Letter to the Editor-Thursday,November 21:Fear for the future

SCIENTISTS agree that the globe is warming, the levels of greenhouse gases (primarily CO2) are increasing and about half of this increase is caused by human industrial activity through the burning of fossil fuels. (The latest report of the Intergovernmental Panel on Climate Change (IPCC 5) confirmed that human activity is "extremely likely" (95 to 100 per cent probability) to be the cause of this warming).

Scientists also agree that the risks of irreversible damage to the environment would increase significantly should the global average temperature rise above 2 degrees C. To keep below this temperature rise they tell us we have to restrict our emissions of greenhouse gases.

To hold the global increase in temperature to no more than 2 deg C we have to keep the concentration of CO2 in the atmosphere to no more than 450 parts per million.

Each year we are adding to the natural amount of CO2 in the atmosphere, largely through our use of fossil fuels, to generate electricity and to drive our vehicles. Worldwide, each year we are pumping an additional 50 gigatonnes of CO2 approximately into the atmosphere (1 gigatonne equals 1 billion tonnes). CO2 remains in the system for many hundreds of thousands of years.

According to the recently issued United Nations Emissions Gap Report, 2013, "in order to be on track to stay within the 2 deg C target and head off negative impacts" emissions should be kept to "a maximum of 44Gt CO2 by 2020, 40Gt CO2 by 2025, 35Gt CO2 by 2030 and 22Gt CO2 by 2050."

How many billion tonnes are left before we reach the 450ppm limit? In other words how much more fossil fuel can we afford to burn?

Another way of looking at this, offered by the recent IPCC 5 report, is to consider the amount of man-made carbon that can be released into the atmosphere before it reaches 450ppm.

They refer to this as the "Emissions Budget" and put the figure at one trillion tonnes of carbon. i.e. 1000Gt of which 531Gt had already been used by 2011, leaving 469. At the present rate this will be used up in about 34 years.

What happens if we overspend our budget, i.e. emit more then 44Gt globally by 2020, and more than 35Gt by 2030?

According to the Emissions Gap Report 2013, there is a gap between what we are achieving and what we need to achieve by 2020.

"If the gap is not...significantly narrowed by 2020, options to limit temperature increase to a lower (and a much preferable) target of 1.5° C will be closed".

The science is clear. These are the facts, gleaned from various sources, IPCC reports, United Nations Emissions Gap Report 2013, CSIRO reports, Australia's Climate Commission, to name a few. The question now is: What do we do about it?"

We could do nothing much now, and get away with it for the next 10 or 20 years, leaving it to future generations to deal with.

On the other hand, we are already observing many of the predicted consequences of warming, more storms and droughts, hurricanes and floods, and this with temperature increases of a mere 0.8 degrees centigrade.

Frankly, I dread to think what might happen with a further doubling of the temperature increase, let alone increases at the upper level of predictions, namely 4 to 6 degrees. I shall be long gone, but for my children and grandchildren, I fear for their future.

Nick Reeve,

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