Journalists who write about the climate are often accused of alarmism. They would be prone to give too much attention to catastrophic scenarios that the planet it would face until the end of this century – only 80 years to go – if nothing was done to contain global warming.
There is some truth there, Zeke Hausfather and Glen Peters said on Thursday in a commentary to the scientific journal Nature. As neither is a denialist of the climate crisis, quite the opposite, it is worth considering what they have to say – and say that their message is not really reassuring.
Hausfather appeared here in December, as the author of a study showing the correctness of computer models used to predict evolution of the Earth's climate. Your new onslaught has something to do with it.
The starting point for the simulations is the amount of carbon emitted into the atmosphere, such as carbon dioxide (CO2) resulting from the burning of fossil fuels (mineral coal, oil products and natural gas). To run the models, researchers need to make projections on the trajectory of emissions in the coming decades.
More often than not, the IPCC forecast reports (acronym for the UN-linked Intergovernmental Panel on Climate Change) emphasize the comparison between 2 of the 4 scenarios developed for its 2014 evaluation report (AR5). One more optimistic, known among specialists as RCP2.6, and the other more pessimistic, RCP8.5.
The first assumes that governments and companies will adopt measures to decarbonize the economy capable of limiting additional warming well below 2ºC, as established in the Paris Agreement (2015). That is to say, the amount of climate pollution that must be avoided to add less than 1ºC to what the atmosphere has heated up since the Industrial Revolution.
The scenario RCP8.5, generally considered as “business as usual” (more of the same) supposes that none of these measures would be taken, with a continuous increase in carbon emissions and the average global temperature reaching cataclysmic 5ºC. The branch, according to Hausfather and Peters: such a scenario is too pessimistic.
It is projected, for example, that the burning of coal would multiply by 5 by the year 2100. This can be considered highly unlikely, given that the consumption of this fossil fuel has already reached a level; there may be fluctuations, depending on the economic situation, but not the exponential growth built into RCP8.5.
The commentators in Nature argue that, in the next IPCC report (AR6), extreme scenarios such as RCP8.5 are more clearly qualified as unlikely. The idea is to prevent them from being presented to the public as “business as usual”, which they are no longer.
The ideal, they propose, is to compare what decision makers need to adopt to fulfill Paris with the risk of not doing so. Even with a trajectory modified by the continuous fall in the burning of coal and the costs of clean energy sources, such as wind and solar, the average global temperature would still exceed 3ºC, imposing huge impacts on the population and the economy.
It is a matter of checking the speedometer, not removing maximum speed cameras on the road that borders the precipice.
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