The Letter from James Hansen and Makiko Sato published March 2, 2016 by Environmental Research Letters is another in a long series of “must-reads” from climatologist Hansen.
The paper starts with an update on observed global warming in recent decades with emphasis on the shift of the “bell curve” of seasonal mean local temperature anomalies. In other words, “what were once unusually warm conditions now occur more frequently, and the most extreme warm events are now more extreme than others.”
Impacts and consequences of the shifting bell curve are described on a regional basis, based on peer-reviewed studies. Human “livelihood” and health issues are discussed.
They point out the change from the goal stated in the UN 1992 Framework Convention on Climate Change (stabilization of greenhouse gases in the atmosphere to a level that would prevent dangerous anthropogenic interference in the climate system,) to reducing global emissions so as to hold the increase of global temperature to less than 2 degrees Celsius and aspiring to less than 1.5 degrees C (UN CoP21 in Paris.)
They call for a return to the goal of stabilizing greenhouse gases (GHG), of which CO2 is the most important.
“CO2 must be restored to a level no higher than about 350 parts per million, with restoration prompt enough to avoid practically irreversible ocean warming and ice sheet disintegration.” This is possible with reductions of 5-7% a year, beginning immediately.
The “national responsibilities” they call for include a carbon fee collected from fossil fuel companies at the site of production and also at ports of entry, which rises gradually and is distributed uniformly to the public. Other responsibilities: improved agricultural and forestry practices, and international cooperation in generating more affordable carbon-free energies.
Hansen has received numerous awards for his research and science communication. This article (if you leave out the formula for calculating the shift of the bell curves) is quite readable, but if you want a summary there is one at his co-author’s website at Columbia University Earth Institute. http://www.columbia.edu/~jeh1/mailings/2016/20160301_Dice2.PopSci.pdf.