A few hundred years ago a not very well understood climate event took place, typically referred to by the misnomer 'the little ice age.' Because this climate event has been misnamed as 'an ice age', this has led to some rampant speculation on the internet that 'global warming causes an ice age.' This is not true.
According to the Ocean and Climate Change Institute "The Little Ice Age... was a five-hundred-year-long period of cold conditions affecting Europe and eastern North America. Contrary to what the name suggests, it did not involve ice-covered continents, as in a "real" ice age. But it did cause enough cooling to disrupt human activities...(It did) cause severe winters on both sides of the Atlantic."They also point that "many of the models used to study changes in ocean circulation have inadequate representations of ocean processes. The models may also be less sensitive to salinity perturbations than the actual ocean is. As a result, we are not yet in a position to predict these types of ocean circulation changes." However they also point out that a study of ocean sediments does suggest that "The climate history of the earth shows that adding freshwater to the North Atlantic disrupts the ocean circulation in ways that cause regional cooling and alter patterns of rainfall and drought."
Therefore the possibility exists that 'Global Warming', by introducing fresh water into the North Atlantic, could affect the Atlantic Conveyer Belt, an ocean current which transports warm tropical water to the western coast of Europe. The water then sinks to the depths of the ocean as it cools, while the heat is released into the atmosphere, and it is this released heat that is responsible for the moderate winters in Europe as compared to the harsher winters in North America. Therefore, there is a possibility that Global Warming could temporarily create the conditions for much harsher winters, but not an 'ice age'. This is a myth being spread around on the internet caused by the misnaming of the 'little ice age' several hundred years ago, which was not an actual 'ice age' (with glaciers and ice sheets covering continents) but rather a time of particularly harsh winter climates. When summer came the snow melted, and there was no accumulation of vast ice sheets.
Ice Ages follow a pattern which is established by variations in the patterns of the Earth's Orbit around the sun and variations in the earth's tilt and rotation. The Earth does not follow a perfectly circular orbit, but rather it follows an eccentric elliptical orbit, with a cycle of one hundred thousand years. The amount of sun light reaching the earth varies depending on how extreme the distance of the earth is at the maximum of the elliptic as well as the variation of distance during each season. The earth also wobbles as it spins, up to 23.5 degrees, a cycle which takes 41,000 years. This wobble also causes the position of the earth in its elliptical orbit to change, a phenemona known as the precession of equinoxes, which follows a cycle of 23,000 years.
Ice Ages occur when all three of these factors are in favorable alignment resulting in the least amount of summer warmth in the Northern hemisphere when summer occurs at the farthest point in the Earth's elliptical orbit. Summer temperatures therefore plunge to winter like conditions, and snow accumulates from year to year rather than melting. Similarly, the ice age ends when the process is the opposite, resulting in increased summer heat, and summers which take place at the closest point in the elliptical orbit.
Not enough information is available to climate modellers to give a firm prediction of whether or not a period of cold winters will result from global warming processes, which explains why they are always found to be lobbying bodies such as Congress for more research grants. The atmosphere is much better understood than the ocean. You might encounter emphatic statements out on the internet that suggest that it is a definite certainty that there will be another ice age caused by global warming, and this once again is a myth based upon a misunderstanding of both the state of oceanic climate science (it is underfunded, and thus these statements are just the expression of one possibility, typically, you might notice, combined with an appeal for more funding to increase our knowledge, which is then misinterpreted as being statements of exact fact...to make matters worse the term 'little ice age' is a misnomer, and thus once again causes all that speculation out on the internet about coming glaciation and so on, when the worst people could expect would be a particularly nasty winter, since it is not at all probable that summers will become winter due to global warming, thus leading to an ice age, since the process of a true ice age is controlled by rotation, spin, and orbital variations of the earth, and is not driven by any of the factors influenced by global warming processes.
You sometimes hear talk on the internet about a short period of increased glaciation that was linked to disruption of the Atlantic Conveyer Belt about 12,000 years ago, and the suggestion is made that this scenario is therefore applicable to discussion of global warming today. The Younger Dryas occured sometime around 12,000 years ago, when the large ice sheets of the last ice age halted the melting process for about 1,000 years, with the change going into the period and coming out of the period taking place in the span of around a decade, according to ice core samples, which demonstrates how the climate responds in a rapid and non-linear way. However comparisons made between the Younger Dryas and today and not really applicable, since the world was still covered by massive ice sheets at that time, a condition which does not exist today, making some kind of direct comparison between that phenomena and today's climate unreasonable.
According to what I have read, what is believed to have happened is that the Laurentian ice sheet broke apart, much like the Ward Hunt Ice sheet on Ellesmere Island broke apart two years ago, and in both cases this break up allowed a trapped Lake of cold fresh water to suddenly flood out of the center of the ice sheet. In the case of the Laurentian ice sheet this lake was massive in size, carving the St Laurence river system as it was released and introducing large amounts of fresh water into the North Atlantic at the same time.
As much as fifty percent of the winter heat in places like Europe of the East Coast of the United States comes not from solar radiation but rather from heat released from warm tropical water carried northward by the ocean current known as the Atlantic Conveyer Belt, so the disruption caused to the ocean currents by this event then caused sufficient loss of warming to halt the deglaciation...but remember, this was a period of deglaciation to begin with, and so trying to make some kind of comparison between the Younger Dryas and the modern world to suggest that global warming might lead to glaciation as happened during the Younger Dryas is like comparing apples and oranges.
One of the most significant variables today would be the billions of tons of methane which could be released into the atmosphere by the now ongoing melting of Siberia, with a similar warming in process in the tundra areas of North America as well. The last time such large amounts of methane were released into the atmosphere all at once took place during the Thermal Maximum, about 55 million years ago and this resulted in rapid global warming, as one would expect, given the powerful insulating effect of methane gas. This would be what you would expect when you wrap the earth in a blanket...not glaciation, or global cooling, but rather global warming.
Rise in methane
The graph, from IPCC site shows the increase in methane in the atmosphere which rises sharply over the last century and a half...as you can see by the graphic of a farm with silos and a cow in the bottom right corner, this rise in methane is attributed to large scale livestock production. However even this sharp rise in methane levels cannot compare to the amount of methane that could be released by the melting of the permafrost in the frozen bogs of the high north. For comparison purposes, the United States releases about 6 million tons of methane into the atmosphere from livestock operations (mainly cattle) each year, while globally total human related methane release totals 30 million tons. Just the melting of western Siberia has the potential to release up to an estimated 70 billion tons of methane, which is on a scale of about 2,000 times more methane than the total annual anthropogenic forcing introduced currently by human processes. Such a large release of methane naturally then invalidates the conventional climate models which are based on moderate releases of greenhouse gases and predict relatively smooth and linear changes, and then predicts such moderate impacts as 'no sea ice in the arctic by 2100' when what we could actually be seeing is rapid climate, and no ice in the polar regions at all, and all this even before 2100.
Ff course all this is 'alarmist', to speak about 'the Thermal Maximum' when it is barely acceptable to debate 'global warming', but given how the 'moderate' scenarios do not seem to inspire people to take matters all that seriously, maybe a little bit of alarmist rhetoric is called for, especially when recent events would suggest that what is 'alarmist' might actually be what is realistic, while what is 'moderate' is actually dangerously over optimistic. Just to give people some idea of how much water actually exists in a frozen state on this planet, and which would be released during a Thermal Maximum event, consider the following graphic which shows much of the United States under water during the last Thermal Maximum, when the high north was covered with tropical rain forests, rather than ice sheets.
The Thermal Maximum
Some links
Signs of Rapid Arctic warming since 2000 Siberian permafrost is melting, leading to the potential release of up to 70 billion tons of methane, a greenhouse gas 20 times more powerful than carbon dioxide. The last time this happened, during the Thermal Maximum, much of the United States was plunged under water, and became part of the ocean, and this scenario is much more plausible than the misunderstood scenario being spread around on the internet which suggests that the United States will buried under glaciers due global warming.
Arctic ice cap at record low The melting of Siberia has been taking place over the last three or four years, around the same time that the arctic ice cap has been shrinking at an accelerated rate, leading scientists to lower their estimates of an ice free arctic from the year 2100 to the year 2060 given the accelerated rate of melting taking place since 2000. This can be graphically seen on the video linked to on the page below, where the most rapid shrinkage takes place right near the very end of the video.
other climate stories...
