Zones 12/15/21

Science with Richard Bleil

So what’s so bad about global warming anyway?  It gets a little bit hotter in the summer, but winters will be milder, right?  I actually heard somebody on a radio program say something similar to this.  Unfortunately, it’s a little bit more complicated, and far more devastating.

Let’s start with a quick discussion of melting polar ice caps.  This is something I never really understood.  Melting ice won’t affect the sea levels if they’re on water (spoiler alert).  Ice displaces an amount of water equal to the mass of the ice when it floats, so melting ice should not affect the volume of the water at all.  You’ve seen this.  If you’ve ever had a glass of a drink filled with a lot of ice, the drink does not overflow once the ice melts.  It remains constant (less, of course, the amount that you actually drink).  But there are two things about this example that we need to discuss.  First, have you ever noticed that the amount of ice changes very slowly, until the ice is nearing the end?  Once the ice has melted and little remains, it always seemed to me that the remaining ice melts more quickly than when there was far more.  I have no empirical evidence of this; it’s just personal observation, but there is a thermodynamical argument for it.  Ice melts at 32oF, which means, as it is melting, the entire drink is at this temperature provided that there is enough ice to keep it there.  When the ice in insufficient to cool the entire drink, you get a temperature gradient of 32 near the ice, but warmer the further away you get from the ice.  Because heat flows from a region of high temperature to a region of low, this means heat will flow from the warmer drink at the bottom of the glass towards the ice, thereby providing heat that could (or should) melt the ice more quickly.  Recent studies have shown that the polar ice caps seem to be melting faster than predicted, and I’m wondering if this is the reason. 

Back to ocean levels, as I’ve said, if the polar ice is floating on water, the ocean level will not change.  Unfortunately, this is not the case.  The polar ice caps are actually on ground, ground that is now beginning to be uncovered.  It seems logical that the nations nearest this ground (Russia, Canada and the Netherlands) should have the rights to the ground, and Russia is being very aggressive about annexing the new land as it is uncovered.  As ice from land-locked glaciers melt, ocean levels will indeed rise, potentially flooding out low-lying cities and nations and costing enormous amounts of costly damage.  One island has already completely submerged, and island nations are becoming increasingly worried. 

But there’s more to global warming than temperature and glacial melting.  As it turns out, temperate zones will shift.  Most water evaporates around the equator, of course, where the temperature is highest.  This water vapor rises into the sky and begins to migrate towards the poles.  As it moves, the average temperature drops, until it reaches a temperature that cannot hold the amount of humidity caused by the equator, resulting in a band of rain.  This rain reduces the humidity, and the remaining water vapor continues to migrate towards the poles.  The process continues, resulting in a few zones that are naturally higher in rain around the world.  If you look at a map, it’s easy to see the strips of heavier plant growth, as well as bands of desert all running east and west. 

As the temperature rises, this means that the average temperature of these zones will also increase.  Where once the average temperature helped induce a band of rain and growth, the band will move north and south.  Where once we had rich farmland for growing food, it will become dry and more desert like.  If we have time to migrate with the bands, we will be fine, but we really won’t.  The new rain bands will be in locations where the soil is less rich because historically there has been less life to provide nutrients and topsoil.  The result means it will be harder to actually grow food, and therefore food will become scarcer.  That is a little more significant than warmer winters. 

I find it fascinating that so many politicians and businesspeople deny that there is any evidence of global warming while a recent report showed that the US military has already outlined a plan to deal with the changes anticipated by global warming.  The military sees global warming as a threat to national security, while our politicians refuse to do anything to try to avoid it.  At my age I doubt that I’ll live long enough to see significant problems, but if I had children, they would.


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