The Intergovernmental Panel on Climate Change (IPCC) has released its fourth report (summary here), which synthesizes for policymakers attending the forthcoming UN conference in Bali the three reports that it issued earlier this year as part of its Fourth Assessment Report. Some of its conclusions are that
climate change is "unequivocal", that humankind's emissions of greenhouse gases are more than 90% likely to be the main cause, and that impacts can be reduced at reasonable cost.
But climate change may also bring about "abrupt and irreversible impacts" such as glacial melting and extinction of species.
"Approximately 20-30% of species assessed so far are likely to be at increased risk of extinction if increases in global average temperature exceed 1.5-2.5C (relative to the 1980-1999 average)," the summary concludes.
Other potential impacts highlighted in the text include:
- between 75m and 250m people are projected to have scarcer fresh water supplies than at present
- yields from rain-fed agriculture could be halved
- food security is likely to be further compromised in Africa
- there will be widespread impacts on coral reefs
One problem with the IPPC consensus process is that it takes a great deal of time, and thus it is not clear whether the newest report takes into account the accelerated arctic melting seen this year. But it is clear that things are happening faster than anticipated, the BBC reports:
"If you look at the overall picture of impacts, both those occurring now and those projected for the future, they appear to be both larger and appearing earlier than we thought [in our 2001 report]," Martin Parry, co-chair of the impacts working group, told BBC News.
"Some of the changes that we previously projected for around 2020 or 2030 are occurring now, such as the Arctic melt and shifts in the locations of various species."
There are indications that projected increases in droughts are also happening earlier than expected, he said, though that was less certain.
Interestingly, the IPPC finds that absent human factors, the climate would have cooled over the last 50 years (due to volcanoes and solar changes); only models that simulate human effects produce warming over this period. Warming is greatest in the northern polar regions and then in the north temperate and tropical zones (with the exception of the ocean area influenced by the jet stream). It is least in the southern temperate zone and southern seas. Human influences are "very likely" to have led to sea level increases.
The IPPC consensus now exhibits greater confidence in projections about droughts, heatwaves and floods, and their adverse consequences, plus stronger evidence of adverse impacts now on vulnerable ecosystems, such as polar and high-mountain regions and coral reefs.
In the ffuture, as temperatures rise, Africa and Asia will be particularly hard hit, in part because they already face shortages of good water and areas of extreme drought. Overall dry areas will become drier, low-lying areas will be wetter, smaller islands will be imperiled. Arctic areas will be transformed. Climate and weather will become more extreme. The widely-held impression that North America will suffer the least seems to be somewhat true, although serious effects are anticipated in cities that already experience heat waves, as are water shortages in the West, significant variability in agricultural impacts, increased intensity of Atlantic hurricanes and stress on coastal areas generally.
Projected changes are accelerating, and will persist for a millenium even if changes are made, raising the specter of whether, and how soon, we are facing irreversible changes or a "tipping point." Most serious seems to be accelerating Arctic ice melting, as this could cause meters of sea level increases, beyond what the models anticipate. The Jet Stream looks safe to the end of the century, despite some slowing, which will help moderate rising temperatures in Europe. (In case you were wondering, Dubai's spectacular islands have been designed to withstand at least a half meter rise in sea level, which was the high end anticipated by the end of this century. Some projections are now for three times that.)
Dealing with climate change has costs, but so does failing to deal with climate change, given the near certainty of the trajectory of change. The report concludes that
There is high agreement and much evidence that all stabilisation levels can be achieved by deployment of a portfolio of technologies that are either currently available or expected to be commercialised in coming decades, assuming appropriate and effective incentives are in place for their development, acquisition, deployment and diffusion and addressing related barriers.
But we need "substantial investment flows" and "effective technology transfer," meaning lots of money and getting the solutions to where they are needed. The longer we wait, the harder it is, because we need to begin to reverse that nasty increasing trendline, and the longer we wait, not only is it getting steeper, but because of the persistence of greenhouse gases, the stabilization level, and the attendant changes (such as temperature and sea level increases), will be higher. It looks from the chart like we have about ten years if we want things to stabilize at or near 2005 levels of greenhouse gases. If the CO2 peak comes after the 2010-2030 period, the resulting world will look very different from what we have now.
Surprise, surprise. The US representative tried to water the report down. More of the Bush/Cheney regime's attempts to make policy by denying reality. By contrast, the UN chief Ban Ki-moon calls for action.