For a detailed response to Hansen, take a look at:

 http://www.co2science.org/scripts/CO2ScienceB2C/education/reports/hansen/hansencritique.jsp

If you take Hansen as gospel you'll end up having to support a massive increase in state power. The only way to do as he suggests is going to be through more and more regulation, state control and ever more oppressive regimes. His thesis, and it's not supported by empirical evidence, ultimately leads to dictatorship as your force humanity backwards.

"Progressive Contrarian", you're mixing up criticism of Hansen's science with the political programme he (maybe) espouses.

The website you cite is, bluntly, a joke. "Is carbon dioxide a harmful air pollutant, or is it an amazingly effective aerial fertilizer?".

Are you really disputing that CO2 helps plants grow? Come on, this is basic photosynthesis. CO2 is pumped into greenhouses all over the world to improve crop yields. Without CO2 in the atmosphere we'd be stuffed.

Are you disputing the fact that humans' increased emitting of CO2 is causing global warming?

Because if you are, you're calling the thousands of scientists in the IPCC wrong, and you need evidence that's a lot more compelling (and relevant) than "but plants use CO2 in photosynthesis".

who so obviously doesn't want to lift a finger to change your extraordinarily selfish lifestyle. Fuck the future generations, it's "me now" that matters more than anything. Am I right or am I right?
Now kindly fuck off and die in one of your oil wells.

I don't dispute that humans are emitting CO2. I don't dospute that CO2 adds (marginally) to the greenhouse effect. But I do dispute that man-made CO2 is causing the current warming. Look back in the Earth's history and you see a constant cycle or warming and cooling - independent of what we're doing or not doing. Look outside the Earth and you see that other planets and satellites are currently also undergoing warming - again independent of what we are or aren't doing.

If you want to keep people in the developing world poor on the basis of some dodgy climate change models then go for it. You're in good company - Blair, Sarkozy and now Bush too...

more sorted than you... I'm astounded by your solid grasp of the science. Nice one.

Quit your ad hominem ("good company with Blair" etc.) and stick to the facts. If you want to talk about the politics of potential responses to climate change that's something else. I'm talking about the science that you are denying.

.........
"constant cycle or warming and cooling"
Climate has varied in the past, yes. But if you accept that CO2 (and other gases) play a part and that there are more of those gases as a result of human activity, then you have to explain:
(1) why that increase of CO2 is unrelated to the observed increase in mean temperature; and
(2) why the current warming is occurring at a point in the ice core temperature cycle where temperature should be decreasing; and
(3) why the current warming is occurring at a rate 10 times faster than any previous cycle.

"dodgy climate change models"
(1) Regardless of what you think of the models. Warming is happening. It has been and continues to be measured in ways as diverse as:
- satellite temperature readings
- deep ocean radiosonde
- glacial ice melt
- polar ice melt
- boreholes
- sea level rise

(2) And the models work. There are no equivalent models explaining the data that DON'T involve the CO2 emissions of humans.
The warming is real and we need to act now to stop it from getting worse.

"keep people in the developing world poor"
This is baffling. The impacts of mad-made global warming are overwhelmingly and disproportionately upon the developing world. That is a fact, your concern about certain policies is another matter.
...

I note that you have ignored my previous points yet still attempted to claim some kind of scientific high ground. I doubt your sincerity and so this is my last reply to you.

Sometimes being contrary means you are just plain wrong.

CH - I'm sorry you don't want to continue the discussion. In that case I'll only respond to one of your points, which is about the facts of warming itself.

There are enormous technical problems with calculating the scale of temperature change. The generally accepted figure is around 0.6C in the last century, but even thus has been challenged. Not only do measurements need correction to account for the increased presence of man (the urban heat islands effect), but also changes in land use have an effect. Taking account of this and other factors reduces the scale of the rise to about 0.3C. This is hardly perceptible and well within the margin of error, but still it's a rise.

However, things are even more complicated because there are various anomalies at work. For example the Antarctic has shown a cooling trend over the same period. Atmospheric readings show that temperatures have risen in some parts of the atmosphere but not others. There is also new evidence that other factors need to be taken into account - such as the effect of carbon particles on Arctic snow, which reduces the reflectivity of the ice and may be responsible for about 20% of the warming that has occured.

Where does this leave the role man-made of CO2? It's a factor, but a marginal one.

Hi 'Progressive' Contrarian,

Many scientists have spent their lives studying in detail bits of the climate system and related issues. The first anthropogenic climate change model was in 1896! It is extremely unlikely that the literature generated by thousands of people over more than 100 years has missed some crucial issue, that some non-expert like yourself has actually noticed (e.g. the Heat Island effect has been studied to death, and IPCC figures take this small effect into account).

Lets take two issues, first CO2. Its bascially an issue of some basic physics and chemistry of CO2, and this molecules absorption and re-emittion of energy. This was worked out a long, long time ago. As an experiment, take an atmospheric science text book from the 60's (before climate change was on many peoples radar) and read the bit about CO2, then keep taking them decade-by-decade. The answer is basically the same for the same reasons. There has been no big changes in the science of CO2 itself. After decades of work we have a really detailed understanding of CO2, in amazing detail.

On climate change and plants: yes increased yields from increased CO2 concentrations in the atmosphere are occurring (via photosynthesis). But, the costs of respiration to all plants are temperature dependent (chemical reactions go faster at higher temperatures). Both are non-linear, the photsynthesis should be saturating, whereas the respiration will keep increasing with temperature. So at some stage yields will decrease. This is a critical problem for the tropics. Also, a major climate change issue is the speed of climate change and whether agriculturalists can adapt fast enough, as agriculture, especially peasant agricuture relies on the predictability of climate - next year will be more-or-less similar to the previous years. This problem is compounded by increased frequency and severity of extreme weather events.

If you're really on the side of the poor, then you should do everything in your power to get emissions down, as the poorest in society are already being hit hardest, and will certainly be so in the future. This should of course be done in an equitable and socially just way.