- Written by Super User Super User
- Published: 08 August 2012 08 August 2012
by Bru Pearce
We know from observation that the average temperatures of the atmosphere and the seas are rising, further that temperatures are rising faster at the higher latitudes than at the tropics. In addition we have observed that night time temperatures are also higher on average. This is all consistent with a greenhouse effect with more energy being trapped by the earth’s atmosphere than is being radiated into space. We also know that the proportion of green house gasses in the atmosphere is rising fast. Ice core records provide us with samples of the atmosphere going back 400,000 years through several ice age cycles and we can correlate CO ² levels to earths historic temperatures. This tells us that at the depths of the past four ice ages CO ² levels where about 180 ppm and at the warmest parts of the interglacial’s CO ² levels where around 280 ppm. The current interglacial has so far continued for about 12,000 years and under the normal cycle of earth’s orbit we should soon be dipping slowly into another ice age.
However, mans accelerating use of fossil fuels over the past 200 years has increased CO ² levels to over 394 ppm more than the difference between the depths of an ice age and the interglacial warm periods. On our current fossil fuel usage path we will pass 450 ppm sometime around 2020 and hit 500 ppm around 2025 more than double the difference. We also know that our CO ² levels are now rising 1,000 times faster than they have risen before.
Physical observation and measurements tell us that sea ice and ice sheets are melting. Basic physics tells us that white surfaces reflect heat and light and that dark surfaces absorb heat and energy. Open sea absorbs more heat and energy than reflective ice. We may also remember that it takes energy to change from a solid state to a liquid. It’s why ice keeps your drink cold and why it warms up so quickly after the ice has melted, energy was going into melting the ice rather than allowing the drink to warm. It is the same with the top of the world when the Arctic sea ice is gone the sea water beneath warms fast. So more open water means more and faster warming.
20,000 years ago in the depth of the last ice age, sea levels where 60m below where they are now and the shore line had retreated to edge of the continental shelves. It had taken 60,000 years for the sea level to drop and the oceans to retreat. That’s because the mechanism to transport all of that water on to the land and build it up as ice sheets is rain and snow. This build up happens very slowly (although the temperature can drop very fast because a snow white surface is just as reflective however think it is). Melting ice on the other hand, allows melt water to run off at an unlimited rate so seas can rise comparatively fast. Earth 20,000 years ago was a hugely different place. Man has already set up the climate to make as big a change in the other direction with the increasing loss of ice.
Unfortunately this change tips us out of a cycle that has been going on for at least 800,000 years, into entirely new territory. We are about to inadvertently release simply massive quantities of fossil fuel laid down between the ice ages in the tundra and on the now sub surface continental shelves off Siberia and Canada. These are methane hydrates gasses derived from rotted plant matter kept in place up until now because it is frozen. Now as the Arctic seas heat up it is defrosting and huge plumes of methane gas are bubbling up to the surface.
Methane is a far more potent gas than CO ² it breaks down over time to CO ² and its action in the atmosphere gradually reduces. Therefore over 100 years it is reckoned to be about 20 times as damaging is CO ². Unfortunately we don’t have 100 years to react. Over 10 years methane is 100 times more effective as a green house gas. As its action in the atmosphere is to cause more warming, it acts to release more methane, more than replacing the amount of methane that has reduced to CO ². A release of just 1% of the trapped methane will be enough to more than double the current green house effect again and take us to a CO ² equivalent of 800ppm +.
Our modelling has let us down badly!
Because for a time the science on this was unsure and because our climate models did not take into account feedback loops, consensus at the IPPC was that CO ² induced warming would be much slower. All of the IPPC forecasts are being revised upward. The Arctic methane feedback loop had not been expected to kick in until the end of the century. Few had been predicting an ice free North Pole before 2080. Each report revises figures toward higher temperatures and faster melting and measurements now suggest that the Arctic Ocean will be ice free for a month or two in 2015. Changes are now happening faster than our scientific advisory systems can keep up with.
The methane bomb at the top of the world is like a fire work, it is no longer a spark on the touch paper it has started to fizz! The danger is every bit as great as if we had discovered a large meteorite on course to collide with earth in less than 15 years, the longer we leave it to try to deflect it the harder it is going to be.
The good news is that although we probably don’t have the technology to deflect a meteorite, we do have the capability to manage our climate.
Time is very short, and every one of us is feeding the CO² fire, promoting other feedback loops all of which act together to accelerate us towards the abyss. We have to reduce our emissions immediately and move on quickly to start pulling the CO² levels down to at least 330 ppm or below.
by Bru Pearce