The notion that we can reasonably adapt to 4°C is ill-founded because (https://drive.google.com/file/d/0B6hdzDj-9cy6VUlOc1VMRHZwYUk/edit):
• Climate researcher Rachel Warren says that: “In… a 4°C world, the limits for human adaptation are likely to be exceeded in many parts of the world, while the limits for adaptation for natural systems would largely be exceeded throughout the world. Hence, the ecosystem services upon which human livelihoods depend would not be preserved. Even though some studies have suggested that adaptation in some areas might still be feasible for human systems, such assessments have generally not taken into account lost ecosystem services” (Warren, 2010).
• Professor Neil Adger says: “Thinking through the implications of 4°C of warming shows that the impacts are so significant that the only real adaptation strategy is to avoid that at all cost because of the pain and suffering that is going to cost… There is no science on how we are going to adapt to 4°C warming. It is actually pretty alarming” (Randerson, 2008).
• At 4°C hotter, the world would be warmer than during any part of the period in which modern humans evolved, and the rate of climate change would be faster than any previously experienced by humans. The world’s sixth mass extinction would be in full swing. In the oceans, acidification would have rendered many calcium-shelled organisms such as coral and many at the base of the ocean food chain artifacts of history.
Ocean ecosystems and food chains would collapse (literature surveyed by Spratt, 2011).
• Warming of 4oC is sufficient to melt the polar ice sheets and produce 70 metres of sea-level rise over a longer period of time (Hansen, Sato et al., 2013).
• Prof. Kevin Anderson (2011) says there is a widespread view amongst scientists that “a 4°C future is incompatible with an organized global community, is likely to be beyond ‘adaptation’, is devastating to the majority of ecosystems and has a high probability of not being stable”.
One question remains: if the world has practically speaking given up on holding to 2°C and it is not possible for human civilization to survive in a 4°C warmer world, what’s the plan?