The rapid rise of global temperature that began about 1975 continues at a mean rate of about 0.18°C /decade , with the current annual temperature exceeding +1.25°C relative to 1880-1920. Global temperature has just reached a level similar to the mean level in the prior interglacial (Eemian) period, when sea level was several meters higher than today, and, if it long remains at 25 this level , slow amplifying feedbacks will lead to greater climate change and consequences.
This discussion paper is under review for the journal Earth System Dynamics (ESD).
The growth rate of climate forcing due to human – caused greenhouse gases (GHGs) increased over 20% in the past decade mainly due to resurging growth of atmospheric CH 4, thus making it increasingly difficult to achieve targets such as limiting global warming to 1.5°C or reducing atmospheric CO 2 below 350 ppm. Such targets now require “negative emissions”, i.e., extraction 30 of CO 2 from the atmosphere. If rapid phasedown of fossil fuel emissions begins soon, most of the necessary CO 2 extraction c an take place via improved agricultural and forestry practices, including reforestation and steps to improve soil fertility and increase its carbon content. In this case, the magnitude and duration of global temperature excursion above the natural range of the current interglacial (Holocene) could be limited and irreversible climate impacts could be 35 minimized. In contrast, continued high fossil fuel emissions by the current generation would place a burden on young people to undertake massive technological CO 2 extraction, if they are to limit climate change. Proposed methods of extraction such as bioenergy with carbon capture and storage (BECCS) or air capture of CO 2 imply minimal estimate d costs of 104-570 trillion dollars this century, with large risks and uncertain feasibility. Continued high fossil fuel emissions 40 unarguably sentences young people to either a massive, possibly implausible cleanup or growing deleterious climate impacts or both, scenarios that should provide both incentive and obligation for governments to alter energy policies without further delay.