The fourth and final installment of the Intergovernmental Panel on Climate Change’s fourth, summary report is to be released later today. As with earlier versions, certain elements have already been passed on to the press, but there seems to be far less anticipatory chatter than with the previous installments. I hope this isn’t a sign of reduced interest, since this report is considerably more urgent in tone and content than its predecessors.
Having the IPCC share in the Nobel Peace Prize has apparently strengthened the hand of the scientists versus the politicians, leading to more forceful and forthright portrayal of climate change risks. In addition, a tougher stand by developing nations who stand to lose the most from climate change also helped shift the consensus towards more emphasis of the potential dangers.
A preview on the BBC stressed the firm tone of the report:
Among the report’s top-line 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.
The synthesis summary finalised late on Friday strengthens the language of those earlier reports with a warning that climate change may bring “abrupt and irreversible” impacts.
Such impacts could include the fast melting of glaciers and species extinctions.
“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 projected to have scarcer fresh water supplies than at present
yields from rain-fed agriculture could be halved
food security likely to be further compromised in Africa
widespread impacts on coral reefs
However, an article in the New York Times, while confirming that this release presents a more dire picture than the earlier reports, also makes clear that it nevertheless understates the speed of change:
Even though the synthesis report is more alarming than its predecessors, some researchers believe that it still understates the trajectory of global warming and its impact. The I.P.C.C.’s scientific process, which takes five years of study and writing from start to finish, cannot take into account the very latest data on climate change or economic trends, which show larger than predicted development and energy use in China.
“The world is already at or above the worst case scenarios in terms of emissions,” said Gernot Klepper, of the Kiel Institute for World Economy in Kiel, Germany. “In terms of emissions, we are moving past the most pessimistic estimates of the I.P.C.C., and by some estimates we are above that red line.”
The panel presents several scenarios for the trajectory of emissions and climate change. In 2006, 8.4 gigatons of carbon were put into the atmosphere from fossil fuels, according to a study in the proceedings of the National Academy of Science, which was co-written by Dr. Klepper. That is almost identical to the panel’s worst case prediction for that year.
Likewise, a recent International Energy Agency report looking at the unexpectedly rapid emissions growth in China and India estimated that if current policies were not changed the world would warm six degrees by 2030, a disastrous increase far higher than the panel’s estimates of one to four degrees by the end of the century…..
One novel aspect of the report is a specific list of “Reasons for Concern.” It includes items that are thought to be very likely outgrowths of climate change that had been mentioned in previous reports, like an increase in extreme weather events.
But it for the first time includes less likely but more alarming possibilities, like the relatively rapid melting of polar ice. Previous reports focused more on changes the scientists felt were “highly likely.”
“This time, they take a step back and look at the totality,” Dr. Verolme said. “Saying it is less likely to occur, but if it does we are fried.”
One such area is the future melting of ice sheets in Greenland and western Antarctica….While scientists are certain that the sheets will melt over millennia, producing sea-level rises, there is now evidence to suggest that it could happen much faster than this, perhaps over centuries.
“In my view that would make it not just difficult, but impossible to adapt successfully, some of my colleagues would say catastrophic,” said Dr. Oppenheimer. “If they say that it’s possible that melting could occur in centuries leading to meters of change, that’s a headline.”
This final report also puts more emphasis on the ripple effect of small degrees of temperature change, some of which are already being seen, such as species extinctions and loss of biodiversity.
“A relatively modest degree of warming — one to three degrees — spells a lot of trouble and I think that was not clear in the previous report,” Dr. Oppenheimer said. He said part of the reason for the lack of clarity was that governments had “messed around” with the language and structure of the report during the approval process.