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

By Meteorologist Randy Mann
Chart and Article Updated: July, 2024

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 slightly to about a half-degree above 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 a record-breaking global temperature of 58.69 degrees Fahrenheit was reported. In 2023, the reading hit 59.12 degrees, the highest in modern history.

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", and more are creating extensive harmful pollution and leading to substantial warming of our planet. However, some of the long-term warming and cooling of global temperatures in the past may be the result of climatic cycles, solar activity, sea-surface temperature patterns and more.

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 Neoproterozoic 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 to be as high as 73 degrees Fahrenheit, over 13 degrees above current levels. Ocean sediments and fossils indicate that massive amounts of carbon dioxide were released into the atmosphere during that era.

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 to 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.

Many scientists believe that the Earth's temperature reached a record level in 2016 was, at least in part, to the very strong El Nino in the waters of the south-central Pacific Ocean that formed in 2015 and the increased greenhouse gases. El Nino is the abnormal warming of ocean waters that often leads to warmer air temperatures and less snowfall during the winter seasons. However, from 2021 to 2024, there were three La Nina events and global temperatures did not cool down.

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 being absorbed by the oceans. Researchers are constantly finding new active underwater volcanoes and thermal vents that may be contributing to the warmer temperatures. It’s very possible that we’ll find more of these thermal vents in the future as over 80 percent of the Earth’s oceans haven’t been explored or mapped.

Researchers 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 shows 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 portion of the global warming recorded during the past 50 years.” Also, ocean waters have been considerably warmer in recent years, especially in the Arctic regions where readings have been as much as 10 degrees warmer than normal in the late 2010s. Ocean waters have also been warming at “historic” levels in the Atlantic and Caribbean waters that have led to more destructive hurricanes, especially in recent years.

By contrast to the Arctic ice melt largely due to the warmer waters, 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. It was recently discovered that heat from the Earth’s interior may have contributed to some of the melting in Antarctica. However, there has been a large 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." 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 likely helped to slightly lower global temperatures 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.

Dr. Wheeler also discovered that a much warmer and drier climatic cycle affects our planet. The last such "warm and dry" peak occurred in 1930s, around 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.

We believe that we’re in the next “warm and dry” climatic phase, and it’s scheduled to peak around the mid-2030s. It's very possible that we could see an average global temperature rise above 60 degrees by the end of this decade. This would be largely due, according to most climate scientists, to the continuation of adding more greenhouse gases, like carbon dioxide, into the atmosphere. A major volcanic eruption would likely be the one and perhaps only natural event to drop the Earth’s temperature.

During the “warm and dry” phases, based on history, there has been minor to major global unrest. In early 2022, droughts have covered much of the western and portions of the central U.S. California reservoirs are around the lowest levels in history, especially in Southern California where a new “megadrought” is likely in place and is already considered to be one of the worst in recent geologic history. Major droughts have also been reported in South America and other countries in the world. Record warmth has also been reported in Siberia in 2021. As temperatures are expected to warm further and many areas are turning drier, we’re seeing significant global unrest with increasing chances of major world wars. In 2024, global tensions have been at their highest levels since World War II.

Based on current data, this warmer period caused by increased carbon dioxide, cycles and perhaps other unknown factors could produce even hotter and drier weather patterns in the coming decades. However, if there was a major volcanic eruption or other events that would send vast amounts of sun-reflecting materials into the atmosphere, global temperatures would likely reverse. We also believe that our prolonged period of wide weather “extremes,” the worst in at least 1,000 years, will continue and perhaps become more severe in the years to come.

Tens of thousands of scientists will state that based on the evidence, humans are the main cause of climate change. The burning of fossil fuels is putting an estimated 9.5 billion metric tons of carbon into the atmosphere every year and it’s obvious that humans are having an impact. However, climate patterns have also shown various types of cycles and admittedly, after studying climate for many decades, it's difficult to say where we go from here.

Since 2,500 B.C., it’s estimated that there have been over 70 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.