On page 26 we find the kind of lingo I live for.
"Integrated assessment of the economic costs and benefits of different mitigation pathways shows that the economically optimal timing and level of mitigation depends upon the uncertain shape and character of the assumed climate change damage cost curve. To illustrate this dependency:
If the climate change damage cost curve grows slowly and regularly, and there is good foresight (which increases the potential for timely adaptation), later and less stringent mitigation is economically justified;
Alternatively if the damage cost curve increases steeply, or contains non-linearities (e.g. vulnerability thresholds or even small probabilities of catastrophic events), earlier and more stringent mitigation is economically justified [3.6]."
• Climate sensitivity is a key uncertainty for mitigation scenarios that aim to meet a specific temperature level. Studies show that if climate sensitivity is high then the timing and level of mitigation is earlier and more stringent than when it is low [3.5, 3.6].
• Delayed emission reductions lead to investments that lock in more emission-intensive infrastructure and development pathways. This significantly constrains the opportunities to achieve lower stabilization levels (as shown in Table SPM.6) and increases the risk of more severe climate change impacts [3.4, 3.1, 3.5, 3.6]
Translation: "We gotta do it, gotta do it now, don't lock in the infrastructure, a small risk of catastrophe can be avoided, go go, now now, Go, go,
Go Johnny go, go,
Go Johnny, go go
Go Johnny go, go,
Go Johnny go, go
Johnny B. Good"
Okay that last bit wasn't the IPCC.
p28 The cost:
"Policies that provide a real or implicit price of carbon could create incentives for producers and consumers to significantly invest in low-GHG products, technologies and processes. Such policies could include economic instruments, government funding and regulation (high agreement, much evidence).
• An effective carbon-price signal could realize significant mitigation potential in all sectors [11.3, 13.2].
• Modelling studies (see Box SPM.3) show carbon prices rising to 20 to 80 US$/tCO2-eq by 2030 and 30 to 155 US$/tCO2-eq by 2050 are consistent with stabilization at around 550 ppm CO2-eq by 2100. For the same stabilization level, studies since TAR that take into account induced technological change lower these price ranges to 5 to 65 US$/tCO2eq in 2030 and 15 to 130 US$/tCO2-eq in 2050 [3.3, 11.4, 11.5].
• Most top-down, as well as some 2050 bottom-up assessments, suggest that real or implicit carbon prices of 20 to 50 US$/tCO2-eq, sustained or increased over decades, could lead to a power generation sector with low-GHG emissions by 2050 and make many mitigation options in the end-use sectors economically attractive. [4.4,11.6]" emphasis mine.