What caused the global temperature decline between 1945 and 1978?

Question

If you look at the GISS land-ocean index data, you will see that between 1945 and 1978, the average global temperature declined slightly. Why did this occur?

Answer 1

Sorry -- I left the refrigerater door open.

Answer 2

I don't think anyone really knows, despite AGW theory proponents self-proclaimed God-like understanding of the earth's climate systems. As a laymen and a mere mortal, my educated guess would be changes in the sun's output, and or our distance from it. Long ago people worshiped the sun because of there basic understanding of it's importance in every aspect of their lives. What happened to us that we should give the sun a cold shoulder?

Answer 3

the cars back then did not have a smog check so that is why

Answer 4

No one knows for sure why it went down--- just like no one knows why it went up--- and now back down again.

Answer 5

"None of the advocates of the theory of anthropogenic global warming claim that CO2 is the only factor controlling temperature in the ocean-atmosphere climate system. It is a large and complex system, responsive on many different timescales, subject to numerous forcings. AGW only makes the claim that CO2 is the primary driver of the warming trend seen over the last 100 years. This rise has not been smooth and steady -- nor would it be expected to be."

"If you look at the temperature record for the 1990s, you'll notice a sharp drop in '92, '93, and '94. This is the effect of massive amounts of SO2 ejected into the stratosphere by Mount Pinatubo's eruption. That doesn't mean CO2 took a holiday and stopped influencing global temperatures; it only means that the CO2 forcing was temporarily overwhelmed by another, opposite forcing."

"The situation is similar to the cooling seen in the '40s and '50s. During this period, the CO2 warming (a smaller forcing at the time) was temporarily overwhelmed by by other factors, perhaps foremost among them an increase in human particulates and aerosol pollution. Pollution regulations and improved technology saw a decrease in this latter kind of emissions over the '60s and '70s, and as the air cleared, the CO2 signal again emerged and took over. Below, courtesy of Global Warming Art, is an image of the current understanding of the factors and their influence for the climate of the past century."

"As the graph shows, in addition to aerosol pollution (the sulphate line), volcanic influences were increasingly negative during the period of global cooling, and solar forcing slightly declined. All forcings taken together and run through the model are a very good match for the observations. (Please see the source page for details of what model and what study this image is derived from.)"

"Rather than confounding the climate consensus, mid-century cooling is actually a good test for the climate models, one they are passing quite convincingly."

"Addendum: The opposing effect of cooling from airborne pollutants is often referred to as "Global Dimming", and Real Climate has a couple of articles on it."

"One emerging concern is that as the pollution causing this effect is gradually cleaned up, we may see even greater greenhouse gas warming."

http://gristmill.grist.org/story/2006/11...

go to the link to see the charts mentioned

Jello  says it's all because of the Sun

"This is a job for satellites. According to PMOD at the World Radiation Center there has been no increase in solar irradiance since at least 1978, when satellite observations began. This means that for the last thirty years, while the temperature has been rising fastest, the sun has not changed."

"There has been work done reconstructing the solar irradiance record over the last century, before satellites were available. According to the Max Planck Institute, where this work is being done, there has been no increase in solar irradiance since around 1940. This reconstruction does show an increase in the first part of the 20th century, which coincides with the warming from around 1900 until the 1940s. It's not enough to explain all the warming from those years, but it is responsible for a large portion. See this chart of observed temperature, modeled temperature, and variations in the major forcings that contributed to 20th century climate."

http://gristmill.grist.org/story/2006/12...

"Most studies suggest that before the industrial age, there was a good correlation between natural “forcings" – solar fluctuations and other factors such as the dust ejected by volcanoes – and average global temperatures. Solar forcing may have been largely responsible for warming in the late 19th and early 20th century, levelling off during the mid-century cooling (see Global temperatures fell between 1940 and 1980)."

"The 2007 IPCC report halved the maximum likely influence of solar forcing on warming over the past 250 years from 40% to 20%. This was based on a reanalysis of the likely changes in solar forcing since the 17th century."

"But even if solar forcing in the past was more important than this estimate suggests, as some scientists think, there is no correlation between solar activity and the strong warming during the past 40 years. Claims that this is the case have not stood up to scrutiny (pdf document)."

"Direct measurements of solar output since 1978 show a steady rise and fall over the 11-year sunspot cycle, but no upwards or downward trend."

"Similarly, there is no trend in direct measurements of the Sun's ultraviolet output and in cosmic rays. So for the period for which we have direct, reliable records, the Earth has warmed dramatically even though there has been no corresponding rise in any kind of solar activity."

http://environment.newscientist.com/chan...

Answer 6

Two primary reasons:

1. Sulfur dioxide emissions increased from 24.1 TgS to 73.1 TgS between 1945 and 1978. SO2 is a significant reflective aerosol, and the more of it there is in the air, the less sunlight reaches the surface.

By the way, world SO2 emissions reached an all-time peak in 1979, at 74.8 TgS.

2. The St. Augustine volcano (Alaska) had a major eruption in 1976 from which was still affecting the global temperature anomaly. Volcanoes throw large amounts of dust into the air, which also blocks sunlight.

Answer 7

Mostly the use of coal.

If you were around during that time, you would remember a stench and many black clouds in the sky.

Answer 8

Aerosol emissions, which we got under control with Clean Air Acts, which caused SO2 emissions to level off around 1970 and decrease since 1980.

Answer 9

I think your question has been adequately answered.  I just want to call attention to the fellow who chides the non-denialists for claiming "God-like" understanding of the climate, and follows that with advocacy of sun worship.  h**l yeah!  A little human sacrifice and we'll be right back in the bronze age.

Answer 10

Because the amount of "smoke" (an approximate term) we emitted from smokestacks with no pollution controls, held greenhouse gases in check.

In the 1970s two things happened.  Pollution controls started to seriously reduce smoke levels, and increasing wealth throughout the world made for a huge increase in greenhouse gases.

This graph, from the source below, shows what happened nicely.

http://www.globalwarmingart.com/wiki/Ima...

"Sulphate" is the particular type of smoke which blocked the most Sun.

Answer 11

Natural factors that are not yet understood.  We've seen some dramatic shifts in the climate of other planets & we can't explain that either except with theories.  

The Earth's climate is not something that we can do controlled experiments on.  With ather fields of science, you come up with a theory, do a statistically significant number of controlled experiments and test your theory.  With the climate, you come up with a theory to explain some phenomona and that's as far as it goes.  There's no experimental confirmation of a theory.

Answer 12

This decrease coincided with a reduction of sunspots.

The Sun is the source for all warming and cooling on Earth.

Answer 13

Actually I would say it is flat during that period, not a decline.  The localized peak around 1942 looks like an anomaly.