@CTG

And once again someone misses my point that we are still talking about different timescales.

'Since the 19th century temperature has been steadily increasing' Yes, we came out of the little ice age, so temperatures went up. You talk of the last 70-80 years as being a significant amount of time, but the problem is that we actually don't know what the temperature *should* be without anthropogenic influences.

We don't know what caused the little ice age. We don't know if the medieval warm period was normal or out of the ordinary.

Take a look at the graph at http://www.giss.nasa.gov/research/briefs/schmidt_01/

It is a record of a particular isotope of oxygen found in greenland icesheets and gives a good idea of temperature changes. Spot the trend? Over the last 250k years the variation has been getting more severe compared with earlier. The highs are higher and the lows lower than at say 500k years. We also don't know why this is. What you do see though is that our current temperature is abnormally high when compared with the historical record, but roughly equates to the 125k year high.

By referring to solar output, I'm talking about a process of centuries and more not decades - did the amount of solar input change between 1000 & 1400, or 1400 & 1800? The data is rarely published outside of university circles so I can't say.

The first thing I learned about graphs in statistics is that they are usually biased to promote or hide something. Look for changing scales, asymmetric axes, and particularly choosing beneficial points of origin. I can't find it now, but regularly reprinted are temperature graphs where the timescale is logarithmic or keeps changing timescales, so the variation in the last 1000 is shown as being more extreme than the 500k years beforehand. Transposed onto a graph with a constant timescale, and the variation becomes much more regular.

Simplistic comment is everyone lies somewhere, the issue is keeping an open mind to all possiblities until they can be definitively ruled out and I find most of the ideas on the 'denial' side of the fence are being shouted down rather than proved wrong because actual proof for or against is harder to obtain.

I'm not actually in favour of either side in this debate, I'm supporting contrary views on here because the majority of people won't consider them.

@Mayhem

You really need to broaden your reading. One of the common memes put about by the denialist spin campaign is that "climate scientists believe that CO2 is the only cause of the greenhouse effect, and ignore all other possible sources like the sun". This is completely untrue.

Climate science is very clear that the greenhouse effect has multiple components. The biggest source of the effect is actually from water vapour. Then there is the effect from trace gases like CO2, CH4 etc. The effect is then further modulated by solar activity (i.e. the sunspot cycle) and internal negative and positive feedbacks from oceanic oscillations and the like.

Now, in the absence of any one of these factors changing significantly, the climate would still exhibit a lot of noise, as all of the various factors play off against one another. But since the 19th century, one of the variables has been steadily increasing - CO2. Result? Temperatures have also increased, exactly as the greenhouse theory predicts.

Solar activity has been pretty much constant over the last 6 or 7 solar cycles (i.e. 70 or 80 years), whereas temperatures have climbed steadily over that period. There is absolutely no evidence whatsoever that incoming energy from the sun has increased during this period of temperature increases, so it must be something else, i.e. CO2.

What about the big hot thing?

@AC Also before you bring it up, yes I am aware that ozone is itself a GHG and the ozone layer acts to increase absorbtion & raise the temperature.

But to elaborate on the point I had initially mentioned in passing with E(in) = E(out)+ E(abs)

E(in) is the total amount of solar energy entering the atmosphere

E(out) is the amount that is directly reflected back into space again due to the albedo (~30%)

E(abs) is the amount that is absorbed and later radiated back out as heat (~70%)

The fundamental thing is that the total amount entering always matches the total amount leaving. The difference for us is in what percentage the balance lies. More reflection, cooler climate. More absorbtion, warmer climate.

See http://eosweb.larc.nasa.gov/EDDOCS/radiation_facts.html for more details

The big point which often seems to get overlooked is that increasing the amount coming in will naturally increase the amount that must leave, and since our albedo is fairly constant that means the temperature will rise until the albedo changes to bring things back into balance, whether through increasing from water clouds, or forest fires or whatever..

What attention is being put towards studying increases/decreases in solar activity since CO2 became the be-all and end-all of climate change?