What the Medieval Warm Period Can Tell us about the Future of Global Warming and World Civilization

[Time for change]

The scientific consensus on global warming is clear: Global warming is real, is produced by greenhouse gases due to industrial activities, is highly likely to have catastrophic effects on the world population, and can be mitigated only by changing the industrial causes of the production of greenhouse gases.

The extent of that consensus was shown by a study conducted by the Intergovernmental Panel on Climate Change (IPPC), of 928 papers on the subject appearing in peer reviewed scientific journals between 1993 and 2003. Of those papers, 75% agreed with the above stated consensus, while the other 25% dealt with methodological issues and did not voice an opinion on the consensus either way. Not a single paper disagreed with the consensus.

In addition to the IPPC, all other major scientific organizations in the United States with expertise on this issue agree with the consensus. These include the American Meteorological Society, the American Geophysical Union, and the American Association for the Advancement of Science.

On the other side of the issue are corporations whose profits depend largely on the continued emission of greenhouse gases, several politicians who receive money from those corporations, and some of the national news media.

One issue that the opponents of the scientific global warming consensus bring up to support their argument is the Medieval Warm Period, a period of generalized global warming occurring approximately between 800 A.D. and a little after 1200 A.D. They make two points with respect to this period: 1) This warming period clearly was not the result of greenhouse gas emissions; and, 2) There is much historical evidence from Europe which suggests that, far from being a period of unmitigated catastrophe, this period represented more of a welcome change from previous centuries of unpleasant cold climate.

Brian Fagan addresses this issue in detail in his new book, “The Great Warming – Climate Change and the Rise and Fall of Civilization”. In that book he describes in great detail the world wide effects of the Medieval Warm Period, and then what this period has to tell us about the future of global warming and its effects on world civilization. But before considering his research, let’s take a look at the scale of recent global mean surface temperatures, and projected future temperatures, compared to those estimated to have occurred during the Medieval Warm Period.


Comparisons of Medieval Warm Period global mean surface temperatures with current and projected temperatures

In the one hundred years ending in 2005, the global mean surface temperature increased about 0.75 degrees Centigrade (1.35 degrees Fahrenheit).

Projections for the 21st Century, assuming current trends in greenhouse gas emissions, are for a substantial acceleration of global warming – a rise in global mean surface temperature of about 4 to 5.5 degrees Centigrade. Compared to the 0.75 degrees Centigrade increase during the 20th Century, that is about a 6-fold rise in the rate of global warming.

The graph below compares global temperatures during the medieval warm period, compared to the past century, by showing global temperature trends over the past thousand years. It’s difficult to ascertain the precise magnitude of the temperature increase during the Medieval Warm Period by looking at this graph, because of the different estimates and because it doesn’t cover the time preceding the Medieval Warm Period. But it appears that the mean global temperature during the Medieval War Period (prior to 1000 A.D. to about 1200 A.D.), compared with the following several centuries (called the “Little Ice Age”), was only about 0.3 degrees Centigrade warmer, at most.



There are three things worth noting about this graph: 1) the variability of the different temperature estimates during the early centuries of the Second Millennium; 2) the fact that current temperatures already exceed even the highest estimates of temperatures that characterized the Medieval Warm Period; and 3) the great acceleration in temperature rise during the 20th Century.

The bottom line is that current global temperatures and temperature increases are substantially higher than those seen during the Medieval Warm Period. And worse still are the projections for the 21st Century, which dwarf temperature increases seen during the 20th Century.


CLIMATE EFFECTS DURING THE MEDIEVAL WARM PERIOD

Fagan devotes the first chapter of his book to the effects of the Medieval Warm Period in Europe, where the effects were indeed positive – as Europe was one of the colder areas of the civilized world. But in marked contrast to the effects in Europe, the effects in many other parts of the world were catastrophic. And the biggest element of those catastrophic effects was drought. Fagan explains in the preface to his book:

We cannot understand the significance of the Medieval Warm Period without traveling far beyond Europe, where the effects of the warmer centuries were strongly positive and the continent saw the cultural flowering we now call the High Middle Ages…

While Europe basked in summer warmth… much of humanity suffered through heat and prolonged droughts. A huge swath of the world… experienced long periods of severe aridity. Drought cycles settled over the Saharan Sahel… creating havoc. Farmers went hungry, civilizations collapsed, and cities imploded… Drought was the silent killer of the Medieval Warm Period.

Fagan goes on to describe his research on the effects of the Medieval Warm Period in several parts of the world other than Europe. He concludes the second to last chapter of his book by saying “Looking at the global picture, it is tempting to rename the Medieval Warm Period the Medieval Drought Period.” Let’s consider a sampling of that global picture.


Central Asia and the Mongol conquests – Drought as a cause of war

Unlike Europe, much of the steppes of central Asia were located far from the temperature moderating influences of large bodies of water. That area was therefore much more susceptible to extremes of temperature and consequent droughts. Largely because of the great susceptibility of central Asia to drought, its human inhabitants were dependent upon horses to move quickly to inhabitable lands when cyclical climate conditions changed for the worse. Fagan describes their situation when their climate became too dry:

The nomads were forced to eat their dead horses. If the dry cycle lasted two or three years, the effects would be even more disastrous. Unable to find food, deprived of their horses .… they had no option but to join other groups, starve to death, or move… There was only one solution: move to better grazing. This usually lay… on the margins of – or often on – lands settled by farmers…

Each temperature change and rainfall shift dramatically altered the relationship between the nomads and their environment. Drier periods, with their life-threatening droughts, brought stunted pasture, decimated herds, extended searches for grass and water, and inevitable, often violent encroachment into neighbors’ territories.

Fagan then goes on to talk about the probable relationship between the widespread conquests of the Mongols under Genghis Kahn and the Medieval Warm Period:

(The evidence) places Ginghis Khan’s conquests within an extended warm period during which frequent droughts may have wreaked havoc on steppe pastures in a world where people depended on horses… If the Mongolian tree-ring sequence is a reliable barometer of the cyclical temperature and rainfall of the Great Khan’s time – and there is every reason to believe that it is – then it’s clear that the climatic pump of the steppes acted… putting nomads and their restless movements into play on the steppe and bringing them into conflict with their neighbors… Ginghis Khan rose to power at a time when drier conditions shrank pasturage on the steppe.

Ginghis Khan’s incursions into China and his merciless smashing of the Seljuk Turks’ empire in central Asia in 1220 and 1221 brought the Mongols deep into settled lands… The conquests continued after Ginghis was gone… Batu, a grandson of Ginghis, soon conquered the Crimea, then ravaged what is now Bulgaria as well as fourteen Russian cities… Next he turned his attention to Europe… conquered Poland and Hungary, and swept into Austria, where they prepared for a probe into the heart of Europe in 1241.

And then it stopped. Fagan explains:

Batu Kahn’s withdrawal coincided with the return of cooler, wetter conditions, which brought improved pasturage to the steppes. His kingdom flourished during generations of good pasturage, when warfare died down… There was no incentive for ambitious conquests when grazing was plentiful…But what would have happened if the climatic pendulum had not swung… Warfare and restless movement would have continued… Perhaps as early as early as 1250, Europe would have become part of a huge western Mongolian empire.

Africa

The Saharan Desert and its surroundings resemble the Eurasian steppes in that it is very sensitive to climate changes. During dry periods the desert expands, while during wetter periods it contracts. The following excerpts from Fagan’s book give some idea of what the inhabitants of this area went through during the Medieval Warm Period:

When drought years descend on the Sahara, water sources and grazing dry out, and the sparse desert populations move out… Between A.D. 900 and 1100, there was an abrupt transition to much more unstable conditions… Such unstable phases, with often prolonged droughts – and one stresses the word “prolonged” – would have been periods of remarkable difficulty and change for those who experienced them… During dry cycles… the numbers of dead and exhausted beasts could be enormous; casualties were often in the hundreds from one caravan alone. The bleached skeletons of camels and their drivers littered the routes.

The collapse of the Anasazi

The Anasazi resided in current day Southwestern U.S., including parts of Utah, Arizona, New Mexico and Colorado. This area first became populated with humans around 11,000 B.C., though agricultural societies in that area did not arise until about A.D. 1. Anasazi civilization lasted from about A.D. 600 to 1200. The reason for their demise is described by Jared Diamond, in his book “Collapse – How Societies Choose to Fail or Succeed” (Chosen as “Best Book of the Year” by The Boston Globe, the Los Angeles Times, The Washington Post, the San Francisco Chronicle and others).

The Anasazi environment was very fragile, owing mainly to the lack of water and the related problem of deforestation, which was due to slow re-growth of trees because of the paucity of water. That environment could have supported a very thinly populated society, but as the population grew the environmental pressures rose. Most important, a larger population required more water, so water tables became depleted, resulting in a dangerous scarcity. Droughts periodically resulted in widespread starvation.

Chaco Canyon was the capital of Anasazi civilization. The Anasazi were a highly hierarchical society, such that a well fed elite living in luxury came to occupy Chaco Canyon, while the peasantry did all the work and produced the food that supported the elite. Diamond notes that “Chaco Canyon became a black hole into which goods were imported but from which nothing tangible was exported. Into Chaco Canyon came those tens of thousands of big trees for construction…”

The final blow was a drought in about A.D. 1130. Chaco Canyon became abandoned as many probably starved, people killed each other, and others fled the region. Diamond sums up what happened:

Over the course of six centuries the human population of Chaco Canyon grew, its demands on the environment grew, its environmental resources declined, and people came to be living increasingly close to the margin of what the environment could support. That was the ultimate cause of abandonment. The proximate cause, the proverbial last straw that broke the camel’s back, was the drought that finally pushed Chacoans over the edge; a drought that a society living at a lower population density could have survived… The initial conditions of abundant nearby trees, high groundwater levels… had disappeared.

The fall of Mayan civilization

The Maya were the most advanced civilization in pre-Columbian America, and the only one with extensive preserved writing. They occupied parts of Mesoamerica, which extended from present day central mid-Mexico to Honduras. The so-called Classic period of Mayan civilization began around A.D. 250. The Mayans were a highly hierarchical society. Diamond explains:

There was a tacitly understood quid pro quo: the reason why the peasants supported the luxurious lifestyle of the king and his court… and built his palaces was because he had made implicit big promises to the peasants… Kings got into trouble with their peasants if a drought came, because that was tantamount to the breaking of a royal promise.

Though the Mayan environment was much less fragile than the environment in which the Anasazi resided, the collapse of Mayan civilization has much in common with that of the Anasazi. Deforestation exacerbated water scarcity problems because of the role that trees have in maintaining the water cycle. Perpetual wars among the Mayan people also exerted a heavy toll. A severe drought starting in the early tenth century was the proximate cause of the fall of Mayan civilization, as between 90 to 99% of the former Mayan population disappeared. With regard to the Mayan response to its environmental crises, Diamond has this to say:

We have to wonder why the kings and nobles failed to solve these seemingly obvious problems undermining their society. Their attention was evidently focused on their short-term concerns of enriching themselves, waging wars, erecting monuments, competing with each other, and extracting enough food from the peasants to support all those activities. Like most leaders throughout human history, the Maya kings and nobles did not heed long term problems…

PORTENTS FOR THE FUTURE

Comparison of the Medieval Warm Period with today

In the final chapter of his book, Brian Fagan puts the Medieval Warm Period in perspective by comparing it with today’s situation:

Our current warming has not lasted nearly as long as the period studied in this book. It is, however, a steady and well-documented trend, with no downward curve in sight. And unlike the situation a millennium ago, humans are numerous enough, and our outputs profuse enough, to push the trend further and faster. What is not debatable is that if we reenact the climate history of a millennium ago – let along see the earth get even warmer – we will see how vulnerable humans are to the forces of their environments. But if you look at the warm centuries with a global perspective, the wide incidence of drought is truly striking and offers a sobering message about tomorrow’s world. Prolonged aridity was widespread in medieval times and killed enormous numbers of people. Evidence is mounting that drought is the silent and insidious killer associated with global warming. The casualty figures are mind numbing. About 11 million people between Kenya, Somalia, Ethiopia, and Eritrea were in serious danger of starvation as a result of multiyear droughts in 2006.

A projected future if greenhouse gas emissions continue at current levels

Fagan explains that, notwithstanding the misery in which much of our world’s inhabitants currently live, the outlook for the future is far bleaker if nothing is done to substantially reduce greenhouse gas emissions into the earth’s atmosphere:

Computer models of future aridity resulting from the impacts of greenhouse gas emissions are truly frightening. At present, extreme drought affects 3% of the earth’s surface. The figure could rise as high as 30% if warming continues, with 40% suffering from severe droughts, up from the current figure of 8%... Then the center ran the model factoring in the impact of greenhouse gases… The results implied that future changes in drought without anthropogenic warming would be very small indeed…

The United Nations Environment Program reports that 450 million people in 29 countries currently suffer from water shortages. By 2025, an estimated 2.8 billion of us will live in areas with increasingly scarce water resources… Contaminated water supplies are a worse killer than AIDS in tropical Africa… The number of food emergencies in Africa each year has already almost tripled since the 1980s… Future drought-related catastrophes will make these preliminaries seem trivial…

A thousand years ago, with many fewer people to feed… (people) could adapt their irrigation strategy to prolonged droughts. Their modern successors, living in crowded cities, shantytowns, and an increasingly congested rural landscape, cannot do so… When one realizes that droughts in the sparsely inhabited Saharan Sahel claimed over 600,000 lives in the droughts of 1972-75 and again in 1984-85, one can only imagine what the magnitudes of these disasters would have been had farming populations been at today’s levels… Today, the number of people in the world who are highly vulnerable to drought is enormous and growing rapidly, not only in the developing world but also in densely populated areas such as Arizona, California and southwestern Asia… The droughts of the future will become more prolonged and harsher… Today, we are experiencing sustained warming of a kind unknown since the Ice Age. And this warming is certain to bring drought – sustained drought and water shortages on a scale that will challenge even small cities, to say nothing of thirsty metropolises like Los Angeles… Now we confront a future in which most of us live in large and rapidly growing cities, many of them adjacent to rising oceans and waters where Category 5 hurricanes or massive El Ninos can cause billions of dollars of damage within a few hours. We’re now at a point where there are too many of us to evacuate… beyond the capacity of even the wealthiest governments to handle.

On the coming wars, Fagan has this to say:

Imagine how many people might uproot themselves if the choice were between famine and food. Many believe the wars of coming centuries will not be fought over petty nationalisms, religion, or democratic principles, but over water, for this most precious of all our commodities may become even more valuable than oil. They are probably correct.

The need for an expanded way of thinking

Fagan explains that, though the temptation is to think in terms of short-term palliatives, that kind of thinking will be grossly inadequate to the challenges that we now face. He explains:

Drought and water are probably the overwhelmingly important issues for this and future centuries, times when we will have to become accustomed to making altruistic decisions that will benefit not necessarily ourselves but generations yet unborn. This requires political and social thinking of a kind that barely exists today, where instant gratification and the next election seem more important than acting with a view to the long-term future…

Thanks to a new generation of science and thanks to activists ranging from Al Gore to university students, global warming has become a political issue… Yet it’s striking, and very frightening, that the spectre of drought is still so widely ignored.

THE U.S. PRESIDENTIAL CANDIDATES ON GLOBAL WARMING

The challenges of the environmental crisis that we face today are far too great to think that one U.S. Presidential election will come near to solving them. But still, the differences between the two major party candidates on this issue are so great that this post wouldn’t be complete unless I mentioned them.

John McCain’s rhetoric would make you think that he takes our global warming challenge seriously. But even if we forget about McCain’s recent flip flops on offshore oil drilling, a look at his record reveals that his plans and actions have never been consistent with his rhetoric on global warming.


Positions on capping greenhouse gas emissions

Mark Hertsgaard explains some of the problems with McCain’s plan to combat global warming. Noting that Obama’s plan for an 80% cut on greenhouse gas emissions by 2050, using a “cap-and-trade” system that “sells corporations permits to emit greenhouse gases and then invests the revenue in green energy development and rebates to Americans hit with higher energy prices”, is consistent with what scientists say is necessary, Hertsgaard notes that McCain:

supports a 60 percent emissions cut by 2050. But it is doubtful that McCain's approach would actually deliver such large cuts, since his cap-and-trade system would give most permits away free, a provision environmentalists attack as a corporate giveaway.

In other words, aside from advocating a much smaller cut in emissions than Obama, McCain seems to hold the opinion that purely voluntary cuts in greenhouse gas emissions by industry will work. And furthermore, he doesn’t even appear to understand the difference. Joseph Romm explains:

In a recent Republican debate, he (McCain) denied that a cap and trade system is a mandate, even though it would arguably be the most far-reaching government mandate ever legislated. Moreover, like most conservatives, he doesn't understand or accept the critical role government must play to make that system succeed.

The roles of judges, including the U.S. Supreme Court justices

McCain’s affiliation for anti-environment Supreme Court justices poses another big obstacle to the success of any efforts he might advance as President to combat global warming, especially considering that John Paul Stevens is now 87 years old and Ruth Bader Ginsburg is in bad health.

McCain has made it abundantly clear that he plans to appoint judges who are what he calls “strict constructionists” and won’t “legislate from the bench”, meaning ones like Scalia, Thomas, Alito, and Roberts. Yet in a recent case where the USSC ruled in a 5-4 decision that the EPA has the responsibility to regulate carbon dioxide as an air pollutant, Scalia (joined by McCain’s three other favorite USSC justices) argued in dissent that carbon dioxide, “which is alleged to be causing global climate change”, is not an air pollutant.


Clean energy development

When McCain was asked his opinion on subsidies for clean energy technology such as wind and solar, he said:

I'm not one who believes that we need to subsidize things. The wind industry is doing fine, the solar industry is doing fine. In the '70s, we gave too many subsidies and too much help, and we had substandard products sold to the American people, which then made them disenchanted with solar for a long time… There’s a point where you should let the free-enterprise system take over.

Yet, McCain has sponsored legislation, “The 2007 Climate Stewardship and Innovation Act”, in collaboration with Joe Lieberman, which would provide $3.7 billion in subsidies for nuclear power plants.

In marked contrast, Obama has detailed extensive specific plans for clean energy development, including:

As part of his $150-billion proposal, Obama plans to suggest a $50-billion Capital Technologies Venture Fund, with $10 billion a year invested over five years, to help move new clean-energy technology to market.

Energy efficiency

Another essential part of any comprehensive energy plan to lower greenhouse gas emissions is energy efficiency. Joseph Romm points to California’s program as a model in this area, noting that the average Californian generates one third of green house gas emissions as the average American, while maintaining the same electricity costs. He notes the following components as the reasons for their “remarkable achievement”:

 The strongest building-energy codes in the country
 A state energy commission that oversees subsidies and deployment programs for energy efficiency and renewable energy
 The toughest air pollution regulations in the country
 Smart utility regulations

Romm notes that Obama’s plan is very specific in these areas, whereas McCain has no plans for improving energy efficiency at all, though he does sometimes use the words “energy efficiency”.


Voting records

Most surprising of all, given McCain’s positioning himself as a maverick on global warming, is his actual voting record. The non-partisan League of Conservation Voters (LCV) gives him a 24% lifetime score for his global warming policies, and a 0% score for 2007. His overall environmental score with the League of Conservation voters was 0% for 2007.

Then there were two recent instances (December 2007 and February 2008) where the Senate missed by one vote an effort to end a filibuster that would have provided billions of dollars for clean energy incentives. Those two examples of 59-40 failures had one thing in common: McCain was the only Senator who didn’t vote. And for one of those votes he was in Washington D.C. at the time.

In stark contrast to McCain’s 24% lifetime LCV rating for his global warming policies, Obama received a rating of 86%.

[madrchsod]

1. very good job of presenting these historical references

the sad thing is we have lost 8 years of progress on a country wide unified plan. individual states have done the work so far. the federal government is the only force that can unify the resources necessary to achieve the goal of reduced emissions and alternate fuel.

[Time for change]

11. Thank you -- That's a terrible shame

As the most powerful nation on earth, and as the emitter of 25% of the world's greenhuse gases, we should be taking a leading international role on this issue. Instead, George W. Bush unsigned the Kyoto treaty that Bill Clinton signed, and systematically censored government scientists who tried to discuss the problem of global warming publicly.

[Spouting Horn]

30. The Senate

rejected Cap and Trade (Kyoto) 99-0.

Is consensus a scientific argument in and of itself? (Ie, does it follow the Scientific Method?)

Also, James Hansen, Government scientist, has given over 1,400 interviews and speeches (as a gov't employee) in the last several years.

[Time for change]

33. No, consensus isn't a scientific argument in and of itself

But this particular consensus is based on tons of scientific arguments

[opihimoimoi]

2. McNemic has an Enimic Green to his proposals....he is a fraud..pretending green when its really a

Puke Green....not a nice green at all....more like sick green...

[Time for change]

12. Yes

Diarrhea green.

I even received e-mails from him, telling of his work to address global warming, and how important that work is, and asking for money.

Jesus, he doesn't have a clue. His plan to reduce greenhouse gases by 60% by 2050 relies on VOLUNTARY agreements by corporations who emit greenhouse gases to cut down on them. That's because he doesn't believe in mandates. rofl rofl:

He wants to have it both ways. Green to environmentalists, while a "free market" defender against mandates to corporate polluters.

[opihimoimoi]

14. Trying to thread the tiny needle with a 16 penny spike....The Dufus keeps trying

but FAILS to understand the mechanics of the whole picture...Very Few on the Right do...

Tell what...them scrubbers to cleanse the shit coming outa them chimney's.is not that expensive if we engineer it right... Those Spanish moss things seen hanging from trees in the South....they are able to reduce Co2...tests done in the 60's confirm this...if engineered to take out most of the crap, if not all of it...would help immediately...but thats only one part of the equation...

He has not ventured into the other side of the equation at all...Dufus that he is....Unprepared and under-educated...

[Psyop Samurai]

3. k&r....nt

[bertman]

4. OUTSTANDING!!! THANK YOU FOR POSTING THIS.

[Time for change]

16. My pleasure, thank you

[Maine-ah]

5. bookmarked for when I have a little more time

interesting what I read so far, great post!

[Prophet 451]

6. Global warming doesn't exist!

It's all because of the sun! Or volcanos! Or something. Whatever it is, it's nothing I can do anything about so leave me and my SUV alone! I'm series, I saw a show about it and Rush told me so and Rush never lies!

Fox, do I get my own show yet? I can keep the faux righteous indignation going for hours!

[JNelson6563]

7. Kicked, rec'd and bookmarked

Bravo! Well done!

Julie

[Time for change]

17. Thank you

[Duppers]

18. same here - BRAVO!

Time for change

[Uncle Joe]

8. I don't have time to do your post justice by reading it all tonight.

So I'll just kick it now and come back tomorrow.

Thanks for the thread, Time for change.

[NewJeffCT]

9. Meanwhile, the RWers were orgasming over some group today

that supposedly changed their position from saying that climate change is man-made to saying that some aspects of global warming need further study...

didn't say that it wasn't happening, mind you, just that some aspects needed further study.

[desktop]

10. Interesting that Obama has an 86 favorable score and McCain 24

If you hadn't read these scores here or somewhere else, you would swear McCain was just as green as Obama. Because that is what the main stream media continually tells us.

[Time for change]

15. It's not just the scores for their voting records

McCain's plan to reduce greenhouse gases by 60% by 2050 relies on VOLUNTARY agreements by corporations who emit greenhouse gases to cut down on them. That's because he doesn't believe in mandates.

He wants to have it both ways. Green to environmentalists, while a "free market" defender against mandates to corporate polluters.

[alfredo]

13. K&R

‘A new scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually die, and a new generation grows up that is familiar with it.”
Max Planck, a German physicist (1949)

will there be a new generation?

[AZ Criminal JD]

19. The OP is trying to have it both ways

First he/she can not explain the increase in temperature in the Medieval Warm period so he/she says that it really didn't increase as much as the present conditions. But then he/she tries to present a situation of drought and chaos during that period based on a minor increase of less than 1 degree C. That is absurd on its face. The fact is we don't have a clue what the actual temperatures were 1000 years ago. It is pure speculation based on various theories which may or may not have some foundation in reality. What we do know is the earth warmed up 1000 years ago and then cooled off.

[Ichingcarpenter]

20. Interesting 3rd Grade Science you got going on there

Ignoring tree rings and ice cores.

[AZ Criminal JD]

22. Sorry there is no scientist who will tell you a tree ring or ice core can tell the exact degrees.

They can give ranges of cooling and warming. If you were home schooled tell your mother to get you some books written in the last 100 years.

[Time for change]

24. There are several ranges indicated in the graph in this OP

They all estimate degrees of cooling following the Medieval Warm Period that are less than 20th Century increases in global temperature. Are you aware of any estimates that contradict that?

[Time for change]

21. There are several estimates of temperatures during this period

made by climatologists, that I presented in the graph in the OP. All of them suggest much smaller temperature increases than we are now experiencing. You say that we don't have a clue as to what temperatures were then, yet you don't present the slightest reason for saying that.

The information on droughts that I presented are based on a ton of research by the authors of the books that I cite. Keep in mind that when global temperatures increase, the increase is seen much more over land than it is over water.

What information do you have to contradict any of this, other than your baseless assertion that "We don't have a clue"?

Anyhow, the projection for the 21st Century is 4-5.5 degrees Centegrade, which is close to 10 degrees F. And again, the increase would be much more on land than on water. You don't think that would cause droughts?

[AZ Criminal JD]

23. It may cause droughts somewhere and increase land for food production elsewhere.

The biggest land masses in the world right now are largely unused for food production. That would be eastern Russian, Northern areas of China, large areas of Canada and Alaska, and Mongolia. That is not the point however. The question is whether warming is man made or not. You have ignored the warming cycles and cooling cycles in the past.

[Time for change]

25. Name a warming cycle in the past that compares with the current warming

of three quarters of a degree centigrade over a single century.

So, you're claiming that current warming isn't man made? You disagree with every scientific peer reviewed paper on the subject that has appeared in recent years?

[AZ Criminal JD]

26. I can't name one because it can't be done scientifically.

We think we know broad ranges of temperatures for different eras but we really don't know, particularly down to a century and down to a degree C. That is just foolish and you would be laughed out of any university if you stated that. I am not going to argue with you about papers because it is a fools errand. You are a true believer and anything I say you would just ignore or say that I am receiving money from corporations or something. There are plenty of scientists who believe any warming that may be occurring (went down a degree in the last 10 years -- ouch!) is not man made. The people who condemned Galileo were peer reviewed also.

[Time for change]

28. What makes you think you know more about this than the IPPC,

the American Meteorological Society, the American Geophysical Union, and the American Association for the Advancement of Science?

Who are these scientists you claim who believe the warming of the past century is not man made, and who pays them?

[AZ Criminal JD]

31. I don't look at other peoples W-2s

Who pays the scientists you quote? What is the ideology of people giving out grants to write papers at the National Science Foundation? Do you seriously think people who don't come up with man-made warming stats would be given a grant? If so, you know nothing about how grants and "peer reviewed" papers are done.

[Time for change]

32. With all your blabber, you haven't cited a single source that supports your point of view

Go ahead, try to find one that isn't in the pay of the oil companies.

[AZ Criminal JD]

34. And you haven't been able to answer one question I asked.

Your thinking is in defiance of everything we know about geology and other earth sciences. Why does the earth go through warming and cooling cycles? Are you saying that it hasn't? Why is this one (if it occurring -- again down 1 degree C in the last 10 years -- facts are such ugly things) the result of man and the others not? Got to go see if the mailman delivered my oil company check.

[judasdisney]

27. The Big Difference -- the Medieval Warming Period didn't have a feedback loop

especially regarding the "tipping point" of loss of reflectivity of ice. At a certain unknown future point, returning seasonal ice cover does not return. Consequently, the sunlight which would have been reflected off the white polar ice, away from the earth, is instead absorbed, creating a heating loop to which there is no upper limit.

It's not like "Alaska will have nicer weather," but more like "Everything below the Arctic Circle becomes a desert, and we don't know what happens above the Arctic Circle yet. Not to mention the ocean die-off."

http://www.ecobridge.org/content/g_fbk.htm

[cprompt]

29. excellent

read, thanks for taking the time for this, K&R

[dougolat]

35. War on Terra

It's not just the warming, ( that's threatening the benefits of all those ice-ages; when the methane escapes, we're not putting it back)(and, strangely enough, the CO2 greenhouse effects have been partly countered by increased albedo from our dust and high-altitude pollution)
How about those petro-chemical plastics? They're degrading into small particles that harm the base of the ocean food chain. Along with acidification, which can dissolve sea shells, the oceans are heading for a population of mostly jellyfish.
The geological record shows trees in Antarctica, but that means nothing to those who think the world is 5,000 years old.(They're worried about gay marriage)
One of the reasons we stay in Iraq and Afghanistan must be to keep things stirred up: if it settles down they might notice the depleted uranium. ( plenty more to go around: Hannaford has big leaks,Russia has several Chernobyl zones and the French aren't still dumping in the ocean, are they?)
When all those tropical diseases reach Canada, maybe we'll regret wasting all that research on boners and baldness.
The upside is that when conditions change enough, we'll see what some of that dormant DNA does!