Climate and Civilization for the past 4,000 years

By Andy May

The Holocene Thermal Optimum ended at different times in different parts of the world, but it had ended everywhere by 4,000 BP (BP here means the number of years before 2000) and the world began to cool. The timeline shown in Figure 1 shows the GISP2 Central Greenland ice core temperature proxies in blue and the HadCRUT 4.4 surface temperature estimates for the same area in red.

Figure 1 (click on the figure to download in full resolution)

Major events in human civilization are noted on the graph. If you download the pdf it prints well on 8.5×11 inch paper. This timeline provides more detail for the last 4,000 years than I could fit on my previous timeline to 18,000 years. The principal reference for the ice core study can be seen here. While the Alley Greenland ice core temperature reconstruction shown is the most popular, the Vinther reconstruction is more accurate, see Figure 2 here. At the top of the graph the Blytt and Sernander climate periods are noted, these periods are based on their studies of Danish peat bogs and the names are still used in the literature.

Of necessity, this post covers the climate and human events in the northern hemisphere. Some of the climatic events described, like the Medieval Warm Period, were worldwide events. But, some may have only occurred in the northern hemisphere. Nearly all of the historical notes are from Professor Wolfgang Behringer’s excellent book A Cultural History of Climate. The book was suggested to me by Dr. Ronan Connolly and I highly recommend it. It was originally published in German in 2007, I read the 2010 English translation by Patrick Camiller. The translation is quite good and the book is very readable, even addicting.

The GISP2 temperature record covers the interval from 95 years ago to 50,000 years ago. I pulled a Michael Mann “trick” and spliced measured Greenland (HadCRUT 4.4) surface temperatures onto the ice core record to bring the graph up to the year 2000. That way it shows the modern warm period. The spliced measured temperatures are smoothed with a 20 year moving average. The HadCRUT 4.4 worldwide gridded temperature anomalies were read from a NetCDF dataset. The R script for reading and mapping the data can be seen here. The script is in a Word file due to WordPress restrictions, save it as an “.R” text (ascii) file if you want to run it.

The worldwide HadCRUT temperature anomaly grid is a 5° by 5° grid and many of the points over Greenland are unpopulated (null). The populated points near the GISP2 ice core site were averaged over the 166 year span of the record (since 1850). The points used and the location of the GISP2 ice core are shown in Figure 2 (made with Google Earth) below. The smoothed anomalies were added to the ice core temperature average in the overlapping interval, from 1850 to 1905.

Figure 2

Ice core data from this far north are very useful. It has long been known that ocean and atmospheric temperatures at or near the equator have not changed much for millions of years, but temperature changes at the poles have been large, especially near the North Pole. This has often been called “polar amplification.” As global temperatures rise, evaporation increases in the tropics keeping tropical temperatures steady. As temperatures are “evaporatively buffered” in the tropics, global energy balance constraints force temperatures to increase in the high latitudes during a global warming event. So data from this far north show larger temperature swings than the world at large and they are easier to see.

Newell and Dopplick computed that the maximum temperature of the atmosphere over the ocean is 303K or 30°C (see also Hoffert, et al., 1983 and Sud, et al., 1999). This is very similar to the equatorial sea surface temperature today (see Figure 3) and going back to the Cretaceous Period 65 million years ago. In the Cretaceous the higher sea surface temperatures covered much more of the oceans and there was no polar ice. They conclude that 30°C is the limiting temperature based on the balance between radiative input energy and energy lost due to the evaporation of sea water. Because the world ocean heat capacity is 1,000 times the heat capacity of the atmosphere, this is a very reasonable conclusion. For the details of the heat capacity calculation see the spreadsheet here. One should also consider that while the equatorial ocean surface temperature is about 30°C (Figure 3), the temperature of the world ocean at 2000 meters depth is only about 2°C. For this reason, the oceans are a huge temperature dampener, making the idea of a runaway atmospheric temperature increase unlikely.

Figure 3, Modern Ocean surface temperatures, whole year average, Deg. C (NOAA MIMOC)

Comparing northern hemisphere human history to the Greenland ice core record, it is apparent that large swings of temperatures in Greenland are related to European, Middle Eastern, Asian, and American events. Thus, we can safely assume these temperature swings affected most, if not all of the northern hemisphere. Behringer discusses this relationship in rich detail in his book. Comparing Antarctic ice core temperature proxies to the Greenland ice core records shows that the shorter events are different, or occur at different times in the southern hemisphere. The major events, for example the last glacial maximum and the Holocene Thermal Optimum (when human civilization began, the so called Neolithic Revolution) are apparent in both records.

The timeline begins at 4,000 BP and it shows steady cooling to the Little Ice Age (roughly 1250 to 1850 AD). It is easy to see that the Roman Warm Period was cooler (at least in Greenland) than the Minoan Warm Period and the Medieval and Modern Warm Periods are cooler than the Roman Warm Period. The Little Ice Age was a horrible time for mankind according to Behringer. Glaciers advanced in the Alps and destroyed homes, it was a time of perpetual war, famines and plagues. Horrible persecutions of Jews and “witches” were common. Society was suffering from the cold and lack of food and they needed to blame someone. They chose Jews and old unmarried women unfortunately. Over 50,000 witches were burned alive. Tens of thousands of Jews were massacred. Not because there was any proof, just because someone had to suffer for the bad climate. Some people, the masses mainly, seem to need to blame someone or humanity’s sins for natural disasters. Behringer notes that in The Little Ice Age: “In a society with no concept of the accidental, there was a tendency to personalize misfortune.”

Today environmental zealots assume that climate change is not only man-made but dangerous. They have no proof of either assertion, of course, but they “believe” with religious fervor in both ideas. Then we see, in Behringer’s book, the following quote from Archbishop Agobard of Lyons (769-840 AD) in his sermon “On Hail and Thunder:”

“In these parts nearly everyone – nobles and common folk, town and country, young and old – believe that human beings can bring about hail and thunder…We have seen and heard how most people are gripped by such nonsense, indeed possessed by such stupidity…”

Behringer offers up a 1486 woodcut of a sorceress conjuring up a hailstorm, I show this below in Figure 4. Behringer labels this woodcut “Anthropogenic Climate Change.” This is on page 129.

Figure 4: Anthropogenic Climate Change

One needs to ask “Have we, as a society, learned anything since 1486?” Why do some need to assume that certain people must be to blame for natural disasters?

Conclusions

There are several lessons to be learned from Behringer’s book and the timeline. First, there is no perfect temperature. Man, even in pre-industrial times, adapted to a variety of temperatures and he has always done better in warm times and worse in cold times. Second, why would anyone want to go back to the pre-industrial climate? The Washington Post says the goal of the Paris Climate Conference was to get the world to agree to limit global warming to less than two degrees above pre-industrial temperatures. Pre-industrial times? That’s the Little Ice Age, when it snowed in July, a time of endless war, famine and plague. According to the Greenland ice core proxy data, temperatures 180 years ago were nearly the coldest seen since the end of the last glacial period 10,000 years ago! Why measure our success in combating anthropogenic warming, if there is any such thing, from such an unusually cold time? It makes no sense; those times were awful.

As Behringer explains, the Neolithic (new stone age) revolution and the rise of ancient civilization became possible when temperatures were one to two degrees warmer than today. At the current rate of warming, even in polar amplified Greenland, this will take at least 200 years to reach. Why not set the limit at two degrees above the temperatures in the Holocene Thermal Optimum? That was the temperature that allowed civilization to begin after all. I, for one, would like to go back to that period much more than the Little Ice Age. Why have a limit? Evaporation limits the maximum temperature to 29-30 degrees anyway, we go to places with that temperature for a winter vacation all the time.

Currently temperatures are evaporatively buffered in the tropics at 29°-30°C. The rest of the planet could rise to nearly this temperature over many thousands of years, but it isn’t likely, and it isn’t a catastrophe. Further, the Earth has already been there in the Paleocene-Eocene Thermal Maximum 55 million years ago (also see here) and in the Cretaceous Period 65 million years ago when the Earth was ice free and palm trees grew in both Alaska and Antarctica. If warming continues, man-made or not, the ice at the poles will melt over time; but we can move to higher ground, we can adapt. It will not happen quickly but over many generations, most will not even notice it is happening. We are much more advanced today and can adapt more easily than our ancestors and they adapted to even more extreme climatic events.

The last part of Behringer’s book is a good summary of the climate change debate in 2007. We have to admire the way he presents both sides of the debate in a “just the facts” manner. The following quote is from the penultimate page of the book:

“…cooling has always resulted in major social upheavals, whereas warming has sometimes led to a blossoming of culture. If we can learn anything from the history of culture, it is that, even if humans were ‘children of the Ice Age’, civilization was a product of climatic warming.”

“The future is hard to foresee. Serious scientists should refrain from slipping into the role of Nostradamus. Computer simulations cannot be better than the premises that guided the input of data: they show what is expected to happen, not the actual future. The history of the sciences is also a history of false theories and wrong predictions.”

Not much to add to that.

Note, I updated this post in 2024, the update version is here.

June 22, 2016

Old Schlumberger Film

May 8, 2016

I got this old Schlumberger film from Leon Williams and we don’t know who made it.  If anyone does, let us know.  The narration of the video is hilarious, make sure your sound is on.

Using R and JAMSTEC NetCDF Files to Examine Ocean Temperatures

By Andy May

It doesn’t matter if you think fossil fuel CO2 emissions are going to end the world or lead us to a greener and more beautiful one. Either way, to be a true climate change geek you need access to climate data! Unfortunately, much of the climate raw and gridded raw data comes in a very difficult to read format called NetCDF. Worldwide temperature data is complex, the dimensions of climate arrays are latitude, longitude, depth (or the equivalent pressure in the atmosphere or ocean), year, and month. It is very hard to simplify it more than that. NetCDF does handle data of this complexity in a machine independent way, but you will not be able to read it with Excel. So how do we do this?

Continue reading “Using R and JAMSTEC NetCDF Files to Examine Ocean Temperatures”

An Open Letter to Hillary Clinton

Dear Mrs. Hillary Rodham Clinton,

I know you’re busy, so I will summarize my key points briefly. I do agree with you on most issues, but some of your positions are show stoppers for me. My entire focus in this presidential campaign is on jobs and the economy. I realize your website says you want to create good-paying jobs and stimulate small business growth. But most of us work for large businesses or government agencies and your policies regarding large businesses are at odds with your stated desire to create good jobs. To create and keep good jobs in America we must support businesses, both large and small, encouraging them to invest in the USA, and make the USA the best place in the world to start and grow a business. All of the money we have comes from businesses large and small, neither the government nor non-profits make any money.

Continue reading “An Open Letter to Hillary Clinton”

The Exxon Climate Papers

By Andy May

April 18, 2016

Note: Many of the links in this post are busted. See here to download the files I had on my hard drive, this includes the internal memos and the peer-reviewed articles.

New York Attorney General Eric T. Schneiderman has accused ExxonMobil of lying to the public and investors about the risks of climate change according to the NY Times and has launched an investigation and issued a subpoena demanding extensive financial records, emails and other documents. Massachusetts, the US Virgin Islands, and California are also investigating ExxonMobil. It is interesting that all but one of the attorneys general are Democrats. The remaining attorney general is Claude Walker of the US Virgin Islands who is a Green leaning Independent. So, this is a very partisan investigation, carefully coordinated with anti-fossil fuel activists. How much is there to it?

Continue reading “The Exxon Climate Papers”

Prof. Robert Carter: Evidence for man-made climate change

By Prof. Robert M. Carter, James Cook University, Queensland, Australia December 9, 2009

Edited by Andy May [comments in square brackets]

I’ve always liked this essay, written by the late Dr. Bob Carter in 2009. It has been plagued by some formatting issues that detract from the excellent content. This version fixes the formatting problems in the original. In particular the spacing is improved and the “°” symbols in the original had been made into zeros. Besides fixing the formatting issues, adding some graphs, a few hyperlinks and updates in square brackets, I’ve left it as Professor Carter wrote it.

Continue reading “Prof. Robert Carter: Evidence for man-made climate change”

Greenpeace Crimes and Lies

By Andy May

There is an updated version of the post here.

Donations to Greenpeace for 2014 are a reported $318 million.  Fund raising costs are reported to be 36% or $116 million.  Administration, including generous salaries for the executives, is another 16% or $51 million. Since over half of the money collected is spent on fund raising and salaries they receive a lot of criticism.  India recently froze their bank accounts, accusing them of misreporting funds.  New Zealand rejected Greenpeace’s charitable status in 2010 with the charitable commission stating:

Two of Greenpeace’s objectives – promoting “peace” and “disarmament” – were political, not charitable.

Greenpeace was involved in illegal activities, such as trespassing; therefore it was not maintained exclusively for charitable purposes as illegal purposes are not charitable.

Continue reading “Greenpeace Crimes and Lies”

The Value of Petroleum Fuels

By Andy May

It is difficult to compare 1840 to 2015, so much of what we have today didn’t exist then.  But, they had to move people and goods from place to place as we do now.  They had farms then as we do now. They used wagons pulled by horses, mules or oxen.  We use cars and airplanes. They used muscle power to farm, we use tractors, combines, grain carts, and trucks powered by petroleum fuels. In 1840 crude oil and natural gas production and use were rare. Coal was used in manufacturing, but steam engines were still in their infancy. So the world in 1840 was fossil fuel free for the most part. Biofuels, that is burning wood and dung, were common.  Wind power and hydro-power have been around for thousands of years.  But, windmills suitable for pumping water on small American farms would not appear until 1854. Practical hydropower was not in common use until after 1849.

Continue reading “The Value of Petroleum Fuels”

Holocene Thermal Optimum

By Andy May

The Holocene Thermal Maximum, also called the Holocene Thermal Optimum or the Holocene Climatic Optimum, occurred at different times in different parts of the world but generally between 10,000 BP and 4,000 BP.  I use BP to indicate years before 2000.   The world ocean was probably 0.7°C warmer than today 8,000 BP. This is remarkable because the ocean heat capacity is 1000 times larger than the atmosphere’s according to the IPCC and NOAA.  Simple high school physics is all that is required to verify this, the calculation is described here.  What this means is that if you heated the atmosphere to 1000°C and transferred all of that heat to the ocean, the ocean would only warm 1°C once the heat was well mixed. We can draw two conclusions from these facts. First, the world was much warmer 8,000 BP than today and the total heat stored in the atmosphere and in the oceans was much greater. That 0.7°C represents the heat required to warm the atmosphere to over 700°C. This would never happen, of course, ocean-atmosphere heat transfer processes would work to move heat from the ocean to the atmosphere and back again to keep temperatures moderate and stable.

The second conclusion is that there is no magic 2°C tipping point. Raising todays atmospheric temperature 2°C involves an insignificant amount of heat relative to the total ocean/atmosphere heat present only 8,000 years ago. If the oceans absorbed 2°C worth of atmospheric heat, the ocean temperature would only go up a trivial and unmeasurable 0.002°C.

Bob Tisdale shows while we have good Argo float data from 0-2000 meters, these depths only include about one-half of the volume of the oceans. NASA has shown that the water below 2000 meters has shown no detectable warming. The key point is that the oceans will mitigate any atmospheric warming, man-made or not. Direct infrared radiation from greenhouse gases probably warms the oceans a little, but direct solar radiation does most of the work. Longer term ocean/atmospheric heat transfer (like evaporation, ENSO and other processes) do transfer a lot of heat from the atmosphere to the oceans and back again to stabilize the system. The graph below (Figure 1), made from data from the NOAA web site, shows that the world ocean average temperature has gone up only 0.1°C in the last 60 years, less than the error in the data. The precision of the ARGO thermometers is very good, +-0.002°C, but the accuracy is only 0.5°C over most of the world ocean.

Figure 1

There seems to be general agreement that the cause of the Holocene Thermal Maximum is the Earth’s precession cycle. As described in Michael Bender’s book “Paleoclimate,” a part of the Princeton Primers on Climate series:

“The orientation of Earth’s spin axis has changed over the past 10 Kyr so that northern summers now occur when Earth is farthest from the sun, whereas at 10 Ka [10,000 BP] they occurred when Earth was closest to the sun. Northern summertime insolation reached a maximum at about 10 Ka and has declined to the present, when it is near the minimum.”

Bender has determined that remnants of the Laurentide Ice Sheet (LIS) from the last glacial period contributed to cooling many northern areas and delaying their warm periods. These areas, like Western Europe had their climate optimum between 4,000 BP and 7,000 BP. In Germany and Scandinavia mean annual temperatures were warmest 6,000 BP to 7,000 BP and they have since fallen 2.5°C. In Alaska and western Canada the thermal maximum occurred 4,000 years before it occurred in northeast Canada and again the LIS was to blame.

The world ocean is all connected and currents distribute heat from one area to another. While the ocean is never at thermal equilibrium, over long periods (hundreds of years) heat can be redistributed all over the world. Rosenthal, et al, 2013 chose an area in Indonesia that is well located to reconstruct past Pacific Ocean heat content. They used a suite of sediment cores from the sea floor of the Makassar Strait and the Flores Sea (see Figure 2 below) to perform the reconstruction. These areas are major conduits for the exchange of water between the Pacific and the Indian Oceans and collectively they are referred to as the “Indonesian Throughflow.” The shallower current (0-200 meters) is from the North Pacific Ocean and the deeper current gets a large contribution from the Banda Sea and the South Pacific. The study uses both Magnesium/Calcium ratios and Oxygen isotope ratios in Foraminifera to reconstruct the temperatures of the past. Because the Foraminifera studied live at different depths reconstructions of both the surface temperatures and the intermediate depth temperatures were possible.

Figure 2

Figure 3 is taken from a portion of Figure 2 in Rosenthal, et al. 2013. In graph A the green curve is the reconstructed average surface water temperature for 30°N to 90°N latitude and the red curve is the reconstructed global average surface water temperature. In graph C the Northern Hemisphere (30°N to 90°N latitude) reconstructed average intermediate water temperature for a depth of 500 meters is plotted. Both plots show that Northern Hemisphere ocean temperatures between 9,000 BP and 7,000 BP were 2.5°C+-0.4°C warmer than the late 20th Century. Global Ocean temperatures are estimated to be 0.7°C warmer than in the late 20th Century.

Figure 3

In addition to warming the northern oceans, the Earth’s precession cycle also moves the “ITCZ” or the Intertropical Convergence Zone according to Michael Bender’s “Paleoclimate.” The ITCZ is a zone of warm rising air and high precipitation. This zone follows the sun, so when the Earth was closest to sun in the northern summer 10,000 BP the ITCZ was farther north and the Northern Hemisphere tropics received more rain. Currently the ITCZ is roughly centered on the equator (5.3°S to 7.2°N). In Africa, as everywhere on land, it moves a lot from summer to winter. However, it stays south of the Sahel, about 15°N. This process contributed to the Sahara region becoming a desert roughly 5,000 BP as the ITCZ moved south. In China, An, et al, have found that the peak monsoon precipitation event moved from northern China 10,000 BP to Southern China 3,000 BP. This suggests that China has been getting progressively cooler and drier over the last 10,000 years.

Climate and climate change are long term processes. Looking long term, it is clear the Earth and especially the Northern Hemisphere are cooler today than 7,000 BP and we are in a cooling trend. For a longer perspective see my previous post “Climate and Human Civilization over the last 18,000 Years.” Might this trend be changing and might it be due to man’s influence? Perhaps, at least in part. But, it is very premature to predict a disaster based on a shaky 150 year surface temperature record. Particularly when the record does not agree with existing atmospheric balloon and satellite datasets that are of arguably better quality. Further, it is clear that the enormous heat capacity of the world ocean will dampen any radical atmospheric temperature changes. Basically, there is nothing to worry about, no radical action is required.

One more point, the media and the climate alarmists like to say that the reason atmospheric temperatures are not rising with the increase in carbon dioxide is that the extra heat is “hiding” in the deep ocean. It has to be the deep ocean because measurements of shallow ocean temperatures have not shown any excess warming. Certainly, as we have seen, most of the heat is going into the oceans. But, the temperature rise caused by that transfer is very small. Since heat only moves from a warmer object to a cooler object, the heat will never exit from the ocean until the atmospheric temperature drops. At that point we will want that heat. If indeed, carbon dioxide is causing more heat to be trapped in the atmosphere, the oceans are the perfect place for it to go.

December 20, 2015

 

Climate and Human Civilization over the last 18,000 years, updated

By Andy May

This is an updated timeline of climatic events and human history for the last 18,000 years. The original timeline was posted in 2013. The updated full size (Ansi E size or 34×44 inches) Adobe Reader version 8 PDF can be downloaded here or by clicking on Figure 1. It prints pretty well on 11×17 inch paper and very well on 17×22 inch paper or larger. To see the timeline in full resolution or to print it, you must download it. It is not copyrighted, but please acknowledge the author if you use it.

Continue reading “Climate and Human Civilization over the last 18,000 years, updated”