Global Temperature Trends From 2500 B.C. To 2040 A.D.

By Climatologist Cliff Harris and Meteorologist Randy Mann

Article and Chart Updated: April 8, 2020

Until late 2006, global temperatures were more than a degree Fahrenheit warmer when compared to the 20th Century average. From August of 2007 through February of 2008, the Earth's mean temperature dropped to near the 20th Century average of 57 degrees. Since that time, land and ocean readings have rebounded to the highest levels in recorded history in 2016 with a temperature of 58.69 degrees Fahrenheit. For 2019, the global temperature was 58.71 degrees Fahrenheit.

We, Climatologist Cliff Harris and Meteorologist Randy Mann, believe in rather frequent climate changes in our global weather patterns. Geologic evidence shows our climate has been changing over millions of years. The warming and cooling of global temperatures are likely the result, at least in part, of long-term climatic cycles, solar activity, sea-surface temperature patterns and more. However, Mankind's activities of the burning of fossil fuels, massive deforestations, the replacing of grassy surfaces with asphalt and concrete, the "Urban Heat Island Effect" are likely creating more harmful pollution and the additional warming of our planet. Yes, we believe we should be "going green" whenever and wherever possible.

Our planet seems to be in a cycle of constant change. According to an article by the National Oceanic and Atmospheric Administration (NOAA) on Climate.gov in August, 2014, our planet likely experienced its hottest weather millions of years ago. One period, which was probably the warmest, was during the Neoproterozic around 600 to 800 million years ago. Approximately 56 million years ago, our planet was in the Paleocene-Eocene Thermal Maximum as global mean temperatures were estimated as high as 73 degrees Fahrenheit, over 15 degrees above current levels. Ocean sediments and fossils indicate that massive amounts of carbon dioxide were released into the atmosphere.

By contrast, evidence shows there have been at least five major ice ages on Planet Earth. One of the most well-documented and largest, occurred from 850 to 630 million years ago, is called the Cryogenian period. Glacial ice sheets likely reached all the way the equator producing a "Snowball Earth." Scientists believe that this massive ice age ended due to increased underground volcanic activity and, perhaps, a much warmer solar cycle.

One reason scientists believe that the Earth's temperature reached a record level in 2016 was the very strong El Nino in the waters of the south-central Pacific Ocean that formed in 2015. El Nino is the abnormal warming of ocean waters that often leads warmer air temperatures and less snowfall during the winter seasons.

In 2007-08, a moderately strong La Nina, the cooler than normal sea-surface temperature event, combined with extremely low solar activity (storms on the sun), resulted in a period of slight global cooling and record snowfalls across many parts of the northern U.S., Europe, Asia and the Former Soviet Union.

Climate scientists are not completely certain why ocean waters suddenly warm up and cool down over a period of months or years. The warming of sea-surface temperatures may be due, at least in part, to increased underwater volcanic activity or the addition of carbon dioxide into the atmosphere. Researchers are constantly finding new active underwater volcanoes and thermal vents that may be contributing to the warmer temperatures.

Recently, scientists discovered at least three to six times more heat-spewing thermal vents along the seafloors where tectonic plates are pulling apart. In 2003, at least nine hydrothermal vents along the Gakkel Ridge in the Arctic Ocean were found. Arctic ice has been melting at a steady pace in recent years and may be due to the warmer than normal ocean waters. In April 2015, an underwater volcano known as the Axial Seamount, about 300 miles off the coast of Oregon, erupted for a month and added 88 billion gallons of molten rock to the ocean floor.

Since the 1950s, data suggests that ocean temperatures have been getting warmer. According to research at the University of Alabama in 2013, climate models indicate “a natural shift to stronger warm El Nino events in the Pacific Ocean might be responsible for a substantial portion of the global warming recorded during the past 50 years.”

By contrast to the Arctic ice melt, glaciers were thickening in Antarctica's eastern interior. That portion of the continent was experiencing increased snowfall and had a gain of about 100 billion tons of ice per year from 1991 to 2008. But, there has been loss of glacier mass in Antarctica's western region.

From the late 1940s through the early 1970s, a climate research organization called the Weather Science Foundation of Crystal Lake, Illinois, determined that the planet's warm, cold, wet and dry periods were the result of alternating short-term and long-term climatic cycles. These researchers and scientists also concluded that the Earth's ever-changing climate likewise has influenced global and regional economies, human and animal migrations, science, religion and the arts as well as shifting forms of government and strength of leadership.

Much of this data was based upon thousands of hours of research done by Dr. Raymond H. Wheeler and his associates during the 1930s and 1940s at the University of Kansas. Dr. Wheeler was well-known for his discovery of various climate cycles, including his highly-regarded "510-Year Drought Clock" that he detailed at the end of the "Dust Bowl" era in the late 1930s.

One of the most recent cold periods was "The Little Ice Age," a 500-Year plus span that extended from the early 1300s to the mid 1800s. During that time, there was little solar activity, or solar storms, which scientists refer to as the “Maunder Minimum.” There were also numerous volcanic eruptions in the 1800s like Krakatoa and Mt. Tambora. In 1815, Mt. Tambora has a major eruption which was the largest recorded one in human history. The explosion sent thousands of tons of ash and dust into the atmosphere resulting in the lowering of Earth's temperature by several degrees and numerous extremes. The event also led to a "year without a summer" in 1816 across parts of northern Europe and U.S. as snow was reported in each month of the year, including the summer season.

During the early 1970s, our planet was in the midst of a colder and drier weather cycle that led to concerns of another "Little Ice Age." Inflationary recessions and oil shortages led to rationing and long gas lines at service stations worldwide. Since that time, global temperatures have steadily climbed to the levels they are today. But, there were several interruptions of this global warming cycle. In June, 1991, Mt. Pinatubo erupted in the Philippines leading a temporary drop of about one degree of the Earth's average temperature. In the late 2000s, a strong La Nina and very low solar activity helped to send our planet's average temperature down to near the 20th Century average of 57 degrees before rebounding in the early 2010s.

The Weather Science Foundation also predicted, based on these various climate cycles, that our planet would turn much warmer and wetter by the early 2000s, resulting in general global prosperity. They also said that we would be seeing widespread weather "extremes." There's little doubt that most of their early predictions came true.

In the decade of the 2010s, hundreds of thousands of weather records, more high than low, were broken worldwide. That trend is expected to continue for current decade and beyond.

Dr. Wheeler also discovered that approximately every 102 years, a much warmer and drier climatic cycle affects our planet. The last such "warm and dry" peak occurred in 1936, at the end of the infamous "Dust Bowl" period. During that time, extreme heat and dryness, combined with a multitude of problems during the "Great Depression," made living conditions practically intolerable.

The next “warm and dry” climatic phase is scheduled to arrive in the early 2030s, probably peaking around 2038. It's quite possible we could see an average global temperature near or even above 60 degrees, assuming there isn't a major volcanic eruption to disrupt this cycle.

Based on current data, this new warmer cycle could produce even hotter and drier weather patterns than we saw during the late 1990s and early 2000s. We also believe that our prolonged cycle of wide weather “extremes,” the worst in at least 1,000 years, will continue and perhaps become more severe in the years to come.

We should remember, that the Earth's coldest periods have usually followed excessive warmth. Such was the case when our planet moved from the Medieval Warm Period between 900 and 1300 A.D. to the sudden “Little Ice Age,” which peaked in the 17th Century. Since 2,500 B.C., there have been at least 78 major climate changes worldwide, including two major changes in just the past 50 years. In terms of upcoming cooling and warming periods, only time will tell.

Global temperature chart was complied by Climatologist Cliff Harris that combined the following resources:

"Climate and the Affairs of Men" by Dr. Iben Browing.

"Climate...The Key to Understanding Business Cycles...The Raymond H. Wheeler Papers. By Michael Zahorchak

Weather Science Foundation Papers in Crystal Lake, Illinois.