The Intergovernmental Panel on Climate Change (IPCC) has assessed as many as 400 climate scenarios in his latest study. Only 50 of them predict that we avoid a global warming of no more than 1,5 ° C.
Of these, then, only 20 include realistic hypotheses on options, such as the extent of the removal of CO2 from the atmosphere, or the number of trees to be planted (which alone would never be enough, under any circumstances).
Finally, these 20 scenarios need in a very decisive way to “pull a lever” among those necessary for mitigation. This is why the world runs a huge risk of exceeding a global warming of over 1,5 ° C.
Let me rephrase, for clarity: the realistic window to reach the +1,5 ° C target is closing very quickly.
It is not the first study on the subject, and like the others it is not listened to enough. Between ourselves: what chance do we have of avoiding what now seems inevitable?
If all climate mitigation levers are pulled, it may still be possible to limit global warming to + 1,5 ° C.
“The emission scenarios differ in their dependence on each of the five mitigation levers we examined. Yet all scenarios that we believe to be realistic pull at least several levers to challenging levels, "says lead author. Lila Warszawski of the Potsdam Institute for Climate Impact Research (PIK).
None of the realistic scenarios are based on a single fix.Lila Warszawski
The few "positive" and realistic scenarios pull all possible levers
Il energy sector it is obviously essential to reduce the global temperature rise to no more than 1,5 ° C reduction of energy demand and on the other the decarbonisation of energy use and production. Yet the energy sector alone is not enough.
Also the CO2 removal and its "Captures" underground it turns out to be almost indispensable. Finally, the methane gas emissions they must be cut from animal production, but they must also be cut from the extraction of oil and gas. There are many things to do.
Global warming: a triple challenge for humanity
“Against global warming we need an immediate acceleration of global action to reduce greenhouse gas emissions. By all means available, ”says the co-author Tim Lenton of the University of Exeter.
The rhythms of the sustainability they must overcome those of the industrial revolution. It is a systemic challenge: fragmented actions and rhetorical commitments will not save us.Tim Lenton
"Humanity must win a triple challenge to stabilize global warming without significantly exceeding 1,5 ° C," says the co-author Nebojsa Nakicenovic of the International Institute for Applied Systems Analysis, IIASA.
The first: halve global emissions every decade. It requires a huge effort to decarbonise by gradually eliminating fossil energy, while also adopting climate-friendly behaviors and diets.
The second: help pursue carbon removal through afforestation and land use change.
The third: ensure the safe operation of earth systems which already now remove half of global emissions from the atmosphere.
It makes no sense to focus on just one factor.
Scenarios classified by the analysis as unrealistically optimistic tend to overestimate the potential for carbon capture and storage. Others overestimate energy savings, or the reduction of greenhouse gases. Still others do far too bold assumptions about plant foods or risk advantages deriving from the limited population growth.
Global warming: the Sky scenario
The authors also took a closer look at the global warming scenarios provided by the International Energy Agency (IEA) in 2018, and the one called 'Sky' produced by the oil company Shell.
Both predict net emissions to drop to zero globally by 2070.
“Shell's scenario is extremely optimistic,” says the co-author Gail Whiteman of the University of Exeter Business School. “From a scientific point of view, this is quite clear. In the business world it is popular because it seems to offer, compared to other scenarios, a relatively easy way out of the climate crisis. Our analysis shows, however, that there will be no easy way out. "
Global warming, it's easier to fail
The necessary emission reductions are difficult to achieve, technically and even politically. They require unprecedented innovation in lifestyles and international cooperation.
“I understand anyone who thinks we may fail the goal of containing global warming to within 1,5 ° C,” concludes the co-author Johan rockström.
We need to try at all costs. Limiting global warming would avoid the risk of causing an overturn in the Earth system. To avoid the disappearance of the ecosystems of the Amazon rainforest, or the melting of ice caps.