Carbon Dioxide and Global Temperature levels

[Massacure]

I was looking at This Post and decided to do some searching regarding exactly how much 450 ppm is because it seems so abstract. I came across this graphic though:



It came from This Site.

That data makes me wonder. Why exactly is the climate so cold today, why is the CO2 level so low, and what the ramifications are for humanity. As humans we do not have the moral authority to do as we please to this planet. However 450 ppm of CO2 isn't exactly out of the normal, and Earth's temperature is rather low compared historically. It makes me wonder if Earth is about to go back and start another cycle or if humanity is involved, or if it is both.

I want to play devil's advocate right now though. Let us take morality out of the picture. Shouldn't life be able to adapt if say, the temperature rises 4 or 5 degrees Celsius as predicted and the CO2 concentration increase to 450 ppm or even say 500? What about humanity? Can humanity adapt? I bet we would like to live in a never changing world, but is that really possible?

I feel so guilty thinking this out loud. Climate change may kill off many species, but curiosity will kill this cat.

[ayeshahaqqiqa]

1. Personally, I think a massive die off of humanity is indeed possible

The pressures of climate change and population alone will make it so that we have more civil strife, especially if breadbaskets dry up and food becomes scarce.

[NNadir]

2. Here are some assumptions you need to think about.

First off, you need to think about solar evolution.

The sun is not in the same place on the main sequence that it was in 600 million years ago.

Next you need to consider what sort of terrestrial life existed when coal was being formed. Thermophilic organisms - and we know know there are many - live almost exclusively in aquatic environments.

Secondly you need to look at the time axis in the graph. What was the rate of change in carbon dioxide/temperature variability? Life can adapt easily to slow changes; but the slate is almost wiped clean with rapid changes. The present changes of carbon dioxide content is a rate of doubling on the order of centuries, not millions of years.

There have been rapid changes in the atmosphere that have immediately catastrophic effects on most life. One such event that is known to have happened is the evolution of photosynthesis, a catastrophic even that changed the earth from a reducing atmosphere to an oxidizing atmosphere. Mostly it killed things, but things in those days were unicellular.

Thinking about these questions may disabuse you of any feeling of comfort.

The fact is that the human species, and most other large terrestrial animals and megaflora are certainly in a vulnerable spot. Clearly most living species have not evolved at a mean temperature of 22C. Humans certainly didn't. I think we can all agree that most people regard the survival of humanity as a desired thing - even if we don't necessarily deserve to survive.

There are definitely some extremophiles that may survive global climate change. On the other hand, it is very possible that nothing will survive. It is thought that Venus once had a stable atmosphere and climate that was relatively mild, even benign enough to have theoretically supported life. More than anything it was solar evolution that eliminated this stability, but the final death throes are thought to have been sudden and to have involved feedback loops, the so called runaway greenhouse effect. If extremophiles existed on Venus, they have certainly been rendered extinct now, since it is difficult to conceive of carbon based life without water.

[Dead_Parrot]

3. The problem is the speed of change.

The low CO2 we've got today - or had - is mainly down to carbon capture: Generally speaking, Carbon spewed out from volcanic activity is gradually soaked up by plant life. The jumps in CO2 on the graph coincide with bouts of planetary flatulence: these are followed by a more gradual reduction as it get sequested into fossil fuels. The similar pattern we've got today just happens to be caused by monkeys, not volcanoes, but it too will get soaked up over the next 30,000,000 years or so.

On your second point, the drop from 450 to 200 ppm took about 30 million years: Enough time for whole ecosystems to migrate and for species to adapt to the new conditions. The change we're going through at the moment will take a couple of centuries for the major changes: Evolution hasn't got a cat in hells chance of keeping up. The closest thing we've 'seen' to the current shambles in the permian-triassic "great dying" I tend to bang on about.

As to humanity surviving, it depends on your definition. I certainly can't see homo spaiens oxymoronicus being wiped out - we're too widespread and too adaptable for that - but between climate change and peak oil what we laughingly refer to as "civilisation" is going to take a hell of a beating. Most of our manufacturing is a giant ponzi scheme: when the population starts falling - even by a little - the markets will vanish whole house of cards will come crashing down, bringing banking, communications and transport with it. We'll be back to subsistence farming before you can say "Oh bugger". So long as you've got land still capable of farming, that is.

I daresay we'll bounce back after a few generations, and whatever remains of the biosphere will adjust and flourish once we've stopped poking at it. It'll be quite a ride, though.

[Odin2005]

4. The Sun has slowly warmed up through Earth's history.

During fusion 4 hydrogen nuclei (protons) become one helium nulceus (alpha particle). this causes the sun's core to slowly become more compact and therefore hotter, increasing the rate of fusion. 4 billion years ago the sun was 30% dimmer than now, but the Earth was still quite warm (although I disagree with the opinion that the temperatures were close to the boiling point) because there was a lot of CO2 (though a lot less then what it started with. The Earth started out with as much CO2 as Venus, but most of that CO2 had become limestone by 4 billion years ago, leaving a Nitrogen-CO2 atmosphere slightly thicker than the modern atmosphere). As the sun slowly brightened CO2 was slowly taken out of the atmosphere by forming limestone. When it warms up the rate of chemical weathering of rock increases, leading to more calcium ions in the oceans, increasing the rate of limestone depostion relative to the amount of CO2 released by volcanos. similarily, a cooling trend would reduce the weathering rate, allowing more volcanic CO2 to stay in the atmosphere. This is the Earth's most important negative feedback loop, it is what keeps Earth's average temperature within a narrow range.

The pricipitous drop in CO2 levels in the Devonian and Early Carboniferous is associating the the rapid expansion of terrestrial plant life and therefore the start of the soil as a carbon sink. Also, respiration from plant roots pumps CO2 into the groundwater, increasing it's acidity and, therfore, ability to chemically weather rock, making limestone depostion more efficient.

Oh, and one shouldn't take that chart's CO2 levels as dogma, I've seen a similar chart on Wiki (one of the images here: http://en.wikipedia.org/wiki/Paleoclimatology ) showing lower CO2 levels during the Mesozoic (1000ppm instead of 2000ppm). the orange line is the same data as in the chart in the OP, the data I most agree with is shown on the green line. The dark blue line is the consensus estimite. The data shown by the purple line looks like nonsense. I also don't like that graph because it simplifies the climate data way too much.

[Kolesar]

5. I wish I had your library

Where did you read that account of geologic history? For that matter, what book on climate change do you recommend? :hi:

[Odin2005]

6. Too many books to remember. :-O

The Life and Death of Planet Earth, by paleontologist Peter Ward and astronomer Don Brownlee is a good read for info on Earth's climate history in the deep past; Lovelock's books are good too, but are over 15 years old so the data is somewhat dated (his hypothesis that the earth's oxygen levels has stayed at 21% since the origin of land plants has been falsified, for example). The most up-to-date book for info on global warming is The Weather Makers by ecologist (and former GW skeptic) Tim Flannery, excellent book.

[Kolesar]

10. thanks. We ought to start a thread on recommended climate reading

Ross Gelbspan, "Boiling Point", covers the topic of GW, the politics and the disinformation campaign.
Jeremy Rifkin, "The Hydrogen Economy" , A long development on the fossil fuel economy before he gets to the hydrogen details.

[Dogmudgeon]

7. Something else to keep in mind: Cyclic ice ages

Look at the temperature minima on that graph: 150, 300, 450 MYA, and there was also one around 600 MYA that the graph doesn't show, and evidence for two more, around 750-775 MYA and 900 MYA. The temperature also hits a minimum in our own era. These correspond to planetary ice ages; we are in a macro-ice-age right now, although we're in a break of warm weather sometimes called an interstadial epoch.

These ice ages are theorized to be caused by the solar system traveling through diffuse nebulae of dust and gas that are occur roughly equidistantly as curved "spokes" in our galaxy's structure. That's actually more of a well-educated guess than the God's Honest Truth, but such are scientific theories.

As the graph suggests, these ice ages come on pretty quickly in terms of astronomical and geological time, but from the point of view of organisms and ecosystems, they come on pretty slowly.

Aside from the ice ages, brief warm-ups and cool-downs have taken place at more frequent intervals. These are known as Heinrich (cooling) and Dansgaard-Oeschger (warming) Events (consult Google and Wikipedia for more information).

The last big one was about 10 kYA, when the temperature spike is estimated to have raised the temperature of Arctic ecosystems by about 30C -- ON TOP of the usual 12-15C "normal" temperatures. In other words, for a few brief and strange years, the temperature at the North Pole averaged over 100F; after which, the temperature turned sharply colder, and a lot of species went from "dominant" to "extinct", perhaps in as little as a decade or two.

A lot of these processes, while being very long long-lived, depend on very small and subtle changes in sunlight, CO2, infalling dust from space, etc. The contribution of humanity to just the gas balance -- the CO2 -- has increased the global temperature by about 1C already. But the effects seem to be overwhelming all of the sudden. My own explanation is that our relatively small contribution had a way of kicking the props out from under a number of natural processes. It's sometimes called "The Butterfly Effect", from Ray Bradbury's story A Sound of Thunder, about a time traveler who kills a butterfly 100 million years ago.

Well, we've spent the past century killing butterflies.

--p!

[Odin2005]

8. Most people reject that hypothesis for ice ages.

the accepted view is that ice-house periods are associated with lots of mountain building activity (maximum weathering = maximum limestone depostion) and low levels of volcanism while hot-house conditions are associated with lots of volcanism and little mountain-building activity. The cyclilcal patern is related to the cycle of supercontinent formation and breakup. Our current ice-house mode starting 40 million years ago was started by mountain-building activity associated Himalayas, the Alps, and parts of the Rockies; as well as the isolation of Antarctica. the drawdown of CO2 caused by the formation of the great mountaon ranges caused the isolated Antractica to freeze and the ice sheet that resulted caused the chilling of the deep ocean needed for the switch from hot-house to ice-house conditions.

The switch to Ice-house sets the stage of the start of an ice age proper. The final decent to the current ice age was caused by the formation of the isthmus of Panama 3 million years ago, strengthening the Gulf Stream and so increasing snowfall in Scandinavia and Canada, enough snow that it would not all melt during the summer. Runaway ice sheet formation was the result. Oh, and you are confusing interglacials, the major warm periods in an ice age, and interstadials, which are smaller warm spells within a glacial period

[Odin2005]

9. Oh and thats site's contention about global warming is bull.

It tries to use the "CO2 levels were high during the Ordovician Ice Age" argument, which I've heard before and I think is rubbish. The high CO2 levels before the expansion of land plants was probably balanced by the fact that bare land is lighter in color, therefore absorbing less sunlight. Also, the continental configuraton during the Ordovician was quite unusual, with most of the world's landmass near the south pole in the supercontinent Gondwana (and the parts of Gondwana that were away from the south poles helped bring moisture to grow the ice sheets, similar to how the Gulf Stream supplies moisture to the northern ice sheets in our current ice age), that means the rest of the globe was dominated by vast seas with well defined currents going straight east or west without being deflected north or south, creating a great temperature gradient between the tropics and the poles, this configuration allowed an ice age even with relatively high CO2 levels, it seemed to have been totally diffent kind of ice age then the ice ages typical of Icehouse phases. The Ordivician Ice Age was as weird blip in the middle of a hothouse phase, probably triggered by the formation of the Caledonian (the Scottish Highlands and the mountains Norway) and northern Appalachian Mts. at the same time that Gondwana was particularily vulnerable to runaway glaciation.