< 350ppm CO2 : Where we need to aim
 

350.org

On Saturday, there was a worldwide rally to promote James Hansen's theory of 350ppm atmospheric CO2 as a "safe" level for sustainable life on Earth. About 5200 different organized rallies occurred all over the world.

I just wanted to give a heads up to everyone here on Ecomodder. Even if it makes you think for a second, or if it adds to your ecomodding edge, i think its information everyone should know.

Here is James Hansen's original paper published on the topic suggestion 350ppm as a safe point. Earth used to be about 260-270ppm before civilized human life thrived. That number is considered the natural atmospheric CO2 levels for earth. We are currently at levels of 387ppm CO2. If we reach levels any higher (and we WILL given current trends), we will face complete loss of ice caps on the planet and we will see species pass.

http://arxiv.org/ftp/arxiv/papers/0804/0804.1126.pdf

THIS IS WHY WE ECOMOD! :turtle:

I found out about just before Saturday: The Big Ask. (Oh, how I love crosslinking:) )
Here in Warsaw they were supposed to be collecting signitures between 10am-1pm. I called up a friend and showed up at 12:30 and there wasn't any one there! Just the usual groups of tourists. No banners, no balloons, no tables where we could sign the petition. My wife says that they probably quickly got the number of signitures they needed and didn't want to sit in the cold and rain. Not nice of the organisation that was responible for it :(

Please don't blast me for saying this, but I have a bone to pick with Hansen's science. While I do not doubt that global warming is real and it is, to some extent, anthropogenic, I have doubts about how bad moderate warming is. Why?
First, 90% of the past 400,000 years have been characterized by ice age. Ice ages are, to put it mildly, going to be detrimental to food production for humans and other species. Let's say that we bring down CO2 to Hansen's 260-270ppm level. Well, during the "Little Ice Age" (approx. 1550-1850AD), CO2 levels hovered around the 280ppm level. The twelve thousand year Holocene era, which we live in, has also been warmer - between 2-5ºC warmer! That warm time period, about 7000 - 5000BC, was associated with the rapid transition from nomadism to the development of agriculture and sustainable human culture. Humanity also thrived during the Medieval Warm Period, ~800 - 1300AD, where temperatures were ~1ºC warmer than today.
I have two points here: a) It is not the hottest it's ever been and b) Warmer temperatures are not historically linked to humanity fairing poorer.

This is not the case. Biological productivity is highest in the Arctic and Antarctic oceans, while human food production is greatest in the temperate regions. Tropical jungles give a misleading impression, because much of the tropical world (including those pretty clear blue ocean waters) is in fact desert.

You might consider the megafauna that ranged North America during the last Ice Age: everything from wooly mammoths to the sabertooths & dire wolves that preyed on them. Fast-forward to immediate pre-Columbian times, and only a few moderately large herbivores remained - buffalo, moose, & elk.

I think you're looking at this backwards, and that it's more likely that agriculturally-supported urbanism arose because the warmer climate made it harder to support the nomadic lifestyle. Whichever's the case, though, you might want to consider the quality of life of the nomad versus the typical urban dweller (not the elites, IOW). Indeed, you might think about their relative quality of life nowadays, too. Urbanism may have been a necessary phase in human history, but it sure wasn't and isn't a quality life.

I'm not sure how you are defining "biological productivity." Biological density is higher, by an order of magnitude, in temperate climates than in Arctic and Antarctic.
Umm... you seem to be saying that nomadism is a preferred life style? Weird.

Setting arbitrary Co2 benchmarks is pure bull****. Especially if such figures don't really reflect a correlation to global quality of life and food production.
The climate always has and always will change. We're not evenly remotely close to global temperatures being "too high".

Besides the above: Co2 levels are not the cause of temperature averages, they are an outcome.

Arbitrary?

How do you think the atmosphere keeps in the heat from the sun?

Changes have always been happening sure -- but how FAST were the changes in the past? Going up or down a degree C in 100,000 years is easy, but having that change in ~100 years is another thing altogether.

We will probably lose all the ice in the Arctic in the summer within the next 10 years. This will accelerate the warming, because of the low albedo of open water vs the higher albedo of snow and ice. Additional warming will then melt the permafrost more quickly -- which will release lots of methane -- which is ~20X stronger greenhouse gas than is carbon dioxide. And so the very quick warming will become even quicker.

Biological productivity = amount of living matter produced per unit area. You need to look at the oceans as well as the land.

Why would you think so? Don't want to get into a long discussion, but just look at the differences. On the one hand you've open space, natural surroundings, varied food available for the hunting & gathering, which takes a few hours a day, the chance to do different things every day. On the other hand, your typical urban dweller of those days crammed a family into a single room, and survived on a sparse diet of mostly grains. Even into Shakespeare's time and later, streets were often open sewers, the air was full of smoke & stink, disease abounded. The great majority of people worked long hours for little return beyond survival. Humm... seems like some things haven't changed all that much :-)

Not so. Google "8.2k event". During the Holocene Climatic Optimum (the warm period mentioned in my post above), there was a climatic, uh, bump in the road. As ice sheets retreated, a large North American fresh water lake suddenly drained into the North Atlantic, generating a large scale shift in ocean currents. The fallout was this: in a five year time span, the earth cooled by an astounding 6ºC and remained this cold for about 60 years. Also, to counter jamesqf's belief that a nomadic culture is happier, this event seems to coincide with the collapse of the first human settlements (archeological sites in Iraq, Israel, and Jordan) and their remission into hunter-gatherer culture. When the climate did recover from this cold snap, it then warmed up 6ºC in just 100 years. By comparison, some of the worst-case climate models show us warming by 5ºC in the next 100 years (as a note, these models are already showing divergence from actual conditions, ie, we're not as warm as we should be). The return to warm conditions coincides with the rise of the ancient cultures of the fertile crescent we know so much about. And again, global temperatures were higher than the present day.

I won't go so far as to say "arbitrary" - but I don't believe that 350ppm is scientifically justified. Why? Simply this: Water vapor and clouds are the dominant players in the greenhouse game. They account for 66-85% of the greenhouse effect. CO2 contributes about 9-25%, with methane and other GHGs filling out the rest. (FYI - The variability in the percentage is largely dependent upon relative humidity and cloud cover.) The CO2 reinforcement of the positive feedback loop of the water vapor cycle is mitigated by two forces: 1) dust generation in dry conditions leads to cloud formation and 2) the power of evaporative cooling. On the first, clouds reflect solar radiation even while they absorb re-radiated heat from earth. On the second, yes, higher atmospheric temperatures mean a larger capacity for water vapor, but getting more vapor in the atmosphere takes tremendous amounts of solar energy, which puts negative feedback into the loop.

Please do not misunderstand or misrepresent my opinions here. I do believe that we must work on being better stewards of the Earth and our resources. I do believe that we should develop cleaner and more efficient energy sources. I also believe that cheap, clean and efficient energy sources has the potential to raise billions of people out of poverty - meaning that developing this clean energy is imperative from a humanitarian perspective. While I do believe in anthropogenic climate changing forces, I do not believe that anthropogenic warming is, as of yet, the dominant force in our global climate. I believe this to be the case because of the past.
http://www.geocraft.com/WVFossils/Pa...0-400k_yrs.gif

Climate changes in the past have been sudden and dramatic. Did humans, 130,000 years ago, cause the temperature peak shown in this graph? Unless our great(5x 10^3)grand-daddy Ugg the Clumsy accidently started the largest forest fire ever, obviously not. No, other forces, Milankovitch cycles for example, are a bigger player than we could ever pretend to be.

In urban settings, we do have different worries, to be sure. But why would cultural evolution favor urbanism over nomadism? If nomadism provides better life and health, why didn't that lifestyle come to dominate modern human populations? Simply this, nomads were too busy with their "few hours a day" hunting and gathering and surviving in general to develop things like writing and science. (Just curious, have you ever tried to live off the land, lacking any tool you could not make from wood or stone? I haven't, but rumor has it that it is tough. Starvation is one of many occupational hazards. I wouldn't spend too much time romanticizing this life.)

From an earlier post:
Much of the rise and fall of the warm-blooded megafauna has to do with thermal regulation. In a cold climate, heat retention is a big deal and large animals do better than small animals there. For small animals, the caloric requirement per pound of body mass needed only to maintain body temperature becomes a problem. In very warm climates, heat dissipation becomes the dominant issue, favoring smaller animals. A large animal (apart from special adaptations - the ears of the African elephant being one) exerting itself can quickly die from overheat. A wooly mammoth in a warm environment would be forced to either move slowly (making it easy, high calorie prey!) or risk dying of overheating (which early humans probably prodded the animals into doing - again easy prey).