The document unambiguously blames human factors for the century long temperature increase and says the turning point “must come soon”. If we are to limit warming to 2 degrees above pre-industrial values, global emissions must peak by 2020 at the latest and then decline rapidly. The scientists warned waiting for higher levels of scientific certainty could mean some tipping points will be crossed before they are recognised. By 2050 we will need to be in a post-carbon economy if we are to avoid unlivable temperatures.
The document puts the lie to the refrain of denialists that temperatures have gone down since 1998. The reality is the last ten years have been warmer than the previous ten and the long-term trend is unambiguously upward. In 2008 there were two temporary cooling influences, a La Nina (ENSO) and low solar output (the lowest level of the last 50 years). The Copenhagen Diagnosis says these two factors should have resulted in the 2008 temperature being among the coolest in the instrumental era, whereas it was the ninth warmest on record.
Ten year variations such as sunspots and ENSO are why the IPCC choose 25 year cycles to show trend lines. Most NASA measures of the 1990s have shown a warming between 0.17 and 0.34 °C and with an increase of 0.19 °C between 1998 and 2008. The British Hadley Centre’s most recent data had smaller warming trend of 0.11 °C for 1999-2008 but this excluded the Arctic, which has warmed strongly in recent years. The Northwest and Northeast Passages were simultaneously ice-free in 2008 for the first time in living memory and the feat was repeated in 2009.
The document says climate change will almost certainly cause more extreme weather events. This means more frequent hot days, hot nights and heat waves, fewer cold days and cold nights, more frequent heavy rain, more intense and longer droughts over wider areas, and an increase in intense tropical cyclone activity in the North Atlantic. There is also evidence of more drought, typhoons and bushfires all linked to anthropogenic climate change.
The document is timely as the Australian parliament debates the Carbon Pollution Reduction Scheme. Whatever the merits of the scheme, its opponents should remember just one in four Australians think climate change fears are exaggerated. The other 75 percent may not agree on what to do but accept their scientists are telling them there is a problem. They look to lawmakers to chart out a future to best ride out the unpleasant shocks, not pretend the shocks do not exist.
Copenhagen is happening in a week’s time. None of the 198 governments want to be there and none will win from climate change. But all recognise it exists and needs to be dealt at the global level. Other than the powerless Pacific island nations, no country is yet obviously threatened enough to make it a success. The vested interest of each government will ensure less action will occur than is needed. Copenhagen will result in pious platitudes and little concrete action.
Australia has a small but significant role to play to ensure there isn’t a tragedy of the commons. It consumes less than 2 percent of the world’s resources but that is a significant amount for a country with just 0.003 percent of the world’s people. The CPRS is unlikely to reduce carbon usage by much. Yet its potency as a symbol is undeniable. The CPRS is a referendum on climate change. This is something the Nationals and right-wing Liberals intuitively understand and the Greens do not. The Greens have missed a golden opportunity to be on the side of the symbol (and they can fix it when they gain the balance of power after the next election). In a rare moment of sense among the Liberal horserace shenanigans, Malcolm Turnbull expressed it best yesterday. No political party with any pretensions to govern responsibly can afford to turn their back on climate change.
The exact future of climate may be unknowable but the study of our past is providing overwhelming evidence of trends that cannot be ignored. Scepticism is justified only when the facts are unclear or ambiguous and the Copenhagen diagnosis is neither. A simple fact needs to be stated and there is no polite way to say it. Those people who say anthropogenic global warming is a myth are either liars protecting vested interests or mental incompetents. Either way, the only proper course is to ignore them. The stakes are too high.