Methane threatens to bake humanity like Turkeys in an Oven
Global Warming could accelerate out of control 20 times current trends
Compiled by Peter Mackenzie
The Canadian National Newspaper
1-31-07
A study co-authored by a Florida State University scientist and published in the Sept. 7 issue of the journal Nature has found that as the permafrost melts in North Siberia due to climate change, carbon sequestered and buried there since the Pleistocene era is bubbling up to the surface of Siberian thaw lakes and into the atmosphere as methane, a greenhouse gas 20 times more potent than carbon dioxide.
In turn, that bubbling methane held captive as carbon under the permafrost for more than 40,000 years is accelerating global warming by heating the Earth even more --- exacerbating the entire cycle. The ominous implications of the process grow as the permafrost decomposes further and the resulting lakes continue to expand, according to FSU oceanography Professor Jeff Chanton and study co-authors at the University of Alaska-Fairbanks.
"This is not good for the quality of human life on Earth," Chanton said.
The researchers devised a novel method of measuring ebullition (bubbling) to more accurately quantify the methane emissions from two Siberian thaw lakes and in so doing, revealed the world's northern wetlands as a much larger source of methane release into the atmosphere than previously believed. The magnitude of their findings has increased estimates of such emissions by 10 to 63 percent.
Understanding the contribution of North Siberia thaw lakes to global atmospheric methane is critical, explains the paper that appears in this week's Nature, because the concentration of that potent greenhouse is highest at that latitude, has risen sharply in recent decades and exhibits a significant seasonal jump at those high northern latitudes.
Chanton points to the thawing permafrost along the margins of the thaw lakes -- which comprise 90 percent of the lakes in the Russian permafrost zone -- as the primary source of methane released in the region. During the yearlong study, he performed the isotopic analysis and interpretation to determine the methane's age and origin and assisted with measurements of the methane bubbles' composition to shed light on the mode of gas transport.
"My fellow researchers and I estimate that an expansion of these thaw lakes between 1974 and 2000, a period of regional warming, increased methane emissions by 58 percent there," said Chanton. "Because the methane now emitted in our study region dates to the Pleistocene age, it's clear that the process, described by scientists as 'positive feedback to global warming,' has led to the release of old carbon stocks once stored in the permafrost."
In addition to Chanton, the John Widmer Winchester Professor of Oceanography at FSU, co-authors of "Methane bubbling from Siberian thaw lakes as a positive feedback to climate warming" include K. M. Walter (Institute of Arctic Biology, University of Alaska-Fairbanks); S. A. Zimov (Northeast Science Station, Cherskii, Russia); and D. Verbyla (Forest Science department, University of Alaska-Fairbanks).
Methane clathrate, also called methane hydrate or methane ice, is a form of water ice that contains a large amount of methane within its crystal structure (a clathrate hydrate). Originally thought to occur only in the outer regions of the solar system where temperatures are low and water ice is common, extremely large deposits of methane clathrate have been found under sediments on the ocean floors of Earth.
Global Warming amplification?
One explanation of rapid climate change at the end of the last glaciation, argues Dr. Euan Nisbet of the University of Sakatchewan, is that it was initially driven by methane from natural gas fields and gas hydrates during a period of extreme insolation.
Methane hydrates are solids which lock methane gas up under pressure in an ice-like lattice of water molecules. They are present under the oceans and permafrost in vast quantities. In the offshore Arctic, the cold allows their formation at sufficiently shallow depths that warming can reach them and destabilize them.
Nisbet is one of a number of geologists who fear methane hydrates as a potentially major positive feedback. He wrote in a 1989 paper that "any slight warming of the Arctic water will release hydrate from the sea floor almost immediately. A temperature change of a few degrees will liberate methane from the uppermost sea-floor sediments at this depth within a few years." The worst- case analysis is grim indeed: "the danger of a thermal runaway caused by methane release from permafrost is minor, but real ...even if there is only a 1 per cent chance that such events will occur, the social implications are profound." (E. Nisbet, "Climate change and methane," Nature, v. 347, p. 23, September 1990).
Fire in Ice: What Are Gas Hydrates?
In 1810, Sir Humphrey Davy discovered a new class of materials, known as gas hydrates or clathrates. These ice-like structures form when high pressure and low temperature trap light natural gases within rigid cages of water molecules. The trapped gas can be methane (hence "methane hydrate"), butane, propane, ethane or a number of other light natural gases.
The hydrates containing hydrocarbons, such as methane, are truly "fire in ice." If you light a methane hydrate deposit, it will burn like an oil lantern wick.
Gas hydrates occur in permafrost regions as well as beneath and just above the seafloor on the slopes flanking every continent, where the pressure is high and the temperature is low. Both industry and the academic community are studying the substances to better understand their past, present and future roles for climate, energy and development.
Some researchers speculate that blowouts of marine gas hydrates in the geologic past may have released enough methane, a potent greenhouse gas, to drive up global temperatures. Additionally, some researchers hypothesize that when hydrates broke away from steep slopes on the seafloor, they could have triggered massive seafloor avalanches and even tsunamis. Other scientists are cynically investigating the potential of gas hydrates, onshore and offshore, as a future energy source.
Estimates show that oceanic gas hydrates currently hold somewhere between 1,000 and 22,000 gigatons of carbon as methane, with most studies suggesting about 10,000 gigatons. Considering that our atmosphere contains about 700 gigatons of carbon, even the low mass estimates make gas hydrate a major component of the global carbon cycle.
This carbon pool, however, is sensitive to relatively small changes in deep-ocean temperature and sea level. Thus, in the past, gas hydrates may have destabilized, releasing methane into the atmosphere through gas bubbles rising rapidly through the water column or gas hydrates floating to the surface. Because methane is about 10 times more powerful a greenhouse gas than carbon dioxide, its release could have resulted in a potentially abrupt climate change.
Conceivably, we live in a world with an enormous amount of gas hydrate and free gas that affects climate and global systems over time. Most current models for global carbon cycling and climate change, however, have continued to omit the large and dynamic seafloor methane cycle. We may be sitting on the brink of a major shift in thinking about the carbon cycle and climate change, one that would permeate throughout the broad geoscience community.
Atmospheric CO2 Emissions Background context
Up to now it has been generally assumed that global warming will be a linear process. However evidence from the geological past linked with climate modelling that takes into account the global warming that is already locked into the system indicates that there may not be a linear response to rising CO2 levels. There is a danger that at some point we will cross a threshhold when global warming accelerates. By continuing to increase the amount of CO2 in the atmosphere we are getting closer to that point.
From the analysis of the bubbles of air trapped in ice cores taken from the Greenland icecap that are up to 500,000 years old it has been shown that the temperature of the Earth's atmosphere and the CO2 content has followed a regular 100,000 year cycle of change with the CO2 content and temperature closely linked and following the same graph line. Within this regular cycle there are some recently discovered very short periods of approximately only a few hundred years duration when temperatures rise dramatically by 8 degrees centigrade above the slower rises of up to 7 degrees centigrade. This gives a total range of 15 degrees centigrade from peak to trough. These records show natural processes at work before the impact of man's activities. We are currently in the lower temperature part of the cycle.
During the period covered by the ice core research the CO2 content of the atmosphere has varied between 170 and 280 ppm. (parts per million). From 1850 to today with the added input from the burning of fossil fuels the CO2 content has risen to 350 ppm. So we are now well outside of the historic range of values and CO2 levels are going to continue to rise for a long time yet and temperatures will follow.
Recent research has shown that the Amazon rain forest is not a stable mature forest with growth and decay in balance but is in fact an expanding forest that is being fertilised by the excess atmospheric CO2. The trees are getting bigger and there is a net take up of 5000 kg of carbon per hectare per year ( 1 hectare = 100 x 100 metres ). The total area of forest is 400 million hectares so the whole forest could be absorbing 2 billion tons of carbon per year.
Research in the savanah lands to the east of the Amazon Basin has established that the crucial factor determining the development of the rain forest is the length of the dry season. The savanah to the east of the Amazon Basin and the eastern Amazon rain forest both receive about the same amount of rainfall, 1500 mm per year. However in the savanah the dry season lasts 6 months but in the rainforest the dry season only lasts 4 months.
As a result of the longer dry season the savanah catches fire an average of twice in ten years whereas the rainforest with the shorter dry season does not dry out and remains damp enough to prevent fire. In the savanah the fires destroy most of the vegetation and this prevents the savanah developing into a rainforest. If the dry season in the rainforest was extended to 6 months by climate change effects then the rainforest would dry out and burn and could not then re-establish itself. If the rainforest burnt this would release the CO2 currently being absorbed year by year. So the forest would change from being a buffer which for a hundred years has absorbed our excess CO2 into a major source of CO2 releasing tens of years build up of CO2 in a matter of weeks.
It is accepted by all, including climate change sceptics, that increasing the amount of CO2 in the atmosphere will lead to increased global warming and many computer models have been constructed giving a rise in average atmospheric temperature of between 2 and 6 degrees centigrade by the end of the century i.e. by 2100.
But only now are models being constructed that incorporate a feed-back into the model of the effects of changes in world climate due to the changes in temperature that are predicted by the model as the model programme runs. One of the most important effects of climate change is the release of carbon dioxide from natural processes as atmospheric temperature rises.
Because of the "above normal" level of CO2 already in the atmosphere we are already committed to a certain amount of global warming because the excess CO2 will remain effective for many years. In addition the continued burning of fossil fuels will continue to add to the atmospheric burden of CO2. This warming will inevitably cause some climate change.
The area of the world most vulnerable to the effects of global warming induced climate change is the Amazon basin. The climate change models show that rising sea temperatures in the Pacific Ocean result in less rainfall and a longer dry season in the Amazon Basin. As described above this could lead to a reversal of the Amazon basin acting as a CO2 sink and it becoming a major source of CO2 returning the billions of tons of carbon to the atmosphere that have been stored there.
If the Amazon rainforest burns and releases billions of tons of CO2 into the atmosphere in a short period then this will be a further boost to global warming that will result in significantly higher end of century temperatures.
Runaway Methane Global Warming
The above-described accelerated CO2 precipitated Global Warming described in could lead to a runaway methane global warming effect due to the release of methane currently trapped in unstable methane hydrate deposits in the arctic (and ocean floors) that could be destabilised by accelerated overall global warming effects.
Core samples taken from old ocean sediment layers have been used to trace back in time the climate changes that have occurred over the past tens of millions of years. By analysing the incidence of different fossil shell remains of sea creatures occurring in these sediments it is possible to track the changes in the sea water temperatures and levels of atmospheric CO2 occurring at the time the shells were formed and deposited. These shells contain carbon from the CO2 in the atmosphere which was dissolved in the sea water in which the creatures lived just as takes place today.
From these records it appears that there have been short periods of only a few hundred years in the geological past when rapid increases of the Earth's temperature have occurred superimposed on top of the rise and fall of average temperatures over the longer term. For these short periods temperature rises of up to 8 degrees centigrade appear to have occurred on top of existing long term rises of 5 to 7 degrees to give temperatures up to 15 degrees centigrade warmer than today. Temperatures then fell back to the long term trend, the whole rise and fall only lasting a few hundred years.
The most likely cause of this rapid global warming over such a short period is the release of methane into the atmosphere. Methane is 60 times more powerful than CO2 as a greenhouse gas but only remains in the atmosphere for about ten years and so looses it's greenhouse effect quickly compared to CO2 which remains in the atmosphere for 100 years. CO2 would not be available in sufficient quantities to achieve the rapid warming and if CO2 was the cause then the raised temperatures would last a lot longer.
Methane hydrates occur extensively today all over the world. They consist of methane stored within unstable water bound deposits that if disturbed release the methane. They occur in major river deltas such as the Amazon delta and in old delta areas such as the Gulf of Mexico. Major rivers carry millions of tons of silt containing vegetable matter that continues to decay after the silt is deposited in the river delta. This anaerobic decay produces methane which gets trapped in the silt as methane hydrates until the conditions of water temperature and pressure change which can release the methane in vast quantities very quickly. Another form is a frozen slush/ice methane hydrate where the methane is trapped in an ice/water mixture which releases the methane when it warms up or the pressure on the ice is reduced. Frozen methane hydrates can contain 170 times their own volume of methane. These frozen hydrates occur in the seabed deposits of the Arctic Ocean.
Methane can also be trapped by permafrost layers which over-lay lower unfrozen layers of vegetable material that is decaying and producing methane which remains trapped by the frozen permafrost on top. If the permafrost layer were to melt then the methane in the layers below would escape into the atmosphere. Given the vast areas of permafrost in northern latitudes there is a significant potential for methane to be trapped that would be released if the permafrost melted as a result of global warming.
The theory for these rapid rises and falls of temperature, based on the geological records from 55 million years ago, is that gradual global warming due to some natural cause had resulted in temperatures 5 to 7 degrees centigrade higher than average ( i.e. higher than today's temperatures). At this point methane trapped in methane hydrate deposits started to be released into the atmosphere and accelerated the rate of warming. This would result in further warming releasing more methane. As the atmosphere warmed different types of methane deposits would start to be released and so a cycle of methane release leading to increased warming leading to more methane release from other areas of methane deposits elsewhere in the world would become established as global warming effected different areas of the world.
There is an intriguing photograph of what appears to be a methane plume coming up out of the Arctic ice sheet which indicates that the phenomenon described above can occur. There have also been incidences of oil drilling inadvertently triggering large releases of methane from hydrate deposits. One theory to explain the loss of ships in the so called Bermuda triangle is that they have been engulfed in a sudden methane release which reduces the buoyancy of the sea water so that the ship sinks.
So, does methane pose a threat today? Let us review the situation. We know there are extensive methane hydrate and permafrost deposits all around the world. We have evidence that we are at the beginning of a period of global warming that is probably being made worse by the continuing build up of CO2 in the atmosphere due to fossil fuel burning. Recent computer modelling incorporating the feed back effects of global warming that has already occurred suggests that by about 2050 we may start to loose the beneficial effects of the Amazon rain forest as a carbon sink. This could lead to temperature rises of 5 to 8 degrees centigrade by 2100. This would be uncharted territory and no one really knows at present how the world's environmental systems would change but we now have the evidence from the geological past. On the basis of this evidence global warming can lead to methane releases which once started would escalate. This would be the worst possible thing to happen because once started there would be no way of stopping a runaway methane global warming event. We CAN reduce our CO2 emissions from fossil fuels but we COULD NOT reduce methane emissions once they started, huge natural forces would take over and change our world. This would probably result in the melting of the Antarctic icecap which would raise sea levels by 50 metres and would completely change the climates of the world.
So what should we do? We should be careful and not risk starting the sequence events described above. To do this we must reduce total CO2 emissions from now onwards and take measures to protect carbon sinks such as the Amazon rainforest.
This is the third of this series of articles describing scenarios resulting from CO2 induced global warming over the next100 years. If we all carry on burning so much fossil fuel as we do now we will be running the risk of starting an unstoppable runaway methane global warming event within the foreseeable future. Only major absolute reductions in CO2 emissions NOW will avoid this risk.
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