How much does human activity contribute to climate change?

I suppose after a while, the lack of an answer becomes an answer. The answer being that nobody really knows (or a few well formed google searches would reveal it).

I like the natural world. I like animals and plants and lots of clean water and fresh air. So there are lots of good reasons for us to stop dumping nasty things into the environment, but hoping to affect climate change may not be one of them. But I'm willing to change my mind if some meaningful answers ever do come along.

Several considerations are not being given much or any weight in what is all too often an hysterical response to allegations of human-induced global warming. We don't have, for example, reliable models of oceanic salinity in response to temperature levels (salinity impinges significantly on how much heat the oceans retain, and how much is radiated into the atmosphere when it is "night time" over a particular section of the ocean). An additional consideration of oceanography is the extent to which the pelagic biosphere acts to regulate average annual temperature. Algal blooms resulting from increased heat and CO2 levels are known to affect both the composition of the atmosphere, and the albedo of the open ocean.

Another consideration is that humans once burned wood (the most primitve "fossil" fuel) for heating and cooking, and millions of wood fires are far more productive of greenhouse gases relative to the thermal energy harvested than are forms of electrical generation which burn fossil fuels. This is not true simply of cooking and heating fires, either. Metal smelting is a significant consideration. Lest anyone consider that ridiculous, i would point out the the Romans used lead for plumbing (and they built aqueducts all over their empire) and to replace other metals in any building projects in which a soft metal could safely be used--and they smelted lead to such a significant extent that ice core samples from Antarctica show a significant increase in lead in the atmosphere in the years corresponding to the period of the Roman Empire. If there were sufficient lead smelted to leave an atmospheric record in Antarctic ice, one has to ask how much greenhouse gas was released in the process of smelting not just lead, but copper, brass, bronze, gold, silver, and, of course, iron. The Romans were not, of course, the only ones smelting metal--you also have metals smelted by the Kelts of Europe (when Caesar invaded Gaul, the Gauls had a metallurgy equivalent too, and arguably superior to the Roman metallurgy, and produced iron in greater quantities), as well as metals smelted in Africa, the middle east, the Asian subcontinent and China.

There is also the question of how much greenhouse gas was produced by the vast herds of ungulates and other grazing animals in Eurasia, Africa and North America--both in terms of "wildlife farts," as well as from the decay of their manure. In pre-Columbian times, bison, elk, "antelopes" (the prong horns are not true antelopes), deer, megaceros and mammoth existed in North America in the tens of millions, and perhaps more. At one time, herds as vaster or larger existed in Europe of bison (to a much lesser extent than North America), elk, deer, megaceros, various forms of wild cattle including the massive aurochs, wild oxen, horse and wild asses.

In none of this am i suggesting that human action is not a significant contributor to the production of greenhouse gases. What i do question is the reliability of climatology models. Do they take such matters into consideration? Is not the accuracy of such models a matter of degree, rather than a series of absolute statements? If there is a significant contribution by human activity, one has to question the extent to which it represents an increase. At one time, the earth was covered by far more forests, and forest fires raged unchecked. So what i am suggesting is that we not only don't have sufficient data (most temperature records come form only the last two centuries, and were collected in "heat islands" near dense human population centers), we don't have reliable models.

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I raised such objections in the past, but got "slapped down" by the global warming political rectitude party pretty damned quickly, and so i've been unwilling to discuss the topic since then. We don't have reliable models which take into account historical sources of greenhouse gases which no longer exist (widespread use of wood or coal for primitive and inefficient energy generation, vast herds of grazing animals which dwarfed in numbers the amount of domestic livestock we now graze), and the possible regulatory effect of the biosphere.

I am glad that Ros has started this thread.

Setanta wrote-



I suppose that means that getting "slapped down" causes Setanta to go off in a sulk.

But now he has recovered his composure.

What changed?

Chum wrote-



You only have to sit in a traffic jam and meditate upon the number of ICEs (an ironic acronym for internal combustion engine) in the world to become aware of what an obvious yardstick they represent. Or the 20,000,000 barrels of oil a day the US consumes to which figure it is justifable to add the oil consumed in other countries manufacturing cheap goods for the US market. And the millions of years of sunlight it took to make the organisms which become oil (and coal and natural gas) And factor in the spread of the Chernobyl pollution.

All this blather about bison farts and amounts of lead the Romans used when compared to our usage, and not only of lead, and 2 week junkets in Bali to discuss terms for discussing how to set an agenda for more discussions are somewhat akin to a vicar officiating at a wedding taking the opportunity to give the congregation a bollocking about sexual misdemeanour.

The GW scaremongers have not the slightest intention of reducing their standard of living or of not demanding that it gets better. They just wish to sound responsible and caring and associated things.



Yes-- the only realistic solution which nature will impose if we fail to address it ourselves. But it isn't much help to the rabid consumer.

On the one hand the serious polluters are fannying around in Bali and on the other the central banks are pumping, so far, $100 billion of liquidity into the markets so as not to dent retail sales during the upcoming festive jamboree when all the fine talk will be lost to the four winds.

So- we are in the ****. Well- not us actually. We have cast caution to the winds along with the empty blather.

It's all just an opportunity to sound off and make displays of responsibility and virtue, i.e attention seeking.

I don't rightly know how this emphasis on global warming came about to the point where it seems to eclipse many other environmental concerns, many of which (if your views are correct) would be much easier to substantiate than global warming.

Surely even if global warming is true, that should not be our sole nor major reason to clean up our act. The destruction of massive amounts of natural habitat, and the clean environment that goes with it should be impetus enough one would think.

So how did global warming get center stage?

It could be a very tough future that awaits us if population reduction occurs through war / disease / poverty / ignorance.

I have a hard time getting my head around the belief that any computer model is powerful enough to assess the results of the present conditions, even if all the data were available for input.

After all, weather prediction modeling is not that great, and it would seem to me that weather prediction modeling would need far fewer variables over far shorter time spans than would global warming modeling.

Probably through good marketing

I agree.

We can't dismiss the possibility that human activity really is making the natural warming trend catastrophically worse, and therefor global warming should take center stage. However, without differentiating human activities from natural warming trends, we can't say with any reasonable degree of certainty. Unfortunately if such information exists, the scientific community and the politicians are not making it obvious (which doesn't help their case).

Another possibility is that catastrophic warming is merely a focal point to try to drive the population in a direction we should probably go anyway.

But all of this is throttled by economic realities, which are really what drive change.

And I'm running out of ways to say, look at the numbers.
The global average air temperature near the Earth's surface rose about 0.74 °C during the last 100 years, or about 0.0074 °C per year
the IPCC predicts an upper bound 6.4 °C of heating during the 21st century, or .064 °C per year
the numbers I ran gave .0859 °C per year.

To me, this suggests that we were on a warming cycle that has sped up, and that our activity more than accounts for that change in heating.

These charts show that while popular myth has it that we are in a warming trend, which may even be true if you go back far enough in the past, over the last 1000 years we have been at best in stasis (the dotted red line in the second graph actually shows a overall decline but I'm allowing for experimental error). Even using the most helpful choice of the second standard deviation data points, i.e. low temps at 1000 AD to high points at 1800 AD, the slope of temperature increase is not even close to the slope of the temperature increase over the past 150 years (though it is a bit difficult to see the last 100 years data slope in this graphic, sorry).

When you superimpose the increase in green house gasses onto this chart the data, to me, becomes impressive for heating due to increase greenhouse gasses. If you superimpose the amount of greenhouse gasses due to man this again shows a very strong correlation. I don't know what other conclusion to draw. As I said in your previous post on this subject, in most fields of scientific research correlations this close are rare. I too have about run out of things to say.

However I'm afraid if we took a poll it would be, like most posts, A2K'ers 1 experts 0.

OK you believe the data shows global warming over the last 150 years as a significant and accelerating manmade development, right?

To be more specific, I think the data shows CO2 Levels over the last 150 years as a significant and accelerating manmade development.

I hate to pick nits, but I need to be accurate on this.

Please continue on with what you were going to suggest, I want to see where it goes...

Bump