Climate Change Drivers (Part 3)


by Bru Pearce

Human population expansion has led to deforestation at an increasing rate, releasing CO2. Agricultural land holds a fraction of the carbon that a forest holds and our agriculture releases methane and nitrous oxide which are even more toxic greenhouse gases. Burning fossil fuels – coal, oil and gas to power, heat, cool and transport us, all lead to a build up of green house gases in the atmosphere,  which as a result, trap more of the suns energy leading to further heating of the atmosphere and oceans.


Carbon feedback sources


The blanket of greenhouse gases reduces the amount of heat that radiates back out into space. Think of clear nights, which are much colder than those with a warm blanket of cloud. Green house gases act in the same way, you just can’t see them. The result is that warmth is trapped in the atmosphere and is distributed around the world by the winds making the Poles warm disproportionally and night time temperatures higher (less heat radiates back out into space). These effects are precisely what we are observing in our temperature records now.

So we are seeing a reduction in the temperature differential between the tropics and the Arctic and Antarctic regions. It is the temperature differential that drives our weather systems and as the differential reduces our weather patterns change, this is what has been causing the big loops in the jet stream and are making our weather more extreme, dry areas are dryer and wet areas are wetter. The Arctic Sea with its thin lair of ice is far more venerable than the Antarctic where that ice has built up kilometres think over the land mass.

The huge loops in the jet stream are themselves feedback loops that positively reinforce warming the more the warm and cool air that is transported to and from the pole the greater the reduction in temperature deferential is and the more pronounced and prolonged become the oscillations in the jet stream. This is a very fast acting feedback which is also acting on the Greenland ice sheet.


Recent observations have shown that the melt mechanisms within glaciers allow for far faster melting and movement than previously thought. So expect to see new predictions for sea level rise that are greater and faster. 4+ meters by the end of the century and 25cm in the next 20 years, after which it will rise increasingly faster. 25cm is enough to do severe damage to many of our coastal cities and it leaves very little time to build defences. In fact it is probably going to pay to make 'early abandonment and rebuild' decisions.

The accompanying extreme weather (Hurricane Sandy was a direct result, as was the American drought, Europe’s appalling summer and the wildest Typhoon season on record in the far east) have all contributed to the world’s crop production being down this year by about 20% and reserves are running low, in five years time expect crop and food production to be down 40% on current levels.

Now ask your self can the world economy stand that?

More on Feedback Loops

The heating kicks off a number of natural feedback loops. Scientists refer to these as positive feedback loopsmeaning that they exacerbate climate change making everything worse.

    •    Ice and snow melt, leading to dark expanses of ocean and land which absorbs much more of the sun’s energy creating more heat which increases ice loss

    •    Defrosting tundra releases methane, a very potent green house gas which leads to more heating and more methane release

    •    Warmer conditions in the Arctic mean that shrubs whose growth had been restricted by cold can now grow into trees, which trap heat and reduce the reflectivity of the landscape (as the trees grow they capture CO2 but the gain is outweighed)

    •    Melting methane hydrate start to releases massive amounts of methane causing more heating

    •    Peat decomposing as it dries out releases more methane and CO2 as well as having the potential to catch fire and burn

    •    Rain forests drying out burn more easily releasing CO2 into the atmosphere adding more heating

    •    As climate warms forest fires become more widespread increasing CO2 released

    •    Desertification leads to destruction of humus in top soil this releases CO2 and methane to atmosphere - more heating

    •    A warmer atmosphere holds more moisture which is itself is a greenhouse gas trapping more heat and causing more extreme rainfall

    •    CO2 uptake in the ocean makes the sea more acidic preventing reef formation and reducing the number of life forms in the ocean – thus it ceases to be a carbon sink and becomes a net carbon emitter leading to faster warming

    •    Further as the ocean gets saturated with CO2 its ability to absorb it reduces


Part 4 coming soon