Malthus and Global Warming

[Ara Pacis]

The tipping points that concern me and many others involve feedbacks like large scale release of methane clathrates from tundra and seafloor deposits, if that happens as would seem almost inevitable with a business as usual model of CO2 release then we are dealing with some very catastrophic changes in the global environment.

Perhaps in the Arctic, but deep water methane clathrates probably won't for quite some time, if ever.

To tie this into Malthus, we can look at the possible results. If methane does boil up from arctic sediments and permafrost, it could cause O2 to permeate out of the water, killing marine life. Once on land, this mixture of gases could be heavier than air (unlike pure methane) and flow over land, suffocating surface life and perhaps becoming ignited by lightning, other natural causes or human causes to cause fires. These fires might put smoke and dust into the atmosphere. Smoke does two things, it shades the surface, causing local cooling, but it also absorbs heat, causing atmospheric warming, which will eventually probably mix down to the surface again.

[Robert Tulip]

Malthus held that population increases exponentially and food supply increases arithmetically, making famine inevitable. The global food security crisis of 2008 arose from falling rates of agricultural productivity growth and the diversion of food to biofuel causing price spikes in corn and other staples. Rising education and wealth slow population growth, with the UN predicting global numbers will stabilise at nine billion by 2050. Agricultural productivity growth is not fast enough to feed this expected population increase.

The challenge of achieving exponential food productivity increase is constrained by conversion of prime crop land to housing, and also by climate change. The Malthus dilemma could be solved if humans were rational, but the inability to base public policy on evidence suggests that we still retain much of our instinctive emotional baggage that prevents rational policy. If our genetics cause us to expand in numbers when we can, beyond the carrying capacity of our natural systems, then correction is inevitable. Jared Diamond's book Collapse and Tim Flannery's The Future Eaters present Easter Island as a parable for the fate of the earth. Irrational focus on symbolic ritual (building stone statues) led to social conflict and catastrophic population decline. The global parallel is that natural systemic constraints could produce conflict and war which would then cause famine and death on large scale.

With CO2 emissions rising exponentially to fuel economic growth, we are on track for a six degree global temperature increase this century. A fever of four degrees is deadly for a person, so emissions are a poisonous byproduct of growth, serving as a nemesis. Changing weather patterns, the possibility of sea level rise from a tipping point and the increase of pests, diseases and weeds all mean that achieving the food production levels required to prevent famine will be difficult. Famines are generally the result of politics rather than food shortage, but the natural context is not making the prevention of famine any easier.

http://en.wikipedia.org/wiki/Climate...nd_agriculture details expected impact of climate change on agriculture.

[starcanuck64]

Perhaps in the Arctic, but deep water methane clathrates probably won't for quite some time, if ever.

To tie this into Malthus, we can look at the possible results. If methane does boil up from arctic sediments and permafrost, it could cause O2 to permeate out of the water, killing marine life. Once on land, this mixture of gases could be heavier than air (unlike pure methane) and flow over land, suffocating surface life and perhaps becoming ignited by lightning, other natural causes or human causes to cause fires. These fires might put smoke and dust into the atmosphere. Smoke does two things, it shades the surface, causing local cooling, but it also absorbs heat, causing atmospheric warming, which will eventually probably mix down to the surface again.

There are a lot of unknowns when it comes to methane clathrates, first of all how much there is of them, estimates range from 2,000 to 24,000 Gts.

I'd need to search, but I'm pretty sure that James Hansen did a paper on the transfer of deep water submergence from the poles to the mid-latitudes in extreme warming events of the past. If that does occure, then instead of being cooled by cold water that dives to the ocean bottom off of Greenland or Antarctica, ocean deep water could be supplied by relatively warm water from the mid Pacific for instance. At that point deep water methane deposits could become less stable.

Climate and tectonics has favoured the buildup of large amounts of methane clathrates near the poles in recent epochs, isostatic rebound from ice loss and melting permafrost could help release large amounts of CH4.

[starcanuck64]

It's also a question as to whether or not the effects are as bad as certain groups are claiming. While there certainly will be consequences, I have to wonder if it really will be an "imminent threat to global civilization.

What certain groups are you refering to here?

My concerns are based on the information I've sourced from IPCC reports, from NASA and GISS, from NOAA and other academic sources like Ohio State University and the work done by Lonnie Thompson and many others.

It seems to me that if climatologists and paleo-climatologists are sounding serious concerns about the future results of altering the concentration of such an important persistant greenhouse gas in the atmosphere then we would be wise to pay attention.

While it's the changes in orbital dynamics that initiate the glacial and inter-glacial cycles the Earth has been going through in the last several million years, it's the strong feedbacks from forcings like CO2 that allow the massive changes to take place. A few tenths of a watt per metre squared from changes in insolation isn't going to allow the build-up then breakdown of ice sheets that can cover much of the Northern hemisphere miles deep, the several +/-w/m^2 forcing that does result from the increased uptake or release of C02 will.

If changing the concentration of CO2 by about 100ppm can result in such a dramatic change over millenia as we see during the glacial/inter-glacial cycle, then the very important question becomes what will be the result of increasing that concentration by the same amount in a few centuries as we've already done and possibly double that if the trend continues just a few decades more.

It's an experiment on a vast scale in real time, and going by the paleo-climatic evidence this can and sometimes does result in ecological catastrophy. It comes down to a function of time and magnitude. We're currently consuming fossil fuels on a vast scale(billions of tons a year) and meeting both criteria. How long we do this will determine the eventual outcome.

[Ari Jokimaki]

Because, remember, when it is cold, it is weather, but when it is hot, it is global warming.

Can you prove that this drought is not just a drought? That maybe it is weather just as much as last year's cold?

Global warming is expected to increase hot weather events and in some parts of the Earth it is expected to increase droughts. Do you want to hide behind the fact that it is difficult to attribute single heat or drought events to global warming?

[starcanuck64]

Global warming is expected to increase hot weather events and in some parts of the Earth it is expected to increase droughts. Do you want to hide behind the fact that it is difficult to attribute single heat or drought events to global warming?

As James Hansen shows, extreme hot weather events have increased by an order of magnitude in recent years compared to the stable base period between 1951-1980.

http://www.columbia.edu/~jeh1/mailin...DicePopSci.pdf

An important change is the emergence of a subset of the hot category, extremely hot outliers, defined as anomalies exceeding +3σ. The frequency of these extreme anomalies is about 0.13% in the normal distribution, and thus in a typical summer in the base period only 0.1-0.2% of the globe is covered by such hot extremes. However, we show that during the past several years the global land area covered by summer temperature anomalies exceeding +3σ has averaged about 10%, an increase by more than an order of magnitude compared to the base period. Recent examples of summer temperature anomalies exceeding +3σ include the heat wave and drought in Oklahoma, Texas and Mexico in 2011 and a larger region encompassing much of the Middle East, Western Asia and Eastern Europe, including Moscow, in 2010.

[Ara Pacis]

The heat wave, drought and warm winter is consistent with predictions of Global Warming. That's all one can really say or needs to say. Of course, the longer it happens, the less it's weather and more it's climate.

[aquitaine]

I live in the middle of farming country, and I can tell you none of those innovations have made it here. Drought has. Watch next year's food prices...


There are limits to what genetic engineering can accomplish. It's far from being a completed science.

I never said it was available to the market yet, but it has been demonstrated in testing fields. Regulatory approval for GMOs tends to take a while. And I do think it's a little early to say how limited genetic engineering is, since as you say it's not a completed science. That being said, the results have been extremely promising.

I'm not sure if this is directly related to malthusian principles, but much of the earth may be unlivable according to this 2010 paper from Purdue explaining how high wet-bulb temperatures can be incompatible with manmmalian physiology.



To tie this into Malthusian issues, we might consider the effect this might have on livestock, and how it might force people and animals to compete for space in regions that will naturally remain more compatible with life.

How fast might this happen? Probably not within the century, but...


Of course, we might mitigate that with air-conditioning and other technology... but those technologies use energy and all that stuff produces waste heat, and IIRC, a lot of AGW refers to GHG and sunlight and do not take into account man-made waste heat. Someone posted a link about that recently, suggesting that following the waste-heat trend-line we're on now could make earth too hot in a matter of 3-4 centuries.

Actually the only areas that are technically habitable to us are warm, tropical and subtropical climates. One thing our existence should have proven by now, we can live anywhere. From the icy arctic wastes to burning desert dunes. Saying that half the Earth will be uninhabitable sounds extremely alarmist.

In the case of alpine biotas, some of them are isolated from suitable habitats to migrate to and will simply disappear as the average temperatures climb in altitude. For ocean habitats, many species are associated with coral reef ecosystems at some point of their lifecycle which will have to migrate to deeper water or poleward fairly rapidly, something like 16% of coral reefs have been lost already.

This is not hard problem to overcome at all. There are some varieties of coral that have proven to be tolerant of higher ocean temps. So, we can "transplant" those varieties to restore destroyed reefs.

I think the main point about Malthusianism is the argument that species expand to take up what is available, and that there is no built-in mechanism that stops that, so that there is always some kind of environmental catastrophe. I think you can see this very commonly in nature, brewing being a good example. The yeast just eats up the sugar and then dies out when the environment becomes bad. Malthus believed that people would experience the same thing. And you are right about innovation. Humans are inventive, and it allows us to overcome things like that. But I think that history is inconsistent in this regard. There are examples of civilizations that appear to have suddenly collapsed, and many people believe it happened due to environmental catastrophes. While on the other hand, humankind as a whole has continued to progress, but not without glitches along the way.

The only firm example that I know of was the Mayans. There are other examples, like Easter Island, but from what I can tell these are just works of fiction.

If we are emitting greenhouse gases and aerosols on the same scale or larger than flood basalts that in the paleoclimatic record are closely associated with some of the most destructive phases of the geological lifecycle of the planet, then IMO it's irresponsible to ignore the possible consequences...especially if we have alternatives that offer a solution as are currently being discussed on other threads here.

I'm not ignoring the possible consequences, I'm questioning the severity. When I hear things about how the Permian Extinction holds lessons for us today, I cringe. Largely because when that mass extinction actually happened, the average global temperature was more than 25 degrees centigrade, a full 11 degrees hotter than it is today. Even by the IPCC's worst projections by 2100, the temperature rise will be 2 degrees C, a tiny fraction of that amount. So how exactly does one lead to another?

I'm hoping that thorium molten salt reactors will be the kick in the pants that gets things moving this way again.

They will be opposed for the same reasons the uranium reactors are. The problem is politics, not technology. And for obvious reasons those politics will not be discussed on the forum.

The heat wave, drought and warm winter is consistent with predictions of Global Warming. That's all one can really say or needs to say. Of course, the longer it happens, the less it's weather and more it's climate.

To be fair heat waves, droughts, and warm winters are also consistent with the normal behavior of climates. While again I am not denying global warming, there is more than one explaination for this particular event, and to say that global warming can only be the one possible explaination makes climate science sound like the psuedo science we know it isn't.

[Ari Jokimaki]

The only firm example that I know of was the Mayans. There are other examples, like Easter Island, but from what I can tell these are just works of fiction.

Other real examples from China in a recent paper (full text freely available in the abstract page):

http://www.springerlink.com/content/810r8273m1145363/

[Noclevername]

And I do think it's a little early to say how limited genetic engineering is, since as you say it's not a completed science.

Well, it's limited now. It's like if a parent is told that his kid is too small to ride the roller coaster-- it doesn't matter that someday the kid might be very tall. He still can't ride today. And we can only hope that the ride is still open by the time he grows up...

[Robert Tulip]

by the IPCC's worst projections by 2100, the temperature rise will be 2 degrees C

2°C is more like the best case. The worst projection for 2100 temperature rise in the 2007 IPCC report was 6.4°C (A1FI Fossil Intensive). The fifth IPCC report will be interesting reading given the growth of denialism and of emissions in recent years.

http://www.ipcc.ch/publications_and_...ctions-of.html provides the following scenarios for projected global average surface warming at the end of the 21st century.

Temperature Change (°C at 2090-2099 relative to 1980-1999)
Case   Best estimate   Likely range   
B1 scenario   1.8   1.1 – 2.9 
A1T scenario   2.4   1.4 – 3.8  
B2 scenario   2.4   1.4 – 3.8    
A1B scenario   2.8   1.7 – 4.4  
A2 scenario   3.4   2.0 – 5.4   
A1FI scenario   4.0   2.4 – 6.4

Observed emissions rates says between the 1990s and 2000s, the growth rate in CO2 emissions from fossil fuel burning and industrial processes increased. The growth rate from 1990-1999 averaged 1.1% per year. This tripled to an average of 3.5% per year for the time period 2000-2007. The emissions growth rate since 2000 was greater than that projected in the most fossil-fuel intensive SRES A1FI emissions scenario. Human-caused greenhouse gas emissions set a record in 2010, a 6% jump on 2009 emissions, exceeding even the worst case scenario cited in the IPCC Fourth Assessment Report.

[starcanuck64]

This is not hard problem to overcome at all. There are some varieties of coral that have proven to be tolerant of higher ocean temps. So, we can "transplant" those varieties to restore destroyed reefs.

This sounds like the kind of thinking that results in "standard" forests where most of the trees are of one species and much of the associated biota is lost. Coral reefs are highly complex ecosystems and many unique species have already been lost with the close to 1/5 dissappearance of coral reefs already. It's estimated that by the mid-point of the century as much as 90% of coral reefs will be gone along with their associated biotas, that's a huge hit on species diversity.

In an ideal political and physical environment it would be possible to carry out some sort of transplant operation, but when has that ever existed? We'll be dealing with continuing compromises that most likely will see a steady decline in some of the most important biological systems on the planet, with the resulting loss in food security and overall ecological resiliance.

I'm not ignoring the possible consequences, I'm questioning the severity. When I hear things about how the Permian Extinction holds lessons for us today, I cringe. Largely because when that mass extinction actually happened, the average global temperature was more than 25 degrees centigrade, a full 11 degrees hotter than it is today. Even by the IPCC's worst projections by 2100, the temperature rise will be 2 degrees C, a tiny fraction of that amount. So how exactly does one lead to another?

A 11 degree rise is well withing predicted limits and as the IPCC tends to be conservative and as strong feedbacks we can't fully predict kick in an end Permian state may be the result of continued heavy fossil fuel use. Modern climatic conditions have favoured the buildup of massive amounts of carbon in reservoirs that could become very unstable due to rapid warming. We're betting the future of the Earth and doing it with largely incomplete knowledge, I cringe when people claim it's something we'll be able to handle without really knowing some of the key factors that will determine the eventual outcome. We do know for certain that rapid and large scale changes in the Earth climate in the past have resulted in radically different conditions that in some cases have come close to wiping out most of the existing species. If we have alternatives to fossil fuels(and we do) it makes far more sense IMO to not press the limits to find out just how well we understand the complex systems we're fundamentally altering.

[publiusr]

I also agree here---but most of the "powers-that-be" (the ones who control paychecks and market forces) have long been in control of how the world uses its energy resources. All too often energy corporations will follow the path of least resistance---and thereby maximize their returns.

Agreed. The recent dry conditions lead some to call for getting rid of ethanol production--which big oil might like. Much corn goes to farm animals not people. Individuals who are invested in permaculture like David Blume are skeptical on this resistance to ethanol--but agriculture can be worse than drilling if not careful. Farm subsidy folks get criticized--and yet having options--like flex-fuel--encourage gas prices to go down. The recent Chvron refinery explosion on the west coast made me remember this:
http://news.google.com/newspapers?ni...g=1041,1447332

Climate science is advancing--and merchants of doubt have to be countered. Now debate may go on in a responsible fashion--after all workers who produce vaccinee get called industry schills too--and that cannot be tolerated. Follow the money and follow the science--and you won't go wrong.

[Ara Pacis]

Actually the only areas that are technically habitable to us are warm, tropical and subtropical climates. One thing our existence should have proven by now, we can live anywhere. From the icy arctic wastes to burning desert dunes. Saying that half the Earth will be uninhabitable sounds extremely alarmist.

Squirrels might have guns, but they don't have air conditioning. Humans are not the only mammals on the planet.

The only firm example that I know of was the Mayans. There are other examples, like Easter Island, but from what I can tell these are just works of fiction.

The Harappan civilization is listed as one possibility though it depends on how you define collapse and speed. According to the Wiki article, it happened in less than 100 years and may have been due to climate change. From a previous anthropology class, I recall reading that they used up their forests making fired bricks and used up their resources.

To be fair heat waves, droughts, and warm winters are also consistent with the normal behavior of climates. While again I am not denying global warming, there is more than one explaination for this particular event, and to say that global warming can only be the one possible explaination makes climate science sound like the psuedo science we know it isn't.

A heat-wave is weather, not climate. A long term trend of warming or drought, such as the last 18 months, starts to become a climate trend. Weather tends to be chaotic. Climate and long-term trends tend to have identifiable causes, like volcanic dust or greenhouse gases.

[TooMany]

Easter Island is an interesting example of how, despite our large brains, we fall victim to the same fate as yeast. Apparently the Easter Islanders allowed their population to grow and to so thoroughly consume the available resources that the island became barren and was abandoned (and remains largely barren to this day). This also happened in and around the Mediterranean in ancient times. Some islands were stripped almost completely of their cypress trees forests and remain that way still. England consumed much of it's forest's but was saved from disaster by turning to coal mining.

Added to the problem of growing global consumption, global warming could indeed be quite serious even if the temperatures only change by a few degrees. That may be all it takes to force the world to rearrange agricultural areas and abandon or dike it's major cities. Even if this year's Midwest drought is just odd weather, it demonstrates how fragile our global food supplies are in the face of climate change.

If the world fails to directly address climate change (which seems likely), then the question is how fast can the world adapt to the changes. How much of the population will starve and how will civilization be affected, if we cannot adapt rapidly enough? All over the Southwestern US there are remains of native-american civilizations that collapsed as the climate got warmer and drier.

[lomiller1]

I'm not ignoring the possible consequences, I'm questioning the severity. When I hear things about how the Permian Extinction holds lessons for us today, I cringe. Largely because when that mass extinction actually happened, the average global temperature was more than 25 degrees centigrade, a full 11 degrees hotter than it is today.

Absolute temperatures mean nothing because life evolves to adapt to them. What causes mass extinctions is the change in temperature and how rapidly it occurs. For comparison sake the earth warmed ~6 deg C over ~5000 years at the end of the last glaciation. That's ~0.1 deg C per century or 0.01 Deg C per decade. At that pace there is still time for ecosystems to adapt to the disruption, but when you stat looking at that much change in 100 to 200 years it becomes a different story. Most ecosystems simply can't move that fast.

To be fair heat waves, droughts, and warm winters are also consistent with the normal behavior of climates. While again I am not denying global warming, there is more than one explaination for this particular event, and to say that global warming can only be the one possible explaination makes climate science sound like the psuedo science we know it isn't.

What other explanation do you propose?

The have been several events over the last couple years that go outside the bounds of what can plausibly occur in a world that isn't warming, the most recent being this years drought in the US. When we already have an explanation that fits the data and we have no alternative explanation that plausibly fits the data we are justified in saying we have identified the cause of the event/phenomenon. Like all science this is of course only provisionally true as someone could always bring forth new data that changes our view, but we don't wait around for that. This is how science moves forward.

[Jerry]

The Malthusians have been predicting "imminent doom" from "over population" and insufficient food production for 200 years now.



And needless to say every time they have been wrong. The question is why? Well, Malthusianism makes the assumption that people can't innovate, particularly in the area of food production. Today we have the most powerful tool available for adapting our agriculture to climate change: Genetic engineering. There has been a lot of success with testing drought resistant wheat, salt tolerant wheat, and many others. Which begs the question, why exactly is climate change going to reduce food production, except via the self fulfillment of the Malthusian Catastrophe prophecy? I'm seeing a whole lot of psuedoscience here........

This is so wrong, it isn't even wrong.

First:

Malthus made a mathematical prediction based upon observable trends. In any population model, if the behavior of the population changes, the prediction is invalid.
In this case, the largest relevant game changing factor is that India, Europe and China and much of the first world listened and changed their growth behavior. Population growth curtailed dramatically. Yes birth control is a successful technical innovation; but it only works if it is practiced.

Second:

Many third world African, South American, middle east and island nations such a Haiti did little or nothing, and in these potions of the world the dire predictions of Mathus are being realized in some of the worst human suffering imaginable. It is a gross falicy to say that the predictions are not being realize.

Third:

Current extinction rates are possibly the highest ever, and the easily identifiable catastrophy driving the current era of extinction is not volcanic or collisional; but exactly anthropological.


Yes, knowledge and technology have given us the tools we need to reduce the pressure of human breeding on our planet. But we are not in control of nature, and our window of opportunity is shrinking.

[Ara Pacis]

The only firm example that I know of was the Mayans. There are other examples, like Easter Island, but from what I can tell these are just works of fiction.

Also, it depends on what you mean by civilization and if you include culture. The people who lived in Doggerland had to move or die when the North Sea inundated the area. The people living near the ancient Black Sea had to move or die when sea level rise flooded it. There may be others.

[Squink]

Aral Sea fishing culture is looking pretty grim now days.

[ravens_cry]

I prefer the term climate change because it encompasses more precisely the wide range of changes. Some places will encounter drout, others torrential rains and floods. The danger is not everything turning into a desert, but for bread basket regions like the North American prairies climate changing to make such farming untenable.

[Jerry]

For longer than I have been alive, climatologists have been crying about the need for change to avoid impending doom. The time-line always appears to be 40-50 years away. How many predictions need to fail before we dispel climatology as pseudo-science?

Do we really need to fear the days when Antarctica returns to a lush cover of ferns?

How long can you tread water? Or how long have you been sleeping?

http://green.blogs.nytimes.com/2010/...isis-u-n-says/
New York Times 2010
World ‘Dangerously Close’ to Food Crisis, U.N. Says

Climatologist are now using second and higher derivatives to quantify warming trends. The US is currently experiencing the warmest temperatures ever, and the rate at which extreme high temperature records are being broken tells us we are at best in an unusual year following a dramatic climate shift, and at worst, the shift is even greater than high end of our predictions.

The 'warmest consecutive twelve month' record has been broken four times in the last four months, and will certainly fall again at the end of August; and the record is being shattered in an absolutely unprecedented fashion; more than a full degree F higher than the previously most extreme warmth.

Fifty years is right outside your door, and it is going to eat you.

[starcanuck64]

It's also important to remember that much of the persistant positive forcing is being offset by short term negative forcing that would soon be cleaned from the atmosphere if we stopped the burning of so much hydrocarbons.

We're just feeling a little more than half of the true effects of all the additional CO2, CH4, nitrous oxide, CFCs in the atmosphere and removal of natural carbon sinks. As soon as all the particulate material and aerosols leave the air then warming would increase.

[Jens]

In this case, the largest relevant game changing factor is that India, Europe and China and much of the first world listened and changed their growth behavior. Population growth curtailed dramatically. Yes birth control is a successful technical innovation; but it only works if it is practiced.

It's certainly true that population growth was curtailed, but in actuality I don't think it's because we "listened." More likely, it's a result of a rational choice made by individuals regarding the amount of investment put into offspring. Most people today, me included, have only one or two children not because we are considerate of the environment but because we'd rather put our kids through college and it just costs too much to have six children. In fact, there are countries (Singapore being the best example) that are kind of panicked by how far their fertility rate has fallen, but they seem unable to change the trend, even with family support programs and that kind of thing.

[TooMany]

It's certainly true that population growth was curtailed, but in actuality I don't think it's because we "listened." More likely, it's a result of a rational choice made by individuals regarding the amount of investment put into offspring. Most people today, me included, have only one or two children not because we are considerate of the environment but because we'd rather put our kids through college and it just costs too much to have six children. In fact, there are countries (Singapore being the best example) that are kind of panicked by how far their fertility rate has fallen, but they seem unable to change the trend, even with family support programs and that kind of thing.

(I'm not about to panic if birth rates fall below replacement.) You make a good point. In an agrarian culture, more children can be beneficial economically because they can become laborers in just 5 years or so. Now, children bring nothing to the family economically and only stop taking when they graduate at about 22. (Even that's not true anymore. I hear of more and more cases of college graduates living at home because they cannot afford their own living space.)

There are also cultural pressures. For example Mormons are expected to raise an absolute minimum of three children. There appears to be a similar ethic in the US Hispanic culture. It's not that they fail to use birth control. If they did not use it, their families would be huge. They do stop having children but typically only after 3 or 4.

[Jens]

(I'm not about to panic if birth rates fall below replacement.)

There sort of is a reason to panic, though it sort of depends on how old you are. The problem is about the structure of the population. If you have many young people and few old people, then the young people only have to give part of their work to taking care of the elderly. If you have a situation like Singapore, then you'll end up having only one person in the working age group for two people who are elderly, and the young people will have to spend all their time giving nursing care to the elderly! Everybody will be working in nursing homes, so who will make the food?

[Ara Pacis]

I prefer the term climate change because it encompasses more precisely the wide range of changes. Some places will encounter drout, others torrential rains and floods. The danger is not everything turning into a desert, but for bread basket regions like the North American prairies climate changing to make such farming untenable.

I actually prefer "Climate Destabilization", a phrase I made up. I think everyone should start using it. Of course, Global Warming is still valid because the Earth as a whole gets warmer. AGW making some thing cooler can be explained with the simple analog of a refrigerator: the inside might get cold, but the coils on the outside get warm. "Climate Change" can be spun politically either way, good or bad and can sound like a natural phenomenon.

[Ara Pacis]

It's also important to remember that much of the persistant positive forcing is being offset by short term negative forcing that would soon be cleaned from the atmosphere if we stopped the burning of so much hydrocarbons.

We're just feeling a little more than half of the true effects of all the additional CO2, CH4, nitrous oxide, CFCs in the atmosphere and removal of natural carbon sinks. As soon as all the particulate material and aerosols leave the air then warming would increase.

Actually, certain aerosols do cause warming, such as smoke. It will seem cooler at the surface, but at altitude the carbon heats up the atmosphere and creates an unnatural stratification. This also affects the lower atmosphere negatively with regards to precipitation, If I recall the study correctly.

[HenrikOlsen]

The only firm example that I know of was the Mayans. There are other examples, like Easter Island, but from what I can tell these are just works of fiction.

Just consider the American 'Dust Bowl' of the 30's. Had it been individual states rather than Unites States, Oklahoma and several other states could have gone the way of the Mayans.

The Anasazi (the Pueblo makers of the Four Corners area) are considered another civilization that likely got destroyed by topsoil erosion combined with bad weather/climate, there are indications that early human deforestation was influential in creating much of the desert in that area,

[starcanuck64]

Actually, certain aerosols do cause warming, such as smoke. It will seem cooler at the surface, but at altitude the carbon heats up the atmosphere and creates an unnatural stratification. This also affects the lower atmosphere negatively with regards to precipitation, If I recall the study correctly.

It's definitely a complex issue, here's an interesting article:

http://environmentportal.in/files/Gl...rightening.pdf

The aerosol influence on the more recent transition
phase from dimming to brightening and the subsequent
brightening is better documented. Wild et al. [2005] examined
SSR at worldwide distributed BSRN stations and
found brightening tendencies during the 1990s not only
under all-sky conditions, but also in cloud-free conditions.
This indicates that aerosol changes may have contributed to
the recent brightening. Streets et al. [2006] noted a qualitative
agreement between changes in the anthropogenic
emissions of sulphur and black carbon and the widespread
transition from dimming to brightening found by Wild et al.
[2005] in various regions around the world. The historic
emission inventories suggest that global sulfur emissions
peaked in late 1980s, and decreased thereafter [Stern, 2006;
Streets et al., 2006]. The decline in the emissions of sulphur
and black carbon was particularly strong in large areas of
the industrialized world over the period 1980–2000, after
increases in previous decades [Streets et al., 2006], in line
with the changes noted in the SSR records. This reversal in
the emission trends is likely related, on one hand, to the air
pollution legislations that have started to become effective
in many developed nations in the 1980s. On the other
hand, economic crises also led to reduced emissions in
eastern Europe and the former Soviet Union from the late
1980s onward, and in Asia in the 1990s [Streets et al.,
2009].

[Ara Pacis]

It's definitely a complex issue, here's an interesting article:

http://environmentportal.in/files/Gl...rightening.pdf

I was thinking of the study by Ramanathan in 2008, but there's probably new data by now.