The evidence is suggesting that we have tipped 2-4 of the 22 tipping points in the global biogeophysical climate system. The historical record indicates that when we last had the current CO2 levels, the seas were 5 metres higher than now. We are at the Point of No Return. Jack Williams (Climate Change (Australia)) wrote: “To my wonder, I found that for an ECS of three degrees C, our planet would cross the dangerous warming threshold of two degrees C in 2036, only 22 years from now. When I considered the lower ECS value of 2.5 degrees C, the world would cross the threshold in 2046, just 10 years later [see graph on pages 78 and 79]. Furthermore, the notion that two degrees C of warming is a “safe” limit is subjective. It is based on when most of the globe will be exposed to potentially irreversible climate changes. Yet destructive change has already arrived in some regions. In the Arctic, loss of sea ice and thawing permafrost are wreaking havoc on indigenous peoples and ecosystems. In low-lying island nations, land and freshwater are disappearing because of rising sea levels and erosion. For these regions, current warming, and the further warming (at least 0.5 degree C) guaranteed by CO2 already emitted, constitutes damaging climate change today.” scientificamerican/article/earth-will-cross-the-climate-danger-threshold-by-2036/ This year we estimated that the required improvement in global carbon intensity to meet a 2°C warming target has risen to 5.1% a year, from now to 2050. We have passed a critical threshold – not once since World War 2 has the world achieved that rate of decarbonisation, but the task now confronting us is to achieve it for 39 consecutive years. The 2011 rate of improvement in carbon intensity was 0.7%, giving an average rate of decarbonisation of 0.8% a year since 2000. If the world continues to decarbonise at the rate since the turn of the millennium, there will be an emissions gap of approximately 12 gigatonnes of carbon dioxide (GtCO2) by 2020, 30 GtCO2 by 2030 and nearly 70 GtCO2 by 2050, as compared to our 2-degree scenario. Even doubling our current rate of decarbonisation, would still lead to emissions consistent with 6 degrees of warming by the end of the century. To give ourselves a more than 50% chance of avoiding 2 degrees will require a six-fold improvement in our rate of decarbonisation. pwc.co.uk/sustainability-climate-change/publications/low-carbon-economy-index-overview.jhtml
Posted on: Mon, 21 Apr 2014 13:36:00 +0000
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