28 December 2009

climate change seems to be speeding up


The Copenhagen Diagnosis is a report which was published to coincide with the UN Climate Change Conference in December 2009. It is aimed at providing policymakers with a synthesis of the latest climate science published since the last report by the Intergovernmental Panel on Climate Change. The report serves as an interim evaluation of the evolving science midway through an IPCC cycle. The last IPCC report was published in 2007 and the next one is due in 2013. The Copenhagen Diagnosis was written by 26 authors, many of whom were lead authors of chapters in the 2007 IPCC report.

See here for the most significant recent findings:

 

Surging greenhouse gas emissions

Global carbon dioxide emissions from fossil fuels in 2008 were 40% higher than those in 1990. Even if global emission rates are stabilised at present-day levels, just 20 more years of emissions would give a 25% probability that warming exceeds 2ºC. Even with zero emissions after 2030. Every year of delayed action increase the chances of exceeding 2ºC warming.

Recent global temperatures demonstrate human-based warming

Over the past 25 years temperatures have increased at a rate of 0.19ºC per decade. Even over the past ten years, despite a decrease in solar forcing, the trend continues to be one of warming. Natural, short- term fluctuations are occurring as usual but there have been no significant changes in the underlying warming trend.

Acceleration of melting of ice-sheets, glaciers and ice-caps

A wide array of satellite and ice measurements now demonstrate beyond doubt that both the Greenland and Antarctic ice-sheets are losing mass at an increasing rate. Melting of glaciers and ice-caps in other parts of the world has also accelerated since 1990.

Rapid Arctic sea-ice decline

Summer-time melting of Arctic sea-ice has accelerated far beyond the expectations of climate models. The area of summertime sea-ice during 2007-2009 was about 40% less than the average prediction from the climate models underlying the IPCC 2007 report.

Current sea-level rise underestimated

Satellites show that the global average sea-level rise (3.4 mm/yr over the past 15 years) is 80% above past IPCC predictions. This acceleration in sea-level rise is consistent with a doubling in contribution from melting of glaciers, ice caps and the Greenland and West-Antarctic ice-sheets. Sea-level prediction revised By 2100, global sea-level is likely to rise at least twice as much as projected by the 2007 IPCC report. For unmitigated emissions it may well exceed 1 metre. The upper limit has been estimated as a 2 metres sea level rise by 2100. Sea levels will continue to rise for centuries after global temperature have been stabilised and several metres of sea level rise must be expected over the next few centuries.

Delay in action risks irreversible damage

Several vulnerable elements in the climate system (e.g. continental ice-sheets. Amazon rainforest, West African monsoon and others) could be pushed towards abrupt or irreversible change if warming continues in a business-as-usual way throughout this century. The risk of transgressing critical thresholds (“tipping points”) increase strongly with ongoing climate change. Thus waiting for higher levels of scientific certainty could mean that some tipping points will be crossed before they are recognised.

The turning point must come soon

If global warming is to be limited to a maximum of 2ºC above pre-industrial values, global emissions need to peak between 2015 and 2020 and then decline rapidly. To stabilise climate, a decarbonised global society – with near-zero emissions of CO2 and other long-lived greenhouse gases – need to be reached well within this century. More specifically, the average annual per capita emissions will have to shrink to well under 1 tonne of CO2 by 2050. This is 80-90% below the per capita emissions in developed nations in 2000.

You can read the full report here: http://www.copenhagendiagnosis.org/default.html