I've been following the story of the extinction of Australia's megafauna for some time. It originally seemed reasonable to blame man as the extinction occurred at about the same time as we arrived in Australia - about BC 40,000. This fitted the pattern of other extinctions in other parts of the world where the arrival of the highest order predator in the history of the world led to various beasts dying out.

The most recent research, reported by the Herald Sun http://www.news.com.au/heraldsun/story/0,21985,20837553-5005961,00.html suggests that it was climate change that did it, not the mighty hunter. This research has an AGW application. If you check out the East Antarctica temperature chart I published in a blog post http://ambit-gambit.nationalforum.com.au/archives/001708.html you'll see that 40,000 years ago it was very much colder than it is now (40,000 years ago coincides with the second trough from the right).

Somewhere around this time, without any help from manmade CO2 emissions, there were significant temperature fluctuations of around 2.5 to 3.5 degrees. We probably don't know how much these contributed to the change in rainfall, but what it does demonstrate is that climate change is a constant, even in the absence of man. And it underscores the fact that this is a world where climate can and does change.

In the face of this our response to increasing CO2 levels is to wring our hands and talk about taming CO2 as a way of "combatting climate change", when the correct response ought to be to ensure that, unlike the mega-fauna, we are in a position to adapt to it. We also invent excuses for our inaction, such as - "This is the worst drought in 100/1,000 years". You can't absolutely fight climate change, but as evolution shows, you can learn to live with it. But that sometimes means taking tough decisions.

Graham, the fact that something occurs naturally does not mean that this one is natural nor does it mean that management of greenhouse gasses won't lessen the impacts of the process natural or otherwise.

I'm hoping that this is not where you are coming from but it seems that the case against global warming has been
- deny it is happening until the evidence becomes overwhelming.
- when the evidence becomes overwhelming insist that it is a natural occurance and that therefore there is no point at trying to stop it.

I don't know the science well enough to be confident in the balance between entirely natural, natural with some assistance from mankind or entirely man made but whatever the balance I do think we should be looking at ways of minimising how far it goes.

40,000 years ago there was no industrial contribution to climate change. Even if it is partly natural this time around our contributions may be the thing that tips it past the point of survivability.

It appears certain that we will have to adapt to a changed climate but that does not mean that we should not try and lessen how far it changes.

R0bert

I've made this point a couple of times before,yet it seems to fall on deaf ears.The fossil fuels we burn today were a result of plants taking co2 from the air and turning it into carbon and oxygen.In other words the jurassic period had a lot more co2 in the atmosphere and still life prospered.The dynamics of our environment and climate are not the same,but we should not assume that total destruction will befall our planet because we are once again releasing levels of co2 that existed millions of years ago.

We have also the factor of increased sun spot activity which has an enormous impact on weather.

On this forum I've read that it is the pollution of the oceans that has more impact on global warming than co2 gases.To me it makes a lot of sense.The particulate matter in water absorbs a lot of energy.Most of the sun's energy pass through the atmosphere and heat both the earth and the oceans which make up 66% of the planets surface.The oceans and land then in turn heat the atmosphere.Now scientists are telling us that the radient heat becomes trapped by co2 gases.Well polluted oceans and denuded land can absorb and trap far more energy than the atmosphere.

The real story is probably a combination of man made changes.If the predominate cause is the pollution is in the oceans,this can be rectified far easier and cheaper than a radical change in energy sources.

I think we are too focused on a single source of pollution,ie co2 gasses,which may not be the prime source of climate change.

Robert, the point I am trying to make is that climate changes, and to a certain extent it doesn't matter why it changes because the most important thing is to be sufficiently adaptive to survive it. I'm not a greenhouse effect denier - there is no doubt that increased CO2 has a warming effect on the planet. But no-one is really sure how much warming will be caused by it and what that warming will cause to happen. There is no "scientific consensus" as various lobbyists have claimed, just a range of estimates.

As Arjay seems to be suggesting, the best geological record seems to suggest that whatever the warming effect is, it won't be catastrophic. Others suggest that it might be well within the range of normal climate variability.

I'm temperamentally inclined against burning fossil fuels because they are a finite resource, and it is a very inelegant way to harness the sun's energy. But that's not going to panic me into spending money on the latest fad energy source that someone is pushing. I think the higher priority is ensuring that we live our lives in such a way that we can adapt. For example, the issue of coastal development is one that deserves attention because of greenhouse, but it's not getting it.

could it be that the climate change/global warming effect that's apparently occurring now is simply the effect of the past big wars ? just look how much burning went on over the past 100 years. all that oil & fuel which is only just now starting to escape from deep water wrecks. all the subterainean tests & underwater atomic blasts must all have had an impact & it's only now that it becomes more apparent. could it be that all the pressures released by letting out so much gas is somehow weakening a part of our planet that we are unable to monitor as yet. remember 100 years is a mere blink so far as nature is conerned. after all, we have only monitored nature for a couple of hundred years which really means that we don't have much evidence at all to start talking patterns in nature. just as it takes time for damage to become apparent it also takes time for rehabiltation to become apparent. how do we know that the environment hasn't already begun to recover after all the battering it received over the last century.

Graham

You state that you don't recommend the burning of fossil fuels because it is finite though you fail to mention the devastating health effects that the burning of these fuels has on all life forms on this planet - that's scientific!

Do you accept that in 1970, scientists estimated that there were 65,000 black rhinos - now 3,000. African elephants were estimated in 1980 to be around 1,200,000 now 500,000 and the tiger population has fallen by 95%. Then you have Scandanavian countries advising women not to eat fish during pregnancy, nor should their children until they reach the age of 8. This advice is to protect them from the heavy metals and other toxins we have dumped in our oceans.

Are you denying that humans' global footprint is not responsible for the reduction in numbers and the extinction of other species or do you put that down to biogenic droughts and climate change?

When humans increase their numbers from 1.5 billion to 6 billion in a little more than a century, surely you must perceive some correlation between humans' destruction of the ecology and habitats with the decline in numbers of other species. When humans capture some 40% of the world's plant and marine growth, 7 million other species are forced to compete for the remainder.

The human global footprint's impact on our ecology is glaringly obvious to some of us. Why then could one assume that the upper troposphere and stratosphere have remained intact? And I have not yet read of any posters denying the scientific theory that man-made CFCs and other organochlorines are responsible for ozone depletion!