The Intergovernmental Panel on Climate Change (IPCC) published a special report (hereafter called SR15) on the impacts of global warming of 1.5 °C above pre-industrial levels on October 8, 2018. The report says the cost of mitigating CO2 emissions in 2030 to prevent temperatures from exceeding 1.5 °C above pre-industrial levels is about 880 US$2010 per tonne of CO2 ($/tCO2). The benefit of doing so, according to the report, is 15 $/tCO2. Using a climate sensitivity based on observations including effects of natural climate change, urban warming and the best available economic model, the mitigation proposal will prevent a benefit of 8.2 $/t CO2, for a total loss of 888 $/tCO2 mitigated. In other words, each $1000 spent on mitigation of CO2 emissions will cause another loss $9.20.

The SR15, presents various emissions pathways to limit the projected rise of temperatures from pre- industrial times, estimated to be the temperature average from 1850 to 1900, to the year 2100, and to limit the temperature rise to 2.0 °C by 2100. According to the IPCC, temperatures have increased by about 1.0 °C from pre-industrial times to 2017. Therefore, the emissions pathways to limit warming allows only 0.5 °C temperature rise from 2017, assuming there is no natural caused climate change.

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