Causes of climate change

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SHEBA (Surface Heat Budget of the Arctic Ocean) researchers taking data in a melted area of the Arctic Ocean ice pack. (Source: Donald K. Petrovich)


March 5, 2010, 11:10 am
May 14, 2021, 04:14 pm

Introduction

Causes of climate change generally have been natural factors throughout the Earth history. Changes in the state of the climate system can occur externally (from extraterrestrial systems) or internally (from ocean or atmosphere) through any one of the described components. For example, an external change may involve a variation in the sun's output which would externally vary the amount of solar radiation received by the Earth's atmosphere and surface. Internal variations in the Earth's climatic system may be caused by changes in the concentrations of atmospheric gases, mountain building, volcanic emissions, and changes in surface or atmospheric reflectivity (albedo).

The most reliable measure of Earth temperature change is ocean temperature, since terrestrial measures are subject to biases from the urban heat island effect, whereby many of the global temperature sensors are steadily being encroached upon by urbanization. Using proxy methods covering both the Atlantic and Pacific Oceans, it has been found that the recent trend in the last 9000 years is one of steady ocean cooling; this effect has been attributed partially to the melting of polar ice, creating cooler oceans. The trend has continued through the Industrial Revolution and into the current era. (Rashid & Polyak, 2011) This current long term ocean cooling amounts to approximately 1.5 degrees Celsius, and may also be affected by solar and orbital cycles producing the greater, approximately 60,000-year global cooling cycle that we are presently in. The present Earth mean temperature has generally declined over the last five thousand years, except for upticks in the Roman Period and Medieval warming Period; thus, even with the recent increases in greenhouse gases, temperature globally is less than the preindustrial era. (Briffa et al, 2007)
New Zealand and Tasmania proxy temperature records over the last millennium. Source: Cook et al, 2002
To view a longer-term perspective on terrestrial temperature records, one can view a 1000-year account of New Zealand and Tasmania temperatures, from one of the most detailed tree ring studies that span the last millennium. (Cook et al, 2002) As one can see, the millennium graph does not conclude a warming trend in the current period associated with greenhouse gas rise; in fact, there are at least seven prior decadal instances with higher temperatures than the prior century. Thus, the millennium record produces no evidence of a present global warming trend. Nor is there any basis for concluding that carbon dioxide emissions or any other greenhouse gas is producing a warming trend in the current era.

The work of climatologists has found evidence to suggest that only a limited number of factors are primarily responsible for most of the past episodes of climate change on the Earth. These factors include:

  • Variations in the Earth's orbital characteristics.
  • Changes in ocean circulation
  • Man-made energy expenditures and urban heat islands
  • Atmospheric greenhouse gas variations.
  • Volcanic eruptions
  • Variations in solar output.
  • Albedo variation
Figure 1: Factors that influence the Earth's climate. (Source: PhysicalGeography.net)

From a review of 11,944 scientific papers reviewed, the following consensus was revealed: only 0.3 % of the research concluded that humans are responsible for most of the warming of the Earth since 1950; 32.4% of the research concluded that mankind is responsible for some of the Earth warming of the recent century. As a practical matter the majority of the research had no opinion as to whether human activity has had any impact on Earth temperature change in the last century. (Cook, 2013)

Variations in the Earth's Orbital Characteristics

Figure 2: Modification of the timing of Aphelion and Perihelion over time (A = today; B = 13,000 years into the future). (Source: PhysicalGeography.net)

The Milankovitch theory suggests that normal cyclical variations in three of the Earth's orbital characteristics is probably responsible for some past climatic change. The basic idea behind this theory assumes that over time these three cyclic events vary the amount of solar radiation that is received on the Earth's surface.The first cyclical variation, known as eccentricity, controls the shape of the Earth's orbit around the sun. The orbit gradually changes from being elliptical to being nearly circular and then back to elliptical in a period of about 100,000 years. The greater the eccentricity of the orbit (i.e., the more elliptical it is), the greater the variation in solar energy received at the top of the atmosphere (Atmosphere layers) between the Earth's closest (perihelion) and farthest (aphelion) approach to the sun. Currently, the Earth is experiencing a period of low eccentricity. The difference in the Earth's distance from the sun between perihelion and aphelion (which is only about 3%) is responsible for approximately a 7% variation in the amount of solar energy received at the top of the atmosphere. When the difference in this distance is at its maximum (9%), the difference in solar energy received is about 20%.

The second cyclical variation results from the fact that as the Earth rotates on its polar axis, it wobbles like a spinning top changing the orbital timing of the equinoxes and solstices (see Figure 2). This effect is known as the precession of the equinox. The precession of the equinox has a cycle of approximately 26,000 years. According to illustration A in Figure 2, the Earth is closer to the sun in January (perihelion) and farther away in July (aphelion) at the present time. Because of precession, the reverse will be true in 13,000 years and the Earth will then be closer to the sun in July (illustration B, Figure 2). This means, of course, that if everything else remains constant, 13,000 years from now seasonal variations in the Northern Hemisphere should be greater than at present (colder winters and warmer summers) because of the closer proximity of the Earth to the sun.

The third cyclical variation is related to the changes in the tilt (obliquity) of the Earth's axis of rotation over a 41,000 year period. During the 41,000 year cycle the tilt can deviate from approximately 22.5 to 24.5°. At the present time, the tilt of the Earth's axis is 23.5°. When the tilt is small there is less climatic variation between the summer and winter seasons in the middle and high latitudes. Winters tend to be milder and summers cooler. Warmer winters allow for more snow to fall in the high-latitude regions. When the atmosphere is warmer it has a greater ability to hold water vapor and therefore more snow is produced at areas of frontal or orographic uplift. Cooler summers cause snow and ice to accumulate on the Earth's surface because less of this frozen water is melted. Thus, the net effect of a smaller tilt would be more extensive formation of glaciers in the polar latitudes.

Periods of a larger tilt result in greater seasonal climatic variation in the middle and high latitudes. At these times, winters tend to be colder and summers warmer. Colder winters produce less snow because of lower atmospheric temperatures. As a result, less snow and ice accumulates on the ground surface. Moreover, the warmer summers produced by the larger tilt provide additional energy to melt and evaporate the snow that fell and accumulated during the winter months. In conclusion, glaciers in the polar regions should be generally receding, with other contributing factors constant, during this part of the obliquity cycle.

The dominant long term driver of climate change is orbital variation, which places the Earth in a long term cooling trend starting in around 6000 BC and enduring to present. Computer models and historical evidence suggest that the Milankovitch cycles exert their greatest cooling and warming influence when the troughs and peaks of all three cycles coincide with each other.

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Urban heat islands

A major factor induced by heat islands is their encroachment upon historic temperature sensors. The global network used for tracking worldwide temperature change, by definition, is a rather static network of thermal sensors; this is intentional so that one can portray a theoretical objective account of the time history of temperature. However, a major bias has become inherent, in that most of the sensors were placed seventy to 140 years ago in suburban or rural areas. At present most of these sensors have been subsumed into ever growing urban heat islands. Thus the portrayal of one degree temperature rise worldwide over the prior 140 years is a complete distortion and exaggeration of temperature rise. This is a considerable problem, in that some countries are placing large energy policy investments, based upon a fallacious assumption of exaggerated temperature increase.

Li and Zhao found that the urban heat island effect is responsible for between 0.14 and 0.25 degrees Celsius of the reported decadal termperature rise in meteorological reporting stations analyzed in China (Li and Zhao, 2012). Similarly Huang analyzed 41 meteorological stations in the Yangtze River basin and found that  0.18 to 0.48 degrees Celsius of reported temperature rise was attributed to urban heat island effects, and not atmospheric global warming. (Huang, 2015)  The Huang study spanned the interval 1957 to 2013, the very period when global temperature reports showed the largest rise in global temperatures. Huang states that "Cities have a warmer climate than rural areas due to the urban heat island, which represents one of the most significant human-induced changes to earth’s surface climate". Raj et al. studied 44 major cities in India and concluded the urban heat island effect (not global warming) accounts for approximately 2 degrees Celsius rise in reported temperature rise. (Raj et el, 2020).

Zwang et al analyzed energy consumption in Asia and North America, concluding that anthropogenic energy sources (especially in Northern Hemisphere winter) accounts for about 1.0 degrees Celsius of the reported global temperature rise of the last century in those regions, or the great majority of reported surface temperature change. (Zwang et al, 2013). They "conclude that energy consumption is probably a missing forcing for the additional winter warming trends in observations." Broadbent et al. (Broadbent et al. 2020) )studied 47 US cities, concluding that the projections of significant temperature rise in North America should be focused on selected major US cities where population increase and urban heat island exacerbation will create greater temperature rise than greenhouse gases; some of these major cities are New York, Washington DC, Los Angeles, Miami, Atlanta and Austin.

Hansen et al (Hansen et al, 2001) report that urban local warming is an important aspect of reported global warming and that "post-1930s cooling was much larger in the United States than in the global mean. The U.S. mean temperature has now reached a level comparable to that of the 1930s, while the global temperature is now far above the levels earlier in the century. The successive periods of global warming (1900-1940), cooling (1940-1965), and warming (1965-2000) in the 20th century show distinctive patterns of temperature change are suggestive of roles for both climate forcings and dynamical variability. The U.S. was warm in 2000 but cooler than the warmest years in the 1930s and 1990s."
Furthermore temperatures in the most recent fifty years are much cooler than in historic periods such as the Medieval Warm Period and Roman Warm Period, both of which were flourishing eras of low disease, low mortality and high crop production.

Atmospheric greenhouse gas variation

Figure 3: The following graph illustrates the rise in atmospheric carbon dioxide from 1744 to 2005. Note that the increase in carbon dioxide's concentration in the atmosphere (Atmosphere layers) has been exponential during the period examined. An extrapolation into the immediate future would suggest continued increases. (Source: PhysicalGeography.net)

Researchers of the 1970s CLIMAP project found strong evidence in deep-ocean sediments of variations in the Earth's global temperature during the past several hundred thousand years of the Earth's history. Other subsequent studies have confirmed these findings and have discovered that these temperature variations were correlated to the (a) concentration of carbon dioxide in the atmosphere and (b) variations in solar radiation received by the planet as controlled by the Milankovitch cycles. Measurements indicated that atmospheric carbon dioxide levels were about 30% lower during colder glacial periods. It was also theorized that the oceans were a major store of carbon dioxide and that they controlled the movement of this gas to and from the atmosphere. The amount of carbon dioxide that can be held in oceans is a function of temperature. Carbon dioxide is released from the oceans when global temperatures become warmer and diffuses into the ocean when temperatures are cooler. Initial changes in global temperature were triggered by changes in received solar radiation by the Earth through the Milankovitch cycles. The increase in atmospheric greenhouse gases then amplified warming by enhancing the greenhouse effect.

Over the past three centuries, the concentration of greenhouse gases has been increasing in the Earth's atmosphere partially because of human influences (Figure 3). Human activities like deforestation, combustion of fossil fuels, human population growth producing increased respired CO2, conversion of natural prairie to farmland, and deforestation have caused the release of carbon dioxide and water vapor into the atmosphere. From the early 1700s, carbon dioxide has increased from 280 parts per million to 380 parts per million in 2005. Twenty first century studies show that the forcing effect of carbon dioxide is highly non linear, in the sense that further rise in CO2 will lead to much smaller change in temperature. These analyses indicate that the warming effect of atmospheric carbon dioxide may peak after addition of a further twenty percent rise in carbon dioxide; (Knutti and Hegeri, 2006) in fact, such a peak may have already occurred or may soon occur.

However, no scientific analysis has concluded that carbon dioxide is responsible for climate change. In fact, a number of scientific papers have concluded that carbon dioxide cannot be the source of modern weather variations. (Principia Scientific, 2023) Moreover, there is no data that suggests global climate is changing in a manner different from the millennia of natural climate change cycles.

More recently, bitcoin mining has significantly contributed to concentrations of carbon dioxide. However, there is a greater present percentage increase of the more potent greenhouse gas, Nitrogen Trifluoride Some scientists believe that higher concentrations of greenhouse gases in the atmosphere will enhance the greenhouse effect. Scientists globabelieve we may be already experiencing global warming due to an enhancement of the greenhouse effect; however, recent trends since 2007 show a cooling trend in global temperature and an expansion of Arctic sea ice and expansion of the Earth's largest ice sheet, the East Antarctic Ice Sheet; thus, Earth may actually be in a global cooling era beginning in about 2010.

Volcanic Eruptions

For many years, climatologists have noticed a connection between large explosive volcanic eruptions and short-term climatic change (Figure 4). For example, one of the coldest years in the last two centuries occurred the year following the Tambora volcanic eruption in 1815. Accounts of very cold weather were documented in the year following this eruption in a number of regions across the planet. Several other major volcanic events also show a pattern of cooler global temperatures lasting one to three years after their eruption.

Figure 4: Explosive volcanic eruptions have been shown to have a short-term cooling effect on the atmosphere (Atmosphere layers) if they eject large quantities of sulfur dioxide into the stratosphere. This image shows the eruption of Mount St. Helens on May 18, 1980 which had a local effect on climate because of ash reducing the reception of solar radiation on the Earth's surface. Mount St. Helens had very minimal global effect on the climate because the eruption occurred at an oblique angle putting little sulfur dioxide into the stratosphere. (Source: U.S. Geological Survey, photograph by Austin Post).
Figure 5: Ash column generated by the eruption of Mount Pinatubo on June 12, 1991. The strongest eruption of Mount Pinatubo occurred three days later on June 15, 1991. (Source: U.S. Geological Survey).


Initially, scientists thought that the dust emitted into the atmosphere from large volcanic eruptions was responsible for the cooling by partially blocking the transmission of solar radiation to the Earth's surface. However, measurements indicate that most of the dust thrown in the atmosphere returned to the Earth's surface within six months. Recent stratospheric data suggests that large explosive volcanic eruptions also eject large quantities of sulfur dioxide gas which remains in the atmosphere for as long as three years. Atmospheric chemists have determined that the ejected sulfur dioxide gas reacts with water vapor commonly found in the stratosphere to form a dense optically bright haze layer that reduces the atmospheric transmission of some of the sun's incoming radiation.

In the last century, two significant climate-modifying eruptions have occurred. El Chichon in Mexico erupted in April of 1982, and Mount Pinatubo went off in the Philippines during June, 1991 (Figure 5). Of these two volcanic events, Mount Pinatubo had a greater effect on the Earth's climate and ejected about 20 million tons of sulfur dioxide into the stratosphere (Figure 6). Researchers believe that the Pinatubo eruption was primarily responsible for the 0.8 degree Celsius drop in global average air temperature in 1992. The global climatic effects of the eruption of Mount Pinatubo are believed to have peaked in late 1993. Satellite data confirmed the connection between the Mount Pinatubo eruption and the global temperature decrease in 1992 and 1993. The satellite data indicated that the sulfur dioxide plume from the eruption caused a several percent increase in the amount of sunlight reflected by the Earth's atmosphere back to space causing the surface of the planet to cool.

Figure 6: The following satellite image shows the distribution of Mount Pinatubo's sulfur dioxide and dust aerosol plume (red and yellow areas) between June 14 and July 26, 1991. Approximately 45 days after the eruption, the aerosol plume completely circled the Earth around the Equator forming a band 20 to 50° of Latitude wide. Areas outside this band were clear of volcanic aerosols. Within a year, the sulfur dioxide continued to migrate towards the North and South Pole until it covered the entire Earth because of the dominant poleward flow of Stratospheric winds (stratospheric winds circulate from the equator to the polar vortices at the North and South Poles). These observed patterns of aerosol movement suggest that tropical explosive [[volcanic] eruptions] probably have the greatest effect on the Earth's climate. Diffusion of aerosols by stratospheric winds from a tropical source results in the greatest latitudinal coverage of the sulfur dioxide across both the Northern and Southern Hemispheres. (Source: SAGE II Satellite Project - NASA)

Variations in Solar Output

Until recently, many scientists thought that the sun's output of radiation only varied by a fraction of a percent over many years. However, measurements made by satellites equipped with radiometers in the 1980s and 1990s suggested that the sun's energy output may be more variable than was once thought (Figure 7). Measurements made during the early 1980s showed a decrease of 0.1 percent in the total amount of solar energy reaching the Earth over just an 18 month time period. If this trend were to extend over several decades, it could influence global climate. Numerical climatic models predict that a change in solar output of only 1 percent per century would alter the Earth's average temperature by between 0.5 to 1.0° Celsius.

Figure 7: Image of the sun taken by the Solar and Heliospheric Observatory (SOHO) satellite on 14 September 1997. The sun is essentially the only source of energy for running the Earth's climate. Thus, any change in its output will result in changes in the reception of insolation and the generation of Heat energy which drives the climate system. (Source: Solar and Heliospheric Observatory)

Scientists have long linked sunspots to climatic change. Sunspots are huge magnetic storms that are seen as dark (cooler) areas on the sun's surface. The number and size of sunspots show cyclical patterns, reaching a maximum about every 11, 90, and 180 years. The decrease in solar energy observed in the early 1980s correspond to a period of maximum sunspot activity based on the 11 year cycle. In addition, measurements made with a solar telescope from 1976 to 1980 showed that during this period, as the number and size of sunspots increased, the sun's surface cooled by about 6° Celsius. Apparently, the sunspots prevented some of the sun's energy from leaving its surface. However, these findings tend to contradict observations made on longer times scales. Observations of the sun during the middle of the Little Ice Age (1650 to 1750) indicated that very little sunspot activity was occurring on the sun's surface. The Little Ice Age was a time of a much cooler global climate and some scientists correlate this occurrence with a reduction in solar activity over a period of 90 or 180 years. Measurements have shown that these 90 and 180 year cycles influence the amplitude of the 11 year sunspot cycle. It is hypothesized that during times of low amplitude, like the Maunder Minimum, the sun's output of radiation is reduced. Observations by astronomers during this period (1645 to 1715) noticed very little sunspot activity occurring on the sun.

During periods of maximum sunspot activity, the sun's magnetic field is strong. When sunspot activity is low, the sun's magnetic field weakens. The magnetic field of the sun also reverses every 22 years, during a sunspot minimum. Some scientists believe that the periodic droughts on the Great Plains of the United States are in someway correlated with this 22 year cycle.

Albedo variation

Albedo, or solar reflectivity at the Earth surface, is affected by several major factors: extent of forestation, extent of glacial ice and snow, microtopography, pavement, for example. Thus human activities such as deforestation, microtopographic

change due to urbanization, and paving with concrete or using reflective roofing contribute to albedo increase and hence to global warming effects. On the other hand, glacial melt decreases albedo, and hence serves as a negative feedback loop to the extent any terrestrial warming occurs.

Major climate change periods

Proxy paleoclimate data for terrestrial lands in the Molucca Sea demonstrate that greatest wildfire frequencies occurred in the Early Holocene, rather than in Industrial Era or modern time. (Haberle et al, 2010) Detailed proxy studies from southern Europe demonstrate that some of the greatest swings in climate occurred in the early and middle Holocene. At about 3700 BC a major change leading to drier conditions contributed to a decline in mesophytes, expansion of pines and junipers, and a significant lake level drop. In these very dry conditions fire frequency and intensity reached their highest points of the last 10,000 years (including current times). Later at the onset of the Roman Warming Period, temperatures rose, but fire frequency declined, partially as a consequence of vegetative biomass reduction from flourishing human activity. Two major arid intervals occurred between 900 and 200 BC. Another period of increasing fire frequency arose in the Little Ice Age. Thus, long time history of the recent 10,000 years demonstrates that wildfire frequency and intensity is not correlated with global warming or aridity. (A. Pérez-Sanz et al, 2013)

Paleocene-Eocene Thermal Maximum

The Paleocene-Eocene Thermal Maximum (PETM) is a climate event that occurred approximately 55.5 million years before present. Earth temperatures rose roughly five to nine degrees Celsius throughout the terrestrial Earth, and this period was the warmest in recent Earth history, defined here as the most recent 65 million years. The cause of this event is not clearly known, except that it was clearly a natural occurrence. The most common hypothesis is that considerable amounts of methane hydrates were released into the atmosphere from ocean sediments, possibly triggered by volcanic eruptions. Considerable increases in ocean and atmospheric CO2 also were present. The thermal event led to a diversity explosion of primates and other mammals, and also proliferation of certain food plants, particularly in the bean family. The thermal event also caused an important proliferation of biotic diversity in the upper oceans, where temperature rose even more than on land. Thus, although thermally disruptive and extreme, the consequences may have paved the way for living conditions favorable to mammals including primates.

Holocene Climate Optimum

The Holocene Climate Optimum (HCO) was a warm period in the interval 9,000 to 5,000 years BC. Terrestrial temperatures increased by three to nine degrees Celsius, with the lesser impacts in tropical areas. Causality is attributed to natural factors, chiefly alterations of the Earth's orbit (Milankovitch cycles). This natural warming period produced extensive glacial melt, and induced the circumstances of wide scale human agriculture, that led to the beginning of modern human civilization. In fact, Glaciers in several mountain regions of the Northern Hemisphere retreated in response to orbitally forced regional warmth between 11 and 5 ka and were smaller (or even absent) at times prior to 5 ka than at the end of the 20th century. (Jansen, 2997) In other words, glacial retreat from purely natural causes roughly 3000 BC was more pronounced than the slight glacial retreats of the post industrial era, which is often attributed to increased greenhouse gase..The African humid period generally coincides with the HCO; its chief manifestation was a verdant epoch in the Sahara associated with productive farming in a landscape dotted with lakes. Other results of the HCO were massive forest growth in central Asia, where deserts presently occur. Man likely played a role in altering the vegetation structure in North Africa toward the latter part of the HCO, by introducing domesticated animals, which contributed to the rapid transition to accelerating aridification of the Sahara.

It is useful to examine the proxy record derived changes in sea surface temperature during the Holocene. Climate reconstructions for the mid-northern latitudes exhibit a long-term decline in sea surface temperature from the warmer early to mid-Holocene to the cooler pre-industrial period of the late Holocene (Johnsen et al., 2001), most likely in response to annual mean and summer orbital forcings at these latitudes (Renssen et al., 2005). Extratropical centennial-resolution records provide evidence for local multi-centennial periods warmer than the last decades by up to several degrees in the early to mid-Holocene. In other words sea surface temperatures as of 2021 are decidedly cooler than Holocene era, which Mid Holocene warming was due to totally natural forcings unrelated to greenhouse gases or the industrial era. (Briffa et al, 2007)

Roman Climatic Optimum

Roman Climatic Optimum or Roman Warm Period occurred between 200 BC and 450 AD; however, warming really began about 500 BC, aligned with the flourishing of the Persian Empire. . This may have been a less global warming than the PETM and HCO, partially since world historic records are most complete in this era in Europe: however, core records in Florida and in the Atlantic region indicate a warming era in part of North America. This warm period amounted to about one to three degrees Celsius increase, and is generally imputed to solar cycles, and certainly to natural causes..

Patterson suggests that the Roman Warm period is responsible for advances in human civilization by producing warming that was conducive to agriculture, human health and comfort. Furthermore, it is certainly true, that the ensuing cooling period coincided with an abrupt decline in Western civilisation and entry to the Dark Ages. It is also interesting that the Roman Warm Period coincides with the peak of the Mayan civilisation, arguably, the most advanced society in the Americas prior to the eighteenth century AD.

Dark Ages

The Dark Ages, also known as the Early Middle Ages, is the period from 500 AD to 1000 AD, best characterized by its European documentation. The era is best known for its global cooling, which led to dramatic decline of crop yields, increased Plague, and a notable decline in culture, art and innovation. (McCarthy, 1895) Estimates of deaths from famine due to cold and crop failure are in the hundreds of millions. (McCarthy, 1895) The most noteworthy example of the civilization collapse of the Dark Ages was the demise of Rome itself; Rome's population peaked in the height of the Roman Warm Period circa 300 AD with about 1,500,000 people. By the middle of the Dark Ages, the population had declined to a mere 20,000. Besides the massive crop failures, and inhospitable cold, (Heinson, 2021) the Justinianic Plague took the majority of the population. Besides the human death toll, there were virtually no new structures or infrastructure built in Rome during the Dark Ages. However, even though the civilization collapse was recorded most notably in Rome, there was a clear global collapse of human civilization; for example the Dead Cities of Syria are a well known relic, (Heinson, 2021) displaying this collapse, and in the Americas, the great Mayan civilization met its final evaporation.

Medieval Warm Period

The Medieval Warm Period (MWP) also known as the Medieval Climate Optimum was a time of warm climate, especially in Europe, the North Atlantic and the Americas from  1000 to 1350 AD. Causes of the MWP are natural: chiefly increased solar activity and decreased volcanic. Temperatures are imputed to be slightly warmer than circa 1900. Major consequences of this era were ice free seas that allowed the Vikings to settle in Greenland and Newfoundland. Also health and prosperity in Europe facilitated recovery from the Dark Ages.

Correlation with Historic Disease

Historical data indicates that global cooling rather than global warming is correlated with major disease outbreaks. For example, the massive Justinianic Plague is closely linked to the known global cooling event that began in 536 AD (Mulholland, 2021). In the Little Ice Age commencing in the Late Medieval Period, there was prolonged disease and plague, especially well documented in Europe.

The Justinian Plague was the first pandemic plague in recorded world history; this contagious disease is caused by the bacterium Yersinia pestis. The disease afflicted the entire Mediterranean Basin, Europe, and the Near East, severely affecting the Sasanian Empire and the Byzantine Empire and its capital, Constantinople.(Arrizabalaga, 2010) The plague is named for the Byzantine Emperor Justinian I (reigned 527–565 AD) who, according to the historian Procopius, contracted the disease at the height of the pandemic which killed about a twenty percent of the population in the imperial capital.  The contagion arrived in Roman Egypt in 541 AD, spread around the Mediterranean Sea and persisted throughout Northern Europe and the Arabian Peninsula, until 549 AD.

Scientists confirmed that the cause of the plague of Justinian was Yersinia pestis, the same bacterium responsible for the Black Death  during the Little Ice Age (1347–1351 AD). (Stathakopoulos, 2018) Ancient and modern Yersinia pestis strains closely relate to the ancestor of the Justinian plague strain have been found in the Tian Shan, a system of mountain ranges on the borders of Kyrgyzstan, Kazakhstan, and China, suggesting that the Justinian plague originated in that Asian region

See Also

References

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Citation

Michael Pidwirny & C. Michael Hogan (2013, updated 2021). Causes of climate change. ed. A. Jorgenson. Encyclopedia of Earth. NCSE. Washington DC. Retrieved from http://editors.eol.org/eoearth/wiki/Causes_of_climate_change

1 Comment

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Kainen Unser wrote: 11-16-2010 21:12:19

Informative post. It is great pleasure to read this. Global Warming is big serous problem in the world. The Global warming occurs due to rise in the temperature around the earths atmosphere. The increase in urban heat is not only by the natural causes in climate change but the Green house gases are the main cause of global warming. http://www.globalwarming360.net/