Hello and welcome to just have another think. Our monthly look at the ecological environmental and
social consequences of our 21st century climate emergency. About the middle of September each
year, as the northern hemisphere summer season draws to a close, the Arctic Sea reaches a point
of minimum sea ice cover. As many of you no doubt already know, the extent of that annual minimum
has been declining ever since satellite records began back in the late 1970s,
and in 2012 the region experienced a record low extent of 3.41 million square kilometres,
leading some commentators to suggest we might see an ice-free summer arctic
by 2020. Thankfully that didn't happen and in fact the annual minimums have fluctuated
a little bit since then. This year's minimum was actually only the 12th lowest on record
although it was still well below the level seen in the 1980s. There were some quite well
documented and fairly regional specific weather events causing this year's somewhat unusually
high minimum which are unlikely to combine together in the same way next year so the
trajectory of travel is quite likely to continue inexorably towards zero over the coming years.
Our sea and oceans cover 71 percent of the earth's surface and they're responsible for regulating our
planet's climate and sustaining all life. They've already absorbed about a third of all the carbon
dioxide we've emitted since the industrial revolution and about 90 percent of the earth's
extra heat since the mid-20th century. Our human activity and over-exploitation of ocean resources
is turbocharging natural variation causing unprecedented changes in the composition of
the water itself, the ecosystems within it and the coastlines that surround it. In September 2021 the
Copernicus Marine Service published the latest of their annual reports using a set of parameters
called ocean monitoring indicators to describe measure and monitor the state of the ocean,
observing all the relevant phenomena causing the changes. Those phenomena are grouped into three
categories, the first of which they call the Blue Ocean describing the physical state of the ocean
including things like sea surface temperature, sea level, ocean currents, waves and sea winds
as well as ocean heat content, salinity and density. This year's analysis shows that
sea surface temperatures in all parts of the global oceans increase by an average of 0.01
degrees Celsius every year between 1993 and 2019. That might not sound like a lot on an annual basis
but it adds up to an increase of 0.4 degrees Celsius over just 26 years, with the surface of
the Baltic and Mediterranean warming by almost a full degree Celsius over that time period.
Global sea levels have been rising by just over three millimeters per year
or about eight centimeters since 1993 and the rate of rise is accelerating. Again the Baltic Sea
has seen the biggest rise at almost 12 centimeters. The overall heat content of
the oceans is measured in watts per square meter just in the same way that we measure
the energy from sunlight hitting our planet each day. To maintain stable planetary systems there
should be more or less no increase in land or sea surface temperature, in other words the
heat energy reaching our planet should be balanced by the heat energy escaping our planet each day.
That's pretty much the way things were from the end of the last glacial period about 10 000 years
ago right up to the beginning of the industrial revolution. There are some small variations in
the solar irradiance reaching us as a result of orbital fluctuations in solar activity.
People much smarter than me have calculated the range of those changes as being between 0.05
and 0.15 watts per square meter but this analysis shows that just in the 14 years between 2005 and
2019 the heat content of the oceans from the surface right down to a depth of 2000 meters
has increased by one watt per square meter, which across an expanse of water as vast as that is an
absolutely mind-blowing amount of energy. Why is all that important? Well the report explains that
sea surface temperature plays a vital role in regulating the earth's climate and atmosphere
and in influencing the evolution of severe weather events. Ocean warming contributes about 30 to 40
percent to global means sea level rises worsening the already catastrophic flooding happening in
low-lying areas, damaging coastal infrastructure and disrupting coastal marine environments.
Warmer waters alter ocean currents and reduce the solubility of carbon dioxide in the water which
means more CO2 stays in the atmosphere instead. The extra heat also causes stratification or
temperature layering at different depths making it much more difficult for nutrients to rise up from
the deep waters to feed phytoplankton and other fundamental elements in the ocean's food chain,
which brings us to the second ocean monitoring indicator - The Green Ocean. This one refers
to the biological and biochemical state of the ocean including chlorophyll and nutrient
concentrations as well as ocean acidification and deoxygenation. Ocean acidification is of course
the one that always seems to grab the headlines and we had a close look at it in one of the very
first videos on this channel which you can jump back to by clicking the link up there somewhere.
Essentially the ecosystems in the oceans are extremely sensitive to quite small changes
in pH levels of the water. Between 1985 and 2019 average pH levels have reduced by 0.06
units. Again that sounds tiny as a number but on the pH scale it represents a 30%
increase in acidity posing a severe threat to marine life and especially to corals and shellfish
that increasingly struggle to find the calcium carbonate that they need
for their structures. Roughly half of earth's oxygen production also takes place in the oceans.
As we humans continue to accelerate climate change and release excessive nutrients into the water
from agricultural and chemical runoff, a process known as eutrophication, we're contributing to
dangerous levels of deoxygenation threatening marine life cycles all the way from the seashore
right down to the greatest ocean depths. Then there's The White Ocean,
which as the name suggests refers to the life cycle of floating ice within the polar regions.
The study shows that between 1979 and 2020 the annual average extent of sea ice in The
Arctic has been reducing by more than half a million square kilometers per decade with an
even more dramatic decrease of more than eight hundred thousand square kilometers per decade
in the summer months. A reduction of nearly 13% every 10 years. And you don't need to be Einstein
to work out how that's going to end, as this graphic representation by Andy Lee Robinson
shows all too clearly. Check out the black line representing the annual September minimum. As it
winds around the dial from 1979 through to 2021 you can see how it's spiraling in towards zero or
what some climate commentators refer to as a blue ocean event. The consequences of that eventuality
are very severe indeed not just for marine life but for almost every aspect of human existence on
the planet. I examined the top 10 worst impacts in a deep dive video a couple of years back it
doesn't make for very pleasant viewing I'm afraid but if you want to know the details then you can
click on that link to jump back and have a look at that one. And in case you were hoping that the
losses in the arctic might be compensated by gains in the Antarctic well no such luck I'm afraid.
There has been a slight increase in the Antarctic sea ice extent but according to this report it's
really not enough to be statistically relevant. The impacts of a changing ocean are now being felt
in just about every corner of the planet. Rising sea levels have already engulfed some parts of
the small island nations forcing communities to continuously move from island to island
or try to find a way to relocate to a mainland - something that's much easier said than done.
Low-lying coastal regions like those in Bangladesh will be overwhelmed in the coming years causing
mass migrations of very large populations of people, and the rich western nations won't
escape the consequences either. Venice was a high profile example in 2019 when a combination
of unusually high sea levels a high spring tide and extreme local and regional weather conditions
caused an unprecedented series of exceptionally strong high waters or aqua alta events as the
locals call them. Water levels rose by 1.89 metres which is more than six feet - the highest
recorded level since 1966. Warming ocean waters have also caused many marine species to move
towards cooler waters either going deeper in the ocean or physically migrating towards the poles.
Those migrations are not only depriving regional fishermen of the fish stocks that they and their
families rely on but they're also resulting in the introduction of non-native and invasive species
to different marine ecosystems. In 2019 increasing temperatures in the eastern Mediterranean basin
resulted in an infiltration of the highly predatory lionfish into the Mediterranean sea
from the Suez Canal to the Ionian sea decimating local marine life that had no defences against
this alien invader. And extreme temperature events like marine heat waves are becoming more common
more severe and longer lasting affecting the catches and populations of various marine species.
So what can we do in the face of these mountain catastrophes?
Well in conjunction with all these other agencies and organizations the Copernicus Marine Service
is advocating a global structure of monitoring, communication, education and governance aimed at
shifting human interaction with the oceans towards much more intelligent and sustainable stewardship
as the consequences of climate change continue to worsen.
Observations like those carried out by Copernicus are showing that the oceans have been absorbing
so much of the CO2 and heat energy that we humans have spewed out over the last couple of centuries
that they've really been masking the true severity of our climate predicament.
That can't continue indefinitely of course and there are already signs that the oceans are
reaching the limits of what they can cope with, so initiatives like the Copernicus programme will
play a vital role in raising awareness and urgency in the minds of our world leaders.
Let's hope they find the wisdom to listen and act. Thanks for watching and I'll see you soon