Scientists warn that we crossed the thresholds for dangerous climate change. Climate change will hence get beyond the control of humans. But what is dangerous climate change exactly and why is the 2°C global warming goal so important for climate negotiations?
What is dangerous climate change?
Dangerous climate change means that a rapid irreversible ecological regime shift is triggered by crossing climate thresholds. Under this scenario, global warming will be intensified by positive feedback loops for example by the thawing of permafrost soils who release additional CO2 to the atmosphere or the melting down of glaciers. Other possible potential tipping elements for dangerous climate change can be found in Figure 1. The Earth System will move to another stable state.
Figure 1: Potential tipping elements for dangerous climate change (Source: Lenton et al. 2008, p. 1787)
Apocalyptic world of dangerous climate change
A catastrophic shift is beyond human experience. In a world of serious climate change humans will have difficulties to adapt. Projection for a world estimate an apocalyptic sea level rise of up to 3,5 m and a local warming of up +8°C (Nicolls et al., 2010). Wide landscapes will become uninhabitable. Adaptation costs would explode to an unreasonable level. The worst case scenario leads a forced displacement and abandonment of coastal populations and large scale ecosystem changes. Inhabitants of small island states are today the first suffering the fate that is looming to millions of other people in the world. A highly undesirable world would be left to our children.
Safe operating space for humanity
Exact tipping points for a catastrophic shift of the interlinked Earth system are not yet fully understood. The time lag of between the increase in atmospheric CO2 levels and the response of the Earth System can lead to a false sense of security. Optimists think that we can cope problems with improved environmental engineering. But adaptation strategies cannot replace mitigation efforts because the new stable state (when warming comes to a hold) is not known, so that adaptation becomes a never-ending process. Mitigation of greenhouse gas emissions is rather a precondition for any effective adaptation strategy so that humans are operation in a ‘safe space for humanity’ (Rockström et al., 2009) To avoid that climate change gets beyond the control of humans, the IPCC considered that the threshold of a manageable climate change requires a stabilisation of global warming on a level of 2°C.
Exceeded thresholds of dangerous climate change
Climate scientists warn that we might have crossed this threshold. The cut of global emissions are yet insufficient so that the current global warming curve follows rather the Highest Representative Concentration Pathway (RCP 8.5) of the IPCC scenarios for climate change (Sanford et al., 2014) (Figure 2). Though all Climate scientists are highly alarmed, many of them became silent in the public discourse about climate change. They fear that statements about crossed boundaries, can lead an unwanted fatalism to take any political actions. Many don’t want to give up the 2°C goal too early. But the analysis showed that we have not any more time to wait to take actions.
Figure 2: Trends in global CO2 emissions under four scenario (Source: Sanford, 2014, p. 165.)
© 2014 Heike Huntebrinker. All rights reserved.