Double Trouble in Thirty Years
Atmospheric CO2 levels don't lie either ...
A couple of weeks back my friend David Hamilton sent me a copy of a paper he presented to the Annual Conference of New Zealand’s Institution of Professional Engineers (IPENZ) in 1992. He was ahead of the times. He pointed out the sea levels were rising inexorably, and although the rate of change was small at only 1.4 millimetre per year, future rises in sea level needed to be considered when planning infrastructure that could last for a century or more.
His idea took a while to be adopted, but it eventually had an effect. Consideration of rising sea levels looms large on the horizon for modern day planners. Especially in at-risk cities like Dunedin.
It’s nearly 30 years since he presented the paper. It seems a long time to us, but it’s just the blink of an eye in the wider historical context. The thing that caught my eye was his reporting that CO2 levels back then were already twenty five percent more than in pre-industrial times. That seemed a lot back then (and it was), but we’ve just learnt that they are now fifty percent more. Mankind’s contribution has doubled in just thirty years. And the effects have doubled too. Back then, global temperature had increased by 0.5 C. Now it’s 1.1 C. That’s scary. We knew there was a problem back then, but thirty yeas later we haven’t even started to improve it. It’s still getting worse.
Here’s another way of looking at it. When I was born in 1950, nobody was concerned about increases in carbon dioxide in the atmosphere. Its concentration was just over 300 parts per million (ppm), not far above the pre-industrial level of 280 ppm. Over the first 40 years of my life it increased by 50 ppm to 350 ppm. By then (1990) atmospheric scientists and engineers like David were already worried about its effects. But now, just over 30 years later, it has further increased by close to 70 ppm, and will surpass 420 ppm next year. It’s currently increasing faster than ever. Temperatures too are increasing faster than ever (exactly as predicted by the climate models). As any atmospheric physicist worth his salt can tell you, it’s inevitable. It’s ‘simple’ radiative transfer theory.
David also mentioned that with just a 1 percent reduction in global ice, sea levels would rise by about 0.7 metres. I often put it another way: if all the world’s ice were to melt, sea levels would increase by 70 metres.
That would take several thousand years, but some models predict sea levels could rise by more than 3 metres within the next five hundred years, or even earlier. Please take a moment to imagine how our coastal cities would look with that inundation. If you can’t imagine it, have a look here.
The world needs more engineers with the vision of my friend. And politicians too. The blinkered three to five year time horizon of modern governments just doesn’t cut the mustard.
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Hi Richard, Most predictions of sea level rise assume that the ocean has a fixed size and that more water from melting glaciers and icecaps translates to higher sea level. This is not strictly true. Indeed, measured sea level rise has always been a fraction of what scientists predicted. The reason is that the ocean does NOT have a fixed size. The thin crust of the earth at the bottom of the oceans floats on molten magma. As melting ice from any warming land mass adds to the volume of water in the sea, hydrostatic pressure increases and pushes the ocean floor down deeper into the magma. Simultaneously, the weight and pressure of ice on mountaintops decreases and allows magma to push upwards to make space for the magma which is displaced from the bottom of the oceans, creating a circle of mass movement and a tendency towards equilibrium. Furthermore, the thin crust of the earth is not static. It floats on molten magma and when solar and lunar gravity effects combine in different vectors and changes with solar apogee and perigee, oceans change slightly in depth and pressure, sometimes causing islands to rise very slowly and then fall slowly. Add to that higher than normal wind speeds and equinox king tides and we see more island lakes being swamped. The slight actual mean global rise in sea level through more water coming from warming continents is slight and only a minor contribution.