Fire, flood and mud, this time
It
seems the oceans have been absorbing most of the extra heating caused
by “greenhouse” gases (1) sending back part of the heat
(infrared) emitted by the Earth’s surface (2). Oceans are vast and
deep, and currents move their surface layers from the tropics to the
poles, and back again. These hot flows move north and south, meet
colder water and, finally, the polar ice. Having cooled enough, they
go back where they came from. Moreover, the Earth’s tilt means the
Sun is above the tropic of Cancer in June and above the tropic of
Capricorn in December. Both hemispheres have summers and winters, and
the flows of heat are strong in summer and weak in winter. Ocean
currents and the seasonal distribution of solar heat have kept sea
temperatures constant over the long term. Heating and cooling
balanced out but, over the past few years, North and South Poles have
been losing ice at an accelerating pace. More is melting in summer
and less is freezing in winter. This is due to hotter water from the
tropics warming the Arctic Ocean and the seas around Antarctica. The
oceans are using up their cooling system.
Sea
temperatures in the tropical zones are kept stable by ocean currents
and by the Sun’s seasonal path. And though hot water stays on top,
some of its heat is diffused downwards. This is a much slower process
that is difficult to measure, but it also helps to cool the surface.
The extra heat reflected back (3) by gas molecules in the atmosphere
is absorbed by the ocean depths and by melting ice. This has allowed
atmospheric carbon dioxide to increase from 300 ppm to 400 ppm,
without noticeable effects for most of the world’s inhabitants.
Polar ice caps were melting, glaciers were shrinking and permafrost
was losing its permanence, but few people knew and even less cared.
Some even applauded the idea of hotter weather. One, two, three, or
even four degrees Celsius more were welcomed in the colder temperate
regions, but nothing seemed to happen. Of course, most of the
planet’s inhabitants were poorly or mistakenly informed. The
predicted rises are global yearly averages with considerable regional
disparities, where some may even be colder (e.g. Western Europe
without the Gulf Stream, which is one hypothesis). At present this
has started to sink in, as extreme weather conditions occur more and
more frequently. Up until recently the oceans have managed to keep
the planet cool, but now, like overloaded mules, they are showing
signs of strain and may soon lose their effectiveness altogether.
That
climate disruption is the consequence of humans burning fossil fuels
and tropical forests is still being denied – but then quite a few
believe that the Book of Genesis is factual. Part of that denial is
that the sky seems boundless. And the fact is, it does reach way
beyond the stars, but the troposphere, which contains 80% of the
gases surrounding the planet, is at best 15km high. If Earth was the
size of a basketball, a proportional layer of gases would be a third
of a millimetre thick and scarcely visible. Some deny from ignorance
and some because they prefer not to know. Some express denial though
they accept the facts, because they can see no alternative, or
because fossil fuels and the machines burning them are their
livelihoods. And everyone is in denial when they drive their cars,
receive a delivery, board a train or a plane, turn on their heating,
their lights, their air-conditioning, etc. One of the best informed
organisations in the world, the US military, is as mute as usual but
is making provisions for rising sea levels and massive flooding (4).
And that is what the climate disruption debate should be about, not
if but when and how bad. The 400ppm could be a tipping point, and
there is no going back because carbon dioxide is a very stable
compound and will stay around for centuries. Anyway nobody is
seriously considering an end to burning fossil fuels in the near
future. Gas instead of coal is a palliative that reduces carbon
dioxide emissions but does not stop them. As for electricity produced
by sunlight, wind, tides and waves, it is as capricious as the
natural phenomena it depends on (though geothermal energy is
constant), which explains why it represents such a small fraction of
the world’s energy mix.
The
speed of melting polar ice, shrinking glaciers and thawing permafrost
has taken everyone by surprise. It seems that temperatures are rising
much faster in the coldest regions of the planet than elsewhere.
Ocean and air currents move tropical heat north and south. This
process has been quite stable for a very long time. But global
warming means more calories have to be expended. Warmer winds blow on
snow-capped mountains, and warmer seas flow round the ice-capped
poles. This process cannot be reversed, and will get worse as carbon
dioxide emissions continue unabated, not to mention the methane
seeping out of the Arctic Circle in increasing volumes. As for
electric vehicles, they will reduce air and sound pollution in
cities, but car exhausts are only a fraction of global carbon dioxide
emissions, which seem largely the result of the Northern Hemisphere’s
supplementary use of fossil fuels for heating and lighting in winter,
which is when there is the least photosynthetic activity, and of
deforestation in the Amazon and Congo basins (5). Going “green”
or vegan may be morally uplifting, but the only rational attitudes
are either to hunker down behind flood defences like the US military, or
to just not care like the Trumps.
1.
That is, all molecules of three atoms or more, including water
vapour.
2.
The “reflective” effect of these molecules varies, but the
Earth’s wavelengths are much better reflected than the Sun’s.
3.
In fact, they absorb the heat and re-diffuse it in all directions, so
only part of it goes back to Earth.
For
more reading on all this:
5.
This video dates from 2006, but more recent 3D ones have less visual
precision.
posted by le Lézard at 4:57 AM
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