Changing Scientific Consensus
1970s: Global Cooling A Serious Threat
Today: Global Cooling Never Happened
Until the mid-1980s, it was widely accepted in the peer-reviewed scientific literature that there was an abrupt global cooling trend between the 1940s and 1970s.
The amplitude of the climate change amounted to more than -0.5°C of cooling in the Northern Hemisphere, as documented by NASA (1981).
Hansen et al., 1981 (NASA) “[T]he temperature in the Northern Hemisphere decreased by about 0.5°C between 1940 and 1970, a time of rapid CO2 buildup. … Northern latitudes warmed ~ 0.8°C between the 1880’s and 1940, then cooled – 0.5°C between 1940 and 1970.”
For the globe as a whole, the warming between the late 19th century and 1940 reached an amplitude of about +0.6°C, but a cooling trend of -0.3°C during the decades after the 1940s pulled temperatures more than halfway back to the 1880s.
Benton, 1970 “In the period from 1880 to 1940, the mean temperature of the earth increased about 0.6°C; from 1940 to 1970, it decreased by 0.3-0.4°C.”
Cimorelli and House, 1974 “[B]etween 1880 and 1940 a net warming of about 0.6°C occurred, and from 1940 to the present our globe experienced a net cooling of 0.3°C.”
Between 1958 and 1963 alone, the National Academy of Sciences (NAS, 1975) cited an analysis of about 200,000 measured temperatures that said the Northern Hemisphere’s temperatures plummeted by -0.6°C (Starr and Oort, 1973, introductory graph above). The NAS also concluded that a “serious worldwide cooling” has a “finite probability” to befall the Earth within the next century, or by about 2075.
National Academy of Sciences, 1975 “Starr and Oort (1973) have reported that, during the period 1958-1963, the hemisphere’s (mass-weighted) mean temperature decreased by about 0.6 °C. … Since the 1940’s, mean temperatures have declined and are now nearly halfway back to the 1880 levels. … There seems little doubt that the present period of unusual warmth will eventually give way to a time of colder climate … [T]here is a finite probability that a serious worldwide cooling could befall the earth within the next hundred years. … [A]s each 100 years passes, we have perhaps a 5 percent greater chance of encountering its [the next glacial’s] onset.”
NOAA (1974) also agreed that Northern Hemisphere temperatures declined by about -0.5°C after 1940, but additionally pointed out that a new ice age may be approaching, with scientists linking the 1970s-era droughts and crop failures and ice expansion to the ongoing global cooling.
NOAA, 1974 “Many climatologists have associated this drought and other recent weather anomalies with a global cooling trend and changes in atmospheric circulation which, if prolonged, pose serious threats to major food-producing regions of the world. … Annual average temperatures over the Northern Hemisphere increased rather dramatically from about 1890 through 1940, but have been falling ever since. The total change has averaged about one-half degree Centigrade, with the greatest cooling in higher latitudes.”
“[T]he average growing season in England is already two weeks shorter than it was before 1950. Since the late 1950’s, Iceland’s hay crop yield has dropped about 25 percent, while pack ice in waters around Iceland and Greenland ports is becoming the hazard to navigation it was during the 17th and 18th centuries. … Some climatologists think that if the current cooling trend continues, drought will occur more frequently in India—indeed, through much of Asia, the world’s hungriest continent. … Some climatologists think that the present cooling trend may be the start of a slide into another period of major glaciation, popularly called an ‘ice age’.”
A decades-long cooling trend during the modern era is not convenient for those who advocate for the position that humans control the temperatures of the oceans and atmosphere by burning more or less fossil fuels, or by emitting more or less CO2.
So, instead of allowing the original temperature data showing +0.8°C warming and -0.5°C cooling (Northern Hemisphere) to remain, overseers of temperature data sets decided to gradually remove several tenths of a degree from the warming and cooling amplitudes.
Now, instead of +0.8°C of Northern Hemisphere warming between the 1880s and 1940, it’s about +0.3°C. Instead of -0.5°C of cooling between the 1940 and 1970, it’s been changed to about -0.1°C. About half a degree of temperature change was removed from both trends.
Image Source: NASA
Instead of -0.3°C of global cooling between about 1940 and 1970, NOAA now shows a pause occurred. The global cooling has been removed.
Image Source: NOAA
The problem with attempting to erase hemispheric- and global-scale cooling temperature trends is that extensive scientific records of the “serious threat” of global cooling still exists.
What follows is an abbreviated (93 papers out of over 300) compilation of the hundreds of scientific publications documenting concerns pertaining to the 1960s and 1970s global cooling and Ice Age scare.
Unlike illustrative graphs of hemispheric and global temperatures, this evidence is not so easily erased by anthropogenic global warming advocates.