Global Warming Myths Busted

Ice cores show that carbon dioxide levels in the atmosphere have remained between 180 and 300 parts per million for the past half-a-million years. In recent centuries, however, CO2 levels have risen sharply, to at least 380 ppm (see Greenhouse gases hit new high)

So what's going on? It is true that human emissions of CO2 are small compared with natural sources. But the fact that CO2 levels have remained steady until very recently shows that natural emissions are usually balanced by natural absorptions. Now slightly more CO2 must be entering the atmosphere than is being soaked up by carbon "sinks".

The consumption of terrestrial vegetation by animals and by microbes (rotting, in other words) emits about 220 gigatonnes of CO2 every year, while respiration by vegetation emits another 220 Gt. These huge amounts are balanced by the 440 Gt of carbon absorbed from the atmosphere each year as land plants photosynthesise.

Similarly, parts of the oceans release about 330 Gt of CO2 per year, depending on temperature and rates of photosynthesis by phytoplankton, but other parts usually soak up just as much – and are now soaking up slightly more.

Ocean sinks
Human emissions of CO2 are now estimated to be 26.4 Gt per year, up from 23.5 Gt in the 1990s, according to an Intergovernmental Panel on Climate Change report in February 2007 (pdf format). Disturbances to the land – through deforestation and agriculture, for instance – also contribute roughly 5.9 Gt per year.

About 40% of the extra CO2 entering the atmosphere due to human activity is being absorbed by natural carbon sinks, mostly by the oceans. The rest is boosting levels of CO2 in the atmosphere.

How can we be sure that human emissions are responsible for the rising CO2 in the atmosphere? There are several lines of evidence. Fossil fuels were formed millions of years ago. They therefore contain virtually no carbon-14, because this unstable carbon isotope, formed when cosmic rays hit the atmosphere, has a half-life of around 6000 years. So a dropping concentration of carbon-14 can be explained by the burning of fossil fuels. Studies of tree rings have shown that the proportion of carbon-14 in the atmosphere dropped by about 2% between 1850 and 1954. After this time, atmospheric nuclear bomb tests wrecked this method by releasing large amounts of carbon-14.

Volcanic misunderstanding
Fossil fuels also contain less carbon-13 than carbon-12, compared with the atmosphere, because the fuels derive from plants, which preferentially take up the more common carbon-12. The ratio of carbon-13 to carbon-12 in the atmosphere and ocean surface waters is steadily falling, showing that more carbon-12 is entering the atmosphere.

Finally, claims that volcanoes emit more CO2 than human activities are simply not true. In the very distant past, there have been volcanic eruptions so massive that they covered vast areas in lava more than a kilometre thick and appear to have released enough CO2 to warm the planet after the initial cooling caused by the dust (see Wipeout). But even with such gigantic eruptions, most of subsequent warming may have been due to methane released when lava heated coal deposits, rather than from CO2 from the volcanoes (see also Did the North Atlantic's 'birth' warm the world?).

Measurements of CO2 levels over the past 50 years do not show any significant rises after eruptions. Total emissions from volcanoes on land are estimated to average just 0.3 Gt of CO2 each year – about a hundredth of human emissions (pdf document).

While volcanic emissions are negligible in the short term, over tens of millions of years they do release massive quantities of CO2. But they are balanced by the loss of carbon in ocean sediments subducted under continents through tectonic plate movements. Ultimately, this carbon will be returned to the atmosphere by volcanoes.

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The problem of reducing carbon emissions is the main for aviation and motoring industries, because the most part of the global pollution is from these industries. But analysis shows that II industry and consumer electronics give 2 per cent of global carbon dioxide emissions, which is the same pollution as from aviation and motoring.

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Urederra said:

By posting that, you are part of the problem.

LINKY

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Ball Lightning said:

Over the next few weeks i'll be busting some of the myths about Global Warming.This will be from New Scientist.

Human CO2 emissions are too tiny to matter.

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Knowledge of the evolution of atmospheric carbon dioxide concentrations throughout the Earth's history is important for a reconstruction of the links between climate and radiative forcing of the Earth's surface temperatures. Although atmospheric carbon dioxide concentrations in the early Cenozoic era (about 60 Myr ago) are widely believed to have been higher than at present, there is disagreement regarding the exact carbon dioxide levels, the timing of the decline and the mechanisms that are most important for the control of CO2 concentrations over geological timescales. Here we use the boron-isotope ratios of ancient planktonic foraminifer shells to estimate the pH of surface-layer sea water throughout the past 60 million years, which can be used to reconstruct atmospheric CO2 concentrations. We estimate CO2 concentrations of more than 2,000 p.p.m. for the late Palaeocene and earliest Eocene periods (from about 60 to 52 Myr ago), and find an erratic decline between 55 and 40 Myr ago that may have been caused by reduced CO2 outgassing from ocean ridges, volcanoes and metamorphic belts and increased carbon burial. Since the early Miocene (about 24 Myr ago), atmospheric CO2 concentrations appear to have remained below 500 p.p.m. and were more stable than before, although transient intervals of CO2 reduction may have occurred during periods of rapid cooling approximately 15 and 3 Myr ago.

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Ecofarm said:

The time frame is too short. Levels of CO2 have been MUCH higher in the more distant past (before humans). Selective statistics - plain and simple. The article's argument is the likes of: "my girlfriend walked into the room, and a commercial came on the TV. Obviously, my girlfriend causes commercials" (ignoring the more distant past).

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storealex said:

This is like what? The third time in a month someone suddenly prove how the scientific concensus is wrong, and all the huge majority of scientists don't know what they are talking about?

Everytime it becomes clear that it's bollocks of course.

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Jondalar said:

What I don't understand is why there is such a furor now. If it were up to me, we'd all do our best to live green all the time. It can only help the environment.

I can't understand why people are so against alternative sources of energy. If they work and are better for the environment, why don't we pursue them more aggressively?

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Marsden said:

Fault is too simplistic. It's best not to pollute or waste as a matter of fact, for the environment and ourselves. But I don't believe that global warming is exclusively a human caused phenomenon. If it is, then what caused the end of the "Little Ice Age" to end? And why did it begin in the first place, human kind not industrialized enough to cause warming, is it?

Waits for others to look up what the "little Ice age" is.

How can you form an opinion about something if you're just going of the garbage coming out in the last few years?

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Goa said:

To cite an analogy I found somewhere: Does the fact that forest fires can be cause naturally (by a thunderbolt for example) mean that it's immpossible to me to cause a fir by not taking care with my campfire?

This is a line of argument which comes up very often but which I understand the last, so please explain me: Why do you think the fact that previous climate change have happened is in contradiction to the theory that the present warming is mainly due to human activity?

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Fault is too simplistic. It's best not to pollute or waste as a matter of fact, for the environment and ourselves. But I don't believe that global warming is exclusively a human caused phenomenon.

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Marsden said:

Actually, it's the opposite. How can all previous climate changes been natural but not this one?

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I think it's probably a 30/70 type of thing, something that was going to happen anyway but were not making it any better.

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So if Goa and a lighting bolt start a forest fire and no one else is there, does it make a sound?

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