meteorologist, a denier of global warming.  On May 15, 2014, however, this writer attended a gathering of the New Haven, Connecticut section of the American Chemical Society.  The featured speaker was Art Horn, also a meteorologist, widely known locally from his role as a TV weatherman, talking on “Understanding Climate Change”.  It became quite clear that Mr. Horn is also a denier of the global warming phenomenon, whose opinions require a forceful and immediate rebuttal.

A denier maligns climate researchers.  Mr. Horn presented a slide, which showed a short range global temperature trajectory, whose stated message is “Claims that ‘global warming is accelerating’ are clearly lies to push an agenda, not science” (see the Details section at the end of this post).  As shown in the Details below, this slide is inaccurate in many ways, serving psychologically to goad the viewer to reject conclusions that global warming is happening.  Use of the terms “claims”, “lies” and “agenda” are manipulative but do not contribute to a fact-based discussion of the issue.  Such tactics must not be allowed to stand uncontested.

Allegations that climate scientists utter “lies to push an agenda” must be supported by documented evidence a) that lies (i.e., deliberate untruths) were told, and b) that an agenda exists which the supposed “lies” were intended to support.  Mr. Horn provided no such evidence in the presentation.  Accordingly his allegations must be dismissed out of hand.

A denier accuses climate scientists of conspiring to promote global warming fears.  Mr. Horn further accused climate scientists around the world of colluding to produce reports warning of the dangers of worsening global warming (see Details).  He believes they do this in order to continue receiving funding for their research.

In fact, some leading climate scientists have been subjected to harassment and censorship as they go about their work (see Details).  Clearly, such behavior in the face of threats is not consistent with the alleged conspiracy, for their behavior only serves to make their employment and research funding more insecure, not more certain.

Any assertions that the thousand or more climate scientists around the world engage in self-promoting conspiracies are ludicrous on their face, and must be substantiated by objective evidence openly presented.  In fact the operating rules set up for the release of major global warming reports effectively minimizes the opportunity for collusion (see Details).

Misrepresenting sea level rise.  Mr. Horn also projected selected graphics showing decreasing sea level trends for Alaska, Helsinki and Oslo (see Details).  On their face these data would appear to contradict the widely accepted view that global average sea level is rising.  But in fact, the U. S. National Oceanic and Atmospheric Administration (NOAA) presents an interactive graphic showing data obtained at the large number of sea level recording stations around the globe (see Details).  The vast majority of these stations shows an increase in sea level over the past several decades.  The Fifth Assessment Report, Part 1, The Physical Science Basis, of the United Nations Intergovernmental Panel on Climate Change (IPCC) clearly shows that the global average sea level has been rising continuously since 1900 (see Details). 

The outliers selected by Mr. Horn are explained by the phenomenon of post-glacial rebound, widely known among geologists (see Details).  Thus the exceptions chosen by Mr. Horn inappropriately seek to convey the impression that they are typical in showing that the sea level is decreasing.  In fact just the opposite is true; they are exceptions, since the sea level is rising for the planet considered as a whole.

Conclusion.  A denier resorted to unacceptable tactics during a presentation to a public audience.  His accusations and misrepresentations cannot stand, and must be opposed.  This post refutes the positions taken by the denier.  It insists that attacks on the motives of the messengers, the world’s climate scientists, accusing them of lying to support their agenda, be substantiated by objective evidence, but none has been advanced.  Accusations that scientists are conspiring internationally to gain and maintain funding must be accompanied by clear evidence supporting such allegations.  None was offered. 

A denier’s misrepresentation of worldwide sea level rise has been exposed in this post.  It is incontrovertible that worldwide average sea level has been rising for more than a century.

Deniers may be entitled to their opinions, but they are not entitled to misrepresent objective scientific findings, or to slur the people carrying out such studies.  Global warming is a reality and becoming more pronounced.  The correct response to that conclusion is to reach worldwide agreement on how to minimize its effects and how to protect against damaging processes already under way.

 

Details

 

A denier maligns climate researchers.  Among the misrepresentations in the presentation by Mr. Horn that this writer attended, two stand out for their descent into personal attacks on scientists.  One of the slides he showed, reproduced below, was found on his web site, where one can play numerous videos of his PowerPoint presentations.  Specifically, the following still image from the video “Global Warming Exposed by Art Horn Part 6” was included in his May 15 presentation:

 

Screen shot of a slide from a video by Art Horn.

Source: http://www.theartofweather.com/global_warming.html.

 

There are several problems with the illustrated statement.  First, if the words in quotations represent a statement by an individual or group, the author of the statement must be identified.  A vague assertion of a “claim” leaves open whether anyone actually stated it.  Second, accusing anyone of lying is very serious, because it carries with it the notion of intent to deceive.  If the denier feels so strongly, it is his responsibility to provide evidence for such intent and for the nature of the deception.  Lastly, if the denier believes there is an “agenda”, he must identify its goals and provide evidence that climate scientists are promoting it.

No such corroborations were offered. 

 

A denier accuses climate scientists of conspiring to promote global warming fears.  During the presentation Mr. Horn also explained another slide to the effect that climate scientists around the world are colluding to produce reports warning of the harms anticipated from global warming.  According to Mr. Horn, they do this in order to continue receiving finances for their research from their funding agencies.  (This writer was unable to find a slide image in Mr. Horn’s videos displaying this message; such a slide was shown to an audience of at least 50 during the May 15 presentation.)  In other words, the speaker is accusing the vast majority of the world’s climate scientists of engaging in a vast conspiracy for their own venal purposes.

Statements of this nature are highly reprehensible, since they are directed at the individuals and not at the science underlying the debate.  In other words, if deniers don’t like the message, they presume to be free to attack the messengers instead. This cannot be tolerated.

 

Rather than promoting a worldwide conspiracy, prominent scientists are being harassed and censored.

James E. Hansen is a renowned veteran climate researcher who has been forthright in his warnings about global warming for decades.  During this time he was employed by the U. S. National Aeronautics and Space Administration’s Goddard Institute for Space Studies, a federal agency.  Had his superiors found fault with his scientific capabilities or his professional behavior, they could have relieved him from government employment.  This never happened.  What did happen, however, is utterly inconsistent with the conspiracy theory that Mr. Horn is promoting.  For during the years that President George W. Bush was Dr. Hansen’s boss, the scientist’s publications and public appearances warning of worsening global warming were constrained and/or subjected to prior review by his supervisors for political objectives, not scientific reasons.  In other words, by insisting on speaking the truth about global warming, Dr. Hansen ignored the censorship imposed by his superiors, and acted contrary to any notions of self-promotion and contrary to behavior that would help assure that his research support, indeed his employment, be continued.

 

In a second instance, the University of Virginia was subpoenaed by the State of Virginia to produce internal research documents of veteran climate scientist Michael Mann during his tenure there.  This action, conducted by the Attorney General (the chief prosecutor) of the State of Virginia, could have had the effect of intimidating Dr. Mann from spreading truthful information about global warming.  Again, his resistance to intimidation is contrary to what we might expect if Dr. Mann’s primary objective was to promote his professional standing among his supervisors and employer.

 

These examples of prominent scientists in conflict with their employers and funders are inconsistent with any notion of self-aggrandizing behavior that might be part of a conspiracy, whether national or worldwide.

 

Reports on global warming are prepared with stringent peer review and responsiveness to external oversight.  The extended, rigorous processes used to prepare national and international reports dealing with global warming convincingly eliminate opportunities for alleged conspiracies to be operating.

 

a) The Intergovernmental Panel on Climate Change used the following process to produce its Fifth Assessment Report (AR), including the following details for preparing Part 3:

1. Governments and organizations nominate authors, who are then selected by the organizers of the Working Group (here called a “Part”)
2. 449 coordinating lead authors, lead authors, contributing authors and review editors from over 58 countries were selected to prepare a first draft of Part 3, considering over 10,000 references to the scientific literature;
3. The first draft was reviewed by 1,530 other experts who considered 16,188 comments provided by 602 expert reviewers from 58 countries;
4. 939 individuals prepared a second draft;
5. The second draft was reviewed by 469 expert reviewers from 53 countries, and by 24 governments, who provided 19,554 comments;
6. The final draft of the Summary for Policymakers was prepared by representatives of 37 governments, considering 2,573 comments; and
7. The final draft was approved and accepted by all 195 member nations of the IPCC, and released.

As a result of this thorough drafting and review process, the ARs are rigorously objective.  The reader cannot seriously believe that the ARs offer prejudiced or directed findings or opinions. Indeed, the approval and acceptance process likely leads to consensus positions on unresolved or contentious issues while minimizing the importance granted outlying results or evaluations.

 

b) The United States National Climate Assessment (NCA) used the following process to produce its report.

The NCA was prepared under the supervision of a federal advisory committee whose members were drawn from every department and agency, thirteen in all, substantively involved in an aspect of global change science or policy.  The Assessment itself was assembled by over 300 scientists and experts drawn from academic research settings, federal agencies and research facilities, state agencies, nongovernmental organizations, private consulting organizations, corporations and foreign research organizations.  The Assessment is based on citations to a large number of original research articles published in peer-reviewed journals, and other reports of comparable scientific validity.  A draft version was reviewed by others in federal agencies, the academic community, the public, and the National Academy of Sciences.  The final Assessment took 4,000 comments submitted by such groups into consideration. 

The details of this process provide high assurance that the Assessment communicates the scientific basis of the various aspects of global change treated, without projecting particular points of view not supported by scientific findings.

 

Misrepresenting Sea Level Rise.  During his presentation Mr. Horn projected a slide purporting to cast doubt on the widely understood phenomenon that globally, the sea level has been rising steadily for a long time  (again, this writer could not find this material in Mr. Horn’s videos).  Specifically, he showed decreasing sea level trends for the cases of Alaska, Helsinki and Oslo.  Images likely to be the same ones he presented, shown below, were culled by this writer from the website of the U. S. National Oceanic and Atmospheric Administration (NOAA).

Images of tide gauge readings from 1924 to 2006 for, left to right, Sitka, Alaska; Helsinki, Finland; and Oslo, Norway; showing decreases in the range of 2 to 3 mm/yr.

Source: U. S. National Oceanographic and Atmospheric Administration; http://tidesandcurrents.noaa.gov/.

 

What Mr. Horn neglected to show, however, is a worldwide rendering of sea level changes, such as the following interactive web page from NOAA showing a display of the locations of most (if not all) tide gauge stations worldwide.

 

Locations of tide gauges worldwide with arrows showing sea level rise (upward arrows) and sea level lowering (downward arrows).  The arrows are color coded for the range of the changes in mm/yr or feet/century using the color key included above.  Readings at various locations incorporate data from at least 30 years, and up to 150 years.

Source: U. S. National Oceanic and Atmospheric Administration; http://tidesandcurrents.noaa.gov/sltrends/sltrends.html.

 

(The reader is strongly encouraged to turn to the NOAA web page cited in the caption to the graphic.  Rolling a tracking device over each arrow gives its location and numerical value for sea level change.  One can expand the view to see various regions of the U. S., and can link to gauge locations around the world, including the images shown further above.)

 

It is quite clear from the display above that the vast majority of tide gauges worldwide shows rising, not decreasing, sea levels. 

 

Data such as these underlie the summary graphic for global average sea level shown in the IPCC Fifth Assessment Report, Part 1, The Physical Science Basis, shown below.

Global average sea level change from 1900 to the present.  Different colors represent different data sets.  Shaded bands show corresponding confidence limits.

Source: Intergovernmental Panel on Climate Change, Fifth Assessment Report, Working Group I, Summary for Policy Makers; http://www.climatechange2013.org/images/report/WG1AR5_SPM_FINAL.pdf

 

There can be no doubt from this image that the long-term trend of sea level for more than a century has been a continuous and unrelenting increase.

 

The isolated few examples of a decreasing sea level such as those “cherry-picked” by Mr. Horn are due to the phenomenon, widely recognized among geologists, of post-glacial rebound.  It is prevalent in sub-Arctic latitudes of the Northern Hemisphere (such as Alaska, Helsinki and Oslo), and similarly in Antarctica.  As glaciers melt the weight burden they impose on the underlying land masses is reduced.  As a result the land rises up, buoyed higher on the molten magma on which it floats.  As this process proceeds the apparent sea level is measured to be lower relative to the rising land mass.  Thus the melting of the glaciers and ice sheets producing post-glacial rebound is actually in agreement with the effects of global warming, not contrary to them.  Mr. Horn simply showed examples reflecting this geological phenomenon, perhaps selected to leave the impression that these exceptions are actually the norm, which they clearly are not.  It should be noted that Mr. Horn did not show any examples from the large number available that would actually have shown a rising sea level.

 

 

© 2014 Henry Auer