“If we continue forward on our current path, catastrophe is not just a possible outcome, it is the most probable outcome.”
JR: The recent scientific literature makes that conclusion crystal clear (see “An Illustrated Guide to the Science of Global Warming Impacts“). And that’s the basis of this piece explaining the rationale behind the 2°C (3.6°F) target.
by Dana Nuccitelli, via Skeptical Science
Robert Watson, former Chair of the Intergovernmental Panel on Climate Change (IPCC), recently made headlines by declaring that it is unlikely we will be able to limit global warming to the 2°C ‘danger limit’. This past April, the International Energy Agency similarly warned that we are rapidly running out of time to avoid blowing past 2°C global warming compared to late 19th Century temperatures. The reason for their pessimism is illustrated in the ‘ski slopes’ graphic, which depicts how steep emissions cuts will have to be in order to give ourselves a good chance to stay below the 2°C target, given different peak emissions dates (Figure 1).
Figure 1: Three scenarios, each of which would limit the total global emission of carbon dioxide from fossil-fuel burning and industrial processes to 750 billion tonnes over the period 2010–2050. Source: German Advisory Council on Global Change, WBGU (2009)
Clearly our CO2 emissions have not yet peaked – in fact they increased by 1 billion tonnes between 2010 and 2011 despite a continued global economic recession; therefore, the green curve is no longer an option. There has also been little progress toward an international climate accord to replace the Kyoto Protocol, which suggests that the blue curve does not represent a likely scenario either – in order to achieve peak emissions in 2015 we would have to take serious steps to reduce emissions today, which we are not. The red curve seems the most likely, but the required cuts are so steep that it is unlikely we will be able to achieve them, which means we are indeed likely to surpass the 2°C target.
Thus it is worth exploring the question, what would a world with >2°C global surface warming look like?