Part 3 (2/2)

Climate change is already dangerous. The signs are evident globally: in the polar north; in Darfur's famine; in Australia's depleted MurrayDarling River system; in the collapse of ecosystems across the globe; in the 2007 mega-fires in Greece and California; in the coral stress in the Caribbean and in Australia's Great Barrier Reef; in widespread species losses; in changing monsoon patterns; in the destruction of lowlying communities; and in regional food-production stress. Our world is already at the point of failing to cope. The UN's emergency relief coordinator, Sir John Holmes, warned that 12 of the 13 major relief operations in 2007 were climate related, and that this amounted to a climate-change 'mega disaster'.

Global warming is now close to 1 degree. Many of the results that were forecast are already coming true.

At a warming of just 1 degree over pre-industrial levels, it was predicted that the Amazon would be drying, and increasingly drought and fire affected. During the 2005 drought, some tributaries ran dry; in 1998, forest fires generated by El Nino conditions poured almost half a billion tonnes of carbon into the air - more than 5 per cent of global greenhouse-gas emissions for that year. The Amazon, responsible for more than 10 per cent of the world's terrestrial photosynthesis, is currently near its critical-resiliency threshold.

In the US, it was expected that a 1-degree rise would result in California and the Great Plains states becoming subject to mega-droughts and desertification: a new and permanent 'dust bowl', similar to those seen between 1000 and 1300 AD during the Medieval Warm Period, when devastating, epic droughts. .h.i.t the plains, and whole Native American populations collapsed. This predicted drying is also occurring.

At a warming of just 1 degree, the North Queensland Wet Tropics rainforest will be an environmental catastrophe waiting to happen, according to Steve Williams, a James Cook University senior research fellow. Just 1 degree is likely to reduce the area of this World-Heritage-listed Queensland highland rainforest by half. As predicted, the Barrier Reef is already subject to regular bleaching (loss of colour due to loss of algae), and is now facing extinction: a survey showed that 6095 per cent of it was bleached in 2002. This is the case with most coral reefs around the world.

At 1 degree of warming, it was also expected that world cyclones would be more severe, and that small island states would be abandoned as seas rose. This is happening.

As predicted for a 1-degree rise, ice sheets around the world are suffering severe losses; and as permafrost melts, landslides in the European Alps are already becoming serious. The Mount Kilimanjaro ice cap, which has been intact for at least 11,000 years, is well on the way to disappearing, with an 80 per cent loss in the last hundred years, and the rest predicted to be gone between 2015 and 2020 as surrounding forests die off.

Britain's Hadley Centre calculated that warming of just 1 degree would eliminate fresh water from a third of the world's land surface by 2100, worsening a water crisis that seems already to be a permanent new part of life in many parts of the world.

All of these effects have occurred with a 1-degree warming; yet the most commonly used definition of dangerous climate change is linked to a 2-degree warming threshold, and its corollary, suggested by Sir Nicholas Stern, among others, that our target should be for a 60 per cent reduction in greenhouse-gas emissions by 2050.

It is important to understand how these numbers achieved such prominence in the climate debate. The first goal set by a forum of international significance was in 1988. The International Conference of the Changing Atmosphere in Toronto advocated a 20 per cent reduction of 1988 carbon dioxide levels by 2005.

In 1990, the first IPCC Scientific a.s.sessment Report pointed out - for educational rather than policy purposes - that it would require a 6080 per cent cut in emissions if carbon dioxide emissions were to be stabilised at the then-current level of around 350 parts per million. This guesstimate was superseded four years later when CSIRO scientist Ian Enting and his colleagues reported the results of ten world climate models, eight of which showed that the reductions required to stabilise the atmosphere at 350 parts per million of carbon dioxide would likely be more than 100 per cent - that is, carbon dioxide emissions would need to be completely eliminated, and carbon would need to be taken out of the air, for 5090 years.

By 1997, however, governments were not thinking of cuts on anything like this scale. This was reflected in the Kyoto Protocol's target for developed-country emissions to be only 5 per cent less than the 1990 level by 2012. Achieving this target would result in annual additions of carbon dioxide to the atmosphere of around of 6 billion tonnes, which would not stabilise greenhouse gases in the air for hundreds of years, and would likely see the level of carbon dioxide climb past 1000 parts per million - more than three times the highest level known in the last million years.

In 2000, realising that the Kyoto cuts were inadequate, Britain's Royal Commission on Environmental Pollution recommended that if greenhouse gases were to be stabilised at 550 parts per million carbon dioxide equivalent, emissions from Kyoto Annex I [developed] nations would need to be reduced to 60 per cent below 1998 levels by 2050. It was argued that this target was needed if the world was to avoid a 2-degree warming. Six years later, however, the Stern Review published data indicating that if the atmosphere was stabilised at 550 parts per million carbon dioxide equivalent, there would be a 99 per cent chance of exceeding a 2-degree warming; so the 2-degree target was then s.h.i.+fted to be a.s.sociated with an emissions cap of 450 parts per million. To stabilise the atmosphere at 450 parts per million of carbon dioxide equivalent, a reduction in emissions to at least 80 per cent less than the level in 1990 is required; yet the target of 60 per cent by 2050 remained a popular government policy long after it was shown to be inadequate.

If we accept that the present rise of 0.8 degrees (with more warming in the pipeline) is already dangerous, we can no longer a.s.sume that we have another 40 years in which to reduce emissions to 6080 per cent below 1990 levels, as argued by those advocating a higher temperature cap of 2 degrees. Nevertheless, it is worth looking at the proposed emission scenarios - the scale and speed of emission reductions - necessary to achieve a 2-degree target, because they demonstrate that even this inadequate target will not be achieved by governments acting in their 'business as usual' mode.

The European Union, the IPCC, and the International Climate Change Taskforce, among many others, propose a temperature cap of 2 degrees to avoid 'dangerous anthropogenic interference with the climate system'. For a 2-degree cap, research finds that, in the long run, the Kyoto-defined greenhouse gases need to drop below 400 parts per million, and they need to be significantly less if the risk of overshooting the target is to be low.

Malte Meinshausen of the Potsdam Inst.i.tute for Climate Impact Research in Germany calculates: 'Our current knowledge about the climate systems suggests that only stabilization around or below 400 parts per million carbon dioxide equivalence will likely [85 per cent probability] allow us to keep global mean temperature levels below 2 degrees in the long term.'

Similarly, Simon Rettalack of the Inst.i.tute for Public Policy Research in the UK says that to have an 80 per cent chance of keeping global average warming below 2 degrees, 'greenhousegas concentrations would need to be prevented from exceeding 450500 parts per million carbon dioxide equivalent in the next 50 years and thereafter should rapidly be reduced to about 400 parts per million carbon dioxide equivalent'.

Compared to 'business as usual' scenarios, 2-degree scenarios are characterised by a very sharp turnaround in emissions - falling to, or below, half of the 1990 level by 2050 - and then declining towards zero. The downward-sloping curves are so steep that they can only be called crash programs.

There are large uncertainties about the relations.h.i.+p between the level of greenhouse gases in the atmosphere and the long-term temperatures that will accompany them. This necessitates the expression of ranges, or probabilities, of outcomes. The Stern Review, using calculations by the Hadley Centre in the UK, shows that, in the long term, greenhouse-gas levels of 400 parts per million carbon dioxide equivalent have a 33 per cent probability of exceeding 2 degrees; a 3 per cent chance of pa.s.sing 3 degrees; and a 1 per cent chance of exceeding 4 degrees.

Because today's carbon dioxide level alone is close to the long-term cap of 400 parts per million of carbon dioxide equivalent and emissions are still rising, the 2-degree strategies depend on 'peak and decline'. This means that the maximum target is breached, but because of the time lag between the increase in greenhouse-gas concentrations and the increase in temperature, there is an opportunity to lower emissions and have greenhouse gases drawn down by the carbon cycle before the theoretical maximum temperature is reached.

Meinshausen describes the process: Fortunately, the fact that we are most likely to cross 400ppm [parts per million] CO2eq [carbon dioxide equivalent] level in the near-term, does not mean that our goal to stay below 2C is unachievable. If global concentration levels peak this century and are brought back to lower levels again, like 400ppm, the climate system's inertia would help us to stay below 2C. It's a bit like cranking up the control b.u.t.ton of a kitchen's oven to 220C (the greenhouse gas concentrations here being the control b.u.t.ton). Provided that we are lowering the control b.u.t.ton fast enough again, the actual temperature in the oven will never reach 220C.

For a 7090 per cent chance of staying below 2 degrees, Meinshausen maps an 'initial peak at 475 parts per million carbon dioxide equivalent', leading to the long-term return to '400 parts per million carbon dioxide equivalent'.

'Peak and decline' a.s.sumes that emissions will eventually be cut to below the Earth's net carbon-sink capacity; it a.s.sumes that there is a mechanism operating to remove the excess carbon dioxide from the air to lower the level of greenhouse gases from the peak, before their full force is felt. But if the weakening of the carbon sinks, as predicted and observed, is sufficiently large, this drawdown effect will not be strong enough. In this case, unless the natural carbon sinks are supplemented by a human-organised carbon dioxide drawdown of atmospheric carbon on a huge scale, 'peak and decline' will be a failed strategy, and atmospheric greenhouse gases will be stranded at a far higher level than planned.

A number of researchers have attempted to estimate the level that emissions would need to be cut to stabilise at a 2-degree rise with a carbon dioxide equivalent of 400 parts per million. Research by Paul Baer and Michael Mastrandrea found that global emissions of carbon dioxide would need to peak between 2010 and 2013; achieve a maximum annual rate of decline of 45 per cent some time between 2015 and 2020; and fall to about 7080 per cent below 1990 levels by the middle of the century. At the same time, similarly stringent reductions in the other greenhouse gases would need to occur.

Meinshausen says: 'To avoid a likely global warming of more than 2C and all its consequences, global emissions would need to be reduced significantly, i.e. around 50 per cent by 2050. Per-capita greenhouse-gas emissions would need to be reduced by around 70 per cent, so that global emissions could be halved despite the globally increasing population.'

Using mid-range climate sensitivity, a team led by the Center for International Climate and Environmental Research's Nathan Rive found that even getting to a 50 per cent chance of preventing more than 2 degrees of warming would require a global cut of 80 per cent by 2050, if total emissions were to peak in 2025. For a lower risk of failure than 50 per cent, the emission cuts would need to be substantially higher.

Now comes the crunch for Australia. Because Australian emissions are five times the global average, and the world population will be half as large again by 2050, these scenarios require Australian per-capita emissions to be cut by at least 95 per cent by 2050 - a proposition currently rejected by Australia's Rudd government.

But how worthwhile will those cuts be, in any case, if 2 degrees is too much? A rise of 2 degrees over pre-industrial temperatures will initiate climate feedbacks in the oceans, on ice-sheets, and on the tundra, taking the Earth well past significant tipping points. As we have seen, likely impacts include large-scale disintegration of the Greenland and West Antarctic ice-sheet; the extinction of an estimated 15 40 per cent of plant and animal species; dangerous ocean acidification; significant tundra loss; increasing methane release; initiation of substantial soil and ocean carbon-cycle feedbacks; and widespread drought and desertification in Africa, Australia, Mediterranean Europe, and the western USA. At 2 degrees, Europe is likely to be hit by heatwaves every second year, much like the one in 2003 that killed up to 35,000 people, caused US$12 billion of crop losses, reduced glacier ma.s.s, and resulted in a 30 per cent drop in plant growth that added half a billion tonnes of carbon to the atmosphere.

At 2 degrees of warming, the summer monsoons in northern China will fail, and agricultural production will fall in India's north as forests die back and national production falls. Flooding in Bangladesh will worsen as monsoons strengthen and sea levels rise. In the Andes, glacial loss will reach 40 60 per cent by 2050, reducing summer run-off and causing horrendous water shortages in South American nations. At 2 degrees, California will see a decline in the snowpack of one-third to three-quarters, with a loss of up to 70 per cent in the Northern Rockies, which will devastate regional agriculture as melt run-off declines. Changing climate will have a severe impact on world food supplies: in central and South America, maize losses are projected for all nations but two. In 29 African countries, crop failure and hunger are likely to increase.

After a careful rea.s.sessment of climate sensitivity and the climate history data, James Hansen and seven co-authors are now suggesting that the tipping point for the presence, or absence, of any substantial ice-sheets on Earth seems to be at around 425 parts per million (plus or minus 75 parts per million) of carbon dioxide. This means that the carbon dioxide levels often a.s.sociated with a 2-degree temperature rise may also be the tipping point for the total loss of all ice sheets on the planet, with an eventual sea-level rise of 70 metres.

Despite the catastrophic consequences of a 2-degree warming, the European Union and the International Climate Change Taskforce, among many others, have set 2 degrees as the target towards which the world should aspire.

But if 2 degrees spells disaster, what will the new 'business as usual' target of 3 degrees bring?

CHAPTER 11.

Getting the Third Degree.

The rapid Arctic melt consigns the widely advocated 2-degree-warming cap - always an unacceptable political compromise - to the policy dustbin. Scientific evidence shows it is too high and would be a death sentence for billions of people and millions of species.

In late 2007, Australian government advisor and former chief of CSIRO Atmospheric Research Graeme Pearman wrote: The global climate-science community has indicated that changes of planetary temperature of even one-to-two degrees have the potential to bring about significant global exposures to coastal erosion, sea-level rise, water supply and extreme climatic events, to name but a few. The potential number of humans impacted by a 2-degree change may count in the hundreds of millions. The European Union has already set a target of maximum warming of 2 degrees in the belief that warming beyond this represents an unreasonable risk of 'dangerous' climate change. Such a change in the average global temperature might be regarded by many as small, but it has the capacity to culminate in major consequences, something that scientists feel is still under-appreciated in both public and private policy development.

Despite the dangerous consequences of 2 degrees of warming, we are now being asked by politicians to consider a 3-degree warming cap, because they consider the 2-degree target to be too great a challenge for their 'business as usual' mode of operation.

Thanks to recent developments in paleoclimatology, we have some insights into what a 3-degree world might be like. In the Pliocene, three million years ago, temperatures were 3 degrees higher than our pre-industrial levels. In that era, the northern hemisphere was free of glaciers and ice sheets, beech trees grew in the Transantarctic Mountains, sea levels were 25 metres higher than they are today, and atmospheric carbon dioxide levels were 360400 parts per million, very similar to today. There are also strong indications that, during the Pliocene, permanent El Nino conditions prevailed. Rapid warming today is already heating up the western Pacific Ocean, a basis for a coming period of 'super El Nino'.

At 23 degrees of warming above pre-industrial levels, and perhaps at much lower warming levels than that, the Amazon rainforest will also suffer devastating damage: its plants, which produce 10 per cent of the world's terrestrial photosynthesis, have no evolved resistance to fire, and the warming may result in it becoming savannah. Further, the carbon released by the forests' destruction will be joined by carbon release from the world's warming soils. This will boost global temperatures by 1.5 degrees, on top of the warming of around 4 degrees by 2100 that is projected to occur if we keep to the current fossilfuel intensive path.

The climate-change model at the UK's Hadley Centre predicts that the chances of an Amazon forest drought would rise from 5 per cent now, to 50 per cent by 2030, and to 90 per cent by 2100. Four or five consecutive years of drought would probably dry out areas of the Amazon sufficiently for wildfires to destroy much of it.

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