Sentinel for the Home Planet
https://mailchi.mp/caa/sentinel-for-the-home-planet
7 September 2020
James Hansen
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Two numbers, atmospheric CO2 amount and global surface temperature, have received special prominence, and they deserve attention. However, this third number, Earth’s energy imbalance, is perhaps the most important. CO2 is just one of the forcings that drive climate change, even if the dominant one. Earth’s energy imbalance incorporates the effect of CO2 and all other forcings, including some, such as human-made aerosols, that are poorly measured at best. Earth’s energy imbalance will be our guide during the next several decades as we work to restore a healthy climate for future generations. It deserves greater attention.
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The new paper being published today by von Schuckmann and 37 co-authors concludes that the energy imbalance in 2010-2018 has increased to 0.87 ± 0.12 W/m2. That imbalance must be reduced approximately to zero for the sake of stabilizing climate. The authors note that one way to achieve energy balance would be to reduce atmospheric CO2, presently at about 410 ppm, by 57 ± 8 ppm. That reduction of CO2 would increase Earth’s heat radiation to space by 0.87 ± 0.12 W/m2, thus leaving Earth at energy balance with global temperature close to its present value, which is about 1.2°C above the preindustrial level. This is consistent with an earlier suggestion8 that the initial target for CO2 should be about 350 ppm, if we wish to aim for stable shorelines and avoid other climate problems. As expected, this initial target has not changed much. However, the task of achieving the target is now more difficult. The required reduction of greenhouse gases is larger, and the time that we have to achieve the reduction, even though uncertain, is certainly shorter. Could we not, instead, reduce other greenhouse gases? We suggested in our Young People’s Burden paper7 that there is potential in other greenhouse gases to reduce climate forcing by as much as a few tenth of 1 W/m2. However, we are in the process of doing no such thing. Methane (CH4), in principle, should present the best possibility to rapidly reduce climate forcing, because the lifetime of a methane molecule is only of the order of 10 years. If we reduce the sources, the atmospheric methane amount will decline rapidly. However, in reality, at least in part due to “fracking,” methane has resumed its growth.
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The most disconcerting fact is the seeming absence of understanding by governments of what action is required to achieve climate stabilization, and the certain absence of any plan to achieve that action. As long as the price of fossil fuels does not include their costs to humanity, the climate problem will not be solved. This situation is disconcerting because economists agree that the required actions make sense, independent of concerns about climate change. It is still possible that at least one of the great economic powers – the United States, China or the European Union – might adopt an across-the-board (oil, gas, coal) rising carbon fee. The fee could then be imposed on a near-global basis via border duties on products from countries without an equivalent fee. Economic studies show that such a carbon fee would cause rapid phasedown of CO2 emissions without damaging economies, if the funds collected are distributed uniformly to the public. This procedure is anti-regressive, because wealthy people have a large carbon footprint. About 70 percent of the public would receive more in their dividend than they pay in increased prices for fossil fuels and products made using fossil fuels.