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

Denying Global Warming Has No Scientific Basis

Summary.  A denier of global warming asserts that the recent U. S. National Climate Assessment includes statements “that are (at best) misleading”.  The denier inappropriately claims the Assessment’s use of a graphic image overlaying recent annual carbon dioxide emissions and annual values of global average temperature “shows correlation, and implies causation”.  The denier cites the Medieval Warming Period and the Little Ice Age, having occurred in the absence of significant change in carbon dioxide level, as showing that temperature variations need not even be correlated with carbon dioxide. 

This post shows this view to be overly simplistic.  Here the scientific findings presented in the previous post, “The U. S. National Climate Assessment: Warming Is Due to Human Actions” are summarized.  These demonstrate the scientific and logical rigor leading to the conclusion, based on all the relevant science (not merely a portion portrayed in a single graphic image), that manmade greenhouse gas emissions arising from burning fossil fuels are indeed responsible for global warming.  This post also uncovers inaccuracies and inconsistencies surrounding the denier’s citation of the Medieval Warming Period and the Little Ice Age in support of his assertion that temperature and carbon dioxide level are not connected. 

In fact it is shown here that observed global temperatures result from the combined effects of many climatic factors, of which the CO₂ level is only one.  Carbon dioxide is, however, the principal driver of contemporary global warming.

 

Introduction.  Overwhelming evidence and the concurrence of the vast majority of climate scientists lead to the conclusion that manmade emissions of greenhouse gases are responsible for global warming and its harmful effects.  Even so, there are still those who are skeptical of or deny outright the causative relationship between greenhouse gases and global warming.

One such person is Thomas Wysmuller, a former meteorologist.  He responded to the post “The U. S. National Climate Assessment: Warming Is Due to Human Actions”  (Human Actions) in an email to this writer seeking to discredit the U. S. National Climate Assessment (NCA).

The denier accuses the NCA of “misleading” information concerning the correlation of global average temperature and atmospheric carbon dioxide (CO₂) concentration (see the first graphic in the Human Actions post).  First, the denier’s email incorrectly states that superimposed data for temperature and CO₂ from 1880 to the present “shows correlation and implies causation” (emphasis in original).  Human Actions and the NCA provide a comprehensive set of stringent scientific evidence, of which  the temperature-CO₂ correlation is but a part, that substantiates the causative relationship between emissions of CO₂ from burning fossil fuels, and other sources, and the increase in the long-term global average temperature that is most apparent in the second half of the 20^th century (see Details at the end of this post for full summaries of the data from Human Actions and the NCA).

Second, the denier’s email presented an alternative graphic from the work of Loehle and McCulloch (see Details) depicting positive temperature deviations during about 500-1150 CE (i.e., AD), a period called the Medieval Warm Period (MWP) and negative temperature deviations during about 1400-1900 CE, called the Little Ice Age (LIA); during both of these periods the atmospheric concentration of CO₂, the principal greenhouse gas before the industrial revolution, remained relatively unchanged at about 280 parts per million (ppm; volumes  CO₂ per million volumes of air).  The denier asserts “CO₂ and atmospheric temperature are almost entirely in disconnect”.  There are several problems with these data (see Details). 

The Loehle-McCulloch graphic (see Details) leaves the impression that both the MWP and the LIA are well-defined worldwide phenomena that occur despite no significant change in atmospheric CO₂ levels.  This denier would have us believe that the absence of a relationship between temperature and CO₂ during these intervals shows these properties can never be dependent on each other.

This is a simplistic and improper assumption.  As shown in the Details, numerous scientific publications make clear that there are many factors affecting observed atmospheric temperature of which CO₂ level is only one.  The denier also infers that the MWP and the LIA are worldwide phenomena.  Articles summarized below in Details show that these effects were only regional, not global.

What is significant for contemporary warming is that the increased temperature can be accounted for, after including the effects of all the other drivers of temperature, only by including the excess CO₂ introduced into the atmosphere because humanity is burning fossil fuels for energy.  This factor was absent during geological time periods before the industrial revolution. 

Conclusion

A denier has failed to disprove that contemporary global warming is due to excess emissions of greenhouse gases that arise from human activity, primarily the burning of fossil fuels.

This post summarizes recent scientific reports demonstrating that manmade greenhouse gas emissions are causing contemporary global warming.  It also presents selected scientific articles that consider contributions from many energetic sources that may contribute to global warming.  They correctly emphasize that atmospheric CO₂ concentration is not the sole factor governing warming.  A denier must keep all these contributions in mind.

Finally, a denier must be able to explain the additional consequences of global warming on the complete earth system, not only on the temperature of the air close to the surface of the earth.  These include facts such as a) about 90% of the excess heat from global warming ends up in the ocean, b) the total heat content of the ocean continues to increase, and c) mountain glaciers and ice sheets are melting at more rapid rates than earlier, leading to inexorable sea level rise.

 

Details

 

The Human Actions post and the NCA set out scientifically objective and logically rigorous demonstrations that excess atmospheric CO₂ originating from mankind’s burning of fossil fuels is directly responsible for the increased global average temperature in the last several decades.

First, HumanActions summarizes its conclusion as follows:

1.     Since 1880 the atmospheric concentration of CO₂ and the long-term average global temperature are highly correlated;

2.     Over the same time period emission of carbon (dioxide) into the atmosphere from burning fossil fuels and producing cement follows a time course strongly similar to those for temperature and CO₂, suggesting that burning fossil fuels is a major contributor to the excess accumulation of atmospheric CO₂;

3.     Francey and coworkers (see Human Actions) analyze a particular physical property of atmospheric CO₂, showing unambiguously that the excess CO₂ appearing during the industrial revolution originates from fossil fuels; and

4.     Climate model “hindcasts” show that only by including contributions to atmospheric CO₂ from human factors can the global average temperature record from 1970 to the present be satisfactorily reproduced.

Second, the NCA, in its NCA Highlights, concludes

“Multiple lines of independent evidence confirm that human activities [such as burning of coal, oil, and gas, and clearing of forests] are the primary cause of the global warming of the past 50 years. The[y] have increased the concentration of carbon dioxide in the atmosphere by more than 40% since the Industrial Revolution….Natural factors like the sun and volcanoes cannot have caused the warming observed over the past 50 years….If not for human activities, global climate would actually have cooled slightly over the past 50 years. The pattern of temperature change through the layers of the atmosphere, with warming near the surface and cooling higher up in the stratosphere, further confirms that it is the buildup of heat-trapping gases (also known as “greenhouse gases”) that has caused most of the Earth’s warming over the past half century.”

In conclusion, because of the objective veracity of the scientific underpinnings of global warming, no legitimate assertions questioning these conclusions can be credibly proposed.

Loehle and McCulloch improperly convey misleading information concerning the MWP and the LIA.  The graphic displaying temperature deviations during the MWP and LIA, adapted from the original and cited by a denier, is shown below:

 

The mean relative temperature history of the earth (blue, cool; red, warm) over the past two millennia adapted from Loehle and McCulloch (2008) – highlighting the Medieval Warm Period (MWP) and Little Ice Age (LIA), together with a concomitant history of the atmosphere’s CO₂ concentration (green).
Source: email to this writer from T. Wysmuller, citing Loehle, C. and McCulloch, J. H. 2008. Correction to: A 2000-year global temperature reconstruction based on non-tree ring proxies. Energy & Environment 19: 23-100;

http://www.econ.ohio-state.edu/jhm/AGW/Loehle/Loehle_McC_E&E_2008.pdf

 

First, the adapted graphic incorrectly labels the left vertical axis as “Global Temperature Anomaly”.  The use of the word “Global” is misleading and incorrect.  In the original article the corresponding graphic does not include this word in the label for the vertical axis.  Only this adapted version includes the word “Global”.

Second, labeling the temperature anomaly as “Global” is wrong.  As shown below in the various sections describing the work of other researchers, it becomes clear that the MWP and the LIA are regional in scope, not “global”.

Third, Loehle and McCulloch inappropriately excluded from consideration all temperature data based on analysis of tree ring properties.  In fact, tree ring proxies for temperature continue to be used by other climate scientists up to the present (see descriptions for articles by Kaufman, Villalba, and Mann, below).  This omission potentially introduces an unexplained bias into the Loehle-McCulloch graphic. 

Fourth, it is highly misleading for a denier to imply that CO₂ concentration is the only factor governing average temperature.  Climate scientists have long recognized many other potential energetic factors affecting temperature (see the research articles described below).  What is important is that since the industrial revolution the excess CO₂ added to the atmosphere by burning fossil fuels is the dominant factor driving warming in the recent decades (see Human Actions).

Villalba (Climatic Change 1994, Vol. 26, pp 183-197)  used tree ring and radiocarbon data to characterize temperature and precipitation in southern South America.  At one location studied, a cold interval from 900 to 1070 CE was followed by warmer intervals from 1080 to 1250, and again a cold period from 1270-1660.  At another location glacial advances were observed for the periods 1270–1380 and 1520–1670 C.E.  In a third location glacial advances were found from the late 1600s to the early 1800s.  These are distinct patterns that fail to suggest single worldwide events.  Villalba states that strong El Niño-Southern Oscillation (ENSO) Pacific oceanic trends were likely responsible for these events.

Mann shows that the LIA is regional, not worldwide (Mann, M.E., 2002, “Little Ice Age”, in Vol. 1, The earth system: physical andVolume 1, The Earth system: physical and chemical dimensions of global environmental change, pp 504–509;  M. C. MacCracken and J. S. Perry (editors) John Wiley & Sons, Ltd., Chichester).  Using temperature proxies including tree ring data, Mann presented temperature curves over 1,000 years from several regions in the world, shown below:

 

Estimated relative temperature variations for various regions from 1000 to 2000 CE, smoothed over as much as 100 years to show long-term trends.  The vertical axis shows ºC for panels (a) and (e), and relative variations for panels (b), (c), (d), (f), (g) and (h).  The rectangular box from before 1400 to after 1900 is labeled LIA.  Panel (e) for Central England represents the European Little Ice Age well.  Fennoscandia (panel (f)), Scandinavia.  Panels (b) and (f) are based on tree ring data.

Source, Mann 2002, “Little Ice Age”; http://www.meteo.psu.edu/holocene/public_html/shared/articles/littleiceage.pdf.

 
 

It is evident that the period called the LIA is not a single global event, but is manifested in distinct ways in different regions around the world.  In particular, according to Mann, the variability includes among its causes changes in atmospheric circulation patterns, especially the North Atlantic Oscillation.  This is “the dominant mode of atmospheric circulation variation in the North Atlantic and neighboring regions, [having] a particularly strong influence on winter temperatures in Europe”.  The North Atlantic Oscillation cooled eastern North America and Europe while the western U. S. and the Middle East were warmer than usual, confirming the regional nature of temperature trends.  Volcanic eruptions episodically led to cooling as well.

 

Kaufman et al. (Science 2009, Vol. 325,  pp. 1236-1239) studied proxy temperatures in the Arctic regions of the Western and Eastern Hemispheres over the last 2000 years.  A long-term cooling, more or less linear from 0 to 1900 CE is attributed to weakening solar irradiation from 0 to 2000 CE.  Kaufman et al. find no evidence in the Arctic for either a MWP or a LIA.  Arctic temperatures rise sharply after 1900 CE, deviating from the long preceding downward trend.  This indicates that another climatic factor not previously present causes the strong positive deviation after 1900.

 

Mann et al. (Science 2009, Vol. 326, p. 1256) conclude that the MWP (termed the Medieval Climate Anomaly in their article) is partly due to La Niña cooling in the tropical Pacific, and that the LIA, most evident from 1400 to 1700 CE, is partly due to El Niño conditions and to the North Atlantic-Arctic Oscillation.

 

Miller et al. show that intense volcanic activity led to the onset of the LIA (Miller, G. H., et al., Geophys. Res. Lett., 39, L02708 (2012)).  Based on geological findings based in Northern Canada and Iceland they find that four large, sulfate-laden explosive volcanic eruptions occurred between 1250 and 1300 CE, with a further eruption episode around 1450 CE.  The initial cooling from these events was probably extended for longer times by ice-temperature feedbacks.

 

Marcott et al. studied worldwide and regional trends in temperature over the past 11,000 years (Science 2013, Vol. 339, pp. 1198-1201).  They found that temperature trends differed widely among (a) the Arctic and northern temperate, (b) the tropical, and (c) the southern temperate and Antarctic regions.  This shows that single “events”, such as a worldwide warming period or a worldwide glacial period, did not prevail during this interval. 

 

Data for possible sources for temperature variation were gathered. Solar irradiance was warming for both polar regions but less so for the tropics, effects that weakened as time progressed toward the present.  Atmospheric sulfate aerosols from volcanic activity  (exerting a cooling effect) were strongest in the earliest years but continued throughout the full interval.  Greenhouse gases increased from about 7,000 to about 1,000 years ago; their warming effect opposes the observed cooling trend and so cannot explain it.  The Atlantic Ocean meridional overturning circulation, which carries heat from the tropics to the North Atlantic, contributed cooling to the Northern Atlantic while lessening cooling in the South Atlantic, in agreement with observed land temperatures.  This study clearly points out the many potential contributions to global cooling and heating prior to the industrial revolution, and shows that most effects, when significant, are regional rather than global.



 

© 2014 Henry Auer

The U. S. National Climate Assessment: Warming Is Due to Human Actions

Summary.  The U. S. government released its Third National Climate Assessment in May, 2014.  It shows that emissions from human use of fossil fuels since the industrial revolution began are reflected in increased carbon dioxide concentrations in the atmosphere, and that this is directly responsible for the increase in the long-term global average temperature.  This post summarizes these findings, affirming their validity beyond any credible scientific doubt.

A future post will consider the Assessment’s climate findings.  Warming has already had adverse effects across the U. S., including heat, drought, wildfires, changes in availability of water, floods, ocean storm surges, extreme weather and climate events and socioeconomic effects.  Worsening of these trends is foreseen during this century.

Introduction.  The Third National Climate Assessment (NCA) was issued May 6, 2014 as mandated under the Global Change Research Act of 1990 to “assist the nation and the world to understand, assess, predict, and respond to human-induced and natural processes of global change”.  Its tasks, however, do not include formulation of policies to address global warming.

Significance of the NCA.  The NCA was prepared by hundreds of scientists and experts, overseen by federal officials from thirteen departments and agencies (see Details at the end of this post).  Its procedures assure that the results reflect the highest scientific standards presented in an objective, unbiased manner.  Its importance lies also in its emphasis on observations and projections of climate in the U. S. by region and by the sector of ecological or economic activity.

This post and one to follow are based on a Fact Sheet distributed by email by Bess Evans in the White House Office of Science and Technology Policy, and on the NCA Highlights (Melillo, Jerry M., Terese (T.C.) Richmond, and Gary W. Yohe, Eds., 2014: Highlights ofClimate Change Impacts in the United States: The Third National Climate Assessment. U.S. Global Change Research Program, 148 pp.).  Here the scientific findings leading to the conclusion that global change arises from human activities are summarized.  A second post will present selected findings of the NCA drawn from the regions and segments mentioned above.  

The Earth is warming as a result of “human activities, predominantly the burning of fossil fuels” (NCA).  Carbon dioxide (CO₂) has been recognized as a greenhouse gas since at least the 19^th century.  Although it has been present in the atmosphere for geological time frames, the recent abrupt increase due to human use of fossil fuels has raised its concentration, and that of other man-made GHGs, higher than before these human activities began.  The incremental CO₂ raises average temperatures around the globe.  This has led to several effects identified in the NCA and shown in the following table:

Increasing Values or Amounts	Decreasing Values or Amounts
Primary Effects
Temperature Over Land
Sea Surface Temperature
Temperature Over Oceans
Air Temperature Near Earth’s Surface (Troposphere)
Ocean Heat Content
Consequent Effects
Water Vapor (Moisture Content of Air)	Sea Ice
	Snow Cover
	Glaciers and Ice Sheets

 

Strong Correlation between CO₂ and Global Temperature.  The NCA presents data showing a close correlation between rising atmospheric CO₂ concentration and global average temperature during the industrial era, shown in the graphic below.

Correlation between global temperature and CO₂ concentration from 1880 to 2012.  The thick black line gives the yearly CO₂ concentration in parts per million (volumes of CO₂ present in 1 million volumes of air) with values along the right vertical axis.  The ends of the blue and red lines show the temperature with values along the left vertical axis.  The horizontal line shows the average temperature across this time span.  The ends of the blue lines show the temperature values for years in which the temperature was below the average, and the ends of the red lines show the temperature values for years in which the temperature was above the average.

Source: NCA; www.nca2014.globalchange.gov.

 

The ends of the blue and red lines, ending at the average temperature value for each year, and the solid black line for annual CO₂ concentrations are highly correlated, suggesting a relationship between them. 

 

Emissions of CO₂ have risen sharply from zero since the beginning of the industrial revolution.  The sources of increasing atmospheric CO₂ from 1850 to the present are shown in the following graphic.

Annual rates of emission of CO₂ (evaluated on the basis of the carbon portion of the carbon dioxide molecule) from the three main fossil fuels, plus the production of cement from limestone.  The amounts shown represent about 80% of all human-derived carbon, with most of the remainder arising from human-induced deforestation.

Source: NCA (data from Boden et al. 2012); www.nca2014.globalchange.gov.

 

 

It is important to note that the time course for the annual rate of emission of C from burning fossil fuels in this graphic follows closely the time course for the annual values of atmospheric CO₂ concentration and annual temperature rise shown in the first graphic.   These data strongly suggest that the increased atmospheric concentration of CO₂ during industrial times originates from the burning of fossil fuels, and that the excess CO₂ causes the global temperature rise because of the greenhouse effect.

 

Burning fossil fuels is directly responsible for the increase in the concentration of atmospheric CO₂.  This conclusion is based on use of a distinctive molecular signature for CO₂, a physical property (the isotopic ratio of ¹³C to ¹²C in CO₂) which differs for CO₂ originating geologically in the atmosphere and CO₂ originating from burning fossil fuels.  The time course for this property, measured for the past 1,000 years, also follows the trends shown in the previous graphics.  Significantly, pronounced changes arise only during the industrial period, retracing the time courses shown above for temperature, atmospheric CO₂ and fossil fuel emissions.  The trend of values deviates from those for the first 800 years and curves strongly in the direction characterizing CO₂ originating from fossil fuels as the industrial revolution progresses (R. J.Francey et al., Tellus (1999), 51B, 170–193).   The researchers conclude “The overall [change in the isotopic ratio] during the last 1-2 centuries is attributed to anthropogenic [i.e., man-made] emissions”.  This result removes any credible basis for scientific doubt that the excess CO₂ in the atmosphere accumulating during the industrial period originates from burning fossil fuels.

 

Man-made CO₂ is responsible for global warming.  Climate models that simulate past global average temperature have been run for the cases that a) excess CO₂ originating from burning fossil fuels is omitted, and b) it is included.  The results are shown below.

 

Observed annual average global temperature changes from 1890 to 2010 (black line), and “hindcasts” from climate models shown as light green (models using natural factors only) and gray (models using both natural and human factors).   The change defined as 0ºF is a reference obtained from a temperature average over many of the years in the center of this period.

Source: NCA (data adapted from Huber and Knutti 2012); www.nca2014.globalchange.gov.

 

 

It is important to note that both models reproduce the long-term trend of observed temperature from 1890 to about 1970.  This validates the use of the models for “hindcasting” temperature from 1970 to the present.  The graphic shows, however, that after about 1970 only the climate models that include human factors, i.e., mankind’s use of fossil fuels and deforestation, reproduce the observed temperature data.  This shows unequivocally that the differential increase in global average temperature over the last several decades arises from the incremental addition of CO₂ to the atmosphere that comes from burning fossil fuels, and from deforestation. 

 

Summary.  The NCA Highlights have shown:

1.     Since 1880 the atmospheric concentration of CO₂ and the long-term average global temperature are highly correlated;

2.     Over the same time period emission of carbon (dioxide) into the atmosphere from burning fossil fuels and producing cement follows a strongly similar time course, suggesting that burning fossil fuels is a major contributor to the excess accumulation of atmospheric CO₂;

3.     In a report not included in the NCA Highlights Francey and coworkers analyze a particular physical property of atmospheric CO₂, showing unambiguously that the excess CO₂ appearing during the industrial revolution originates from fossil fuels; and

4.     Climate model “hindcasts” show that only by including contributions to atmospheric CO₂ from human factors can the global average temperature record from 1970 to the present be satisfactorily reproduced.

 

This sequence of results, rigorously and accurately collected by climate scientists over the past several decades, conclusively establishes the validity of the NCA Highlight statement:

“The majority of the warming at the global scale over the past 50 years can only be explained by the effects of human influences, especially the emissions from burning fossil fuels (coal, oil, and natural gas) and from deforestation.”

 

Conclusion

 

The NCA has been prepared by hundreds of scientists and other experts from the academic world, nonprofit organizations, government research facilities, private sector consultants, private corporations and foreign research facilities (see Details below).  Their work was overseen by federal experts drawn from thirteen U. S. federal agencies dealing with aspects of global change.  Their report was subjected to external review, which garnered several thousand comments.  These were accommodated in preparing the final document.  There can be no reasonable basis for doubting or dismissing the impartiality, cogency and veracity of the NCA’s findings.

 

The NCA Highlights state unequivocally that most of the warming of our planet observed over the last 50 years is due to the excess contributions of greenhouse gases to the atmosphere from human activities.

 

Most of the NCA details the effects of the warming of the planet on the U. S.  This will be examined in a coming post.

 

Details

 

Significance of the NCA.  The NCA was prepared under the supervision of a federal advisory committee whose members are drawn from every department and agency, thirteen in all, substantively involved in an aspect of global change science or policy.  The Assessment itself has been 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.  Entry portals to the full document, in sections, are available here . 

 

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.  While remedial approaches are discussed in broad terms, no particular policy position is espoused.

 

The importance of this Third NCA is that it is written almost entirely by American experts and emphasizes aspects of global change manifested in the United States.  (This is in distinction, for example, from the recent Fifth Assessment Report of the United Nations-sponsored Intergovernmental Panel on Climate Change, which addresses the issue at a global level.) 

 

The Third NCA is noteworthy for addressing first, separate results for eight geographic regions of the United States, and second, separate results for twelve climate-based and socioeconomic segments affected by global change.  This more refined approach is enabled, compared to earlier Assessments, because of the accumulation of more detailed, sophisticated information, as well as refinement and enhancements in computational treatment of climate change in the U. S. at the regional level and across various ecological and socioeconomic segments.  These improvements were not available earlier.  A second post will consider some of these aspects of the NCA.

 

© 2014 Henry Auer