lunes, 5 de abril de 2021

"The 1.5C target has become VIRTUALLY IMPOSSIBLE to achieve" - Australian Academy of Science report

 "The 1.5C target has become VIRTUALLY IMPOSSIBLE to achieve"

This statement in the report launched last week by the Australian Academy of Science ('the risks to Australia of a 3C warmer world') has produced a lot of fuss, with discussions between scientists oscillating between a 'how do you dare to say this' to 'finally some honesty in stating things as they are'. The Guardian article below is a sample of these discussions.

In my opinion, it has been a mistake treating society as an immature kid by pretending to stretch always a bit more the 1.5C illusion. Lack of clear communication about the real situation, with the believe that as long as the message was that 'it was still possible to limit global warming to 1.5C with really no need to undertake structural changes', has lead to the non-sense of 2021 transition scenarios and fashion 'net-zero' claims for 2050 still implying about 700-800 GtCO2 gross emissions.

Communication of carbon budgets since the fifth IPCC AR (2014) has always tried to stretch it pretending that 'we are still on track'. Bizarre changes of methodology, reporting as function of temperature blends (near surface air temperate in land with sea water temperature in oceans), astonishing underestimates of earth system feedbacks, superficial uncertainty reporting, and even from time to time interpreting the budget available at the beginning of one year as the emissions that can take place from the end of this year. No wonder that we came to a situation where virtually any scenario can claim alignment with 1.5C, or where most policymakers feel fully satisfied with this net-zero buzzword for 2050. Basically, by addressing society as immature we got an utterly immature response.

First thing for addressing a crisis is acknowledging it as such. And second thing is to foster the maturity needed to address a real challenge.

How we are dealing with this 1.5C thing does not help. Basically we lost the opportunity window for facing and maturely addressing the crisis. We are still in such a fairytale wonderland as to claim net zero in 2050 without blushing. We'll be informed we went by the 1.5C once thermometers say so, and the year before we'll still be told we have a remaining carbon budget for 1.5C...

This approach underestimated the complexity of social systems and its dynamics. And basically will leave us missing the 1.5C target and above all utterly unprepared for the 1.6C, 1.7C, 1.9C... or whatever.

Because the point, both today and 20 - 30 years ago, is to limit global warming as much as we manage to do. Socioeconomic optimization has been extremely simple all the way through: throw the optimization subroutines to the rubbish been and change whatever you need to stop emitting.

The game is not over once we miss the 1.5C. We'll still need to strive for limiting global warming as much as possible. But the time lost with the 1.5C will push us up the thermometer.

And in case you wonder about the Australian Academy of Science carbon budget for 1.5C (66% likelihood), once updating to 2021 (astonishingly they report 2020 budget) it turns out to be 105 GtCO2. So the 'virtually impossible' does not seem too out of place. Moreover, the carbon budget that they report is linked to the blend of near surface air temperature on land and ice and the sea surface temperature in oceans (so mixing air and colder water to make it look as if we still have some more room). If we move to the more consistent metric of near surface temperature, the carbon budget reported by the Australian Academy of Science turns out to be -55 GtCO2, so we can skip the 'virtually' and just call it 'impossible'. The main difference between this carbon budget and the ones emanating from the IPCC 1.5SR is that here they include more earth system feedbacks: while the IPCC in its report mainly makes reference only to melting permafrost, here they include also boreal and Amazon forest dieback effects. Another difference is incorporating here the effect of non-CO2 gases.

But the Australian Academy of Science report does not account for the updates in sea water temperature database updates and underestimates historic emissions in recent years. In any case, the remaining carbon budgets for 1.5C are meager (see here for an update to 2021 with the conservative IPCC estimate of earth system feedbacks) and unless we start properly communicating it to society we are gonna be really in trouble.