Part I of this series was an overview. Part II talks about Prof. Kevin Anderson's "carbon budget," which plots out what's required if we humans are to stay within a "safe" global warming scenario. The international community defined that safe scenario as total planetary warming of no more than 2° Celsius since the beginning of the Industrial Era (1850s) to the end of this century (2100). So far our biosphere has warmed about 0.8°C during that period, leaving just a little more room at a time when world energy demand is growing like a weed and the fossil fuel industries are finding new ways to provide highly profitable oil, gas, and coal products (one example here).
Former DOE Assistant Energy Secretary and renowned blogger Joe Romm has written some authoritative pieces on the beyond 2°C question. According to Joe, the International Energy Agency (IEA), a highly respected and traditionally cautious firm, released a bombshell in their annual world energy report last November. Among other things the IEA states that today's "planned policies ... will lead to irreversible and potentially catastrophic climate change.” The IEA estimates current policies will lead to 6°C warming by the end of this century, and that for every $1 we don’t invest in clean energy technologies before 2020 “an additional $4.30 would need to be spent after 2020 to compensate for the increased emissions.” In short: today’s policies = disaster and waiting to change increases the costs of change by more than 400% next decade.
“The IEA is one of the few organizations in the world with a sophisticated enough global energy model to do credible (i.e non-hand-waving) projections of the cost of different emissions pathways and the costs of delaying efforts to achieve them. Those who counsel waiting for breakthrough technologies are urging us on a path that is unsustainable, irreversible, potentially catastrophic, and economically indefensible, according to the IEA.
“The IEA’s 2008 analysis of the 2°C warming pathway demonstrated that the total shift in investment needed to stabilize at 450 ppm is only about 1.1% of GDP per year — and that is not a “cost” or hit to GDP, because much of that investment goes towards saving expensive fuel."
The IEA therefore advocates that global/industrial greenhouse emissions cannot peak any later than 2017. A graph from their November report:
Click to enlarge.