Climate change far worse than thought before
The Times Of India | 3 January 2010
NEW DELHI: Global alarm over climate change and its effects has risen manifold after the 2007 report of the Intergovernmental Panel on Climate Change (IPCC). Since then, many of the 2,500-odd IPCC scientists have found climate change is progressing faster than the worst-case scenario they had predicted.
Their studies will be considered for the next IPCC report, but since that will come out only in 2013, the University of New South Wales in Sydney has just put together the main findings in the last three years. Most are by previous IPCC lead authors "familiar with the rigour and completeness required for a scientific assessment of this nature", a university spokesperson said.
The most significant recent findings are:
* Global carbon dioxide emissions from fossil fuels in 2008 were 40 percent higher than in 1990. The recent Copenhagen Accord said warming should be contained within two degrees, but every year of delayed action increases the chances of exceeding the two-degree warming mark.
Carbon dioxide is the main greenhouse gas (GHG) warming the atmosphere.
* To keep within the two-degree limit, global GHG emissions need to peak between 2015 and 2020 and then decline rapidly. To stabilise climate, near-zero emissions of carbon dioxide and other long-lived GHG should be reached well within this century.
More specifically, the average annual per-capita emissions will have to shrink to well under one tonne carbon dioxide by 2050. This is 80-95 percent below the per-capita emissions in developed nations in 2000.
* Over the past 25 years temperatures have increased at a rate of 0.19 degree Celsius per decade. The trend has continued over the last 10 years despite a decrease in radiation from the sun.
* The studies show extreme hot temperature events have increased, extreme cold temperature events have decreased, heavy rain or snow has become heavier, while there has been increase in drought as well.
They also show that the intensity of cyclones has increased in the past three decades in line with rising tropical ocean temperatures.
* Satellites show recent global average sea level rise (3.4 mm/year over the past 15 years) to be about 80 percent above IPCC predictions. This acceleration is consistent with a doubling in contribution from melting of glaciers, ice caps, and the Greenland and West-Antarctic ice sheets.
New estimates of ocean heat uptake are 50 percent higher than previous calculations. Global ocean surface temperature reached the warmest ever recorded in June, July and August 2009. Oceanacidification and ocean de-oxygenation due to global warming have been identified as potentially devastating for large parts of the marine ecosystem.
* By 2100, global sea level is likely to rise at least twice as much as projected by the IPCC in 2007; if emissions are unmitigated the rise may well exceed one metre.
The sea level will continue to rise for centuries after global temperatures have been stabilised, and several metres of sea level rise must be expected over the next few centuries.
* A wide array of satellite and ice measurements demonstrate that both the Greenland and Antarctic ice sheets are melting at an increasing rate. Melting of glaciers and ice-caps in other parts of the world has also accelerated since 1990.
The contribution of glaciers and ice-caps to global sea level rise has increased from 0.8 mm per year in the 1990s to 1.2 mm per year today. The adjustment of glaciers and ice caps to present climate alone is expected to raise sea level by about 18 cm. Under warming conditions they may contribute as much as around 55 cm by 2100.
The net loss of ice from the Greenland ice sheet has accelerated since the mid-1990s and is now contributing 0.7 mm per year to sea level rise due to both increased melting and accelerated ice flow. Antarctica is also losing ice mass at an increasing rate, mostly from the West Antarctic ice sheet due to increased ice flow. Antarctica is currently contributing to sea level rise at a rate nearly equal to Greenland.
* Summer-time melting of Arctic sea-ice has accelerated far beyond the expectations of climate models. The area of summertime sea-ice 2007-09 was about 40 percent less than the average prediction from IPCC climate models in the 2007 report.
* The studies say avoiding tropical deforestation could prevent up to 20 percent of carbon dioxide emissions.
* New ice-core records confirm the importance of GHG for temperatures on earth, and show that carbon dioxide levels are higher now than they have been during the last 800,000 years.
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