Wednesday, December 2, 2009

Moving the goalposts

The Copenhagen Diagnosis was recently released to update the 2007 IPCC Fourth Assessment of the scientific basis of climate change. It compiles strong evidence that the changes documented in prior research summaries (increasing global land and sea temperatures, loss of polar ice) are continuing apace, or in many cases, accelerating.

Prominent among these findings is the fact that fossil fuel-based CO2 emissions are about 40% higher than in 1990, essentially following the business-as-usual scenario of continued increase. China and other developing nations have been a significant component of this acceleration, but many industrialized nations, such as the U.S. and Australia, have also significantly contributed.

By rejecting any action on emissions over the two decades since the Rio Summit, the U.S. has made prospects of catching up to initial targets from negotiations like Rio and Kyoto (should the nation ever take this goal seriously) increasingly difficult. The Kyoto Protocol called for the U.S. to reduce its emissions 7% from the 1990 baseline - by 2012. Instead (following US rejection of the Kyoto Protocol) emissions increased by about 17% between 1990 and 2007. The proposal President Obama announced he would bring to Copenhagen is to reduce U.S. emissions 17% from 2005 levels - by 2020. This works out to about only 5% below 1990 levels – almost a decade later than the Kyoto target.

Undoubtedly the two decades between Rio and Copenhagen will be seen as squandered time in retrospect, with future emissions cutbacks incredibly severe (Draconian?) to keep warming from crossing dangerous thresholds. This figure from the Copenhagen Diagnosis makes the game of delay and catch up we are playing quite clear:

Figure 22. Examples of global emission pathways where cumulative CO2 emissions equal 750 Gt during the time period 2010-2050 (1 Gt CO2 = 3.67 Gt C). At this level, there is a 67% probability of limiting global warming to a maximum of 2°C. The graph shows that the later the peak in emissions is reached, the steeper their subsequent reduction has to be. The figure shows variants of a global emissions scenario with different peak years: 2011 (green), 2015 (blue) and 2020 (red). In order to achieve compliance with these curves, maximum annual reduction rates of 3.7 % (green), 5.3 % (blue) or 9.0 % (red) would be required (relative to 2008). (Source: German Advisory Council on Global Change; WBGU 2009).

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