She Blinded Me with Science
One of the things climate scientists worry about is feedback mechanisms. Some feedbacks are positive- they amplify warming, and some are negative - they suppress warming. Let's take a quick look at a graphic showing how cold air is made. Basically, what this graphic is showing us is that at this time of the year, when the Arctic is receiving little sunlight, the radiative input is less than the radiative output. In other words, more energy leaves the Earth than is added by the sun and cooling occurs.
In addition to that part of the equation, the radiative output (energy lost) is increased by the snow and ice on the ground. Anyone who has experienced snow knows how well it reflects light. It is possible to become "snowblind" from exposure to the bright sunlight and UV rays reflected by the snow. You see, it's not just the light that is reflected by snow, it is also the other portions of the sun's energy, including it's heat that is reflected away from the Earth's surface.
So what does this have to do with global warming? You have probably heard about concerns over the diminishing ice in Greenland and elsewhere in the Arctic as well as in Antarctica. In areas where the ice melts, revealing land or ocean beneath it, less of the sun's heat is reflected back to space and more is absorbed. Since it is the sun's energy absorbed by the Earth that warms the atmosphere, the melting ice can become a positive feedback and cause the Earth to warm faster.
Comments (3)
At the same time, the water that's melted increases the Earth's cloud cover, raising the planet's albedo and reflecting more of the Sun's rays. This counteracts the effects you mentioned because, to paraphrase your post, more sunlight is reflected back to space and less is absorbed.
Posted by Chris Christner | November 3, 2006 5:33 PM
With all the energy being used in the world no wonder we are generating more heat, more noticed in summers. Also Look at all the concrete and asphalt. This is another source of absorbing heat. Why do we not use more WHITE building materials and roads? Also cut back on use of autos? IS THAT TRIP NECESSARY? how much is our freedom worth if we have no planet to drive!
ALiEn
Posted by ALiEn | November 3, 2006 9:00 PM
Few discussions of the Arctic include the fact that the Arctic does not warm from solar radiation. The energy density from the Sun's low angle and the long path of this light through the atmosphere decreases the radiant energy to less than a few percent of normal temperate summer solar energy. And most of the energy that open water receives from this energy input is lost almost immediately to the atmosphere as radiant or evaporative energy.
So, why does ice melt in the summer up there? The influx of warmer air from lower latitudes. The constant loss of heat to space is the only thing that keeps the Arctic from getting even warmer than it does in the summer.
Global warming assumptions claim that the atmosphere of the Arctic should be the most sensitive to rising temperatures, but this frantic rise has not been observed. In fact, several land sites around the Arctic rim have seen declining or constant temperatures for almost 30 years and some report increasing long term land ice.
Other good reasons for the current melting include: (1) a huge bolus of warm water pushed north by the North Altantic Oscillation (NAO) a couple of years ago, (2) recent wind patterns which have pushed sea ice to warmer latitudes, (3) the detection of a number of hydrothermal vents and volcanic activity on the Arctic Ocean floor. All of these are sources of warm water which rises as it is lees dense and quite efficiently (compared to air) melts the ice from below.
Do not forget folks, do not look only above the ice, there is a lot going on below.
Also, not often mentioned is that after the big melt in summer 2007, the Arctic ice area the following winter was actually more than the winter before. So, it appears that the trend could go either way in the near future. Those who predict long term changes are basing the guesses on other guesses. There are just too many undiscoverd and undercalculated variables for anybody to reliably predict the future of the Arctic ice.
Just recently NASA reported that the multiyear ice can grow from within as a 12 hour "breathing" or tidal expansion and contraction generates many cracks which can then freeze in. The original idea of this ice being stable came from 1978 or 1979 pictures that showed solid ice at the time and the ice was never really watched very well since, until just recently with better satellite coverage. NASA says that this is an important factor that is in none of the model - it cannot be there as no one knew about it!
Now, this breathing effect and normal freezing of the cracks is a very real mechanism. And also explains the recentloss of the multi-year ice . Cracks do not freeze over very well when the water that floods up from below is warm and not at its usual almost-freezing temperatures. There's the culprit. Global warming is not the problem, the air is simply not warm enough to do all of this melting. BUT, when warm water fills the cracks, guess what happens, melting rather than freezing.
Oh, although Greenland might be melting around the edges, reports indicate that the overall mass is gaining. Greenland was farmable a thousand years ago when it was much warmer than now! It would take a couple of thousand years to melt the Greenland ice shield. And even if it did currently have a net melting each year, contributions to sea level would be essentially unmeasurable. Combined with the current net gain in ice mass in the Antarctic sea level is not going to be problem from these sources. (And Arctic ice, as it is already floating, has not effect on sea level.)
Sincerely,
Dr Colton
Posted by Sabin Colton | June 29, 2008 5:00 PM