"Our parents did not know their actions could harm future generations, we will only be able to pretend"James Hansen, eminent climate scientist and director of NASA Goddard Center, has come out with a new paper Scientific Case for Avoiding Dangerous Climate Change to Protect Young People and Nature (pdf) which lays out in the most simple and direct terms what we face with the current trajectory of climate change.
Global warming due to human-made gases, mainly CO2, is already 0.8°C and deleterious climate impacts are growing worldwide. More warming is 'in the pipeline' because Earth is out of energy balance, with absorbed solar energy exceeding planetary heat radiation. Maintaining a climate that resembles the Holocene, the world of stable shorelines in which civilization developed, requires rapidly reducing fossil fuel CO2 emissions. Such a scenario is economically sensible and has multiple benefits for humanity and other species. Yet fossil fuel extraction is expanding, including highly carbon-intensive sources that can push the climate system beyond tipping points such that amplifying feedbacks drive further climate change that is practically out of humanity's control. This situation raises profound moral issues as young people, future generations, and nature, with no possibility of protecting their future well-being, will bear the principal consequences of actions and inactions of today's adults.Amazingly, in his Summary and elsewhere Hansen is calling for the reduction of short-lived climate forcers. And this as some of you may know is what I have been working on here and at the MIT CoLab. He might just have entitled his piece "Beach Babe you were right all along!" Seriously, Hansen of course explains it so much better than I ever could. And since he wrote this for distribution I'm sure he won't mind my quoting him profusely.
Summary. Humanity is now the dominant force driving changes of Earth's atmospheric composition and thus future climate (1). The principal climate forcing is carbon dioxide (CO2) from fossil fuel emissions, much of which will remain in the atmosphere for millennia (1, 2). The climate response to this forcing and society's response to climate change are complicated by the system's inertia, mainly due to the ocean and the ice sheets on Greenland and Antarctica. This inertia causes climate to appear to respond slowly to this human-made forcing, but further long-lasting responses may be locked in. We use Earth’s measured energy imbalance and paleoclimate data, along with simple, accurate representations of the global carbon cycle and temperature, to define emission reductions needed to stabilize climate and avoid potentially disastrous impacts on young people, future generations, and nature. We find that global CO2 emissions reduction of about 6%/year is needed, along with massive reforestation.
Reforestation and Soil Carbon. The long CO2 lifetime does not make it impossible to return CO2 to 350 ppm this century. Reforestation and increasing soil carbon can help draw down atmospheric CO2, even though the effect on atmospheric CO2 amount decays (Fig. 3a).In recommending reforestation as the most practical carbon sink Hansen is posing the question of where do we get the land to reforest? In my paper with Gerald Wedderburn Bisshop linked above. We outline how reforesting land which was deforested for livestock production is the most viable means to reforestation. Hansen also suggests the reduction of the short-lived climate forcers of Methane, Black Carbon and Ground level ozone which in my paper is used as a bridge to buy us time to reduce C02 in the carbon sink of reforestation. And we show that livestock production is the greatest contributor to all the short lived climate forcers including; Methane, Black Carbon and Ground level Ozone.
The measured energy imbalance affirms that a good initial CO2 target to stabilize climate near current temperatures is "<350 ppm" (20). Specification of a more precise CO2 target now is difficult and unnecessary, because of uncertain future changes of other forcings including other gases, ground albedo, and aerosols. More precise knowledge of the best target will become available during the time that it takes to turn around CO2 growth and approach the initial 350 ppm target.
Ironically, future reductions of particulate air pollution may exacerbate global warming by reducing the cooling effect of reflective aerosols. However, a concerted effort to reduce non-CO2 forcings by methane, tropospheric ozone, other trace gases and black soot might counteract the warming from a decline in reflective aerosols (39).
Indeed, Hansen does touch on reducing meat consumption as the most effective individual action we can take. I think he is correct on focusing on the transition to green energy as that will take governmental policy decisions. But both governmental and individual action will be necessary to mitigate the worst effects of climate change.
Can the human tipping point be reached before the climate system passes a point of no return? What we have shown in this paper is that time is rapidly running out. The era of doubts, delays and denial, of ineffectual half-measures, must end. The period of consequences is beginning. If we fail to stand up now and demand a change of course, the blame will fall on us, the current generation of adults. Our parents did not know that their actions could harm future generations. We will only be able to pretend that we did not know. And that is unforgiveable.In an appropriate sign of the times Teenagers take global warming to the Courts