In the public discussion of Global Warming, much is said about disappearing continental ice sheets and mountain glaciers, as well as growing deserts; with more droughts in some areas and more flooding in other areas. With new research indicating the acceleration of these processes, I would like to add a few thoughts on important aspects of increasing environmental heat that is not generally discussed with respect to this issue.
I need to preface my remarks with a few necessary facts for the reader’s understanding. The average temperature of the oceans throughout their depths is 4° Centigrade; the average temperature of ice in the continental ice sheets and glaciers is about minus-17°Centigrade. One scientific measure of heat is the CALORIE (different than the food Calorie, which is 1000 times greater). By definition, one calorie is equal to the amount of heat required to raise the temperature of one gram of WATER from 14.5°C to 15.5°C at standard atmospheric pressure. After water is frozen, the cooling of ice below 0°C actually requires only removing one-half calorie of heat to gain a drop in temperature of 1°C per gram of ice. So, reversing this process and raising the temperature of the continental ice from its average of -17°C to the 4°C average temperature of the oceans requires adding (8.5 + 4) calories of heat per gram of ice; thus a total of 12.5-calories of heat over this range. EXCEPT FOR ONE SURPRISING FACT!
What is not commonly known is that it requires 80-calories of heat to convert 1-gram of ice at 0°C into 1-gram of water at 0°C. Just to melt ice, without raising its temperature, requires about 6.5 times the amount of heat needed to raise the average temperature of the continental ice and glaciers to the average temperature of the oceans. The melting of environmental ice is a huge heat-sink that is presently buffering the effect of global warming; until we run out of ice.
Equally important for the production of snow and ice, it requires the removal of 80-calories of heat per gram of water-vapor at 0°C to produce 1-gram of snow at 0°C. This heat has essentially two places it can go, to avoid contributing to global warming; it can be radiated into space if the increasing greenhouse gases will let it, or it can be bound up by vegetation to produce woody fibers, as has happened in the past, when a tropical Earth produced the huge forests that became our present day coal and oil supplies (stored Heat). Of course we are presently over-harvesting the forests needed to do this job; we may be running out of trees as well as ice.
Although the fully melted glaciers and ice sheets would only add about 200 feet to the 12,600 foot average depth of the oceans, or about 1.6% by volume; the quantity of heat that would go into melting all of the environmental ice would raise the average temperature of the oceans 1.5° C if it were not for that ice. Actually most of the heat buildup in the oceans will be in the top 100 meters of seawater and very little heat will migrate to depths below 500 meters. So the heating of the oceans surface water would have been several degrees higher even now if it were not for the melting ice buffer. The environmental disaster of very warm ocean surfaces can only be guessed at.
Since the Antarctic and Greenland ice sheets are shrinking and glaciers world wide are receding, the environmental ice that has been present for millennia is proving to be insufficient to do anything but mask the current buildup of heat input into the environment. As more ice melts, reducing the overall surface area of ice exposed to increasing heat from the air and water; more of our heat input will remain in the air, water and soil; and the process of global warming will accelerate.
We must remember that, especially in the northern hemisphere, wintertime can bring enormous amounts of snow to mountains and valleys. The melting of this snow removes significant heat from our springtime environment. If the amount of winter snow declines, because it falls as rain instead, heat will build up earlier in the year and reach higher temperatures in the summer, because the air and ground will retain heat that would have gone into the 80-calorie buffer of melting snow. Late spring is much cooler than early fall, even though the sun angle in the sky is the same, because the heat flowing into the environment in the Spring is being absorbed in the melting of snow and the evaporation of winter and spring moisture, rather than heating the ground we live on.
Similar to the loss of ice sheets and glaciers, the millions of square miles of permafrost in the soils of northern Scandinavia, Russia, Alaska, and Canada are absorbing 80 calories of heat per gram of ice and melting, reducing their overall area and heat buffering capacity, which will also accelerate the effect of Global Warming as this ice source disappears.
We are not running out of oil, or money, or time; we are running out of ice. There are significant consequences in daily and seasonal weather that will be impacted by warmer air and the 80-calorie factor of water to ice to produce snow high in the atmosphere. As the Earth’s atmosphere heats up, it will hold more water as vapor to higher altitudes, forcing clouds and condensation to occur at even higher altitudes (or to not occur at all). The effect of this, in the temperate zones, will be an increase in the type of rain called Virga, rain that evaporates while falling and does not reach the ground. Rain that does reach the ground will be falling over longer distances through warmer air and will also evaporate more, so less will reach the ground and therefore rivers, lakes, oceans, and lands will receive less.
There is another heat buffer at work in our oceans; and that is the converting of water to a vapor. Typically we vaporize water in our kitchens by boiling it. Once we have boiling water (100°C), we must add another 540 calories per gram to convert it into water vapor at 100°C, almost 7-times the heat required to melt ice. Vaporization (evaporation by another name) does not require that all of a given quantity of water be raised to 100°C before vaporization occurs. With billions of water molecules in a gram of water, all colliding with each other thousands and millions of times per second, those water molecules on the surface of the land and oceans will have continuous opportunity to have their energy increased to become water vapor in the atmosphere. Global warming will increase the amount of vaporization and therefore increase the amount of moisture in the atmosphere.
As the ice, snow, and perma-frost disappear, the ongoing heat input that cannot find ice to melt will find water to vaporize. Since it requires less and less heat to evaporate water droplets as altitude increases, a buildup of greenhouse gases and increasing atmospheric heat will both tend toward a lot more water remaining as vapor in the atmosphere, rather than condensing into droplets necessary to form clouds and rain. Similar to the formation of ice from water, the condensing of water vapor into water droplets in the atmosphere requires the removal of heat from each gram of water vapor. This heat must be radiated into space or it will most likely be absorbed by the land and oceans, resulting in increasingly warmer and dryer soils and parts of the oceans that may become too warm to support the food chain.
There is a secondary effect, in the loss of ice and snow and cloud reflectivity that could accelerate global warming. Since ice and snow reflect nearly 100% of the radiation they receive, while rocks and oceans and vegetation absorb a very large portion of the radiation they receive. The reduction of ice and snow will add significant heat to the Polar Regions and mountains ranges; some of which will then be redistributed by the winds to all parts of the Earth. Today the Earth is to a considerable percentage cloaked in clouds and fog continually, a great deal of solar radiation is reflected back into space by clouds. It is very likely that there is a tipping point for the quantity of ice available to absorb heat and for the surface area of clouds, snow and ice to reflect sunlight into space, such that beyond that tipping point global warming could accelerate to an extreme of no ice whatsoever and very little cloud cover; and this could occur in a relatively short time-span.
One final thought on the acceleration of the loss of sea ice in the Arctic regions and loss of ice shelves near Antarctica, concerns the action of salt in seawater. We are all familiar with the use of salt to melt snow and ice on our roads and sidewalks. Those who live in areas that receive a lot of snow and ice each winter also know that salt is very active and efficient at melting ice when the temperature is around the freezing mark, but that salt is not useful or efficient at melting ice when the temperature drops below minus 15°C. How this affects sea ice that is in contact with seawater is this; when the Arctic and Antarctic oceans are very cold, the salt has little or no ability to accelerate the melting of the ice it comes in contact with. But as these oceans rise in temperature, due to global warming, the salt in seawater becomes much more effective at melting sea ice. Rising ocean temperatures that are still below freezing can accelerate the loss of sea ice, because of the effect of salt. And this is exactly what we are experiencing today. The ice in these regions is disappearing faster than anyone had calculated based solely on temperature increases to date; it is the increased effectiveness of salt from rising ocean temperatures that is responsible for the accelerating loss of sea ice.
Of course we may think that we are in dire straights, but it’s not really that bad; compared to the year 2108, when everyone is living and working 20 feet or more underground, to minimize requirements for heating, cooling, avoiding ultra-violet radiation, freak storms, and other calamities. At least we can keep cool today with iced beverages and refrigerated air, while we leave it to our children to ask, what happens after the ice is gone?
© May 2008
Craig D. Hanks
This article is taken from my blog at http://fundamentalscience.blogspot.com/ Other articles on this site deal with Un-intended Consequences of Universe Expansion; and a proper definition of Time.