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THE ENVIRONMENT IN THE NEWS - page 12 / 62

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Stable futures

The report assesses the likely costs to the global economy of stabilising greenhouse gases at various concentrations in the atmosphere.

Stabilisation at reasonable cost is possible, it concludes, commenting: "There is considerable economic potential for the mitigation of global greenhouse gas emissions over the coming decades, that could offset the projected growth of global emisions or reduce emissions below current levels."

The sharpest cuts, keeping greenhouse gas concentrations to levels equivalent to between 445 and 535 parts per million of carbon dioxide, might cost anything up to 3% of global GDP by 2030, while milder curbs could even enhance growth.

COSTS OF STABILISATION

IPCC assesses the likely impacts on global GDP by 2030 if cost-effective routes are used

stabilisation between 445ppm and 535ppm would cost less than 3% of global GDP, it concludes

between 535ppm and 590ppm would cost 0.2-2.5%

between 590ppm and 710ppm would bring anything between a net benefit of 0.6% and a net cost of 1.2%

different greenhouse gases have different impacts on warming per volume; total concentrations are expressed as the equivalent in parts per million of a certain volume of CO2 (ppm CO2-eq)

current concentration is about 425ppm CO2-eq

The current atmospheric concentrations are equivalent to about 425 parts per million of CO2.

Assessing the impacts of a given concentration is not an exact science, but many scientists believe that keeping concentrations below about 450ppm CO2-eq is necessary if the average global temperature rise is to be kept below 2C, and major impacts avoided.

The IPCC suggests that concentrations between 445ppm and 490ppm would keep the temperature rise to 2.0-2.8C. European Union policy is to avoid a rise greater than 2C.

"If you want to stabilise around 450ppm, that means in a decade or two you have to start reducing emissions far below the current level," said Dr Pachauri.

"So in other words, we have a very short window for turning around the trend we have in rising greenhouse gas emissions. We don't have the luxury of time.

Building concensus

Many technologies can play a role in cutting emissions, the IPCC says; but it singles out the building sector as a potential major contributer, and energy efficiency as something that "plays a key role across many scenarios for most regions and timescales".

Nuclear power and carbon capture and storage, where emissions from fossil fuel power stations are captured and buried underground, could play important roles; but with nuclear, "safety, weapons, proliferation and waste remain as constraints".

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