The gravity of the present situation notwithstanding, Hansen believes that hope for a “brighter future” has not yet been entirely stifled. Transitioning from the current atmospheric carbon concentration of 387 parts per million to the “appropriate initial target” Hansen finds in 350 ppm is in his view still practically achievable, though “just barely.” (Strangely enough, Hansen does not address the question of an appropriate CO2-equivalent concentration—that is, a measurement of atmospheric concentrations that includes greenhouse gases other than carbon dioxide, such as methane, etc.; a CO2-e target of 350 ppm would call for a carbon-dioxide concentration of much lower than 350.) Central to the project of realizing a peak in global carbon emissions and a concomitant return to 350 ppm is the phasing-out of coal emissions as rapidly as possible, says Hansen: slowing down the rate of such emissions, in his view, does no good; all such emissions must end by 2020 in the ‘developed’ world. Hansen tells us that most of the world’s remaining supply of fossil fuels—coal, oil, and gas, as well as tar sands and shale oil—must be kept in the ground if future generations are to have a “livable planet.” He sees oil and gas as having to play a role in the transitional period that must begin immediately, but emissions from coal, tar sands, and oil shale are to eliminated—which is not to say that the use of the latter sources is to be discontinued, for Hansen feels that they can be allowed to continue if adequate capture and sequestration technologies can be developed and implemented on a mass scale. He does stress the importance of energy-efficiency gains and renewable-energy sources, but he finds it “extremely irresponsible” to depend entirely on these two strategies to combat global warming; instead, he writes favorably of the prospect of a “nuclear renaissance” driven by the development of fourth-generation nuclear power plants, which he seems to find to be the only viable means by which drastically to reduce carbon emissions in the near term. Both forest preservation and reforestation, moreover, are to play a role in his favored carbon-reduction trajectory, though he warns that tree-planting cannot be taken as a substitute for—an offset of—existing carbon emissions. Though initially skeptical about the place that geo-engineering schemes should have in the struggle against climate change, Hansen does conclude that such options may become necessary if business-as-usual is continued for the foreseeable future, and as such he suggests that research be made into exploring such schemes. Furthermore, he eschews the hegemonically favored cap-and-trade approach for what is referred to as “fee-and-dividend,” a framework whereby fees are collected at the mine or port of entry of a given fossil fuel and then divided equally among legal adult residents of the public, the idea being that those who outstrip their share of carbon-emissions—in most cases, Hansen assures us, economically wealthier individuals—will be financially penalized and hence face incentives to reduce their carbon footprints. Hansen envisions these fees as rising over time, so as to allow households and individuals to adjust their lifestyles accordingly; to prevent more carbon-intensive production from simply shifting their operations to a location where such regulatory frameworks are non-existent, he also insists that the fee-and-dividend approach be globalized