How the CLIMATE will CHANGE
The role of Latent Heat of Fusion in Global Warming
The following is a thought experiment in geophysics performed by Anthony Marr in regards to climate change and how it will unfold over the next few decades. It may or may not be the same as any modeling being conducted by anyone else, past or present. If so, it is a mutual confirmation. If not, it will shed light on how the climate will change not yet been seen.
The crucial item in this consideration is called Latent Heat, or Enthalpy. “Latent” means “hidden”. The following will explain.
On a hot and dry day, sweating will cool the body, because when the sweat evaporates, it absorbs “latent heat of evaporation” from it’s surroundings, mostly your skin. So, in a real sense, heat is removed from your skin to change the sweat from liguid to vapor. Conversely, if steam hits your skin and condenses into water, it would release the latent heat, thus heating your skin even more than boiling water. Simply, latent heat is absorbed when a substance changes from solid to liquid and from liquid to vapor, and it is released when the vapor condenses into liquid, and when the liquid freezes into solid. The latent heat involved in melting and solidification is called the Latent Heat of Fusion (LHF), and that involved in boiling and condensation is called the Latent Heat of Evaporation (LHE). For water, the LHF is 40 calories or 334 jules per gram, and the LHE (at the boiling point) is 280 calories or 2260 jules per gram.
The thing to note about LHF and LHE is this. When heat is applied to water above freezing, say, +10C/+48F, the more heat applied, the higher the temperature of the water becomes, which is common sense. But if heat is applied to a bucket of ice at, say, -10C/+16F, the content of the bucket would warm up to 0C/32F, but no higher, no matter how much more heat is applied. More heat will raise the melting rate, but not the temperature. But once all the ice had melted, the temperature of the result water will rise as more heat is applied. That amount of heat needed to melt all the ice without raising the temperature from the melting point is the Latent Heat of Fusion (LHF). And likewise for the LHE for boiling water.
The Latent Heat of Fusion (LHF) in regards to Arctic, Antarctic, Greenland and glacial ice will play a huge role in determining how future climate change will unfold. Here in a nutshell is what and how and when and why.
The temperature of the sea ice is of course 0C/32F, whereas the water of the Arctic Ocean in the summer is around 5C/40F. Thus, it melts the ice from below. When the ice melts, it abosrbs LHF from both the water below, and the air above. Thus, it cools the air as well as the water.
At the same time, since the sea ice meltdown has exposed the northern shoreline of Europe and Siberia to the warmer water, the water will warm up the air above the land to as far as 1,000 km /600 miles inland, thus melting the permafrost. The melting of the permafrost also absorbs LHF, this time from the land and from the air, thus cooling both, temporarily.
Meanwhile, the melting of the terrestrial and marine permafrost deposits release trapped methane, a powerful green house gas, which in sufficient volume will generate its own positive feedback loop to melt even more permafrost and further warm the ocean and release even more methane.
It is now apparent that as long as there is ice in the Arctic to melt, thus absorbing LHF, global warming will be relatively. The melting of ice is to an extent self-retarding, since LHF cools the surroundings of the substance being melted, thus slowing the rate of melting.
Conversely, in the winter, when the ice refreezes, it release its Latent Heat of Fusion, thus warming the water and slowing the refreezing. And the refreezing of the Arctic has been slowing over the last 5 years.
This implies something of paramount importance. The melting of Arctic ice in global warming tends to cool the summers by abosrbing LHF through melting, and warms the winters by releasing LHF through refreezing. The latter, however, may end up being a cooling of the northern winter, because of the net loss of sea ice in that year, resulting in a net loss of LHF to the northern regions, including, for example, Vancouver, BC, which did experience a cooler winter in 2008/2009. The problem we face in the immediate future is that, as mentioned, the summer melting rate is increasing and the winter refreezing rate is decreasing, resulting in a net loss of ice and a net increase of LHF in the climatic system.
Unfortunately, no matter how fast the ice melts, the LHF absorption rate by ice-melting will decline with the decline of the total amount of ice to be melted. Since 2000, the Arctic has suffered a net-loss of about 2 trillion tons of sea ice. This means that while the planet is warming due to direct solar radiation and greenhouse-gas-heat-entrapment, it is cooled by the LHF removed from the climatic system due to the ice melt. This gives the Arctic ice the well deserved title of the “air conditioner of the planet”. But the capacity of this air conditioner diminishes the less there is left of the sea ice.
To quantify this somewhat, the LHF of water is 334 jules to melt one gram of ice or about 40 calories, which is about 160X the amount of heat needed to raise the same amount of water by 1C/1.6F(!) Since 2000, the Arctic has suffered a 2-trillion-tonne net loss of sea ice. One tonne = 1,000 kg = 1,000,000 g. 2-trillion-tonnes = 2,000,000,000,000,000 grams. At 40 caleries per gram, the total amount of LHF absorbed from the planet by the net ice-loss since 2000 is in the order of 80,000,000,000,000,000 caleries, which is a huge amount of heat removed from global warming. If the ice has completely melted off, this same amount of heat will remain in the system and contribute to global heating.
In fact, the faster the ice melts, the greater the cooling effect in the northern lands, and cold fronts could be more powerful for a few years, inciting comments again of, “Global warming? What global warming?” In this context, a more reasonable approach would be to see that a colder winter could mean faster Arctic ice-melt due to intensified warming of the Arctic Oceam by the Albedo effect.
But of course, the faster the ice melts, the less there will be left to melt, and the less LHF will be absorbed. The air-conditioner will wind down, and eventuall shut down. “Eventually” of course means the time when all the ice in the world has melted, including the Arctic sea ice, the Greenland ice sheet, the mountain glaciers and the Antarctic ice cover. But we don’t have to go that far to begin suffering major calamities all over the world. The Arctic Ocean will be 100% sea-ice-free in the summer of 2013, and it’s being 100% sea-ice-free in the winter will soon follow, meaning, within decades.
By now, any reader still with me will have concluded that this cooling will be short-lived, and we are currently enjoying the maximum of its cooling effect. Although the ice will continue to melt faster and faster, it’s total amount will continue to dwindle, and the amount of LHF absorbed will decline, eventually to zero when there is no ice left. At that point, because there is nothing left to absorb the quintillions of calories in LHFs, global warming speed will take a quantum leap, as if someone had cranked the tial to 10.
Since the Arctic sea ice is now half-gone, the cooling effect of the rest melting will decline. As I wrote earlier, we are currently enjoying the maximum cooling effect of the Arctic sea-ice meltdown. But it won’t last. Long before the Arctic becomes ice-free in the winter, perhaps as early as 2012, the global temperature may have begun an inexorable skyrocketing we may not be able to slow down, much less bring to a halt.
There might be some truth in the December 21, 2012 Doomsday prophesy after all. But if the end of the world is going to happen, the means would not be an asteroid strike or nuclear war war or alien invasion. It will be the detonation of the M-Bomb, known otherwise as the Methane Time-Bomb. While the A-Bomb is in terms of kilotons, and the H-Bomb is in terms megatons, the M-Bomb is in terms of gigatons. It is truly the Doomsday Machine. But it won’t go off in a flash as the A and H bombs do. The M-Bomb is a slow bomb, which will taken decades to spend, by which time there will be little left to live for.
The time to save the planet is – IMMEDIATELY OR SOONER!
Anthony Marr, founder and president
Heal Our Planet Earth (HOPE)