- Education and Science»
- Geology & Atmospheric Science
The History of Global Warming and Origin of The Term Climate Change
Global Surface Temperature 1880 to 2016
The history of global warming and origin of the term "climate change" are fascinating subjects for anyone who wants to understand how the majority of scientists who study the Earth’s climate came to the conclusion that mankind’s activities are causing the Earth to warm. The term “global warming” became a common phrase during the 1980s, as the Earth warmed and politicians such as then Senator Al Gore held high-profile hearings on the topic. However, it actually has a history that goes as far back as the late 19th century. Interestingly, the controversy surrounding whether mankind’s activities can actually cause global warming has been part of the debate throughout its history; it is not a new phenomenon.
A Depiction of The Greenhouse Effect In a Greenhouse
During the 1800s Scientists Studying Ice Ages Started Focusing on the Greenhouse Effect
The hypothesis that a buildup of greenhouse gasses in the Earth’s atmosphere could cause the Earth to warm is an outcrop of scientist’s pursuit of understanding what causes the Earth to cool down and undergo ice ages. In the early 1800s, scientists came to understand that the Earth had undergone ice ages and other climate changes over the years, based on geologic evidence left behind from past ice ages. As the 1800s progressed, changes in the concentrations of heat trapping atmospheric gases (such as carbon dioxide and water vapor) and the natural greenhouse effect were recognized by some in the scientific community as possible contributors to the cooling and warming of the Earth over long periods of time, causing both ice ages and warm inter-glacial periods in-between.
The greenhouse effect is a term that describes how the Earth’s atmosphere traps heat from the sun. The sun’s ultraviolet heat radiation is turned into thermal infrared heat radiation upon coming into contact with the Earth’s surface. As thermal infrared heat radiation tries to escape back into outer space, it is trapped in the Earth’s atmosphere by greenhouse gases (such as carbon dioxide, water vapor and methane) causing the atmosphere to warm. Greenhouse gases make the Earth a habitable planet, since without them the Earth would be incredibly cold and inhospitable.
If you visit a greenhouse on a sunny day, you will feel first-hand how radiation from the sun’s ultraviolet heat rays can heat up the interior, since the glass roof of a greenhouse lets the sun’s ultraviolet radiation in, but prevents most of the resulting thermal infrared heat radiation from escaping, which causes the greenhouse to be much warmer than the air around it.
In the Late-1800s Scientists First Postulated That Mankind’s Activities Could Cause The Earth To Warm
During the late 1800s, while studying reasons why ice ages occurred, a Swedish scientist named Svante Arrhenius calculated how much the Earth would cool if carbon dioxide levels were half of what they were at his time. He concluded that Europe would be 4 to 5 degree Centigrade (7 to 9 degrees Fahrenheit) cooler with such a reduction in the greenhouse gas, as the natural greenhouse effect would be lessened.
One of Arrhenius’ colleagues, Arvid Högbom, took on the task of trying to determine if Arrhenius’ calculations regarding the relationship between carbon dioxide levels in the atmosphere and global temperatures had any basis in the real world. During his investigation, Högbom calculated how much carbon dioxide was being emitted by mankind’s industrial and coal burning activities, and realized that carbon dioxide levels in the atmosphere were slowly increasing due to man’s activities. The two scientists realized that this addition of carbon dioxide to the Earth’s atmosphere could cause warming of the Earth’s temperatures over a long period of time (they were thinking thousands of years). Arrhenius calculated if carbon dioxide levels were doubled from the levels that existed at the time, the Earth would eventually warm by 5 to 6 degree Centigrade (9 to 11 degrees Fahrenheit).
Early 20th Century Skepticism of Carbon Dioxide’s Effect on Earth’s Temperature
A few years later in 1908, Arrhenius published an article and book about the causes of the ice ages that were widely read by the scientific community. In those works, he speculated that warming due to mankind’s greenhouse gas emissions might occur in as little as a few centuries. However, this pioneering scientist’s ideas were far from proven at that time and were highly controversial, since it was assumed that mankind could not put enough greenhouse gases into the atmosphere to upset the Earth’s natural climate equilibrium and that carbon dioxide might not even be capable of causing the greenhouse effect in the atmosphere.
For the first half of the 20th century, the idea that carbon dioxide from mankind’s industrial activities and burning of fossil fuels could affect global temperatures was overwhelmingly dismissed by the scientific community. Scientists believed that water vapor cancelled out any effects of increased carbon dioxide accumulating in the upper atmosphere, since they incorrectly concluded that thermal infrared heat radiation reflecting back towards outer space could not make it through water vapor at lower levels to be trapped by carbon dioxide at higher levels of the atmosphere. They also incorrectly believed that the Earth’s oceans were capable of absorbing and removing far more carbon dioxide from the atmosphere than they actually can.
By The Late 1950s Some In The Scientific Community Became Concerned About Global Warming
Scientist’s skeptical views changed dramatically during the 1950s, as additional scientific research and increased computational power provided by computers proved not only that thermal infrared heat radiation could make it to the upper atmosphere where carbon dioxide accumulates, but also that the oceans could only absorb a fraction of the carbon dioxide put into the atmosphere than was previously believed. By the late 1950s, some scientists began warning that the accumulation of greenhouse gases may create problematic warming of the planet.
The one thing that was still missing was proof that carbon dioxide levels in the Earth’s atmosphere were actually rising. Consistent reliable monitoring of carbon dioxide levels in the Earth’s atmosphere began in the late 1950s in Antarctica and at the Mauna Loa Observatory in Hawaii, at the direction of an American scientist named Charles David Keeling.
Keeling’s Curve, Which Shows The Increasing Carbon Dioxide Trend
During The 1960s Rising Carbon Dioxide Levels Were Confirmed
In 1960, Keeling reported that the baseline level of carbon dioxide measured in Antarctica had risen. While the Antarctica station was scraped in the early 1960s, the Mauna Loa station continues to report carbon dioxide levels to this day. The chart featured to the right shows the choppy rise in carbon dioxide levels over time, as recorded at the Mauna Loa station.
By the early 1960s, the confirmation of the trend of an increasing concentration of carbon dioxide in the atmosphere and realization that the greenhouse effect was a physical reality in the upper atmosphere had some in the scientific community concerned about the long-term effects of this accumulation of carbon dioxide on global temperatures. This was long before a strong global warming trend was identified and before many people had even heard of the greenhouse effect or global warming.
Earth's Global Temperature Over The Last 12,000 Years
1970s Concerns About a Pending Ice Age
During the 1970s, there was actually some concern in scientific quarters that the Earth was slipping into a new ice age. The global temperature trend from the 1940s through the middle part of the 1970s was in a slight downtrend, which made some scientists wonder if an ice age was approaching. This was not an unreasonable concern, since the current inter-glacial warm period, which started about 10,000 years ago had reached the age that many of these warm periods between ice ages have ended, and global temperatures had been on a downtrend for thousands of years. The temperature trends in the graph to the right show how global temperatures peaked about 7,000 years ago, then made a sustained move lower until very recently, when they spiked well above the 7,000 years ago level.
Looking back to that time period from the 1940s through the middle part of the 1970s, atmospheric scientists attribute the slight downward temperature trend to the negative (cold) state that was in place at that time of what is known as the Pacific Decadal Oscillation (PDO). The PDO changes from warm to cold states and back again every ten to thirty years.
During The 1970s The Term “Global Warming” Was Coined
It was during the 1970s that the term “global warming” was coined. Specifically, the term has its roots in the year 1975, when Columbia University Professor Wally Broecker published a paper called "Climate Change: Are We on the Brink of a Pronounced Global Warming" in Science magazine. That is correct, he did actually use the words “climate change” all the way back in 1975. The term “climate change” was not a later invention by those seeking to broaden the definition of the effects of global warming.
During The 1980s & 1990s The Global Warming Trend Became Pronounced
The current upward trend in global temperature has its roots in the 1980s, when the PDO was back in its positive (warm) state. The upward global temperature trend became quite evident during the 1980s and most of the 1990s, with a peak during the super-El Nino event of 1998. El Nino is a term that describes a warming of parts of the tropical Pacific ocean, which can have a significant short-term impact on global temperatures and weather patterns.
It turns out that the 1998 super-El Nino occurred just as the PDO was in the process of flipping into its negative (cold) state. This caused global warming to slow dramatically. However, unlike the prior negative PDO of the 1940s to 1970s, global temperatures did not fall after the 1998 flip to a negative PDO, rather the rate of increase slowed for about fifteen years. By 2015 and 2016 global temperature records were once again being broken and clear uptrend in global temperatures once again became evident.
Global Temperatures & Carbon Dioxide
Global Warming Today
While it is clear that the Earth’s temperatures have continued to warm since the 1980s and carbon dioxide levels are increasing in the atmosphere at a faster rate than in past decades, whether mankind’s emissions of greenhouse gases is the cause of this global warming trend is still a matter of some limited debate. Since there is a lot of noise and misinformation in this debate, perhaps the best indication that mankind is responsible for the current global warming trend is the fact that if mankind were not living on planet Earth, indications are that Earth would be heading into another ice age. Therefore, the global warming trend that has been evident for nearly 40 years is likely not natural.
It could be argued that a little man-induced global warming is a good thing, as an ice age would be problematic for the supply of food and life on Earth. However, too much of a good thing will likely cause dire outcomes in future centuries for future generations, as sea levels rise at an increasing rate, flooding many of the world’s population centers and farmable land becomes arid.
Even if the entire world switched from carbon-based fuels next year, the buildup of carbon dioxide in the atmosphere would affect global temperatures for many centuries to come, since it takes a long time for natural processes to remove carbon dioxide from the atmosphere. Add to that the real possibility of positive feedback loops from global warming, such as the release of massive amounts of methane (a potent greenhouse gas) that is frozen in polar regions of the Earth and under ocean floors, and the future effects of global warming could be quite significant for future generations.