Manmade Global Warming?

[snow hope]

The correct terminology is Anthropogenic Global Warming Theory (AGW) which means global warming where mankind is having a major impact on the warming of our climate.

I am sceptical of the AGW Theory which is based on the fact that CO2 is a Greenhouse Gas (GHG). With an increase of CO2 in our atmosphere, it is theorized that this GHG will cause the global temperature of our planet to heat up. There appears to be a global warming of about 0.6c over the last century. Many scientists and organisations, bodies around the world including our own Met Office consider that a major part of that warming is down to mankind's activities.

But there are some laymen, scientists and countries who remain sceptical that this warming is due to mankind's influence. I am one of these laymen and I think the warming is more likely to be due to natural decadel and centenial swings in our climate, brought about by our local Star, the Sun which provides everything we have in our Solar System. Natural swings in our climate do occur naturally, recent examples being the Medieval warm period (1100 - 1400 approx) and the Little Ice Age (1600-1900 approx).

And as Bandidoz kindly posted in this thread, http://www.powerswitch.org.uk/forum/viewtopic.php?t=163
we can see the Ice Ages which occur about every 100,000 years with about a 10,000 year inter-glacial which we are lucky enough to be enjoying currently. It should be noted that the next ice-age is due now.

The recent Horizon programmes on Global Dimming, Gulf Stream cut-off etc, were enjoyable and quite possible. As is the next Caldera explosion in Yellowstone as well as the next major asteroid impact and flu pandemic. They could start/happen tomorrow or not for 200 or 2000 years. Anything is possible!

Just my opinion folks..

[isenhand]

One question I have with global warming is; how reliable are our measurement? A lot of measurements have been taken in towns and cities, are they recording a global warming or a local warming? Is satellite data useful (given the fact that they are relatively new and recording data that varies over a long period of time)? Etc. etc. etc.

Even if global warming is not made by use I think it is a sensible precaution to assume that it is. If we do something about reducing pollution and global warming is not made by humans then we will not effect global warming but will have fresher air. If global warming is caused by humans than we should do something to stop it. Either way, its better to err on the side of caution.

[Bandidoz]

And as Bandidoz kindly posted in this thread, http://www.powerswitch.org.uk/forum/viewtopic.php?t=163
we can see the Ice Ages which occur about every 100,000 years with about a 10,000 year inter-glacial which we are lucky enough to be enjoying currently. It should be noted that the next ice-age is due now.

The point of the illustrations in that post is to clearly indicate that CO2 levels are far higher than those ever recorded over 400000 years. In the recent National Geographic article, the rise shows as a definitive spike. To me this proves beyond a shadow of doubt that the current CO2 levels are unnatural.

[Sky]

I second Bandidoz,

While the planet does warm and cool naturaly. The way and speed with which it is doing so at present breaks the 'normal' pattern that is historicaly evident. Suggesting that something unusual is happening. I think humans are far more than likely to be that unusual element than anything else.

[kevincarter]

What about the incredible huge hole in the ozone layer, isn't that man made? isn't that going to affect climate change at all?

[grinu]

I agree that climate change is probably caused by people. While the earth's temp does fluctuate a fair bit over a long period of time, the rate at which it has warmed is much greater (as far as I am aware, I may be wrong) than ever before. There are lots of indicators of past temperatures.

[MacG]

I am one of these laymen and I think the warming is more likely to be due to natural decadel and centenial swings in our climate, brought about by our local Star, the Sun which provides everything we have in our Solar System.

I'm with you on this one. I'm a layman when it comes to climatology (and so is everybody else as it seems), but I got a PhD in science - mainly measurements and conclusions in chemistry.

This thing about correlations is nasty stuff. You have a hard time sorting out chickens and eggs. In my book, the ice core data could just as well suggest that athmospheric CO2 is a function of increased solar activity, thus a trailing indicator rather than a leading factor.

What about the ice ages then? How did they come about? And above all, how did they end?? Because of humans setting fire to wood? Or peat?

[snow hope]

Isenhand - good point about the reliability of measurements, but there are as many likely to be a bit high as there are a bit low so this should cancel out. But Urban Heat Islands (UHIs) are a real issue and of course you can guess where most weather stations are placed - yes, near where man mostly lives in our villages, towns and cities. Central London regularly records night time temperatures of 10c greater than outer London temps. And I certainly agree regarding reducing pollution.

Bandidoz - I have looked at the graphs again and they look like we are coming to a CO2 and temp peak very similar to the 4 other peaks in the graph. Looks like business as usual to me. Get ready for the next ice age though!

grinu - we aren't really able to tell how quickly the temperature changed in the past (up or down) as we only started to measure temperature at the very earliest in 1640 in England. Most of the rest of the world didn't start to record temps until the mid nineteenth century or later. The trouble is that this is a very short time period with which to draw conclusions. I think a lot of people nowadays accept that climate changes all the time, in fact it may be quite rare that it is as stable as it has been for the last few hundred years. There are lot of indicators of past temperatures, called proxies, ie we equate measurements of various isotopes to warmer or cooler temperatures. The trouble with this method is that we can only get a rough guide to temperature and some of these proxies are being questioned in terms of whether they reflect temperature or actually water vapour / humidity etc. So things are not completely clear-cut.

I do accept that mankind appears to be adding considerably to the amount of CO2 in out atmosphere and that it takes a while for this to disappear from the atmosphere, but where I have a problem is that I am not at all convinced this will make a single bit of difference to our climate. The various models that the International Panel on Climate Change (IPCC) seem to rely upon so much are by no means proof in my mind of anything. They are a bit like statistics you can make them prove just about anything.
At this point in time I understand they still don't take account of clouds and their impact on heat retention and reflection. We all know what a difference a cloudy day makes in the summer or a cloudless night makes in the winter!

MacG - yes chicken and egg is a good point. I know a number of people who seriously consider that CO2 is increasing because of global warming not that global warming is increasing because of CO2 - hard to disprove this..... please feel free to try anybody.

Good to keep an open mind I think.

[isenhand]

Here is something of interest to people here:

http://news.bbc.co.uk/2/hi/science/nature/4636115.stm

[Sky]

Looking at the graphs in the original post. CO2 has varied between 180 and 300ppmv in the last 4 hundred thousand years ago until 2 hundred years ago, which includes several ice ages. In the last 2 hundred years this has risen to 370 ppmv, far higher than before, and the most likely candidate for that is our burning of fossil fuels. I agree the CO2 could be an indicator rather than a cause, however as a layman I thought we have a pretty good understanding of the chemical properties of CO2, and its ability to trap heat in the atmosphere rather than alowing it to bounce back into space, meaning it is more likely than not to be a cause than an indicator.

If a class 5 (I'd say a class 10, but they oly go as high as 5 -at the moment) Hurricane is forcast to be headed your way, but there is chance the weather man got it wrong, do you batten down the hatches?

[snow hope]

I understand your point Sky, but I suppose it depends on how much it is going to cost you to get hatches fitted! Or if it were a tornado you wanted to protect yourself from how much it would cost to fit a bunker.....I am sure you would only need a bunker if you were pretty sure a tornado would one day come right over your house......