Most analyses of climate change and its consequences today are based on projections that include within them a number of plausible scenarios for human greenhouse gas emissions. The intensity of these future emissions is, however, inherently uncertain, since it depends on socio-economic developments over the length of the 21st century which cannot be accurately predicted. Depending on how emissions evolve, as simulated by current models, the level of planetary warming in 2100 by comparison with pre-industrial norms varies between 1.5 and 5°C or more. Using this approach, we are able then to attach a level of climate change to a particular socio-economic scenario and deduce the impact in a variety of areas. It is also possible, conversely, to determine the global emissions policies compatible with a given temperature-change target. This article by David Salas y Mélia is based on a different style of foresight thinking known as ‘backcasting’, which consists in taking a future climate situation, thinking backwards from it and relating the events that led up to it. Here the author imagines himself in 2101 and examines the chain of events that caused planetary temperatures to rise in 2068 to a peak of 3.1°C above pre-industrial levels, focussing particularly — as part of our series of articles devoted to things maritime — on the oceans. He points to the lack of concern in current times, which will not allow sufficiently vigorous action to be taken to actually limit climate change. He goes on to outline the geo-engineering techniques envisaged as ways of countering these shortcomings and the consequences of the developments that ensue. Finally, he describes the choice of the ‘Big Sunshade’ technique to reflect the sun’s rays back into space before they reach the Earth, which will make it possible to slow down the warming process and avoid the worst scenario, but will not prevent a decline of life on the planet and major losses to our ecosystems. But we are only in 2021… Is there still time to overcome our lack of concern and undertake the drastic actions required of us?
#Climat #Océans #Prospective (étude de cas) #Rétroprospective #Technologie de pointe #Transition écologique