Global Temperature In Climate Change

by Harrison Schmitt

Ten thousand years of natural, post-Ice Age climate variability should give pause to those who maintain that current slow global warming and carbon dioxide increases result largely from human use of fossil fuels.

Public confidence in that position also suffers from the exposure of fraudulent academic and bureaucratic behavior aimed at overriding normal processes of skeptical scientific review and debate.

In the face of diligent and realistic climate observations by others, believers in human-caused global warming and their tightly bound socialist supporters have circled the wagons. The National Academy of Science, Nature and Science magazines, and the mainstream climate establishment have increased the volume, but not the reasonableness, of both their denunciations of disagreeing scientists and their rationalizations for the missteps of other scientists with whom they agree.1 The “human-caused global warming” community continues to talk only to themselves instead of engaging in a reasonable dialog with reputable disagreeing scientists. These latter scientists want objective enquiry to take place before forcing unconstitutional legislative and regulatory decisions on an increasingly skeptical electorate -decisions that will cost both liberty and the American economy dearly.

Observational data and interpretations related to global temperature and atmospheric carbon dioxide deserve close examination before taking irrevocable and dangerous regulatory actions. If there were no other factors affecting temperature at the Earth’s surface, the balance between heat from the sun and heat re-radiated from the Earth to space would give an average surface temperature of about zero degrees Fahrenheit (-18 degrees Centigrade).2 Not good. Fortunately, natural greenhouse heat trapping effects of atmospheric water and to a much lesser extent carbon dioxide and methane, add about 146 thermal watts per square meter (versus the Sun’s irradiance of 1366 watts per square meter) so that the average surface temperature of the Earth becomes about 59 degrees Fahrenheit (15 degrees Centigrade),3 making the planet habitable rather than being a ball of ice covered rock and water with occasional volcanic eruptions.

Geological investigations indicate that over the last 600 million years average global surface temperature appears to have been buffered roughly at a maximum of about 72 degrees Fahrenheit (22 degrees Centigrade)4. The last 53 million years being significantly colder than the previous average5, as indicated by oxygen isotopes of shells in sea floor cores,6 but comparable to other cold periods in the geologic past. During this 600 million year period, major cold perturbations to about 54 degrees Fahrenheit (12 degrees C) occurred about every 150 million years.7 Over that period, carbon dioxide decreased from an estimated maximum of about 7000ppm 550 million years ago to minimum of about 300ppm around 300 million years ago8 (current level at 385ppm) without changing the long-term average temperature at the Earth’s surface.

Around 43 million years ago, declining carbon dioxide concentration reached about 1400ppm, followed by three oscillations during the next 10 million years with amplitudes of about 1000ppm.9 Temperature apparently remained relatively constant during these ancient carbon dioxide oscillations except during the most recent when oxygen isotope ratios indicate a sharp drop in temperature10 33.5 million years ago, that is, about the time ice sheets began to accumulate on Antarctica.11 Relative to today’s values, declining atmospheric carbon dioxide levels remained relatively high (740-1400ppm) as Antarctica cooled.

About 22 million years ago, with its continued slow migration away from Africa, Australia, and South America, the ocean distribution and ocean currents around Antarctica began to resemble modern configurations,12 with partial deglaciation of that continent beginning about 14-15 million years ago.13 A particularly warm two million years for the tropical Earth latitudes developed about 4 million years ago even as sea surface temperatures slowly declined toward present levels.14 This seemingly contradictory situation apparently related to a long-term north-south expansion of the warm tropical ocean waters resulting in a factor of four reduction in the sea surface temperature gradient from the equator to at least 34ºN (~2ºC gradient versus ~8ºC, today) that lasted until about 1.5 million years ago. Along with disruptions of the El Niño Southern Oscillation, convective tropical Hadley circulation apparently slowed during this long period with both effects probably leading to significant global climate impacts.

About 2.75 million years ago,15 major ice ages began to oscillate with periods of warmth (interglacials). This occurred in spite of the concurrent anomaly in the tropical sea surface temperature gradient. Ten specific high latitude ice ages took place in the last million years, apparently correlated with a change in the dominant solar influence on cooling from the Earth’s 41,000-year orbital obliquity cycle to its 100,000-year eccentricity cycle.16 A significant decrease in the overall concentration of atmospheric carbon dioxide occurred at about the same time as this change in orbital influence with even greater, temporary reductions associated with each ice age; however, the reported data do not support a causal association of this decrease in carbon dioxide with the overall cooling during this million-year period.17

Compilations of temperature changes in the oceans and seas, as preserved by oxygen isotope variations in shells from cores of bottom sediments, provide a record of natural cycles of major climate change back for 1.8 million years.18 For example, geological analysis of sea level changes over the last 500,000 years show a remarkable correlation with major natural climate change.19 These data further indicate that the Earth probably is approaching the peak of the warming portion of a normal climate cycle that began with the end of the last Ice Age.20

Terminations of past ice ages appear to be associated with increased solar heating (insolation), as orbital influences changed, and not with triggering increases in carbon dioxide levels; although such increases certainly accompanied the terminations. Recent suggestions that increase in atmospheric carbon dioxide forced temperature changes and ice age terminations over the last 20 million years or so21 suffer from science’s inability to adequately time-correlate changes in carbon dioxide levels with changes in global temperature, i.e., correlation does not, by itself, mean causation. As carbon dioxide release from the oceans due to warming lags warming by hundreds to thousands of years, no support exists for a conclusion that a specific natural carbon dioxide change forced a specific temperature change.

The lesson in these variations in values for atmospheric carbon dioxide and global temperature through geologic time, at least at a million-year or so time-resolution, appears to be that increases and decreases in carbon dioxide have not triggered global temperature changes as derived from fossil oxygen isotope ratios. Other long-term geological and solar-related phenomena may have overwhelmed any broad greenhouse effects related to carbon dioxide; or, alternatively, the proxies used for estimating ancient atmospheric carbon dioxide concentrations may be invalid.22 All we really know at present is that natural variations in climate have been very complex, often extreme, and all before human industrial activity existed.

Studies of Antarctic ice cores indicate that Earth-surface temperatures several degrees warmer than present existed during the four preceding interglacials of the last 420,000 years.23 At a low time-resolution of 1000s of years, carbon dioxide in the atmosphere apparently did not rise above 290ppm (compared to 385ppm today), and its changes would appear to be correlated directly with temperature changes.24 On the other hand, high time-resolution ice core data indicates that both increases and decreases in atmospheric carbon dioxide lag associated increases and decreases in global temperature by hundreds to a thousand years for major long-term temperature variations.25 The rise or fall in average ocean temperature would be expected proceed any effect on stored carbon dioxide due to the oceans’ relatively high mass and slow circulation.

A particularly prolonged warm period in the current interglacial between 9000 and 6000 years ago has been documented, most recently in oxygen isotopic analyses of Greenland ice sheet cores.26 That warm period resulted in significant thinning of Greenland’s ice sheet to thicknesses within a 100m of those of today. Several other warm periods have occurred since, the most pronounced of which has been termed the Medieval Warm Period (500-1300)27 . Warm periods, sometimes referred to as “climate anomalies,” of this nature were largely highly beneficial to fledgling human cultures. During the latter centuries of the Medieval Warm Period, however, overpopulation relative to available technology, severe weather and drought, and other factors forced migrations from many centers of civilization,28 primarily to places with more reliable water resources. These adverse effects of warming, however, stand in contrast to the advantageous migrations of modern humans about 22,000 years ago from Asia into the Americas during the last Ice Age. At that time, low sea levels created a land bridge between Asia and North America.29 Adaptability is the key.

After a century-long transition from the Medieval Warm Period, the Little Ice Age of 1400-1900 recorded the most recent interval of significant global cooling. Global cooling characterized the Little Ice Age in most regions, accompanied in some areas by droughts.30 By 1400, however, Artic ice pack had enclosed Iceland and Greenland and driven Viking settlers away from their farms on those islands.31 By the end of the 1600s, in response to the continued climate cooling, glaciers had advanced over valley farmlands cultivated as those same glaciers receded during the Medieval Warm Period.32 Indeed, essentially all of the consequences of warming prior to 1300 reversed during the next several hundred years of the Little Ice Age.

Since about 1660, gradual global warming of about 0.9 degree Fahrenheit (0.5 degree Centigrade) each 100 years has occurred33, although decades-long cooling events have interrupted this trend. Antarctic sea ice, however, now has been expanding northward for about two decades34 after indications in the Law Dome ice core of an additional gradual decline between about 1960 and 1990.35

As geological proxy records for temperature approach the present, analyses show that measurement of modern, short-term trends in Earth surface temperature are suspect36, if only because thousands of rural measuring stations have disappeared in favor of reliance on airport and other urban stations. 37 Difficulties also arise from many land sensors being located within the expanding effect of urban heat islands38 and many sea surface temperature measurements being inconsistently determined39 . Rigorous investigation and analysis of the sources of data that appear to show Earth surface warming accelerating during the last century indicates many non-climatic factors may influence the quality and magnitude of measurements40 if not the overall trend in slow warming.

After 1979, earth-orbiting satellites have provided precise data on temperature variations through globally averaged, microwave determination of temperatures of the lower atmosphere.41 These measurements are independent of local biases affecting temperatures measured at weather stations42 .

Although the observational, historical, and geological evidence indicates strongly that global scale changes in the climate, ocean chemistry, and biological activity have roots in natural processes, the concentration of human pollution in local areas of the Earth have documented adverse impacts.43 It remains increasingly in the economic and societal interests of the private sector and State governments to stop and reverse the unnatural changes for which they bear constitutional responsibility.

Private sector, State, and Federal control of their contributions to regional local pollution effects, and consumer, shareholder, and voter insistence on prevention and cleanup, form an integral part of the nation’s future. Appropriate and restrained Federal regulation within the Founders’ logically constrained intent of Article I, Section 8, Clause 3, of the Constitution, that is, the Commerce Clause, can contribute greatly to the instigation of this new environmental ethic. On the other hand, unconstitutional coercion will make matters worse while at the same time eroding essential liberties. The long road back to constitutional protection of the environment begins with the elections of 2010.


Harrison H. Schmitt is a former United States Senator from New Mexico as well as a geologist and former Apollo Astronaut. He currently is an aerospace and private enterprise consultant and a member of the new Committee of Correspondence


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41 See www.drroyspencer.com/latest-global-temperatures.

42 D’Aleo, J. and A. Watts, 2010. Surface Temperature Records: Policy Driven Deception?, Science & Public Policy Institute, SPPI (Haymarket, VA) January 29, 2010.

43 Doney, S. C., 2010, The growing human footprint on coastal and open-ocean biogeochemistry, Science, 328, pp. 1512-1516.

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