Representative Lamar Smith Wrongly Asserts Global Warming Has Halted

Representative Lamar Smith of Texas, in a speech in the U. S. House of Representatives, lamented the widespread press coverage of a scientific publication last year showing that global warming had not stopped since about 2000.  He then decried the lack of press coverage for a new article that he wrongly claims “refutes” the earlier work.

In truth, both articles find that warming has continued during this period, contrary to Rep. Smith’s characterization of this period as a “halt” in global warming.  The new article finds that the warming during this period is a “slowdown” (compared to predictions from climate models), but not a “halt”, and thoroughly analyzes the reasons for the slowdown.  An important contribution comes from the decades-long cyclical operation of the Interdecadal Pacific Oscillation.

Representative Smith is wrong in saying that global warming has halted.  The newest global annual average temperatures for 2014 and 2015 have resumed increasing; that for 2015 is a pronounced record high.  Warming continues unabated, even if Representative Smith won’t admit to this reality.

 

In a speech on the floor of the U. S. House of Representatives   on March 21, 2016, Representative Lamar Smith of Texas stated “Americans deserve all the facts that surround climate change, not just those that fit the view the national liberal media wants to promote.”   He disparaged the media for covering a scientific study by the National Oceanic and Atmospheric Administration (NOAA) last year (which he did not identify further) that refutes earlier work characterizing a recent decade-long period as showing what he called a “halt in global warming”.  Rep. Smith then cited a new “study published in the journal Nature [that] confirms the halt in global warming” (again not identified by author or title).  He stated “[a]ccording to one of the study’s lead authors it ‘essentially refutes NOAA’s study’”, and called out the media for not covering this new result.

This writer presumes that Rep. Smith was referring first to the publication by Thomas Karland coworkers at NOAA and other research institutions, published in the peer-reviewed journal Science in June 2015. Contrary to Rep. Smith’s claim that the “scientists altered global surface temperature data to try and refute the two decade halt in global warming” (emphases added), Karl and coworkers carried out a rigorous reanalysis of existing, freely available, temperature records going back to 1880, and included new data from 2012 to 2014 that had not been previously analyzed.  They concluded “based on our new analysis, the IPCC’s [Intergovernmental Panel on Climate Change] … statement of two years ago – that the global surface temperature ‘has shown a much smaller increasing linear trend over the past 15 years than over the past 30 to 60 years’ – is no longer valid.”  Rather, they found that the rate of warming of the world's atmosphere during 1998 to 2014 has continued unabated compared to the warming experienced in earlier decades.

It is important to note that Karl and coworkers did not “alter” temperature data in their reanalysis, but rather applied corrections to account for earlier systematic errors in certain of the datasets used.  Further, they were not trying to “refute the [so-called] halt in global warming”, contrary to the accusation of Rep. Smith.   

Rep. Smith states that a new study published in Nature refutes the earlier NOAA findings.  This writer presumes he was referring to the publication by Fyfe and coworkers (Nature Climate Change  6, 224–228 (2016); doi:10.1038/nclimate2938; Published online  24 February 2016).   Contrary to Rep. Smith’s assertion, Fyfe and coworkers do not “confirm the [so-called] halt in global warming”, nor do they “refute” Karl and coworkers.  Fyfe and coworkers not only reexamined the global mean surface temperature records available, they also examined potential drivers of the observed trends. 

• They found that the data analysis carried out by Karl and coworkers, as well as by other groups, showed that a “warming slowdown is thus clear in observations; it is also clear that it has been a ‘slowdown’, not a ‘stop’.” (Emphases added)  That is, contrary to Rep. Smith, this new work does not “confirm the halt in global warming.” (Emphasis added)

 

• Referring to the work of Karl and coworkers, Fyfe and coworkers write “[r]ecent research that has identified and corrected the errors and inhomogeneities in the surface air temperature record is of high scientific value.”  This appreciation of the work of Karl and coworkers contradicts Rep. Smith when he dismisses the validity of their work.

 

• Fyfe and coworkers write that the issue of “[h]ow unusual a period of reduced warming is, depends strongly on its length.”  The actual rates of warming are highly sensitive to the choices made for the length of time considered, and for the starting points and end points of the warming interval.

 

• Fyfe and coworkers call the recent period, 2001-2014, a “slowdown” largely because the observed temperature trends for this period fall below modeled predictions for the period made by extending assumptions made for earlier decades into the recent period.

 

• The authors point out that man-made contributions to warming did not cease during the slowdown.  Rather they ascribe the slowdown largely to internal variations in factors that affect climate, including the large contribution arising from the operation of the cyclical decades-long Interdecadal Pacific Oscillation (IPO) (as well as certain other variations).  The IPO was in its thermally negative phase during the slowdown period.  This was sufficient to counterbalance part of the man-made warming always present.  Being cyclical, when the IPO reenters its positive phase, warming from the IPO will supplement man-made warming, leading to stronger increases in global average surface temperatures once again.

It is concluded that Rep. Smith’s characterization of the last 15 years of global temperature data as one in which global temperature increases have “halted” is oversimplified and mistaken.  We agree that, in his words, “Americans deserve all the facts that surround climate change.”

The global average atmospheric temperature continues to increase, reaching record levels.  The U. S. National Aeronautics and Space Administration reports that 2015 was the hottest year on record covering the 135 years from 1880.  The land-ocean average was 0.87ºC (1.57ºF) above an average baseline for about 1950 to 1975.   For 2014 that value was 0.74ºC (1.33ºF) above the average.

The Climate Research Unit of the University of East Anglia (UK) similarly finds that 2015 was the warmest on record for data going back to 1850. 

NOAA also reports that 2015 was the warmest year on record, advancing 0.16ºC (0.29ºF) from the previous year, which itself was a record.  NOAA’s graph of annual temperature differences from the 20^th century average is shown here

 

Land and ocean average annual temperature deviations, for 1880 to 2015, from the reference, the average for the 20^th century,.  Left vertical axis in ºC; right vertical axis in ºF.  Blue, annual temperature is below the reference average; red, annual temperature is above the reference average.

Source: NOAA; http://www.ncdc.noaa.gov/cag/time-series/global/globe/land_ocean/ytd/12/1880-2015

 

The image above shows that the land and ocean annual average temperature has been increasing consistently and dramatically since about 1950.  There clearly is no “halt in global warming”, contrary to the floor speech given by Rep. Smith.  Indeed, the rise from 2014 to 2015 is remarkably large.

 

Conclusion

Rep. Lamar Smith of Texas gave a speech on the floor of the U. S. House of Representatives that casts doubt on the continued, dramatic rise of global annual average temperatures.  This post shows unequivocally that the long-term global average temperature continues its long-term increase.  It is widely recognized that the rise in the global average temperature is caused by the increase in man-made greenhouse gases (GHGs), primarily carbon dioxide, emitted into the atmosphere. 

The increased atmospheric burden of carbon dioxide is critical, because once this gas enters the atmosphere it remains resident for centuries or longer (about one-third is absorbed by the waters of the oceans).  Although humanity strives to reduce the annual rate of further emissions of GHGs, such efforts cannot reduce the total amount of GHGs already present.  This means that the extent of warming we are already experiencing cannot be reversed.  The average global temperature will continue increasing until annual emission rates approach zero.  The efforts of those who seek to lull us into a false sense of climate security are for naught; the scientific truths embedded in the global warming issue cannot be reversed simply by willing them so.

© 2016 Henry Auer
 

New Analysis Does Not Support a Warming “Hiatus”

The “Hiatus”.  Annual results for the global average temperature show a break from an earlier high rate of increase, beginning about 1998.  Compared with the preceding three decades, recently recorded global average temperatures have shown only a slight increase.  The reduction in the rate of warming of the globe may be termed a pause, and is generally referred to as a "hiatus".  This difference in warming trends was noted in the Fifth Assessment Report (AR5; Summary for Policymakers and Working Group I: The Physical Science Basis Ch. 2, Observations) of the Intergovernmental Panel on Climate Change (IPCC).  This break has been seized upon by those doubting or denying the reality of global warming as evidence that warming has effectively ceased since about 1998.

A new analysis of global temperature data extending from 1880 to the present was published by Thomas Karl and coworkers, from the National Oceanographic and Atmospheric Administration, the National Centers for Environmental Information, and LMI (McLean, VA), on June 4, 2015.  Climate scientists recognized problems in the ways temperature data have been collected.  Karl and coworkers sought to reevaluate historical data to account for these problems (see Details section at the end of this post).  The scientists conclude “based on our new analysis, the IPCC’s … statement of two years ago – that the global surface temperature ‘has shown a much smaller increasing linear trend over the past 15 years than over the past 30 to 60 years’ – is no longer valid.”  Rather, the rate of warming of the world's atmosphere during 1998 to 2014, averaged over its entire surface, has continued unabated compared to the warming experienced in earlier decades (see Details).

Warming Skeptics.  Almost immediately upon the publication of this report organizations known to be skeptical about global warming, or to deny that it is occurring and/or that humanity is causing it, issued statements questioning the validity of the report.  However it is essentially impossible for these groups to draw such conclusions without actually taking the time to review the data and methods used in the reanalysis.  After all, the authors devoted many months or more to analyze the information available.  The data sets themselves are available to the public, and the report sets out in detail how the analysis was done.  Detractors can only question the validity of the conclusions reached by Karl and coworkers after critically reviewing this information and objectively pointing to any perceived faults in the analysis.  Anything short of such assessment is mere speculation.

Ocean Heat Content.  The reanalysis conducted by Karl and coworkers importantly shows that air temperatures averaged over the surface of the entire globe have continued to increase without any pause from about 1950 to the present.  In addition, the oceans absorb about 90% of the excess heat accumulated by the complete earth system.  Measurements collected over the past decades show that the heat content contained in the oceans has continued increasing without cease during this period.

Melting of Glacial Ice.  The excess heat added to the earth system, both air-based and ocean-based, has resulted in increased rates of loss of land-based ice in both the Arctic and Antarctica in recent years.  This is but one example of the effects of global warming on the Earth.  Ice masses will suffer net melting  if the temperature, averaged over the full year, is higher than the melting point and the water lost to melting is not replaced by new precipitation frozen into place. 

 

New reports published in April and May 2015 exemplify this.  Whereas melting of the Antarctic ice shelves was very low between 1994 and 2003, the rate of loss increased more than 12-fold over 2003-2012, especially in West Antarctica.  Loss of ice mass from glaciers in the Southern Antarctic Peninsula that end in ocean-floating ice shelves has rapidly increased from near none in the 2000s to high rates since 2009.  Adding this ice or its melted equivalent as liquid water to the oceans contributes significantly to rising sea levels around the world.  It is important that both these reports describe increased melting only in the recent years that coincide with the continued increase in global temperatures characterized by Karl and coworkers.

Since warming will continue for decades to come, land-based ice at the poles and in mountain glaciers will continue melting, indeed will do so at increasing rates.  So sea level will continue rising into the indefinite future.  This threatens coastal regions around the world, including many of the world’s cities.  Defensive measures needed to avert the damage wrought by flooding and ocean storm surges will require large investments of money, derived from public sources.

Global agreement is needed.  This post reports that global warming has continued unabated for at least the last fifty years, raising average temperatures of the atmosphere and the ocean.  Since this is truly a global problem it is necessary that all the nations of the world come together to implement meaningful reductions in annual rates of emission of greenhouse gases.  The United Nations-sponsored negotiations involving all nations of the world are under way now, with the goal of reaching agreement on the way forward at a meeting to be held at the end of 2015.  The harms from global warming already underway will only grow worse by 2100 and beyond if an agreement is not reached.  All nations need to agree on limiting emissions, with the goal of transitioning to a decarbonized energy economy by about 2050.  Major efforts by all nations will be needed to reach this goal.

Details

Karl and coworkers examined three sources by which temperature averages could have provided erroneous results in AR5.  An important feature of this reassessment is the use of new data sets for temperatures that were not available when AR5 was prepared.  First, by far the largest number of observation stations in the world is land-based.  But over the last one and one-half centuries their number has grown, and the physical settings of older stations have changed.  Karl and coworkers reassessed land-based measurements accordingly, including incorporating new data sets not previously used.  This process roughly doubled the number of reporting stations.  An important feature of this improvement is far more authoritative reporting from the Arctic, which has in fact undergone a high extent of warming that was not fully accounted for in AR5.

Additionally, the ways of gathering sea surface temperature have changed.  A second factor recognized that historically these data were obtained primarily by ocean-going vessels.  Their numbers likewise have grown, but more importantly, the way in which they routinely measured ocean temperature has changed.  A third factor has been that, over the last 15-20 years, buoys have been deployed across the ocean, one of whose capabilities is real time measurement of air temperature.  Karl and coworkers harmonized the old and new ship-based measurements, and applied a correction to all those values to make them consistent with the buoy-based observations.

The earlier data, such as those presented in AR5 as given by Karl and coworkers in their Supplementary Materials appendix, show a reduction in the rate of increase in global average temperature between 1950-1999 and the interval 1998-2012, from 0.101 ± 0.026 ºC/decade, to 0.039 ± 0.082 ºC/decade.  It is important to note, as climate scientists have recognized, that the single temperature value recorded for 1998 was exceptionally high (see second graphic below) because it was affected by an unusually intense El Nino event.  This has the effect of artificially elevating the starting point for the 1998-2012 data range, thus lowering the steepness of the trend line for this period.

The reevaluation of Karl and coworkers shows that these two temperature rates are now very similar, namely 0.113 ± 0.027 ºC/decade and 0.086 ± 0.075 ºC/decade, respectively.  Thus their reevaluation shows that for the recent interval thought to experience the “hiatus”, the rate of increase of global temperature is more than double than that found earlier in AR5. 

When temperature data extending to the most recent period, up to 2014, are considered, the rate of increase in temperature, instead of decreasing from 1950-1999 to 2000-2014 as AR5 shows up to 2012, actually increases slightly between these two time periods.  This is illustrated in the following graphic:

 

Comparison of the warming trends in ºF/decade for the old analysis (methods as used in AR5) but including data up to 2014, and the new analysis (data and methods used by Karl and coworkers).

Source: Los Angeles Times based on the report by Karl and coworkers;

http://www.latimes.com/science/sciencenow/la-sci-sn-no-global-warming-hiatus-noaa-20150603-story.html#page=1&lightbox=83703423

 

 

The near identity of temperature change rates before and after 1998 is seen in the following graphic showing annual temperatures from 1880 to 2014, with a single statistics-derived line drawn based on analysis of data from 1950 to 2014.

Global average temperature difference in ºF from 1880 to 2014, with the orange Trend line evaluated by Karl and coworkers.  The base line representing 0ºF is the average temperature over 1961 to 1990.

Source: Los Angeles Times based on the report by Karl and coworkers;

http://www.latimes.com/science/sciencenow/la-sci-sn-no-global-warming-hiatus-noaa-20150603-story.html#page=1&lightbox=83703423

  

These two graphics make clear that there has been no “hiatus” in warming after 1998.

 

 

© 2015 Henry Auer

 

2014 Was the Warmest Year Globally Ever Recorded

2014 had the highest global average temperature ever recorded.  The U. S. National Oceanic and Atmospheric Administration (NOAA)  and National Aeronautics and Space Administration (NASA ) jointly announced on Jan. 16, 2015 that the year 2014 was the hottest year since record keeping began in 1880.  This result represents the globally averaged temperature, for both land and ocean surfaces, over the entire year. 

A 1½ minute video from NASA gives more information on this finding.  It includes a speedy review, year-by-year and location-by-location across a map of the globe, of how annual average temperatures, in ºC (multiply by 1.8 for ºF), have increased from 1957 to 2014.  (They are shown as the differences from a 30-year reference period from about 1945 to about 1975).

The ten hottest years on record occurred between 1998 and the present (see Details section at the end of this post). 

[Update added January 26, 2015]: The United Kingdom Met (i.e., meteorological) Office jointly with the University of East Anglia reported, using their own data set, that 2014 was tied with 2010 as the being the warmest year on record, within the 95% confidence limit of their data.  This occurred even though 2014 did not experience a Pacific Ocean warming event known as El Nino.

The “pause” in rising temperatures of recent years is misleading. The new warm record for 2014 is significant because those who doubt the reality of global warming have pointed to an apparent “pause” in warming from about 1998 through 2013 (i.e., up to the time of the new NOAA/NASA report).  The apparent “pause” may be seen in the image below, compared to the clearly rising temperatures before 1998.

                 Global average temperature from 1980 to 2013.
                 Source: Data table from National Aeronautics and Space Administration;
                 http://data.giss.nasa.gov/gistemp/graphs_v3/Fig.A2.txt


The new result for 2014 places its data point slightly higher than the two next-warmest years, 2005 and 2010.  Although it is too early to tell, the new information suggests that the earth may be resuming its climb to higher global average atmospheric temperatures.

The “pause” is understood to be temporary, in any case, in view of the image below.

Global average temperatures from 1850 to 2012, presented as differences from the average temperature from 1961 to 1990.  The different colored lines represent different data records.  Top, annual data points; bottom, 10-year averages with the gray shading showing confidence estimates.

Source: Intergovernmental Panel on Climate Change, 5^th Assessment Report, Part 1; http://www.climatechange2013.org/images/uploads/WGIAR5-SPM_Approved27Sep2013.pdf

The graphic shows that there was an even longer “pause” between the late 1940’s and the mid 1970’s; nevertheless, that “pause” ended and the global average temperature rose dramatically in the three following decades.  Since trends in global warming become apparent only on long time scales, a decade or longer, the bottom panel in the graphic above, presenting atmospheric temperatures as ten-year averages, suggests that the purported “pause” in the first decade of the 21^st century may not be a significant “pause” at all.

Ocean Heat Content.  The temperatures discussed above relate only to surface air temperatures around the globe.  But 90% of the excess heat retained by the earth system is absorbed in the oceans, measured in an upper zone down to a depth of 700 m (2,296 ft), as well as in a deeper zone from the surface to 2,000 m (6,562 ft).  A graph showing the time dependence of the ocean heat content to both depths is seen in the image below.

Five-year averaged relative global ocean heat content through 2013 for the upper zone (0-700 m) and the full-depth zone (0-2000 m), evaluated as the difference from the average heat content between about 1975 and 1990. Source: NOAA; http://www.nodc.noaa.gov/OC5/3M_HEAT_CONTENT/ .

Significantly, the image above shows clearly that during the present “pause” in the global average air temperature (1998-present) heat continued to accumulate in the waters of the oceans down to 2,000 m without any “pause”.  Thus, most of the excess heat absorbed by the earth system due to global warming is stored in the oceans.  Climate scientists have identified the role of the oceans in storing excess heat in recent publications, and pointed out that sooner or later that excess heat will be transferred back to the atmosphere (see Details, below).

Conclusions

The year 2014 had the hottest annual global average air temperature since record keeping began in 1880.  This result, and related information presented by NOAA and NASA, indicate  that there may be no significant “pause” in warming of the air temperature of the Earth, contrary to statements made by global warming skeptics and deniers.  The climate scientist Michael E. Mann, at the Pennsylvania State University, wrote  “It is exceptionally unlikely that we would be witnessing a record year of warmth, during a record-warm decade, during a several decades-long period of warmth that appears to be unrivaled for more than a thousand years, were it not for the rising levels of planet-warming gases produced by the burning of fossil fuels.”  Stefan Rahmstorf, head of earth system analysis at the Potsdam (Germany) Institute for Climate Impact Research stated   “[T]he fact that the warmest years on record are 2014, 2010 and 2005 clearly indicates that global warming has not ‘stopped in 1998,’ as some like to falsely claim.”

Indeed, 90% of the excess heat retained by the earth system is absorbed by the oceans, a process continuing without a “pause” up to the present.  Long-lived ocean currents redistribute this heat around the earth and among zones of varying depth.  It takes many years for heat to re-emerge to the surface and exchange back into the atmosphere.  Yet it is considered essentially certain that this will indeed occur. 

Global warming due to continued emissions of greenhouse gases will continue indefinitely unless greenhouse gas emissions are reduced.  If the peoples of the earth succeed in lowering annual emission rates to near zero, further warming will come to an end, and the earth will experience a new, higher global average temperature than we have now.  We must strive to reduce annual emission rates to (near) zero in order to minimize the additional warming of the earth.

Details

The ten hottest years on record occurred between 1998 and the present.  The second hottest years, only slightly less warm on average than 2014, were 2005 and 2010 (see the first graphic above).   The finding that 2014 exceeded all other records is even more significant because it occurred in a year in which the El Nino Southern Oscillation, a warming pattern in the Pacific Ocean, was absent. 

NOAA presents the global map, below, showing deviations in temperature from the reference period 1981-2010 as color-coded shades grading the deviations from the average.

Global grid showing color-coded deviations of the temperature in 2014 from the average temperature over the period 1981-2010.  Red shades represent temperatures warmer than the average, and blue shades represent temperatures cooler than the average.  (Grey regions had no data available.)

Source: NOAA; http://www.ncdc.noaa.gov/sotc/global/2014/13

  

The image above is noteworthy, since it shows that there were many regions, both on land and oceanic, recording record warmest average temperatures whereas there was only one region, south of South America, having a record coldest average temperature.  Indeed, most regions of the earth, both land and sea, had temperatures in 2014 higher than the 1981-2010 average.
 

Climate scientists have pointed out in recent publications that heat is accumulating in the oceans and that sooner or later the excess heat will re-emerge, so that the global average air temperature will resume climbing.

Loeb and coworkers (Nature Geoscience, vol. 5, pp. 110–113 (2012) doi:10.1038/ngeo1375) compared the energy imbalance of the Earth system with ocean heat content.   Combining satellite temperature measurements and ocean heat measurements to 1,800 m (5,900 ft) they found “between January 2001 and December 2010, Earth has been steadily accumulating energy at a [significant rate]. We conclude that energy storage is continuing to increase in the sub-surface ocean.”

Guemas and coworkers (Nature Climate Change vol. 3, pp. 649–653 (2013) doi:10.1038/nclimate1863)  examined the current “pause” in global warming.  Using historical ocean temperature data and a coupled ocean-atmosphere climate model, they “attribute the onset of [the “pause”] to an increase in ocean heat uptake.”  They verify that no reduction in the sun’s radiation was found which could explain the “pause”.

Chen and Tung (Science Vol. 345, pp. 897-903 (2014)  DOI: 10.1126/science.1254937) analyzed earlier data as well as more extensive newer observations gathered by buoys disposed worldwide at various ocean depths.  They found that “the [“pause”] is mainly caused by heat transported to deeper layers in the Atlantic and the Southern oceans….Cooling periods associated with the latter deeper heat-sequestration mechanism historically lasted 20 to 35 years.”  They further conclude “because the planetary heat [reservoirs] in the Atlantic and the Southern Oceans remain intact, the [“pause”] should continue on a decadal time scale. When the internal variability that is responsible for the current [“pause”] switches sign, as it inevitably will, another episode of accelerated global warming should ensue.”

© 2015 Henry Auer

Deniers Mistakenly Say that Global Warming Has Ended

Global Average Temperatures and CO₂.  The global average temperature has increased by about 0.7-0.8ºC (1.3-1.4ºF) over pre-industrial values.  Humanity’s use of fossil fuels to power industrialization emits carbon dioxide (CO₂), a greenhouse gas, leading to warmer average temperatures.  Analysis of the increased CO₂ levels shows that they arise directly from burning fossil fuels, and not from natural causes (see also the U. S. National Climate Assessment).

Climate deniers do not accept that our planet is warming, and/or that human activity is its cause.  Climate skeptics may question that human actions are responsible for warming, or that warming is harmful to human populations and other life forms.  Here both groups will be called “deniers”.

Climate deniers claim that global warming has ended.  They selectively display global temperature data for, say, the period 1980 to the present, as shown in this graphic:

 

 

Yearly values of the global average temperature selected for the interval 1980-2013, shown as their difference from the average temperature for the entire 20^th century.

Source: Data table from National Aeronautics and Space Administration;

http://data.giss.nasa.gov/gistemp/graphs_v3/Fig.A2.txt.

 

 

Other more biased presenters don’t show any data before 1997.  These deniers point to the interval after 1997 as showing that the temperature has remained essentially unchanged (here called the “pause”), breaking with the upward trend from 1980 to 1997.  Since atmospheric CO₂ concentrations continued to increase during the pause period (see below), deniers state that increasing atmospheric concentrations of CO₂ cannot be the cause for global warming.

 

Deniers  cannot selectively choose the data they wish to use while rejecting the entire data set from consideration.  It is unacceptable to focus arbitrarily on only the period supporting their view while ignoring the extended global temperature record.  Data covering most of the industrial era, 1880-present, are shown below. 

 

Yearly values of the global average temperature for 1880-2013, shown as the differences from the average temperature for the entire 20^th century.  Black points and line, annual average temperature differences; Red line, smoothing obtained as a 5-year running window centered at each data point; Green, error bars showing estimates of uncertainty in the measurements.

Source: National Aeronautics and Space Administration.  http://data.giss.nasa.gov/gistemp/graphs_v3/

 

 

The overall trend shows a clear, if uneven, rise in the global average temperature beginning at about 1910, coinciding with increasing atmospheric levels of CO₂ (see below and this post).  Importantly, a seemingly long pause also occurred from about 1950-1975, followed by more than 20 years in which the temperature rose sharply.  It is noteworthy that deniers fail to mention this earlier pause as evidence that warming has ceased.

 

A Simple Inert Earth Model.  Deniers are incorrectly assuming that in the Earth system, the only factor affecting the air temperature around the globe is the amount of CO₂ in the atmosphere.  Such a simple model, featuring an inert Earth, may be illustrated using the following graphic.  

Model for a simplified inert Earth system close to radiation balance.  It re-emits much of the sun’s energy back into space as heat (infrared) radiation.  In this model only the atmosphere retains excess heat.  © Henry Auer

 

In essence, deniers ignore any additional components in the Earth system that affect the energy balance.

A Complex Earth System Model.  Why is the Earth’s temperature record so erratic?  Why do these pauses occur?  The answer to these questions is that the Earth is not a simple object inert to the effects of the sun’s energy.  Rather, the Earth is a complex system that responds to inputs of excess energy from the sun in many ways.  This can be modeled by a complex Earth system in the image below.

Model of the Earth system, including CO₂ in its atmosphere and potential reservoirs of heat in the land, the oceans and the polar ice caps.  This Earth is not in energy equilibrium; less energy is radiated back into space than the energy falling on it from sunlight.  The extra energy heats the entire earth system, with most of the heat being stored in the ocean rather than in the atmosphere. © Henry Auer

 

This more realistic model for Earth is not in energy balance.  Direct satellite measurements of radiation leaving Earth are compared with sunlight energy reaching the Earth.  Because of the greenhouse effect the Earth retains excess heat, rather than re-emitting it back into space.  

Most of the retained heat is stored in the oceans, and not in the atmosphere.  This is why deniers are mistaken by speaking in terms of an inert Earth model, i.e., in assuming that the temperature in the atmosphere is determined only by the atmospheric CO₂ concentration.  This is shown in the following graphic.

 

Top panel: Total heat energy stored in the top half-mile of Earth’s oceans compared to the average from 1955-2006.  Middle panel: Yearly global average temperature compared to the average value for the full 20^th century (repeating the pattern shown in the earlier graphic).  Bottom panel: Direct measurement of atmospheric CO₂ from 1958 in parts per million (ppm).

Source: National Oceanic and Atmospheric Administration;

http://www.climate.gov/maps-data.

 

 

It is seen from the lower panel that the CO₂ concentration has been rising steadily since 1958; indeed a smooth curve such as seen here extends back to pre-industrial times, when the concentration was 280 ppm.  The pronounced variability in the temperature data (middle panel) contrasts with the smooth, steady increasing trend seen  for CO₂.  This suggests, as indicated above, that factors other than only the atmospheric CO₂ concentration are at play. 

 

90% of the excess heat retained in the Earth system is stored in the oceans.  The data in the top panel show that heat energy absorbed by the oceans has been steadily increasing since at least about 1970, including the prior pause of global atmospheric temperature, and has continued to increase even during the current pause.  Instead of ending up warming the atmosphere, excess heat has been absorbed into the oceans, warming them (see the Details section at the end of this post).  Since oceans have decade-long cycles of vertical as well as lateral currents, this heat remains latent in the oceans, but will eventually be transferred back to the atmosphere, renewing the trend of increasing global atmospheric temperature.  

 

Conclusion

 

The long-term global average temperature has increased by about 0.7-0.8ºC over pre-industrial temperatures.  A current pause of annual global temperatures began after 1997 even though the atmospheric concentration of CO₂ continued to increase during this period.  Global warming deniers have seized on this pause to say that warming of the Earth has ended, since the air temperature has not responded to the increased CO₂ concentration on a year-by-year basis. 

 

In fact direct measurements of the Earth’s energy balance show that it does retain excess heat, but does not store it in the atmosphere.  Rather, the excess heat enters the oceans.  It is stored there as deep as 1,500 m (4,920 ft) in slow-moving ocean currents, both lateral and vertical.  As the warmer water is lifted to the surface again, it will exchange this stored heat with the atmosphere, resuming the warming of the air.  Similar processes happened in an earlier pause event.  Global (atmospheric) warming continues on the extended time scales dictated by Earth system processes.  Global warming deniers are mistaken in saying that global warming has ended.

 

Details

 

Guemas and coworkers (Nature Climate Change vol. 3, pp. 649–653 (2013); doi:10.1038/nclimate1863)  examined the current pause in global warming.  They used earlier data as a baseline to project sea surface temperatures forward up to 2010 using a coupled ocean-atmosphere climate model.  From their results they “attribute the onset of [the pause] to an increase in ocean heat uptake.”  They verify that no reduction in the sun’s radiation can explain the pause.

 

Loeb and coworkers (Nature Geoscience, vol. 5, pp. 110–113 (2012); doi:10.1038/ngeo1375) compared the energy imbalance of the Earth system with ocean heat content.  They measured radiated heat energy and sea temperatures.  They found that the energy imbalance of the Earth system and the increase in the upper-ocean heat content are similar in magnitude.  Combining satellite temperature measurements and ocean heat measurements to 1,800 m (5,900 ft) they found “between January 2001 and December 2010, Earth has been steadily accumulating energy at a [significant rate]. We conclude that energy storage is continuing to increase in the sub-surface ocean.”

 

Chen and Tung (Science Vol. 345, pp. 897-903 (2014)  DOI: 10.1126/science.1254937) analyzed earlier data as well as more extensive newer observations gathered by buoys disposed worldwide at various ocean depths.  They found that “the [pause] is mainly caused by heat transported to deeper layers in the Atlantic and the Southern oceans….Cooling periods associated with the latter deeper heat-sequestration mechanism historically lasted 20 to 35 years.”  They further conclude “because the planetary heat [reservoirs] in the Atlantic and the Southern Oceans remain intact, the [pause] should continue on a decadal time scale. When the internal variability that is responsible for the current [pause] switches sign, as it inevitably will, another episode of accelerated global warming should ensue.”

 

© 2014 Henry Auer