Remarks relating to the IPCC Fourth Assessment Synthesis Report

released on 17 November 2007

by Dr. Barrie Pittock, PSM

Former leader of the Climate Impact Group in CSIRO and author of book “Climate Change: Turning Up the Heat”

The new Synthesis Report is the result of work by hundreds of scientists. It has been adopted with the approval of the governments that signed the UN Framework Convention on Climate Change, including countries like the UK, China, India, Australia and the United States. It is the most authoritative report yet available on the subject of human induced climate change and on the likely consequences of policy options to adapt to climate change impacts and to reduce the magnitude of climate change.

The Report confirms that climate change is happening now and is largely due to human influences, and that it is already having noticeable impacts that are going to get worse.

The Report under-estimates some of the risks because it is based on published research only up to the middle of 2006. Many new studies since then show that greenhouse gas emissions, climate change and sea-level rise are happening faster than the climate models so far have indicated.

Despite that, it has many useful things to say.

Most relevant to impacts on Australia, the Report confirms that mid-latitude storm tracks in the Southern Hemisphere are expected to move further polewards, leading to reduced rainfall in southern Australia. This is already happening, resulting in the prolonged “droughts” in the southwest and more recently in southeastern Australia. The present water crisis in southern Australia is a combination of natural variability and climate change. We are moving into a more arid climate and are unlikely to pull out of the present “drought”.

The Report highlights, in its Table SPM-2, four major areas of adverse impacts on Australia. This should motivate Australians to insist that we do something to reduce greenhouse gas emissions. Projected impacts in many other countries, including those of Asia and North America similarly should motivate other key countries to act as well, notable China, India and the United States. The report thus provides a basis for international action arising out of the common threat to all major countries.

Regarding sea-level rise, the Report notes that the numerical estimates given for sea-level rise do not include recent evidence for more rapid discharge of ice from Greenland and Antarctica that could lead to more rapid sea-level rise. Global greenhouse emissions and sea-level rise are already tracking at the highest levels of the range of uncertainty reported by IPCC.  My judgement, based on this new evidence is that sea-level rise by 2100 is unlikely to be under 1 metre, and could be considerably larger. This will have enormous implications for present coastal infrastructure and slow down coastal development.

The Report lists, in its Table SPM-4, a wide range of measures to adapt to climate change that could well be undertaken. Similarly, in Table SPM-5 it provides a large shopping list of measures that could be taken to reduce greenhouse emissions. Both these lists need to be studied carefully and many implemented in Australia, urgently. The Report also notes the important achievements of the Kyoto Protocol in stimulating appropriate actions, despite the failure of the United States and Australia to ratify the Protocol. While not yet sufficient, these achievements are a good start.

The Report clearly states that “Delayed emission reductions significantly constrain the opportunities to achieve lower stabilisation levels and increase the risk of more severe climate change impacts.”

The key information, in Table SPM-6, is that concentrations of  greenhouse gases (including carbon dioxide, methane and others) somewhere between 445 and 490 parts per million, expressed as equivalent amounts of carbon dioxide, will likely lead to global warmings of 2.0 to 2.4ºC. This concentration is widely considered by most climate scientists to be close to “dangerous”, although that is a value judgement that IPCC, as an advisory body, cannot make.

To stabilise concentrations at this level, Table SPM-6 indicates that emissions need to be reduced by 50 to 85% by 2050, that is, by some 2 to 3% each year from now. In fact this target concentration has already been reached, with carbon dioxide concentrations alone reaching about 384 ppm. So we will have to reduce greenhouse gas emissions drastically to stop further rises in concentration, and eventually take carbon dioxide out of the atmosphere.

The Report provides, in Table SPM-7, estimates of the global economic costs in 2030 and 2050 of reducing emissions to targets as low as 445 ppm (CO₂ equivalent). It finds that the resulting reduction in GDP in 2050 is less than 5.5%, which means that the annual GDP growth rates is at most some 0.12% less.

The IPCC Report finishes with the statement that “balancing the economic costs of more rapid emissions reductions now against the corresponding medium-term and long-term climate risks of delay” is at the centre of the policy debate regarding emissions reduction. The Report provides evidence that reducing global greenhouse gas emissions can be done at quite moderate costs, far less than the costs of failing to do so. To date, we in Australia, and indeed the world community, do not have policies in place to do what is necessary.

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