Hmm, I thought we had >800,000 years of ice core data on temperature, co2 concentration etc. Why does this debate have to have become so irrational. The Times seems to be taking a measured view but its readers seem like they shoot first and ask questions later? Why is that? Can't the two sides actually listen to each other, criticize and test their own views as Karl Popper would suggest. To me it seems the probability of human causes of climate change is increasing and the correlation with the sun's activity is poor. It's like insurance: there is no perfect view of the future but the scenario of major human caused problems grows more likely by the day so we need to act. I wish it were not so as the world has plenty of other problems to tackle. Though I think there are huge opportunities to tackle the problem creatively, that will be good for the economy, reduce waste, reduce use of scarce fossil fuels and maybe like war time Britain be good for the national soul: an end to Eyorism.

ed sketch, Ann Arbor, USA

Not so long ago the world was flat according to popular opinion. Didn't make it true though. Just a little something to cinder for everyone that knows the answers to everything.

Sure global warming may not be true, but I for one hate breathing in the crappy air around london day in day out.

Justin, London,

Dr Kevin Law
Well said i agree totally with what you say and i have an idea why the politicians are so eager to get us on board the al gore bandwagon
by using FEAR on the poulation they can mould public opinion.
currently nuclear power is unpopular with the public so building more nuclear power stations is very unpopular .
the russians, americans and uk want to upgrade their old nuclear weapons in order to do this they need to build many more power stations but the public won't allow this to happen so they have to invent an enemy 'carbon' and tell us we are all going to die if we don't get rid of 'carbon'.so they persuade us to abandon fossil fuels as these produce carbon. we are already told this in the media every day. so if we phase out fossil fuels how do we produce our electricity ? the same governments who have demonised 'carbon' are not keen on wind farms and solar energy in fact they havn't told us yet what their solution is . enter nuclear power our saviour . smell a rat yet

col, leeds, uk

"mass extinction"

U.S has an easier method by using their nuclear arsenal. Now that is the one we all should be more concerned about.

stanzler, ny, usa

If people take the trouble to study the findings of dedicated scientists working in all aspects of Climate Change from Palaeoclimatology to Carbon Dioxide Sequestration you will come to realise the need for urgent action is real.

Join a local geological society in your area and become involved in the debate.

PK, Barnoldswick, UK

What a WONDERFUL result we have from the NATURAL PRUNING of past ages!

Why would we want to stop up all the Volcanos, Cows, and kill off all the bacteria devouring the rotting wood in the Rain Forests just to slow down the INEVITABLE weather cycles that have been going on for eons?

I am EAGER to see Mastadon roaming Canada, Russia, and Alaska ONCE AGAIN!

Don Dutkowski, CHILLIwack, B.C., Canada

251 million years ago? And we are still here? what exactly is the problem?

I don't fancy the idea of having had to share this place with dinosaurs. The figures you use of a 6 degree increase have already been shelved because the hockey stick needs some sticky tape. Have a look at David Bellamy's article to get a sense of proportion and balance

jim, norwich, uk

When water vapour is taken into account (because it too is a greenhouse gas), the entire human kind contribution of C02 is just 0.03% of the total greenhouse gases.
Which is more likely to cause warming - the thermonuclear reaction in the sky that can burn skin at a distance of millions of miles, or 0.03% of the greenhouse gases.....

W Smith, Oldham,

Global warming hype:

Did the change in species populations cause the climate change (as apparently is happening now) or was caused by - as your article suggests?

Max jalil, Birmingham, UK

I don't get it either !

How is it then that populations on other continents explode, even when hardship prevails, yet here there is IVF . Is our climate to blame for decreased fertility?

Here in our Jurassic landscape , you wonder how the violent earth survived, and newer creatures replaced the the monsters whose fossilised bones are regularily found in our cliffs and quarries. If we become extinct, we will only go the way of the most fearsome predators that lived in that period!!

maggie snook, wool wareham, Dorset UK

while I oppose any global warming taxes, I can't see how can anybody get out and breath that thick smog and still think it has nothing to do with global warming!

Acibeb, London, UK,

Fools...

Global Warming is caused by the Sun. And there's absolutely nothing we can do about it.

The Mayans warned us.

Mick, Liverpool,

You win some and you lose some.

Billy, Belfast,

Dont beat around the bush Kev, tell us what you think..........

AJ, Lincoln,

This is fascinating. I had no idea there were cars, poisoning industrial activity, and belching power stations all those millions of years ago. Perhaps dinosaurs were particularly flatulent.

Or maybe these events were caused by an as-yet-poorly-understood natural cycle of climate change.

Steve, Exeter, Devon

I am sorry but this is utter nonsense. It is scientific illiteracy. There are so many things wrong with this study, but let us just look at an obvious one. These phases of extinction are measured over vast time scales. Certainly several hundred thousand years. The Permian extinction is a perfect example of this. You cannot in all seriousness compare that to the present day when data extends only over several 10's of years, A hundred at most. This is ridiculous. It also takes no notice of volcanic activity, which is known to have a profound effect on extinctions phases (such as that in the Ordovician period). This is nothing more than a crass attempt to link geological catastrophy to modern theories on climate change. This is not science. It is political propaganda

Dr Kevin Law, Dundee, UK