No co2 levels have been directly measured for 50 years, and the rise of human emissions during that time period have been more than enough to explain that increase.
The Keeling curve and rise in CO2 in the atmosphere

Rising temperatures don't cause co2 to rise as much as they have since pre-industrial times. co2 rises 100ppm from 10C warming in the ice core record (http://cdiac.ornl.gov/trends/co2/gra...vostok.co2.gif), and that's after thousands of years of increase. So 100ppm increase since preindustrial average (ie 280ppm to 380ppm) is not going to be caused by a <1C temperature rise in that time.

Plus the little ice age was at least 0.5C cooler than 1900 temperature, yet co2 levels were only about 10ppm lower. Temperature does dictate the equillibrium level of co2, but it isn't sensative enough to explain the 100ppm rise in the last 200 years.

They have been ruled out because nature is absorbing more co2 than it emits. So it cannot be the cause of the recent rise.

It cannot be proven, but it's extremely unlikely that it would have risen this far this century without our contribution, and I cannot emphasize how unlikely it would be. Take the bottom graph on this page for context of the recent rise in the past 1000 years:
The Keeling curve and rise in CO2 in the atmosphere

And this one again for context over the past 450,000:
http://cdiac.ornl.gov/trends/co2/gra...vostok.co2.gif

Currently levels are 380ppm and rising about 2ppm per year. They can't even fit that value on either of those graphs it is so off the scale.

You are confusing "equillibrium level" with the level co2 is actually is at. The actual level of co2 can be above or below the equillibrium level, and whether it is above or below determines whether nature will absorb more or emit more. The equillibrium level is determined by temperature. During the little ice age the equillibrium level was slightly lower (about 275ppm), and so co2 levels fell slowly to that level.

Currently co2 is far above the equillibrium level, which is why nature is currently a net absorber of co2.

Both. But currently co2 concentrations are rising primarily due to human emissions.

The atmosphere will absorb more co2 than it emits if atmospheric co2 is above a certain level - a level determined by temperature. Humans have pushed co2 well above this level, which is why nature is absorbing more co2 (and the rate of absorption has been increasing over the past 50 years)

If humans were not currently emitting co2 (ie if stopped tomorow), co2 levels would be falling. It's simply not the case that nature would "notice" humans had stopped emitting co2 and would start emitting more co2 elsewhere to make up the 28 billion tons less.

From the second image in the link I posted you can see they did "stop" during the past few hundred years and co2 levels were floating around 280ppm throughout with no significant change (even the little ice age only bought it down about 10ppm). What do you think happened in the 20th century which would have changed that trend if only humans hadn't emitted any co2?

co2 concentrations do fluctuate naturally, mainly when temperatures fluctuate. The ice core record dramatically shows how co2 follows temperature (ie temperature is determining the equillibrium level that co2 moves towards). But it shows a 100ppm increase in co2 requires about 10C increase in temperature.

Given the warming in the early 20th century occured naturally, without human emissions co2 would probably be today a bit higher than the pre-industrial baseline at about 285ppm. But not 380ppm which from the ice core records is an unprecedented level for co2 in at least the last 700,000 years.

You say that in a joking way, but the climate has consistantly found this 280ppm level during interglacial periods:



It appears that the temperatures of interglacial periods do dictate a equillibrium level for co2 at around 280ppm.

The mechanism for co2 emissions (from any source) causing co2 rises is pretty self explainatory. You just need the new emission source to tip the balance towards more in than out.

As explained above, the co2 rise has far exceeded the sensitivity of co2 to temperature.

No, the nature at this time is the act of absorbing more co2 than it is emitting. So no nature is actually absorbing some of the co2 concentration increase. If it wasn't then the full 28 billion tons of human emissions would cause a 4ppm rise in the atmosphere each year. Rates are only rising at 2ppm, showing that nature is not acting as a cause of the increase, but is actually countering it to a degree.

Until we got to approximately 280, and as co2 levels approach that value nature will absorb at a slower rate.

If the absorption rate decreased then co2 levels would be rising far faster than they are, so we do know it's rising because the emission rate has increased.

Take man's emissions out and there would be no rise because there would be less co2 entering the atmosphere than leaving it.

Nothing is provable but this stuff is certain to the point of 99.99%. A man could get fried on less evidence.

It "decided" to do that once co2 rose above the level that could be supported by temperature.

Because it takes time for co2 to fall, a long time. The rate of absorption is proportional to how far co2 is above the equillibrium point. The measured co2 trends show that nature is absorbing co2 at a faster pace as the co2 levels in the atmosphere increase.

CO2 rise = Natural Contribution + Human Contribution

two of these are known - co2 rise, and human contribution. So the third can be calculated.

Natural Contribution = CO2 rise (2ppm) + Human Contribution (4ppm - ie ~28 billion tons co2)

So Natural Contribution is about minus 2ppm, so nature is absorbing more than it emits.

Not everything in climate is unknowable. Lots of things are well understood and known. The carbon cycle happens to be something better understood. But also in other cases - eg "If sun doubles in output, then earth warms" and "If el nino year, then warmer global temperatures" are very certain "if A, then B" statements to do with climate.

I don't know why, but almost with anything raised you try and find the smallest little detail to nit-pick over.

The Mauna Loa observatory has prominence only because it stretches back the furthest. But there are also global stations that measure co2 levels, and the trend from those match the Mauna Loa records well:

Global Monitoring Division
But it isn't. A 10C rise was required to cause a 55% co2 rise.

No that's not right at all. Humans are emitting 28 billion extra tons of co2 today. Not 15 tons.

As this site mentions:
Now 305 billion tons of carbon is equivalent to 1128 billion tons of co2 (a co2 molecule weighs 3.7 times more than a carbon atom).

So humans since 1751 have emitted 1128 gigatons of co2 into the atmosphere (an atmosphere that currently holds about 2800 gigatons).

That's a quantity of 40% of the current atmospheric concentration of co2 has been emitted by man over the past 250 years, most of which was emitted in the last 50 years.

Nothing in the "short blurb" even suggests that. It reads:
Which part tells us the figures aren't even close to accurate?

The method is given here: TRENDS: CARBON DIOXIDE EMISSIONS

As I said you can derive the total natural contribution from the knowns. What you cannot easily do is split that up into how much co2 is being absorbed naturally and how much is emitted naturally, but you can easily tell that more is being absorbed than emitted by nature. That is overall nature is absorbing about half the rate of human emissions.

It's not true that everything in nature is chaotic and unpredictable. Certainly the seasons are a prime example of the most predictable aspects of climate. The carbon cycle is fairly simple at a macro level, and is fairly well understood. It's not true that we know nothing and cannot reach a good conclusion on this subject of the cause of co2 rise. It is beyond doubt that co2 levels are rising, and beyond doubt that human activity is the cause.